Non-target effects of ten essential oils on the egg parasitoid Trichogramma evanescens
Side effects of essential oils on pest natural enemiesRecommended by Cedric Pennetier based on reviews by Olivier Roux and 2 anonymous reviewers
Integrated pest management relies on the combined use of different practices in time and/or space. The main objectives are to better control pests, not to induce too much selective pressure on resistance mechanisms present in pest populations and to minimize non-targeted effects on the ecosystem . The efficiency of such a strategy requires at least additional or synergistic effects of chosen tools against targeted pest population in a specific environment. Any antagonistic effect on targeted or non-targeted organisms might reduce control effort to nil even worst.
Van Oudenhove et al  raised the question of the interaction between botanical pesticides (BPs) and egg parasitoids. Each of these two strategies used for pest management present advantages and are described as eco-friendly. First, the use of parasitoids is a great example of biological control and is massively used in a broad range of crop production in different ecological settings. Second, BPs, especially essential oils (EOs) used for a wide range of activities on pests (repellent, antifeedant, antiovipositant, ovicidal, larvicidal and simply pesticidal) present low-toxicity to non-target vertebrates and do not last too long in the environment. Combining these two strategies might be considered as a great opportunity to better pest control with minimized impact on environment. However, EOs used to target a wide range of pest might directly or indirectly affect parasitoids.
Van Oudenhove et al  focused their study on non-target effects of 10 essentials oils with pesticide potential on larval development and egg-seeking behaviour of five strains of the biocontrol agent Trichogramma evanescens. Within two laboratory experiments mimicing EOs fumigation (i.e. contactless EOs exposure), the authors evaluated (1) the toxicity of EOs on parasitoid development and (2) the repellent effect of these EOs on adult wasps. They confirmed that contactless exposure of EOs can (1) induce mortality during pre-imaginal development (more acute at the pupal stage) and (2) induce behavioural avoidance of EOs odour plume. These experiments ran onto five strains of T. evanescens also highlighted the variation of the effects of EOs among parasitoid strains.
The complex and dynamic interaction between pest, plant, parasitoid (a natural enemy) and their environment is disturbed by EOs. EOs plumes are also dynamic and variable upon the environmental conditions. The results of van Oudenhove et al. experimentally illustrate such a complexity by describing opposite effects (repellent and attractive) of the same EO on the behaviour of two T. evanescens strains. These contrasting results led us to question more broadly the non-target effects of pest management programs based on EOs fumigation on natural enemies.
Finally, the limits of this experimental study as discussed in the paper draw research avenues taking into account biotic variables such as plant chemical cues, odour plume dynamics, individual behavioural experiences and abiotic variables such as temperature, light and gravity  in laboratory, semi-field and field experiments. Facing such a complexity, modelling studies at fine scale in time and space have the operational objective to help farmers to choose the best IPM strategy regarding their environment (as illustrated for aphid population management in the recent review by Stell et al. ). But before such research effort to be undertaken, Van Oudenhove et al study  sounds like an alert for a cautious use of EOs in pest control programs that integrate biological control with parasitoids.
 Fauvergue, X. Biocontrôle Elements Pour Une Protection Agroecologique des Cultures; Éditions Quae: Versailles, France, 2020.
 van Oudenhove L, Cazier A, Fillaud M, Lavoir AV, Fatnassi H, Pérez G, Calcagno V. Non-target effects of ten essential oils on the egg parasitoid Trichogramma evanescens. bioRxiv 2022.01.14.476310, ver. 4 peer-reviewed and recommended by PCI Zoology. https://doi.org/10.1101/2022.01.14.476310
 Victor Burte, Guy Perez, Faten Ayed, Géraldine Groussier, Ludovic Mailleret, Louise van Oudenhove and Vincent Calcagno (2022) Up and to the light: intra- and interspecific variability of photo- and geo-tactic oviposition preferences in genus Trichogramma, Peer Community Journal, 2: e3. https://doi.org/10.24072/pcjournal.78
 Stell E, Meiss H, Lasserre-Joulin F, Therond O. Towards Predictions of Interaction Dynamics between Cereal Aphids and Their Natural Enemies: A Review. Insects 2022, 13, 479. https://doi.org/10.3390/insects13050479
A pipeline for assessing the quality of images and metadata from crowd-sourced databases.
Harnessing the full potential of iNaturalist and other databasesRecommended by Matthias Foellmer based on reviews by Clive Hambler and Catherine Scott
The popularity of iNaturalist and other online biodiversity databases to which the general public and specialists alike contribute observations has skyrocketed in recent years (Dance 2022). The AI-based algorithms (computer vision) which provide the first identification of a given organism on an uploaded photograph have become very sophisticated, suggesting initial identifications often down to species level with a surprisingly high degree of accuracy. The initial identifications are then confirmed or improved by feedback from the community, which works particularly well for organismal groups to which many active community members contribute, such as the birds. Hence, providing initial observations and identifying observations of others, as well as browsing the recorded biodiversity for given locales or the range of occurrences of individual taxa has become a meaningful and satisfying experience for the interested naturalist. Furthermore, several research studies have now been published relying on observations uploaded to iNaturalist (Szentivanyi and Vincze 2022). However, using the enormous amount of natural history data available on iNaturalist in a systematic way has remained challenging, since this requires not only retrieving numerous observations from the database (in the hundreds or even thousands), but also some level of transparent quality control.
Billotte (2022) provides a protocol and R scripts for the quality assessment of downloaded observations from iNaturalist, allowing an efficient and reproducible stepwise approach to prepare a high-quality data set for further analysis. First, observations with their associated metadata are downloaded from iNaturalist, along with the corresponding entries from the Global Biodiversity Information Facility (GBIF). In addition, a taxonomic reference list is obtained (these are available online for many taxa), which is used to assess the taxonomic consistency in the dataset. Second, the geo-tagging is assessed by comparing the iNaturalist and GBIF metadata. Lastly, the image quality is assessed using pyBRISQUE. The approach is illustrated using spiders (Araneae) as an example. Spiders are a very diverse taxon and an excellent taxonomic reference list is available (World Spider Catalogue 2022). However, spiders are not well known to most non-specialists, and it is not easy to take good pictures of spiders without using professional equipment. Therefore, the ability of iNaturalist’s computer vision to provide identifications is limited to this date and the community of specialists active on iNaturalist is comparatively small. Hence, spiders are a good taxon to demonstrate how the pipeline results in a quality-controlled dataset based on crowed-sourced data. Importantly, the software employed is free to use, although inevitably, the initial learning curve to use R scripts can be steep, depending on prior expertise with R/RStudio. Furthermore, the approach is employable with databases other than iNaturalist.
In summary, Billotte's (2022) pipeline allows researchers to use the wealth of observations on iNaturalist and other databases to produce large metadata and image datasets of high-quality in a reproducible way. This should pave the way for more studies, which could include, for example, the assessment of range expansions of invasive species or the evaluation of the presence of endangered species, potentially supporting conservation efforts.
Billotte J (2022) A pipeline for assessing the quality of images and metadata from crowd-sourced databases. BiorXiv, 2022.04.29.490112, ver 5 peer reviewed and recommended by Peer Community In Zoology. https://doi.org/10.1101/2022.04.29.490112
Dance A (2022) Community science draws on the power of the crowd. Nature, 609, 641–643. https://doi.org/10.1038/d41586-022-02921-3
Szentivanyi T, Vincze O (2022) Tracking wildlife diseases using community science: an example through toad myiasis. European Journal of Wildlife Research, 68, 74. https://doi.org/10.1007/s10344-022-01623-5
World Spider Catalog (2022). World Spider Catalog. Version 23.5. Natural History Museum Bern, online at http://wsc.nmbe.ch. https://doi.org/10.24436/2
A simple procedure to detect, test for the presence of stuttering, and cure stuttered data with spreadsheet programs
Improved population genetics parameters through control for microsatellite stutteringRecommended by Michael Lattorff based on reviews by Thibaut Malausa, Fabien Halkett and Thierry Rigaud
Molecular markers have drastically changed and improved our understanding of biological processes. In combination with PCR, markers revolutionized the study of all organisms, even tiny insects, and eukaryotic pathogens amongst others. Microsatellite markers were the most prominent and successful ones. Their success started in the early 1990s. They were used for population genetic studies, mapping of genes and genomes, and paternity testing and inference of relatedness. Their popularity is based on some of their characteristics as codominance, the high polymorphism information content, and their ease of isolation (Schlötterer 2004). Still, microsatellites are the marker of choice for a range of non-model organisms as next-generation sequencing technologies produce a huge amount of single nucleotide polymorphisms (SNPs), but often at expense of sample size and higher costs.
The high level of polymorphism of microsatellite markers, which consist of one to six base-pair nucleotide motifs replicated up to 10 or 20 times, results from slippage events during DNA replication. Short hairpin loops might shorten the template strand or extend the new strand. However, such slippage events might occur during PCR amplification resulting in additional bands or peaks. Such stutter alleles often appear to differ by one repeat unit and might be hard to interpret but definitively reduce automated scoring of microsatellite results.
A standalone software package available to handle stuttering is Microchecker (van Oosterhout et al., 2004, which nowadays faces incompatibilities with updated versions of different operating systems. Thus, de Meeûs and Noûs (2022), in their manuscript, tackled the stuttering issue by developing an OS-independent analysis pipeline based on standard spreadsheet software such as Microsoft Office (Excel) or Apache Open Office (Calc). The authors use simulated populations differing in the mating system (pangamic, selfing (30%), clonal) and a different number of subpopulations and individuals per subpopulation to test for differences among the null model (no stuttering), a test population with 2 out of 20 loci (10%) with stuttering, and the latter with stuttering cured. Further to this, the authors also re-analyse data from previous studies utilising organisms differing in the mating system to understand whether control of stuttering changes major parameter estimates and conclusions of those studies.
