Czech Academy of Sciences, Institute of Vertebrate Biology

Palaeohydrological changes can profoundly shape biological diversification and are key to reconstructing the biogeographic history of ancient lakes. In Lake Baikal, the Pleistocene formation of the Irkut/Angara outlets connected the lake to the Arctic-draining Yenisei River, potentially leading to profound changes in the lake’s faunal development. Here, we investigated population structure, demographic history, and colonization of a widely distributed salmonid fish ( Thymallus baicalensis ) across the Yenisei River system, including Lake Baikal, using genome-wide single nucleotide polymorphism (SNP) data. We found strong population structure with three major genetic groups across the river system and, for the first time, evidence of population substructure within Lake Baikal, possibly reflecting distinct phenotypes. While population expansion of T. baicalensis within Lake Baikal (∼125 ka) coincides with a late Pleistocene formation of the Irkut/Angara outlet, divergence time estimates among the three groups (536–804 ka) substantially predate this event and may reflect earlier phases of hydrological connectivity between Lake Baikal and the Angara–Yenisei system, consistent with previously estimated mitochondrial dates. The most likely scenario of gene flow suggested migration following outlet formation, with gene flow between Lake Baikal and riverine populations both upstream and downstream. Overall, the results support an initial colonization of Lake Baikal by T. baicalensis from the Yenisei River system, followed by a subsequent upstream expansion into the Selenga River and Lake Chovsgul. Notably, this relatively recent colonization stands in contrast to the lake’s ancient age, underscoring the complexity of its biogeographic history and the need for comparative studies across its diverse taxonomic groups.

Climate change is significantly affecting biodiversity, and organisms that depend on external temperature – such as ectotherms – are particularly vulnerable to these effects. Microhabitats provide refuge for species, thereby reducing exposure to thermal and hydric stress under climate change. Using a mechanistic modelling approach, we assessed how microhabitat variability and physiological traits influence activity behaviour, time spent in preferred temperature, shade selection, and water loss under different climate change scenarios on two green lizard species. We classified study area microhabitats using high‐resolution geospatial data and applied biophysical models to simulate organismal responses under current and future climate change scenarios (+2°C and +4°C). We first calibrated microhabitat‐specific microclimate models using field data and adjusting key parameters that determine surface energy balance and soil heat transfer, including surface roughness height, substrate longwave emissivity, and soil density. We then performed steady‐state ectotherm models and extracted physiological responses such as foraging and basking times, times spent in preferred temperature, selected shade, and water loss under current and projected climate scenarios. Our results revealed differences between species in terms of thermoregulatory and water‐loss dynamics: Timon lepidus showed higher foraging and basking activity, particularly in open rocky microhabitats. In contrast, Lacerta schreiberi relied more on shaded vegetated microhabitats and exhibited higher size‐corrected evaporative water loss. Foraging activity in T. lepidus increased in low‐slope areas, whereas L. schreiberi foraged more in steeper microhabitats, where both species also selected greater shade. Activity increased on south/west slopes, while shade selection was greater on north/west slopes. Activity periods may increase under warming conditions, but this may come at the cost of higher selected shade and water loss. These results go beyond recognizing the buffering role of microhabitats in climate change, by linking fine‐scale thermal and hydric variation to physiological strategies of lizard species. By integrating microclimate and ectotherm models, our work illustrates how species‐specific traits interact with microhabitat heterogeneity to shape differential vulnerability under warming conditions.

Abstract Conservation success stories, such as the recovery of the isolated populations of mountain gorilla ( Gorilla beringei beringei ), are increasingly threatened by emerging health challenges. In the Virunga Massif, strongylid‐associated gastrointestinal disease has been linked to significant morbidity and mortality of mountain gorillas, posing a critical threat to this population's long‐term survival. Using metabarcoding of faecal samples (~65% of the population) and spatial and habitat analyses, we examined the composition and drivers of strongylid nematode communities and their role in clinical disease emergence. We identified Hyostrongylus nematodes, known pathogens in suids, as the primary contributors to gastric lesions observed in necropsied gorillas. Spatial variation in strongylid communities is correlated with environmental gradients, indicating that environmental factors such as climate and vegetation play a significant role in shaping strongylid community composition. Additionally, limited genetic diversity resulting from historical population bottlenecks may negatively impact the health of gorillas affected by parasites. Our findings suggest that the high absolute abundance of pathogenic Hyostrongylus is concentrated in specific high‐altitude regions, aligning with observed cases of severe gastritis. Synthesis and applications . These findings highlight an emerging health threat for mountain gorillas, with implications for other isolated wildlife populations facing similar ecological and evolutionary pressures. The study calls for continued monitoring of parasitic diseases in wildlife populations, especially those in fragmented habitats with limited capacity for expansion, to mitigate potential risks to their conservation.

