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. 

References

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

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.

References

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

Human African Trypanosomiasis (HAT), or sleeping sickness, is caused by trypanosome parasites. In sub-Saharan Africa, two forms are present, Trypanosoma brucei gambiense and T. b. rhodesiense, the former responsible for 95% of reported cases. The parasites are transmitted through a vector, Genus Glossina, also known as tsetse, which means fly in Tswana, a language from southern Africa. Through a blood meal, tsetse picks up the parasite from infected humans or animals (in animals, the parasite causes Animal African Trypanosomiasis or nagana disease). Through medical interventions and vector control programs, the burden of the disease has drastically reduced over the past two decades, so the WHO neglected tropical diseases road map targets the interruption of transmission (zero cases) for 2030 (WHO 2022).

Meaningful vector control programs utilize traps for the removal of animals and for surveillance, along with different methods of spraying insecticides. However, in existing HAT risk areas, it will be essential to understand the ecology of the vector species to implement control programs in a way that areas cleared from the vector will not be reinvaded from other populations. Thus, it will be crucial to understand basic population genetics parameters related to population structure and subdivision, migration frequency and distances, population sizes, and the potential for sex-biased dispersal. The authors utilize genotyping using nine highly polymorphic microsatellite markers of samples from Chad collected in differently affected regions and at different time points (Ravel et al., 2023). Two major HAT zones exist that are targeted by vector control programs, namely Madoul and Maro, while two other areas, Timbéri and Dokoutou, are free of trypanosomes. Samples were taken before vector control programs started.

The sex ratio was female-biased, most strongly in Mandoul and Maro, the zones with the lowest population density. This could be explained by resource limitation, which could be the hosts for a blood meal or the sites for larviposition. Limited resources mean that females must fly further, increasing the chance that more females are caught in traps. 

The effective population densities of Mandoul and Maro were low. However, there was a convergence of population density and trapping density, which might be explained by the higher preservation of flies in the high-density areas of Timbéri and Dokoutou after the first round of sampling, which can only be tested using a second sampling. 

The dispersal distances are the highest recorded so far, especially in Mandoul and Maro, with 20-30 km per generation. However, in Timbéri and Dokoutou, which are 50 km apart, very little exchange occurs (approx. 1-2 individuals every six months). A major contributor to this is the massive destruction of habitat that started in the early 1990s and left patchily distributed and fragmented habitats. The Mandoul zone might be safe from reinvasion after eradication, as for a successful re-establishment, either a pair of a female and male or a pregnant female are required. As the trypanosome prevalence amongst humans was 0.02 and of tsetse 0.06 (Ibrahim et al., 2021) before interventions began, medical interventions and vector control might have further reduced these levels, making a reinvasion and subsequent re-establishment of HAT very unlikely. Maro is close to the border of the Central African Republic, and the area has not been well investigated concerning refugee populations of tsetse, which could contribute to a reinvasion of the Maro zone. The higher level of genetic heterogeneity of the Maro population indicates that invasions from neighboring populations are already ongoing. This immigration could also be the reason for not detecting the bottleneck signature in the Maro population. 

The two HAT areas need different levels of attention while implementing vector eradication programs. While Madoul is relatively safe against reinvasion, Maro needs another type of attention, as frequent and persistent immigration might counteract eradication efforts. Thus, it is recommended that continuous tsetse suppression needs to be implemented in Maro.  

This study shows nicely that an in-depth knowledge of the processes within and between populations is needed to understand how these populations behave. This can be used to extrapolate, make predictions, and inform the organisations implementing vector control programs to include valuable adjustments, as in the case of Maro. Such integrative approaches can help prevent the failure of programs, potentially saving costs and preventing infections of humans and animals who might die if not treated.

References

Ibrahim MAM, Weber JS, Ngomtcho SCH, Signaboubo D, Berger P, Hassane HM, Kelm S (2021) Diversity of trypanosomes in humans and cattle in the HAT foci Mandoul and Maro, Southern Chad- Southern Chad-A matter of concern for zoonotic potential? PLoS Neglected Tropical Diseases, 15, e000 323. https://doi.org/10.1371/journal.pntd.0009323

Ravel S, Mahamat MH, Ségard A, Argiles-Herrero R, Bouyer J, Rayaisse JB, Solano P, Mollo BG, Pèka M, Darnas J, Belem AMG, Yoni W, Noûs C, de Meeûs T (2023) Population genetics of Glossina fuscipes fuscipes from southern Chad. Zenodo, ver. 9 peer-reviewed and recommended by PCI Zoology. https://doi.org/10.5281/zenodo.7763870

WHO (2022) Trypanosomiasis, human African (sleeping sickness). https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness), retrieved 17. March 2023

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.

References

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

It is now widely accepted that anthropogenic climate change is a severe threat to biodiversity, ecosystem function and associated ecosystem services. Assessing the vulnerability of species and predicting their response to future changes has become a priority for environmental biology (Williams et al. 2020).

Over the last few decades, oxygen concentrations in both the open ocean and coastal waters have been declining steadily as the result of multiple anthropogenic activities. This global trends towards hypoxia is expected to continue in the future, causing a host of negative effects on marine ecosystems. Oxygen is indeed crucial to many biological processes in the ocean, and its decrease could have strong impacts on biogeochemical cycles, and therefore on marine productivity and biodiversity (Breitburg et al. 2018).

Whenever facing such drastic environmental changes, all organisms are expected to have some intrinsic ability to adapt. At shorter than evolutionary timescales, ecological plasticity and the eco-physiological processes that sustain it could constitute important adaptive mechanisms (Williams et al. 2020)

Marine sponges seem particularly well-adapted to oxygen deficiency, as some species can survive seasonal anoxia for several months. This paper by Strehlow et al. (2023) examines the mechanisms allowing this exceptional tolerance. Focusing on two species of sponges, they used transcriptomics to assess how gene expression by sponges, by their mitochondria, or by their unique and species-specific microbiome could facilitate this trait. Their results suggest that sponge holobionts maintain metabolic activity under anoxic conditions while displaying shock response, therefore not supporting the hypothesis of sponge dormancy. Furthermore, hypoxia and anoxia seemed to influence gene expression in different ways, highlighting the complexity of sponge response to deoxygenation. As often, their exciting results raise as many questions as they provide answers and pave the way for more research regarding how anoxia tolerance in marine sponges could give them an advantage in future oceanic environmental conditions.

References

Breitburg et al. (2018): Declining oxygen in the global ocean and coastal waters. Science 359, eaam7240. https://doi.org/10.1126/science.aam7240 

Strehlow et al. (2023): Transcriptomic responses of sponge holobionts to in situ, seasonal anoxia and hypoxia. bioRxiv, 2023.02.27.530229, ver. 4 peer-reviewed and recommended by Peer Community in Zoology.  https://doi.org/10.1101/2023.02.27.530229 

Williams et al. (2008) Towards an Integrated Framework for Assessing the Vulnerability of Species to Climate Change. PLOS Biology 6(12): e325. https://doi.org/10.1371/journal.pbio.0060325 

Williams et al. (2020):  Research priorities for natural ecosystems in a changing global climate. Global Change Biology 26: 410–416. https://doi.org/10.1111/gcb.14856