Stuttering of microsatellite loci might result in increased heterozygote deficits. The authors utilise the FIS (inbreeding coefficient) as a tool to compare the different treatments of the simulated populations. Their method detected stuttering in pangamic and selfing populations, while the detection of stuttering in clonal organisms is more difficult. The cure for stuttering resulted in FIS values similar to those populations lacking stuttering. The re-analysis of four previously published studies indicated that the new method presented here is more accurate than Microchecker (van Oosterhout et al., 2004) in a direct comparison. For the Lyme disease-transmitting tick Ixodes scapularis (De Meeûs et al., 2021), three loci showed stuttering and curing these resulted in data that are in good agreement with pangamic reproduction. In the tsetse fly Glossina palpalis palpalis (Berté et al., 2019), two out of seven loci were detected as stuttering. Curing them resulted in decreased FIS for one locus, while the other showed an increased FIS, an indication of other problems such as the occurrence of null alleles. Overall, in dioecious pangamic populations, the method works well, and the cure of stuttering improves population genetic parameter estimates, although FST and FIS might be slightly overestimated. In monoecious selfers, the detection and cure work well, if other factors such as null alleles do not interfere. In clonal organisms, only loci with extremely high FIS might need a cure to improve parameter estimates.
This spreadsheet-based method helps to automate microsatellite analysis at very low costs and thus improves the accuracy of parameter estimates. This might certainly be very useful for a range of non-model organisms, parasites, and their vectors, for which microsatellites are still the marker of choice.
Berté D, De Meeus T, Kaba D, Séré M, Djohan V, Courtin F, N'Djetchi KM, Koffi M, Jamonneau V, Ta BTD, Solano P, N’Goran EK, Ravel S (2019) Population genetics of Glossina palpalis palpalis in sleeping sickness foci of Côte d'Ivoire before and after vector control. Infection Genetics and Evolution 75, 103963. https://doi.org/0.1016/j.meegid.2019.103963
de Meeûs T, Chan CT, Ludwig JM, Tsao JI, Patel J, Bhagatwala J, Beati L (2021) Deceptive combined effects of short allele dominance and stuttering: an example with Ixodes scapularis, the main vector of Lyme disease in the U.S.A. Peer Community Journal 1, e40. https://doi.org/10.24072/pcjournal.34
de Meeûs T, Noûs C (2022) A simple procedure to detect, test for the presence of stuttering, and cure stuttered data with spreadsheet programs. Zenodo, v5, peer-reviewed and recommended by PCI Zoology. https://doi.org/10.5281/zenodo.7029324
Schlötterer C (2004) The evolution of molecular markers - just a matter of fashion? Nature Reviews Genetics 5, 63-69. https://doi.org/10.1038/nrg1249
van Oosterhout C, Hutchinson WF, Wills DPM, Shipley P (2004) MICRO-CHECKER: software for identifying and correcting genotyping errors in microsatellite data. Molecular Ecology Notes 4, 535-538. https://doi.org/10.1111/j.1471-8286.2004.00684.x
Within and among population differences in cuticular hydrocarbons in the seabird tick Ixodes uriae
Seabird tick diversification and cuticular hydrocarbonsRecommended by Felix Sperling based on reviews by 2 anonymous reviewers
Ticks are notorious vectors of diseases in humans and other vertebrates. Much effort has been expended to understand tick diversity and ecology with the aim of managing their populations to alleviate the misery they bring. Further, the fundamental question of whether ticks are usually host generalists or host specialists has been debated at length and is important both for understanding the mechanisms of their diversification as well as for focusing control of ticks .
One elegant resolution of this question is to consider most tick species to be global generalists but local specialists . This is well illustrated in a series of studies of the seabird tick, Ixodes uriae, which is comprised of host-specific races that show genetic , morphological  and host performance  differences associated with the seabirds they feed on. Such a pattern has clear ramifications for sympatric speciation; however, the factors that potentially act to drive these differences have remained elusive.
Dupraz et al.  have now made intriguing and important steps toward bridging the gap between demonstrating local patterns of tick host association and understanding the physiological mechanisms that may facilitate such divergences. They collected I. uriae ticks from the nests of two seabirds – Atlantic puffins and common guillemots – on the north side of Iceland. Four populations of ticks were sampled, with one island providing both puffin ticks and guillemot ticks, to give two tick populations from each of the two seabird host species. They then washed the ticks in solvent and analyzed the dissolved cuticular hydrocarbons (CHCs) using GC mass spectrometry, revealing 22 different hydrocarbon compounds common to most of these samples. CHCs are known to be important across arthropods for a variety of functions ranging from reducing water loss to facilitating communication and recognition between individuals with species.
Dupraz et al.  found three hydrocarbons that distinguished puffin ticks most consistently from guillemot ticks. A cross-validation test for host type also assigned 75% of the tick pools to the seabird host of origin. However, with these limited sample sizes, statistical analysis revealed no significant difference in CHC profiles between the host types, although a tendency was evident. Nonetheless, this study revealed a number of potentially diagnostic CHCs for tick host type, as well as some that may be more diagnostic of locations. This provides a fascinating and actionable foundation for further work using additional sites and host types, as well as an entry point into discerning the mechanisms at play in producing the diversity, complexity and adaptability that make ticks such medical menaces.
 McCoy, K.D., Léger, E., Dietrich, M., 2013. Host specialization in ticks and transmission of tick-borne diseases: a review. Front. Cell. Infect. Microbiol. 3. https://doi.org/10.3389/fcimb.2013.00057
 McCoy, K.D., Chapuis, E., Tirard, C., Boulinier, T., Michalakis, Y., Bohec, C.L., Maho, Y.L., Gauthier-Clerc, M., 2005. Recurrent evolution of host-specialized races in a globally distributed parasite. Proc. R. Soc. B Biol. Sci. 272, 2389–2395. https://doi.org/10.1098/rspb.2005.3230
 Dietrich, M., Beati, L., Elguero, E., Boulinier, T., McCoy, K.D., 2013. Body size and shape evolution in host races of the tick Ixodes uriae. Biol. J. Linn. Soc. 108, 323–334. https://doi.org/10.1111/j.1095-8312.2012.02021.x
 Dietrich, M., Lobato, E., Boulinier, T., McCoy, K.D., 2014. An experimental test of host specialization in a ubiquitous polar ectoparasite: a role for adaptation? J. Anim. Ecol. 83, 576–587. https://doi.org/10.1111/1365-2656.12170
 Dupraz, M., Leroy, C., Thórarinsson, T. L., d’Ettorre, P. and McCoy, K. D. (2022) Within and among population differences in cuticular hydrocarbons in the seabird tick Ixodes uriae. bioRxiv, 2022.01.21.477272, ver. 5 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2022.01.21.477272
Improving species conservation plans under IUCN's One Plan Approach using quantitative genetic methods
Quantitative genetics for a more qualitative conservationRecommended by Peter Galbusera based on reviews by Timothée Bonnet and 1 anonymous reviewer
Genetic (bio)diversity is one of three recognised levels of biodiversity, besides species and ecosystem diversity. Its importance for species survival and adaptation is increasingly highlighted and its monitoring recommended (e.g. O’Brien et al 2022). Especially the management of ex-situ populations has a long history of taking into account genetic aspects (through pedigree analysis but increasingly also by applying molecular tools). As in-situ and ex-situ efforts are nowadays often aligned (in a One-Plan-Approach), genetic management is becoming more the standard (supported by quickly developing genomic techniques). However, rarely quantitative genetic aspects are raised in this issue, while its relevance cannot be underestimated. Hence, the current manuscript by Sauve et al (2022) is a welcome contribution, in order to improve conservation efforts. The authors give a clear overview on how quantitative genetic analysis can aid the measurement, monitoring, prediction and management of adaptive genetic variation. The main tools are pedigrees (mainly of ex-situ populations) and the Animal Model. The main goal is to prevent adaption to captivity and altered genetics in general (in reintroduction projects). The confounding factors to take into account (like inbreeding, population structure, differences between facilities, sample size and parental/social effects) are well described by the authors. As such, I fully recommend this manuscript for publication, hoping increased interest in quantitative analysis will benefit the quality of species conservation management.
O'Brien D, Laikre L, Hoban S, Bruford MW et al. (2022) Bringing together approaches to reporting on within species genetic diversity. Journal of Applied Ecology, 00, 1–7. https://doi/10.1111/1365-2664.14225
Sauve D., Spero J., Steiner J., Wheeler H., Lynch C., Chabot A.A. (2022) Improving species conservation plans under IUCN’s One Plan Approach using quantitative genetic methods. EcoEvoRxiv, ver. 9 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.32942/osf.io/n3zxp
Dopamine pathway characterization during the reproductive mode switch in the pea aphid
In search of the links between environmental signals and polyphenismRecommended by Mathieu Joron based on reviews by Antonia Monteiro and 2 anonymous reviewers
Polyphenisms offer an opportunity to study the links between phenotype, development, and environment in a controlled genomic context (Simpson, Sword, & Lo, 2011). In organisms with short generation times, individuals living and developing in different seasons encounter different environmental conditions. Adaptive plasticity allows them to express different phenotypes in response to seasonal cues, such as temperature or photoperiod. Such phenotypes can be morphological variants, for instance displaying different wing patterns as seen in butterflies (Brakefield & Larsen, 1984; Nijhout, 1991; Windig, 1999), or physiological variants, characterized for instance by direct development vs winter diapause in temperate insects (Dalin & Nylin, 2012; Lindestad, Wheat, Nylin, & Gotthard, 2019; Shearer et al., 2016).