ABSTRACT Aim Understanding the distribution and genetic structure of African mammals is key to reconstructing the continent's evolutionary history. While some parts of the continent (e.g., lowlands, mountain forests or savannah biomes) are now relatively well‐studied, arid regions remain underexplored despite offering unique insights into adaptation to extreme environmental conditions. This study aimed to reconstruct phylogeographic patterns and past‐to‐future distributional dynamics of two gerbil genera— Pachyuromys and Desmodilliscus . Location North Africa, including the Sahara Desert and the Sahel. Taxon Two gerbil species from two sister monotypic genera: Pachyuromys duprasi Lataste, 1880 (Northern Sahara) and Desmodilliscus braueri von Wettstein, 1916 (Sahel region). Methods Using the most comprehensive available dataset, we examined mitochondrial markers ( CYTB and COI ) and built ecological niche models across past (Last Glacial Maximum, Mid‐Holocene), present and future climate scenarios to investigate genetic structure and potential distributional shifts of both species. Results Desmodilliscus braueri exhibits a marked East–West phylogeographic structure, influenced by barriers such as the Niger River and Paleolake Chad. In contrast, Pachyuromys duprasi has genetically divergent populations in Egypt (which may be affected by a sampling gap in central‐northern Sahara), but no broader spatial structure in its regions. Niche models suggest range contractions and expansions linked to climatic oscillations for both species. The predicted distribution of Pachyuromys reflects distribution area pulses, aligning with pulses in the extent of the Sahara. Main Conclusions Our findings emphasise the evolutionary significance of arid zones and the need for further research on species' responses to desertification and climate‐driven range shifts. The contrasting patterns between the two species underscore different evolutionary trajectories in different taxa living in arid and semi‐arid environments.

The exquisite eggshell mimicry found in many cuckoo-host systems has been the textbook example of a coevolutionary arms race 1 . In this system, cuckoos lay their eggs in their hosts’ nests leaving these foster parents to rear their young 2 . In defence, most of these hosts have evolved the ability to recognize cuckoo eggs. It is long-assumed that these interactions select for ever-improving eggshell mimicry in cuckoo host-races laying distinct eggs that specifically mimic their host’s eggshell, regardless of its particular colour 3,4 . We challenge this paradigm and demonstrate that coevolutionary arms races and egg colour mimicry are the exception to the rule. Here, using eggshell reflectance spectra from 39 host species and the specific cuckoo eggs found in their nests, we show that eggshell colour mimicry is very uncommon even among frequent hosts. Although cuckoo eggs display considerable variation in eggshell colour, their hosts’ eggshell colours occupy 6 times their colour volume. As a result, mimicry is only achieved for a small subset of the egg colour gamut. Furthermore, cuckoo host-races rarely lay eggs that match their hosts’ eggs better than those of other potential hosts or that are distinct from those laid by other cuckoo host-races. These patterns are inconsistent with the long-held assumption of coevolutionary arms races, but consistent with coevolutionary alternation that is defined by a process of continual host-switching. These findings open new avenues for research in a system that has long served as a model for studying coevolutionary processes.

The orangefin barb, Enteromius eutaenia - a small-sized smiliogastrin barb characterised by orange/yellow fins, a thickened and serrated last unbranched dorsal-fin ray, a dark mid-lateral stripe and a sheath of enlarged scales at the base of dorsal fin - is considered widely distributed across southern Africa. Distinct phenotypic groups suggest unrecognised species-level diversity, but taxonomic progress has been limited by the poor knowledge of true E. eutaenia. Here, we re-examine the type specimens of E. eutaenia and a collection of E. eutaenia-like fishes from the Cunene River system to clarify their taxonomic status, using morphometric/meristic data and mitochondrial cytochrome c oxidase I (COI) sequences. Based on these data, we redescribe E. eutaenia and describe two new species: Enteromius bieensis sp. nov. (found in sympatry with E. eutaenia in the Upper Cunene River close to Huambo, situated on the Bié Plateau, Angola) and Enteromius ruacanaensis sp. nov. (found in the Lower Cunene River, Ruacana Gorge, below the Ruacana Falls at the border between Namibia and Angola).

Recent studies have shown that birdsong is not exclusively a male trait. However, despite increasing research intensity, female singing is still rarely reported in temperate migratory species. Here, we report the observation and description of female vocalization in the great reed warbler, Acrocephalus arundinaceus . We analysed vocal expression of individually marked great reed warbler females in two central European populations in Slovakia and the Czech Republic and show that these vocalizations meet criteria for song. We found that 39.5% of nesting females sang from the nest during early incubation within two hours of video recording. Female mating status, locality, day of the season, and male singing activity did not predict song use in this species, but song rates decreased over the breeding period. Based on current and previous observations, we hypothesize that female great reed warblers use song to signal their territorial presence and reproductive status, potentially deterring conspecific female competitors. However, given that this study was done only in one context and moment in the breeding cycle (early incubation), we encourage further investigation of the functions of female song in this and other temperate migratory species whose female song was overlooked in the past.