Many aphids display cyclical parthenogenesis, a remarkable seasonal polyphenism for reproductive mode (Tagu, Sabater-Muñoz, & Simon, 2005), also sometimes coupled with wing polyphenism (Braendle, Friebe, Caillaud, & Stern, 2005), which allows them to switch between parthenogenesis during spring and summer to sexual reproduction and the production of diapausing eggs before winter. In the pea aphid Acyrthosiphon pisum, photoperiod shortening results in the production, by parthenogenetic females, of embryos developing into the parthenogenetic mothers of sexual individuals. The link between parthenogenetic reproduction and sexual reproduction, therefore, occurs over two generations, changing from a parthenogenetic form producing parthenogenetic females (virginoparae), to a parthenogenetic form producing sexual offspring (sexuparae), and finally sexual forms producing overwintering eggs (Le Trionnaire et al., 2022).
The molecular basis for the transduction of the environmental signal into reproductive changes is still unknown, but the dopamine pathway is an interesting candidate. Form-specific expression of certain genes in the dopamine pathway occurs downstream of the perception of the seasonal cue, notably with a marked decrease in the heads of embryos reared under short-day conditions and destined to become sexuparae. Dopamine has multiple roles during development, with one mode of action in cuticle melanization and sclerotization, and a neurological role as a synaptic neurotransmitter. Both modes of action might be envisioned to contribute functionally to the perception and transduction of environmental signals.
In this study, Le Trionnaire and colleagues aim at clarifying this role in the pea aphid (Le Trionnaire et al., 2022). Using quantitative RT-PCR, RNA-seq, and in situ hybridization of RNA probes, they surveyed the timing and spatial patterns of expression of dopamine pathway genes during the development of different stages of embryo to larvae reared under long and short-day conditions, and destined to become virginoparae or sexuparae females, respectively. The genes involved in the synaptic release of dopamine generally did not show differences in expression between photoperiodic treatments. By contrast, pale and ddc, two genes acting upstream of dopamine production, generally tended to show a downregulation in sexuparare embryo, as well as genes involved in cuticle development and interacting with the dopamine pathway. The downregulation of dopamine pathway genes observed in the heads of sexuparare juveniles is already detectable at the embryonic stage, suggesting embryos might be sensing environmental cues leading them to differentiate into sexuparae females.
The way pale and ddc expression differences could influence environmental sensitivity is still unclear. The results suggest that a cuticle phenotype specifically in the heads of larvae could be explored, perhaps in the form of a reduction in cuticle sclerotization and melanization which might allow photoperiod shortening to be perceived and act on development. Although its causality might be either way, such a link would be exciting to investigate, yet the existence of cuticle differences between the two reproductive types is still a hypothesis to be tested. The lack of differences in the expression of synaptic release genes for dopamine might seem to indicate that the plastic response to photoperiod is not mediated via neurological roles. Yet, this does not rule out the role of decreasing levels of dopamine in mediating this response in the central nervous system of embryos, even if the genes regulating synaptic release are equally expressed.
To test for a direct role of ddc in regulating the reproductive fate of embryos, the authors have generated CrispR-Cas9 knockout mutants. Those mutants displayed egg cuticle melanization, but with lethal effects, precluding testing the effect of ddc at later stages in development. Gene manipulation becomes feasible in the pea aphid, opening up certain avenues for understanding the roles of other genes during development.
This study adds nicely to our understanding of the intricate changes in gene expression involved in polyphenism. But it also shows the complexity of deciphering the links between environmental perception and changes in physiology, which mobilise multiple interacting gene networks. In the era of manipulative genetics, this study also stresses the importance of understanding the traits and phenotypes affected by individual genes, which now seems essential to piece the puzzle together.
Braendle C, Friebe I, Caillaud MC, Stern DL (2005) Genetic variation for an aphid wing polyphenism is genetically linked to a naturally occurring wing polymorphism. Proceedings of the Royal Society B: Biological Sciences, 272, 657–664. https://doi.org/10.1098/rspb.2004.2995
Brakefield PM, Larsen TB (1984) The evolutionary significance of dry and wet season forms in some tropical butterflies. Biological Journal of the Linnean Society, 22, 1–12. https://doi.org/10.1111/j.1095-8312.1984.tb00795.x
Dalin P, Nylin S (2012) Host-plant quality adaptively affects the diapause threshold: evidence from leaf beetles in willow plantations. Ecological Entomology, 37, 490–499. https://doi.org/10.1111/j.1365-2311.2012.01387.x
Le Trionnaire G, Hudaverdian S, Richard G, Tanguy S, Gleonnec F, Prunier-Leterme N, Gauthier J-P, Tagu D (2022) Dopamine pathway characterization during the reproductive mode switch in the pea aphid. bioRxiv, 2020.03.10.984989, ver. 4 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2020.03.10.984989
Lindestad O, Wheat CW, Nylin S, Gotthard K (2019) Local adaptation of photoperiodic plasticity maintains life cycle variation within latitudes in a butterfly. Ecology, 100, e02550. https://doi.org/10.1002/ecy.2550
Nijhout HF (1991). The development and evolution of butterfly wing patterns. Washington, DC: Smithsonian Institution Press.
Shearer PW, West JD, Walton VM, Brown PH, Svetec N, Chiu JC (2016) Seasonal cues induce phenotypic plasticity of Drosophila suzukii to enhance winter survival. BMC Ecology, 16, 11. https://doi.org/10.1186/s12898-016-0070-3
Simpson SJ, Sword GA, Lo N (2011) Polyphenism in Insects. Current Biology, 21, R738–R749. https://doi.org/10.1016/j.cub.2011.06.006
Tagu D, Sabater-Muñoz B, Simon J-C (2005) Deciphering reproductive polyphenism in aphids. Invertebrate Reproduction & Development, 48, 71–80. https://doi.org/10.1080/07924259.2005.9652172
Windig JJ (1999) Trade-offs between melanization, development time and adult size in Inachis io and Araschnia levana (Lepidoptera: Nymphalidae)? Heredity, 82, 57–68. https://doi.org/10.1038/sj.hdy.6884510
Pre- and post-oviposition behavioural strategies to protect eggs against extreme winter cold in an insect with maternal care
New insights into maternal egg care in insects: egg transport as an adaptive behavior to extreme temperatures in the European earwigRecommended by Anna Cohuet based on reviews by Wolf U. Blanckenhorn, Ana Rivero and Nicolas Sauvion
Because of the inability of eggs to move, the fitness of oviparous organisms is particularly dependent on the oviposition site. The choice of oviposition site by mothers is therefore the result of trade-offs between exposure to risk factors or favorable conditions such as the presence/absence of predators, the threat of extreme temperatures, the risk of desiccation, the presence and quality of nutritional resources... In addition to these trade-offs between different biotic and abiotic factors that determine oviposition site selection, the ability of mothers to move their eggs after oviposition is a game-changer in insect strategies to optimize egg development and survival . Oviposition site selection combined with egg transport has been explored in insects in relation to the risk of exposure to egg parasitoids  or needs for oxygenation  but surprisingly has not been investigated in regards to temperatures. Considering egg transport in the ability of insects to adapt their behavior to environmental conditions and in particular to potential extreme temperatures is yet inherent in providing a complete picture of the diversity of behaviors that shape adaptation to temperature and potential tolerance to climate change. In this sense, the study presented by Tourneur et al. , explores whether insects capable of egg-care might use egg transport as an adaptive behavior to protect them from suboptimal or extreme temperatures. The study was conducted in the European earwig, Forficula auricularia Linnaeus, 1758, which is known to practice egg-care in a variety of ways, that presumably includes egg-transportation, for several weeks or months during winter until hatching. The authors characterized different life-history traits related to egg-laying, egg-transport, and egg-development in two device systems with three experimental temperature regimes in two populations of European earwigs from Canada. The inclusion of two populations, which turned out to belong to two clades, allowed the identification of a diversity of behaviors although this did not allow to attribute the differences between the two populations to specific population differences, genetic differences, or to their geographical origins. Interestingly, the study showed that oviposition site selection in the European earwig is driven by temperature and that in winter temperatures, female earwigs may move their eggs to warmer temperatures that are adequate for hatching. These results are original in the sense that they highlight new adaptive strategies in female insects used during the post-oviposition stage to protect their eggs from temperature changes.
In the current context of climate change and potential changes in selective pressures, the study contributes to the understanding of the wide range of strategies deployed by insects to adapt to the temperature. This appears essential to predict and anticipate the consequences of global instability, it also describes from an academic point of view a new and fascinating adaptive strategy in an overlooked biological system.
 Machado G, Trumbo ST (2018) Parental care. In: Insect Behavior, pp. 203–218. Oxford University Press, Oxford. https://doi.org/10.1093/oso/9780198797500.003.0014
 Carrasco D, Kaitala A (2009) Egg-laying tactic in Phyllomorpha laciniata in the presence of parasitoids. Entomologia Experimentalis et Applicata, 131, 300–307. https://doi.org/10.1111/j.1570-7458.2009.00857.x
 Smith RL (1997) Evolution of paternal care in the giant water bugs (Heteroptera: Belostomatidae). In: The Evolution of Social Behaviour in Insects and Arachnids (eds Crespi BJ, Choe JC), pp. 116–149. Cambridge University Press, Cambridge. https://doi.org/10.1017/CBO9780511721953.007
 Tourneur J-C, Cole C, Vickruck J, Dupont S, Meunier J (2022) Pre- and post-oviposition behavioural strategies to protect eggs against extreme winter cold in an insect with maternal care. bioRxiv, 2021.11.23.469705, ver. 3 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2021.11.23.469705
Analyses of symbiotic bacterial communities in the plant pest Bemisia tabaci reveal high prevalence of Candidatus Hemipteriphilus asiaticus on the African continent
Cross-continents whitefly secondary symbiont revealed by metabarcodingRecommended by Yuval Gottlieb based on reviews by François Renoz, Vincent Hervé and 1 anonymous reviewer
Whiteflies are serious global pests that feed on phloem sap of many agricultural crop plants. Like other phloem feeders, whiteflies rely on a primary-symbiont to supply their poor, sugar-based diet. Over time, the genomes of primary-symbionts become degraded, and they are either been replaced or complemented by co-hosted secondary-symbionts (McCutcheon and Moran 2012). In Bemisia tabaci species complex, the primary-symbiont is Candidatus Portiera aleyrodidarium, with seven secondary-symbionts that have been described to date. The prevalence and dynamics of these secondary-symbionts have been studied in various whitefly populations and genetic groups around the world, and certain combinations are determined under specific biotic and environmental factors (Zchori-Fein et al. 2014).
To understand the potential metabolic or other interactions of various secondary-symbionts with Ca. Portiera aleyrodidarium and the hosts, Mouton et al. used metabarcoding approach and diagnostic PCR confirmation, to describe symbiont compositions in a collection of whiteflies from eight populations with four genetic groups in Burkina Faso. They found that one of the previously recorded secondary-symbiont from Asian whitefly populations, Candidatus Hemipteriphilus asiaticus, is also found in the tested African whiteflies. The newly identified Ca. Hemipteriphilus asiaticus forms a different strain than the ones described in Asia, and is found in high prevalence in six of the tested populations and in three genetic groups. They also showed that Portiera densities are not affected by the presence of Ca. Hemipteriphilus asiaticus. The authors suggest that based on its high prevalence, Ca. Hemipteriphilus asiaticus may benefit certain whitefly populations, however, there is no attempt to test this assumption or to relate it to environmental factors, or to identify the source of introduction.
Mouton et al. bring new perspectives to the study of complex hemipteran symbioses, emphasizing the need to use both unbiased approaches such as metabarcoding, together with a priori methods such as PCR, in order to receive a complete description of symbiont population structures. Their findings are awaiting future screens for this secondary-symbiont, as well as its functional genomics and experimental manipulations to clarify its role. Discoveries on whitefly-symbionts delicate interactions are required to develop alternative control strategies for this worldly devastating pest.
McCutcheon JP, Moran NA (2012) Extreme genome reduction in symbiotic bacteria. Nature Reviews Microbiology, 10, 13–26. https://doi.org/10.1038/nrmicro2670
Mouton L, Henri H, Romba R, Belgaidi Z, Gnankiné O, Vavre F (2022) Analyses of symbiotic bacterial communities in the plant pest Bemisia tabaci reveal high prevalence of Candidatus Hemipteriphilus asiaticus on the African continent. bioRxiv, 2021.10.06.463217, ver. 3 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2021.10.06.463217
Zchori-Fein E, Lahav T, Freilich S (2014) Variations in the identity and complexity of endosymbiont combinations in whitefly hosts. Frontiers in Microbiology, 5. https://doi.org/10.3389/fmicb.2014.00310
The initial response of females towards congeneric males matches the propensity to hybridise in Ophthalmotilapia
Experimental evidence for asymmetrical species recognition in East African Ophthalmotilapia cichlidsRecommended by Ellen Decaestecker based on reviews by George Turner and 2 anonymous reviewers
I recommend the Van Steenberge et al. study. With over 2000 endemic species, the East African cichlids are a well-established model system in speciation research (Salzburger 2018) and several models have been proposed and tested to explain how these radiations formed (Kocher 2004). Hybridization was shown to be a main driver of the rapid speciation and adaptive radiations of the East African Cichlid fishes (Seehausen 2004). However, it is obvious that unrestrained hybridization also has the potential to reduce taxonomic diversity by erasing species barriers. In the classical model of cichlid evolution, special emphasis was placed on mate preference (Kocher 2004). However, no attention was placed on species recognition, which was implicitly assumed. There is, however, more research needed on what species recognition means, especially in radiating lineages such as cichlids. In a previous study, Nevado et al. 2011 found traces of asymmetrical hybridization between members of the Lake Tanganyika radiation: the genus Ophthalmotilapia. This recommended study by Van Steenberge et al. is based on Nevado et al. (2011), which detected that in one genus of Ophthalmotilapia mitochondrial DNA ‘typical’ for one of the four species (O. nasuta) was also found in three other species (O. ventralis, O. heterodonta, and O. boops). The authors suggested that this could be explained by the fact that females of the three other species accepted O. nasuta males, but that O. nasuta females were more selective and accepted only conspecifc males. This could hence be due to asymmetric mate preferences, or by asymmetric abilities for species recognition.
This is exactly what the current study by Van Steenberge et al. did. They tested the latter hypothesis by presenting females of two different Ophthalmotilapia species with con- and heterospecific males. This was tested through experiments, making use of wild specimens of two species: O. nasuta and O. ventralis. The authors assumed that if they performed classical “choice-experiments”, they would not notice the recognition effects, given that females would just select preferred, most likely conspecific, males. Instead, specimens were only briefly presented to other fishes since the authors wanted to compare differences in the ability for ‘species recognition’. In this, the authors followed Mendelson and Shaw (2012) who used “a measurable difference in behavioural response towards conspecifics as compared to heterospecifics’’ as a definition for recognition. Instead of the focus on selection/preference, they investigated if females of different species behaved differently, and hence detected the difference between conspecific and heterospecific males. This was tested by a short (15 minutes) exposure to another fish in an isolated part of the aquarium. Recognition was defined as the ‘difference in a particular behaviour between the two conditions’. What was monitored was the swimming behaviour and trajectory (1 image per second) together with known social behaviours of this genus. The selection of these behaviours was further facilitated based on experimental set-ups of reproductive behaviour or the same species previously described by the same research team (Kéver et al. 2018).
The result was that O. nasuta females, for which it was expected that they would not hybridize, showed a different behaviour towards a con- or a heterospecific male. They interacted less with males of the other species. What was unexpected is that there was no difference in behaviour of the females whether they recognized a male or (control) female of their own species. This suggests that they did not detect differences in reproductive behaviour, but rather in the interactions between conspecifics. For females of O. ventralis, for which there are indications for hybridization in the wild, they did not find a difference in behaviour. Females of this species behaved identically with respect to the right and wrong males as well as towards the control females. Interestingly is thus that a complex pattern between species in the wild could be (partially) explained by the behaviour/interaction at first impression of the individuals of these species.
Kéver L, Parmentier E, Derycke S, Verheyen E, Snoeks J, Van Steenberge M, Poncin P (2018) Limited possibilities for prezygotic barriers in the reproductive behaviour of sympatric Ophthalmotilapia species (Teleostei, Cichlidae). Zoology, 126, 71–81. https://doi.org/10.1016/j.zool.2017.12.001
Kocher TD (2004) Adaptive evolution and explosive speciation: the cichlid fish model. Nature Reviews Genetics, 5, 288–298. https://doi.org/10.1038/nrg1316
Mendelson TC, Shaw KL (2012) The (mis)concept of species recognition. Trends in Ecology & Evolution, 27, 421–427. https://doi.org/10.1016/j.tree.2012.04.001
Nevado B, Fazalova V, Backeljau T, Hanssens M, Verheyen E (2011) Repeated Unidirectional Introgression of Nuclear and Mitochondrial DNA Between Four Congeneric Tanganyikan Cichlids. Molecular Biology and Evolution, 28, 2253–2267. https://doi.org/10.1093/molbev/msr043
Salzburger W (2018) Understanding explosive diversification through cichlid fish genomics. Nature Reviews Genetics, 19, 705–717. https://doi.org/10.1038/s41576-018-0043-9
Seehausen O (2004) Hybridization and adaptive radiation. Trends in Ecology & Evolution, 19, 198–207. https://doi.org/10.1016/j.tree.2004.01.003
Steenberge MV, Jublier N, Kéver L, Gresham S, Derycke S, Snoeks J, Parmentier E, Poncin P, Verheyen E (2022) The initial response of females towards congeneric males matches the propensity to hybridise in Ophthalmotilapia. bioRxiv, 2021.08.07.455508, ver. 3 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2021.08.07.455508
Cuckoo male bumblebees perform slower and longer flower visits than free-living male and worker bumblebees
Cuckoo bumblebee males might reduce plant fitnessRecommended by Michael Lattorff based on reviews by Patrick Lhomme, Silvio Erler and 2 anonymous reviewers
In pollinator insects, especially bees, foraging is almost exclusively performed by females due to the close linkage with brood care. They collect pollen as a protein- and lipid-rich food to feed developing larvae in solitary and social species. Bees take carbohydrate-rich nectar in small quantities to fuel their flight and carry the pollen load. To optimise the foraging flight, they tend to be flower constant, reducing the flower handling time and time among individual inflorescences (Goulson, 1999). Males of pollinator species might be found on flowers as well. As they do not collect any pollen for brood care, their foraging flights and visits to flowers might not be shaped by the selective forces that optimise the foraging flights of females. They might stay longer in individual flowers, take up nectar if needed, but might unintentionally carry pollen on their body surface (Wolf & Moritz, 2014).
Bumblebees are excellent pollinators (Goulson, 2010), and a few species are exploited commercially for their delivery of pollination services (Velthuis & van Doorn, 2006). However, a monophyletic group of socially parasitic species – cuckoo bumblebees – has evolved amongst the bumblebees, lacking a worker caste. Cuckoo bee gynes usurp nests of free-living bumblebees, kill the resident queen, and forces the host workers to rear their offspring consisting of gynes and males (Lhomme & Hines, 2019). The level of affected colonies in an area can be up to 42% (Erler & Lattorff, 2010).
The behaviour of the cuckoo bumblebees, especially that of the males, has been rarely studied. The present study by Fisogni et al. (2021) has targeted the flower-visiting behaviour of workers and males of free-living bumblebees and males of the cuckoo species. They used behavioural observations of flower-visiting insects on Gentiana lutea, a plant from south-eastern Europe with yellow flowers arranged in whorls. While all three groups of bees visited the same number of plants, males of both types visited more flowers within a whorl, but cuckoo males spent more time on flowers within a whorl and the whole plant than the free-living bumblebees.
The flower visits of bumblebee workers are optimised, aiming at collecting as much pollen as possible within a short time frame. This, in turn, has consequences for the pollination process by enhancing cross-pollination between different plants. By contrast, males and especially cuckoo bumblebee males, are not selected for an optimised foraging pattern. Instead, they spend more time on flowers, eventually resulting in higher levels of pollen transfer within a plant (geitonogamy), which might lead to reduced plant fitness. This is the first study to relate the foraging behaviour of cuckoo bumblebees to pollination and plant fitness.
Erler, S., & Lattorff, H. M. G. (2010). The degree of parasitism of the bumblebee (Bombus terrestris) by cuckoo bumblebees (Bombus (Psithyrus) vestalis). Insectes sociaux, 57(4), 371-377. https://doi.org/10.1007/s00040-010-0093-2
Fisogni, A., Bogo, G., Massol, F., Bortolotti, L., Galloni, M. (2021). Cuckoo male bumblebees perform slower and longer flower visits than free-living male and worker bumblebees. Zenodo, 10.5281/zenodo.4489066, ver. 1.2 peer-reviewed and recommended by PCI Zoology. https://doi.org/10.5281/zenodo.4489066
Goulson, D. (1999). Foraging strategies of insects for gathering nectar and pollen, and implications for plant ecology and evolution. Perspectives in plant ecology, evolution and systematics, 2(2), 185-209. https://doi.org/10.1078/1433-8319-00070
Goulson, D. (2010). Bumblebees. Behaviour, Ecology, and Conservation, 2nd edn. Oxford University Press, Oxford.
Lhomme, P., Hines, H. M. (2019). Ecology and evolution of cuckoo bumble bees. Annals of the Entomological Society of America, 112, 122-140. https://doi.org/10.1093/aesa/say031
Velthuis, H. H. W., van Doorn, A. (2006). A century of advances in bumblebee domestication and the economic and environmental aspects of its commercialization for pollination. Apidologie, 37, 421-451. https://doi.org/10.1051/apido:2006019
Wolf, S., Moritz, R. F. A. (2014). The pollination potential of free-foraging bumblebee (Bombus spp.) males (Hymenoptera. Apidae). Apidologie, 45, 440-450. https://doi.org/10.1007/s13592-013-0259-9
Up and to the light: intra- and interspecific variability of photo- and geo-tactic oviposition preferences in genus Trichogramma
New insights into oviposition preference of 5 Trichogramma speciesRecommended by Joel Meunier based on reviews by Kévin Tougeron and Eveline C. Verhulst
Insects exhibit a great diversity of life-history traits that often vary not only between species but also between populations of the same species (Flatt and Heyland, 2011). A better understanding of the variation in these traits can be of paramount importance when it comes to species of economic and agricultural interest (Wilby and Thomas, 2002). In particular, the control of the development and expansion of agricultural pests generally requires a good understanding of the parameters that favour the reproduction of these pests and/or the reproduction of the species used to control them (Bianchi et al., 2013; Gäde and Goldsworthy, 2003).
Parasitoid wasps of the genus Trichogramma are a classic example of insects involved in pest control (Smith, 1996). This genus comprises over 200 species worldwide, which have been used to control populations of a wide range of lepidopteran pests since the 1900s (Flanders, 1930; Hassan, 1993). Despite its common use, the egg-laying preference of this genus is only partially known. For example, all Trichogramma species are often thought to have positive phototaxis (or negative geotaxis) (e.g. Brower & Cline, 1984; van Atta et al., 2015), but comprehensive studies simultaneously testing this (or other) parameter among Trichogramma species and populations remain rare.
This is exactly the aim of the present study (Burte et al., 2021). Using a new experimental approach based on automatic image analysis, the authors compared the photo- and geo-tactic oviposition preference among 5 Trichogramma species from 25 populations. Their results first confirm that most Trichogramma species and populations prefer light to shade, and higher to lower positions for oviposition. Interestingly, they also reveal that the levels of preference for light and gravity show inter- and intraspecific variation (probably due to local adaptation to different strata) and that both preferences tend to relax over time.
Overall, this study provides important information for improving the use of Trichogramma species as biological agents. For example, it may help to establish breeding lines adapted to the microhabitat and/or growing parts of plants on which agricultural pests lay eggs most. Similarly, it suggests that the use of multiple strains with different microhabitat selection preferences could lead to better coverage of host plants, as well as a reduction in intraspecific competition in the preferred parts. Finally, this study provides a new methodology to efficiently and automatically study oviposition preferences in Trichogramma, which could be used in other insects with a particularly small size.
Bianchi, F. J. J. A., Schellhorn, N. A. and Cunningham, S. A. (2013). Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies. Agricultural and Forest Entomology, 15, 12–23. https://doi.org/10.1111/j.1461-9563.2012.00586.x
Burte V., Perez G., Ayed F., Groussier G., Mailleret L, van Oudenhove L. and Calcagno V. (2021). Up and to the light: intra- and interspecific variability of photo-and geo-tactic oviposition preferences in genus Trichogramma. bioRxiv, 2021.03.30.437671, ver. 4 peer-reviewed and recommended by PCI Zoology. https://doi.org/10.1101/2021.03.30.437671
Brower, J. H. and Cline, L. D. (1984). Response of Trichogramma pretiosum and T. evanescens to Whitelight, Blacklight or NoLight Suction Traps. The Florida Entomologist, 67, 262–268. https://doi.org/10.2307/3493947
Flanders, S. E. (1930). Mass production of egg parasites of the genus Trichogramma. Hilgardia, 4, 465–501. https://doi.org/10.3733/hilg.v04n16p465
Flatt, T. and Heyland, A. (2011). Mechanisms of life history evolution: the genetics and physiology of life history traits and trade-offs. Oxford University Press. https://doi.org/10.1093/acprof:oso/9780199568765.001.0001
Gäde, G. and Goldsworthy, G. J. (2003). Insect peptide hormones: a selective review of their physiology and potential application for pest control. Pest Management Science, 59, 1063–1075. https://doi.org/10.1002/ps.755
Hassan, S. A. (1993). The mass rearing and utilization of Trichogramma to control lepidopterous pests: Achievements and outlook. Pesticide Science, 37, 387–391. https://doi.org/10.1002/ps.2780370412
Smith, S. M. (1996). Biological Control with Trichogramma : Advances, Successes, and Potential of Their Use. Annual Review of Entomology, 41, 375–406. https://doi.org/10.1146/annurev.en.41.010196.002111
van Atta, K. J., Potter, K. A. and Woods, H. A. (2015). Effects of UV-B on Environmental Preference and Egg Parasitization by Trichogramma Wasps (Hymenoptera: Trichogrammatidae). Journal of Entomological Science, 50, 318–325. https://doi.org/10.18474/JES15-09.1
Wilby, A. and Thomas, M. B. (2002). Natural enemy diversity and pest control: patterns of pest emergence with agricultural intensification. Ecology Letters, 5, 353–360. https://doi.org/10.1046/j.1461-0248.2002.00331.x
First detection of herpesvirus and mycoplasma in free-ranging Hermann tortoises (Testudo hermanni), and in potential pet vectors
Welfare threatened speciesRecommended by Peter Galbusera based on reviews by Francis Vercammen and Maria Luisa Marenzoni
Wildlife is increasingly threatened by drops in number of individuals and populations, and eventually by extinction. Besides loss of habitat, persecution, pet trade,… a decrease in individual health status is an important factor to consider. In this article, Ballouard et al (2021) perform a thorough analysis on the prevalence of two pathogens (herpes virus and mycoplasma) in (mainly) Western Hermann’s tortoises in south-east France. This endangered species was suspected to suffer from infections obtained through released/escaped pet tortoises. By incorporating samples of captive as well as wild tortoises, they convincingly confirm this and identify some possible ‘pet’ vectors.
In February this year, a review paper on health assessments in wildlife was published (Kophamel et al 2021). Amongst others, it shows reptilia/chelonia are relatively well-represented among publications. It also contains a useful conceptual framework, in order to improve the quality of the assessments to better facilitate conservation planning. The recommended manuscript (Ballouard et al 2021) adheres to many aspects of this framework (e.g. minimum sample size, risk status, …) while others might need more (future) attention. For example, climate/environmental changes are likely to increase stress levels, which could lead to more disease symptoms. So, follow-up studies should consider conducting endocrinological investigations to estimate/monitor stress levels. Kophamel et al (2021) also stress the importance of strategic international collaboration, which may allow more testing of Eastern Hermann’s Tortoise, as these were shown to be infected by mycoplasma.
The genetic health of individuals/populations shouldn’t be forgotten in health/stress assessments. As noted by Ballouard et al (2021), threatened species often have low genetic diversity which makes them more vulnerable to diseases. So, it would be interesting to link the infection data with (individual) genetic characteristics. In future research, the samples collected for this paper could fit that purpose.
Finally, it is expected that this paper will contribute to the conservation management strategy of the Hermann’s tortoises. As such, it will be interesting to see how the results of the current paper will be implemented in the ‘field’. As the infections are likely caused by releases/escaped pets and as treating the wild animals is difficult, preventing them from getting infected through pets seems a priority. Awareness building among pet holders and monitoring/treating pets should be highly effective.
Ballouard J-M, Bonnet X, Jourdan J, Martinez-Silvestre A, Gagno S, Fertard B, Caron S (2021) First detection of herpesvirus and mycoplasma in free-ranging Hermann’s tortoises (Testudo hermanni), and in potential pet vectors. bioRxiv, 2021.01.22.427726, ver. 4 peer-reviewed and recommended by Peer Community in Zoology. https://doi.org/10.1101/2021.01.22.427726
Kophamel S, Illing B, Ariel E, Difalco M, Skerratt LF, Hamann M, Ward LC, Méndez D, Munns SL (2021), Importance of health assessments for conservation in noncaptive wildlife. Conservation Biology. https://doi.org/10.1111/cobi.13724
Inference of the worldwide invasion routes of the pinewood nematode Bursaphelenchus xylophilus using approximate Bayesian computation analysis
Extracting the maximum historical information on pine wood nematode worldwide invasion from genetic dataRecommended by Stéphane Dupas based on reviews by Aude Gilabert and 1 anonymous reviewer
Redistribution of domesticated and non domesticated species by humans profoundly affected earth biogeography and in return human activities. This process accelerated exponentially since human expansion out of Africa, leading to the modern global, highly connected and homogenized, agriculture and trade system (Mack et al. 2000, Jaksic and Castro 2021), that threatens biological diversity and genetic resources. To accompany quarantine and control effort, the reconstruction of invasion routes provides valuable information that help identifying critical nodes and edges in the global networks (Estoup and Guillemaud 2010, Cristescu 2015). Historical records and genetic markers are the two major sources of information of this corpus of knowledge on Anthropocene historical phylogeography. With the advances of molecular genetics tools, the genealogy of these introductions events could be revisited and empowered. Due to their idiosyncrasy and intimate association with the contingency of human trades and activities, understanding the invasion and domestication routes require particular statistical tools (Fraimout et al. 2017).
Because it encompasses all these theoretical, ecological and economical implications, I am pleased to recommend the readers of PCI Zoology this article by Mallez et al. (2021) on pine wood nematode invasion route inference from genetic markers using Approximate Bayesian Computation (ABC) methods.
Economically and ecologically, this pest, is responsible for killing millions of pines worldwide each year. The results show these damages and the global genetic patterns are due to few events of successful introductions. The authors consider that this low probability of introductions success reinforces the idea that quarantine measures are efficient. This is illustrated in Europe where the pine-worm has been quarantined successfully in the Iberian Peninsula since 1999. Another relevant conclusion is that hybridization between invasive populations have not been observed and implied in the invasion process. Finally the present study reinforced the role of Asiatic bridgehead populations in invasion process including in Europe.
Methodologically, for the first time, ABC was applied to this species. A total of 310 individual sequences were added to the Mallez et al. (2015) microsatellite dataset. Fraimoult et al. (2017) showed the interest to apply random forest to improve scenario selection in ABC framework. This method, implemented in the DiYABC software (Collin et al. 2020) for invasion route scenario selection allows to handle more complex scenario alternatives and was used in this study. In this article by Mallez et al. (2021), you will also find a clear illustration of the step-by-step approach to select scenario using ABC techniques (Lombaert et al. 2014). The rationale is to reduce number of scenario to be tested by assuming that most recent invasions cannot be the source of the most ancient invasions and to use posterior results on most ancient routes as prior hypothesis to distinguish following invasions. The other simplification is to perform classical population genetic analysis to characterize genetic units and representative populations prior to invasion routes scenarios selection by ABC.
Yet, even when using the most advanced Bayesian inference methods, it is recognized by the authors that the method can be pushed to its statistical power limits. The method is appropriate when population show strong inter-population genetic structure. But the high number of differentiated populations in native area can be problematic since it is generally associated to incomplete sampling scheme. The hypothesis of ghost populations source allowed to bypass this difficulty, but the authors consider simulation studies are needed to assess the joint effect of genetic diversity and number of genetic markers on the inference results in such situation. Also the need to use a stepwise approach to reduce the number of scenario to test has to be considered with caution. Scenarios that are not selected but have non negligible posterior, cannot be ruled out in the constitution of next step scenarios hypotheses.
Due to its interest to understand this major facet of Anthropocene, reconstruction of invasion routes should be more considered as a guide to damper biological homogenization process.
Collin, F.-D., Durif, G., Raynal, L., Lombaert, E., Gautier, M., Vitalis, R., Marin, J.-M. and Estoup, A. (2020) Extending Approximate Bayesian Computation with Supervised Machine Learning to infer demographic history from genetic polymorphisms using DIYABC Random Forest. Authorea. doi: https://doi.org/10.22541/au.159480722.26357192
Cristescu, M.E. (2015) Genetic reconstructions of invasion history. Molecular Ecology, 24, 2212–2225. doi: https://doi.org/10.1111/mec.13117
Estoup, A. and Guillemaud, T., (2010) Reconstructing routes of invasion using genetic data: Why, how and so what? Molecular Ecology, 9, 4113-4130. doi: https://doi.org/10.1111/j.1365-294X.2010.04773.x
Fraimout, A., Debat, V., Fellous, S., Hufbauer, R.A., Foucaud, J., Pudlo, P., Marin, J.M., Price, D.K., Cattel, J., Chen, X., Deprá, M., Duyck, P.F., Guedot, C., Kenis, M., Kimura, M.T., Loeb, G., Loiseau, A., Martinez-Sañudo, I., Pascual, M., Richmond, M.P., Shearer, P., Singh, N., Tamura, K., Xuéreb, A., Zhang, J., Estoup, A. and Nielsen, R. (2017) Deciphering the routes of invasion of Drosophila suzukii by Means of ABC Random Forest. Molecular Biology and Evolution, 34, 980-996. doi: https://doi.org/10.1093/molbev/msx050
Jaksic, F.M. and Castro, S.A. (2021). Biological Invasions in the Anthropocene, in: Jaksic, F.M., Castro, S.A. (Eds.), Biological Invasions in the South American Anthropocene: Global Causes and Local Impacts. Springer International Publishing, Cham, pp. 19-47. doi: https://doi.org/10.1007/978-3-030-56379-0_2
Lombaert, E., Guillemaud, T., Lundgren, J., Koch, R., Facon, B., Grez, A., Loomans, A., Malausa, T., Nedved, O., Rhule, E., Staverlokk, A., Steenberg, T. and Estoup, A. (2014) Complementarity of statistical treatments to reconstruct worldwide routes of invasion: The case of the Asian ladybird Harmonia axyridis. Molecular Ecology, 23, 5979-5997. doi: https://doi.org/10.1111/mec.12989
Mack, R.N., Simberloff, D., Lonsdale, M.W., Evans, H., Clout, M., Bazzaz, F.A. (2000) Biotic Invasions : Causes , Epidemiology , Global Consequences , and Control. Ecological Applications, 10, 689-710. doi: https://doi.org/10.1890/1051-0761(2000)010[0689:BICEGC]2.0.CO;2
Mallez, S., Castagnone, C., Lombaert, E., Castagnone-Sereno, P. and Guillemaud, T. (2021) Inference of the worldwide invasion routes of the pinewood nematode Bursaphelenchus xylophilus using approximate Bayesian computation analysis. bioRxiv, 452326, ver. 6 peer-reviewed and recommended by Peer community in Zoology. doi: https://doi.org/10.1101/452326
Do substrate roughness and gap distance impact gap-bridging strategies in arboreal chameleons?
Gap-bridging strategies in arboreal chameleonsRecommended by Ellen Decaestecker based on reviews by Simon Baeckens and 2 anonymous reviewers
Until now, very little is known about the tail use and functional performance in tail prehensile animals. Luger et al. (2020) are the first to provide explorative observations on trait related modulation of tail use, despite the lack of a sufficiently standardized data set to allow statistical testing. They described whether gap distance, perch diameter, and perch roughness influence tail use and overall locomotor behavior of the species Chamaeleo calyptratus.
Peterson (1984) described already the pattern how and when the tail is moved when bridging the distance from one perch to another. The study by Luger et al. (2020) further explores how this bridging distance, as well as other perch parameters modulate this behavior and the importance of tail use in it. Zippel et al. (1999) study the underlying musculoskeletal anatomy of the tail in chameleons, showing that chameleons have a strikingly different tail anatomy than other prehensile squamates. The difference is (partially) to be seen in the capacity of tail autotomy, that has been lost in chameleons.
Luger et al. (2020) describe the role the tail has in bridging a gap, and show that challenging and acrobatic movements to bridge large gaps, or when grasping on not so rough surfaces, relies heavily on a strong tail. Full body suspension with the tail can explain why tail autotomy has been lost, thus explaining the diverging tail musculature. They speculate on the role of this behavior for sexual selection for males. Sexual selection for males with a higher gripping performance could explain why male chameleons perform better for their size. In addition, boldness could have played a role. The authors state that exploring personality and its links to morphology, performance, and behaviors like grap-bridging would be a worthwhile avenue for future research on sexual selection in reptiles.
Luger, A.M., Vermeylen, V., Herrel, A. and Adriaens, D. (2020) Do substrate roughness and gap distance impact gap-bridging strategies in arboreal chameleons? bioRxiv, 2020.08.21.260596, ver. 3 peer-reviewed and recommended by PCI Zoology. doi: https://doi.org/10.1101/2020.08.21.260596
Peterson, J. A. (1984). The locomotion of Chamaeleo (Reptilia: Sauria) with particular reference to the forelimb. Journal of Zoology, 202(1), 1-42. doi: https://doi.org/10.1111/j.1469-7998.1984.tb04286.x
Zippel, K. C., Glor, R. E., and Bertram, J. E. (1999). On caudal prehensility and phylogenetic constraint in lizards: the influence of ancestral anatomy on function in Corucia and Furcifer. Journal of Morphology, 239(2), 143-155. doi: https://doi.org/10.1002/(SICI)1097-4687(199902)239:2%3C143::AID-JMOR3%3E3.0.CO;2-O
The open bar is closed: restructuration of a native parasitoid community following successful control of an invasive pest.
Raise and fall of an invasive pest and consequences for native parasitoid communitiesRecommended by Stefaniya Kamenova based on reviews by Kévin Tougeron and Miguel González Ximénez de Embún
Host-parasitoid interactions have been the focus of extensive ecological research for decades. One the of the major reasons is the importance host-parasitoid interactions play for the biological control of crop pests. Parasitoids are the main natural regulators for a large number of economically important pest insects, and in many cases they could be the only viable crop protection strategy. Parasitoids are also integral part of complex food webs whose structure and diversity display large spatio-temporal variations [1-3]. With the increasing globalization of human activities, the generalized spread and establishment of invasive species is a major cause of disruption in local community and food web spatio-temporal dynamics. In particular, the deliberate introduction of non-native parasitoids as part of biological control programs, aiming the suppression of established, and also highly invasive crop pests, is a common practice with potentially significant, yet poorly understood effects on local food web dynamics (e.g. ).
In their study, Muru et al.  took advantage of an existing biological control program focusing on the Asian chestnut gall wasp Dryocosmus kuriphilus, an invasive (and highly damaging) pest of chestnut trees. The species is currently a successful invader in many geographic regions, including southern France, where local parasitoid communities failed to provide an adequate control since its widespread establishment in 2010 . In response, the non-native parasitoid species Torymus sinensis, which is highly-specific to the Asian chestnut gall wasp, was massively released in commercial chestnut orchards across several regions in France and the island of Corsica. The pest population outbreak was successfully contained, and thanks to the vast amount of host-parasitoid interaction data collected as part of the program, the authors were able to explore the effects of the large fluctuations in Asian chestnut gall wasp natural abundances on native parasitoid communities, immediately before, and up to five years following the introduction of its natural enemy T. sinensis.
Using co-occurrence and clustering analyses, Muru et al.  demonstrate that the invasion and the consecutive (efficient) control of the Asian chestnut gall wasp by the parasitoid T. sinensis have a significant impact on the structure of local parasitoid food webs. In particular, following decline in the Asian chestnut gall wasp’s populations, native parasitoids markedly switched to alternative hosts, most likely due to their respectively higher relative abundances. This pattern seemed to be driven by the degree of generalism in native parasitoid species. Indeed, when its abundances were still relatively high, the Asian chestnut gall wasp was primarily attacked by species capable of exploiting a broad range of hosts, while at low population densities only specialist parasitoids such as Mesolobus sericeus were able to persist and compete with the non-native T. sinensis.
The current study is important for two major reasons. First, it underscores the value of long-term species interaction data in order to understand the dynamic nature of food webs, namely their structural flexibility in response to changes in the environment or, as in this case, large fluctuation in abundances of a major pest species. In this context, biological control programs could be a great source of data for exploring long-term, large-scale dynamics of species interactions, and their use in ecological studies deserves to be further emphasized. Second, the study adds to the increasing empirical evidence that mobile generalist foragers can display adaptive, frequency-dependent switching behaviour (, ), which has been suggested to act as a key stabilizing mechanism in food webs by buffering fluctuating population dynamics at larger spatial scales ([8- 10]).
However, the timing of such buffering seems important, especially in systems such as commercial chestnut orchards. Despite their capacity to adaptively switch their foraging behaviour, the response of the native parasitoid communities to the new, unfamiliar resource was not fast enough in order to contain the primary outbreak under an appropriate damage threshold, thus requiring the introduction of the more specialized parasitoid T. sinensis. Nevertheless, based on current ecological theory, results presented by Muru et al.  suggest that the response of native parasitoid community to fluctuating host dynamics – i.e. shifts in parasitoid foraging behaviour based on their traits – could be predictable. This is encouraging considering the growing impact of biological invasions and insect pest outbreaks, but also the need to implement efficient, yet sustainable strategies for crop protection. Future studies would show at what extent observations by Muru et al.  are generalizable over longer time periods or other model systems. Noticeably, better understanding about population dynamics and interactions with the broader community of hosts available across habitats should allow to fine-tune predictions about parasitoids’ response to fluctuating resources.
 Eveleigh ES, McCann KS, McCarthy PC, Pollock SJ, Lucarotti CJ, Morin B, McDougall GA, Strongman DB, Huber JT, Umbanhowar J, Faria LDB (2007). Fluctuations in density of an outbreak species drive diversity cascades in food webs. Proc. Natl. Acad. Sci. USA 104, 16976-16981. doi: 10.1073/pnas.0704301104
 Tylianakis JM, Tscharntke T, Lewis OT (2007). Habitat modification alters the structure of tropical host–parasitoid food webs. Nature 445, 202-205. doi: 10.1038/nature05429
 Murakami M, Hirao T, Kasei A (2008). Effects of habitat configuration on host–parasitoid food web structure. Ecol. Res. 23, 1039-1049. doi: 10.1007/s11284-008-0478-0
 Geslin B, Gauzens B, Baude M, Dajoz I, Fontaine C, Henry M, Ropars L, Rollin O, Thébault E, Vereecken NJ (2016). Massively introduced managed species and their consequences for plant–pollinator interactions. Adv. Ecol. Res. 57, 147-199. doi: 10.1016/bs.aecr.2016.10.007
 Muru D, Borowiec N, Thaon M, Ris N, Viciriuc M I, Warot S, Vercken E (2020) The open bar is closed: restructuration of a native parasitoid community following successful control of an invasive pest. bioRxiv, 2019.12.20.884908, ver. 6 peer-reviewed and recommended by PCI Zoology. doi: 10.1101/2019.12.20.884908
 Borowiec N, Thaon M, Brancaccio L, Warot S, Vercken E, Fauvergue X, Ris N, Malausa J-C (2014). Classical biological control against the chestnut gall wasp 'Dryocosmus kuriphilus' (Hymenoptera, Cynipidae) in France. Plant Prot. Q. 29, 7-10.
 Bartley TJ, McCann KS, Bieg C, Cazelles K, Granados M, Guzzo MM, MacDougall AS, Tunney TD, McMeans BC (2019). Food web rewiring in a changing world. Nat. Ecol. Evol. 3, 345–354. doi: 10.1038/s41559-018-0772-3
 Kondoh M (2003). Foraging adaptation and the relationship between food-web complexity and stability. Science. 299, 1388-1391. doi: 10.1126/science.1079154
 McCann KS, Rooney N (2009). The more food webs change, the more they stay the same. Philos. Trans. R. Soc. Lond. B Biol. Sci. 364, 1789-801. doi: 10.1098/rstb.2008.0273
 Valdovinos FS, Ramos-Jiliberto R, garay-Narváez L, Urbani P, Dunne JA (2010). Consequences of adaptive behaviour for the structure and dynamics of food webs. Ecol. Lett. 13, 1546-1559. doi: 10.1111/j.1461-0248.2010.01535.x
The 'Noble false widow' spider Steatoda nobilis is an emerging public health and ecological threat
How the noble false widow spider Steatoda nobilis can turn out to be a rising public health and ecological concernRecommended by Etienne Bilgo based on reviews by Michel Dugon and 2 anonymous reviewers
"The noble false widow spider Steatoda nobilis is an emerging public health and ecological threat" by Clive Hambler (2020) is an appealing article discussing important aspects of the ecology and distribution of a medically significant spider, and the health concerns it raises.
By contrast to previous studies (Dunbar et al., 2018; Warell et al., 1991; Bauer et al., 2019; BBC 2013, 2018), this article, with its extensive media and scientific literature review, shows that S. nobilis (Thorell, 1875) is now an important health concern in Britain. Indeed, the author shows that the population of this spider has significantly increased, at least since 1990, in both southern Britain and Ireland where it has remained greatly under-recorded. In these areas, S. nobilis is now often the dominant spider on and in buildings, in places in which there is a high a risk of bites, some of which are likely to be severe, in humans, with these bites largely under-recorded. According to Clive Hambler "There is thus a possibility of bites being left without adequate rapid treatment and monitoring - with a low but non-trivial risk of necrosis or sepsis".
The author points that one of the reasons for the lack of awareness of the risk is that arachnologists typically have a conflict of interest between the conservation of the species they study and raising concerns about spiders. This may lead them to understate the risk. Clive Hambler therefore calls for a closer, appropriately weighted attention to the frequency and risk of bites, based on all the information available, rather than being "dismissive of the possibilities of bites and impacts simply because many media reports contain major errors or alarmism". He also argues that the British Arachnological Society’s guidance on "false widow spiders" "needs substantive revision, both in terms of the likelihood of bites and the severity of effects."
Indeed, the author demonstrates that many inaccuracies have been published (see Table 3 of his manuscript) and, for each, he provides a correction and/or an alternative opinion. At the end of this MS (see Table 4), he provides testable speculations and hypotheses. As he rightly points out, testing is very important to fuel the debate, because "It will be very difficult to get a balanced and proportionate debate and response for such a confused and emotive issue, especially with the many misleading popular reports." He also suggests that research will require interdisciplinary collaboration between experts in many domains, including pathologists, immunologists, clinicians, ecologists, arachnologists, psychologists, physiologists, climatologists and epidemiologists.
This preprint is clearly descriptive and speculative, but well-written, interesting and certainly useful in terms of a review of the biology, ecology, potential dangerousness and distribution of S. nobilis, particularly for future studies. There is no doubt that arachnologists, the medical community and the media will be interested in this article, which is intended to sound the alarm. Naturalists in general will also be interested in this manuscript because it is an original and successful attempt to increase knowledge about a particular taxon based on diverse information sources.
The structure of the MS is a bit odd, with a certain toing-and-froing between the ecology/biology/distribution of the spider and the risks, dangerousness and venom of bites, but this is not problematic, as shown by the reviews of the manuscript - three reviews (available below) were written, two by specialists in this noble false widow (Michel Dugon and another researcher who wished to remain anonymous).
Despite the controversy surrounding certain of the statements made in this article, I therefore strongly recommend it and look forward to seeing the identified research priorities addressed.
 Hambler, C. (2020). The “Noble false widow” spider Steatoda nobilis is an emerging public health and ecological threat. OSF Preprints, axbd4, ver. 4 peer-reviewed and recommended by PCI Zoology. doi: 10.31219/osf.io/axbd4
 Dunbar J.P., Afoullouss S., Sulpice R., Dugon M.M. (2018) Envenomation by the noble false widow spider Steatoda nobilis (Thorell, 1875) - five new cases of steatodism from Ireland and Great Britain. Clin Toxicol (Phila). 56(6):433-435. doi: 10.1080/15563650.2017.1393084
 Warrell D.A., Shaheen J., Hillyard P.D., Jones D. (1991) Neurotoxic envenoming by an immigrant spider (Steatoda nobilis) in southern England. Toxicon. 29(10):1263-5. doi: 10.1016/0041-0101(91)90198-Z
 Bauer, T., Feldmeier, S., Krehenwinkel, H., Wieczorrek, C., Reiser, N. and Dreitling, R. (2019) Steatoda nobilis, a false widow on the rise: a synthesis of past and current distribution trends. NeoBiota 42: 19–43. doi: 10.3897/neobiota.42.31582
 BBC (2013). False widow spider bites footballer Steve Harris. http://www.bbc.co.uk/news/uk-england-devon-24470023 Accessed 1 November 2018.
 BBC (2018). False widow spider infestation schools to remain shut. https://www.bbc.co.uk/news/uk-england-london-45761046 Accessed 19 December 2018.
Sub-lethal insecticide exposure affects host biting efficiency of Kdr-resistant Anopheles gambiae
kdr homozygous resistant An. gambiae displayed enhanced feeding success when exposed to permethrin Insect-Treated NetsRecommended by Adrian Diaz based on reviews by Thomas Guillemaud, Niels Verhulst, Etienne Bilgo and 1 anonymous reviewer
Malaria is a vector-borne parasitic disease found in 91 countries with an estimated of 228 million cases occurred worldwide during 2018. The 93% (213 million) of those cases were reported in the African Region (WHO 2019). Six species of Plasmodium parasites can produce the disease but only P. falciparum and P. vivax are the predominant species globally. More than 40 species of Anopheles mosquitoes are important malaria vectors (Asley et al. 2018). Intrinsic (genetic background, parasite susceptibility) and extrinsic (feeding host preference, host diversity and availability, mosquito abundance) factors affect the capacity of mosquitoes to vector the disease (Macdonald 1952). Malaria is prevented by chemoprophylaxis, vaccination, bite-avoidance and vector-control measures. The mainstays of vector control are long-lasting insecticide (pyrethroid) treated nets and indoor residual spraying with insecticides (Asley et al. 2018). The widespread use of pyrethroid insecticides forced the emergence of insecticide resistance in malaria vectors reducing the insecticidal effect. Mosquitoes can modify their behaviour avoiding insecticide contact and so potentially reducing vector control tools efficacy. In this sense, Diop et al. (2020) investigated whether pre-exposure to an Insecticide-Treated Net (ITN) modulates the mosquito ability to take a blood meal in Anopheles gambiae. By means of video recording experiments the authors analyzed how the feeding/bitting behaviour was affected by kdr mutation genotypes (homozygous susceptible – SS-, heterozygotes -RS- and homozygous resistant -RR-) when exposed to two different insecticides (permethrin and deltamethrin). According to the results, the blood-feeding success did not differ between the three genotypes in the absence of insecticide exposure. However, authors observed differences in the feeding duration and blood meal size. In example, RR mosquitoes spent less time taking their blood meal than RS and SS. On the other hand, RS mosquitoes took higher blood volumes than RR females. These differences can affect the mosquito fitness by decreasing/increasing the likelihood to be killed by the host defensive behavior or increase the oogenesis so enhancing fecundity. Regarding the effect of exposition to insecticides authors detected a strong relationship between kdr genotype and Knock Down (KD) phenotype when mosquitoes were exposed to Permethrin. Previously, the authors have evidenced that RR mosquitoes prefer a host protected by a permethrin-treated net rather than an untreated net and that heterozygotes RS mosquitoes have a remarkable ability to find a hole into a bet net (Diop et al. 2015, Porciani et al. 2017). With data here obtained, they demonstrated that kdr homozygous resistant An. gambiae displayed enhanced feeding success when exposed to permethrin ITN. The changes observed in the feeding/biting mosquito behaviour can affect their fitness shaping the evolution of the insecticide resistance in mosquitoes’ natural populations. Moreover, this may also alter parasite transmission dynamics by modifying vector/host interactions and so vector capacity.
World Health Organization (2019). World malaria report 2019. Geneva: World Health Organization; 2019. ISBN 978-92-4-156572-1
Ashley EA, Pyae Phyo A, Woodrow CJ (2018). Malaria. Lancet. 391(10130):1608‐1621. doi: 10.1016/S0140-6736(18)30324-6
Macdonald G (1952). The analysis of equilibrium in malaria. Trop Dis Bull 49: 813-828.
Diop MM, Chandre F, Rossignol M, Porciani A, Château M, Moiroux N and Pennetier, C. (2020). Sub-lethal insecticide exposure affects host biting efficiency of Kdr-resistant Anopheles gambiae. bioRxiv 653980, ver. 4 peer-reviewed and recommended by PCI Zoology. doi: 10.1101/653980
Diop MM, Moiroux N, Chandre F, Martin-Herrou H, Milesi P, Boussari O, et al. (2015) Behavioral cost and overdominance in Anopheles gambiae. PLoS ONE. 10(4):e0121755. doi: 10.1371/journal.pone.0121755
Porciani A, Diop M, Moiroux N, Kadoke-Lambi T, Cohuet A, Chandre F, et al. (2017) Influence of pyrethroïd-treated bed net on host seeking behavior of Anopheles gambiae s.s. carrying the kdr allele. PLOS ONE. 12(7):e0164518. doi: 10.1371/journal.pone.0164518
Culex saltanensis and Culex interfor (Diptera: Culicidae) are susceptible and competent to transmit St. Louis encephalitis virus (Flavivirus: Flaviviridae) in central Argentina
Multiple vector species may be responsible for transmission of Saint Louis Encephalatis Virus in ArgentinaRecommended by Anna Cohuet based on reviews by 2 anonymous reviewers
Medical and veterinary entomology is a discipline that deals with the role of insects on human and animal health. A primary objective is the identification of vectors that transmit pathogens. This is the aim of Beranek and co-authors in their study . They focus on mosquito vector species responsible for transmission of St. Louis encephalitis virus (SLEV), an arbovirus that circulates in avian species but can incidentally occur in dead end mammal hosts such as humans, inducing symptoms and sometimes fatalities. Culex pipiens quinquefasciatus is known as the most common vector, but other species are suspected to also participate in transmission. Among them Culex saltanensis and Culex interfor have been found to be infected by the virus in the context of outbreaks. The fact that field collected mosquitoes carry virus particles is not evidence for their vector competence: indeed to be a competent vector, the mosquito must not only carry the virus, but also the virus must be able to replicate within the vector, overcome multiple barriers (until the salivary glands) and be present at sufficient titre within the saliva. This paper describes the experiments implemented to evaluate the vector competence of Cx. saltanensis and Cx. interfor from ingestion of SLEV to release within the saliva. Females emerged from field-collected eggs of Cx. pipiens quinquefasciatus, Cx. saltanensis and Cx. interfor were allowed to feed on SLEV infected chicks and viral development was measured by using (i) the infection rate (presence/absence of virus in the mosquito abdomen), (ii) the dissemination rate (presence/absence of virus in mosquito legs), and (iii) the transmission rate (presence/absence of virus in mosquito saliva). The sample size for each species is limited because of difficulties for collecting, feeding and maintaining large numbers of individuals from field populations, however the results are sufficient to show that this strain of SLEV is able to disseminate and be expelled in the saliva of mosquitoes of the three species at similar viral loads. This work therefore provides evidence that Cx saltanensis and Cx interfor are competent species for SLEV to complete its life-cycle. Vector competence does not directly correlate with the ability to transmit in real life as the actual vectorial capacity also depends on the contact between the infectious vertebrate hosts, the mosquito life expectancy and the extrinsic incubation period of the viruses. The present study does not deal with these characteristics, which remain to be investigated to complete the picture of the role of Cx saltanensis and Cx interfor in SLEV transmission. However, this study provides proof of principle that that SLEV can complete it’s life-cycle in Cx saltanensis and Cx interfor. Combined with previous knowledge on their feeding preference, this highlights their potential role as bridge vectors between birds and mammals. These results have important implications for epidemiological forecasting and disease management. Public health strategies should consider the diversity of vectors in surveillance and control of SLEV.
 Beranek, M. D., Quaglia, A. I., Peralta, G. C., Flores, F. S., Stein, M., Diaz, L. A., Almirón, W. R. and Montigiani, M. S. (2020). Culex saltanensis and Culex interfor (Diptera: Culicidae) are susceptible and competent to transmit St. Louis encephalitis virus (Flavivirus: Flaviviridae) in central Argentina. bioRxiv 722579, ver. 6 peer-reviewed and recommended by PCI Entomology. doi: 10.1101/722579