Zuzana Hiadlovská

Animal colouration serves multiple functions, including camouflage, communication, and thermoregulation, and is shaped by the trade-offs between these roles. In ectotherms, which primarily regulate body temperature through behaviour, colour can influence how much heat they absorb from the environment. The thermal melanism hypothesis predicts that darker individuals heat up faster than lighter ones, particularly in basking species, but the role of colour in thermoregulation is complex and context-dependent. Although ectotherms rely mainly on behaviour for thermoregulation, colour may modulate heat absorption. Here, we tested how environmental and biotic factors influence body temperature and activity timing in sand lizards (Lacerta agilis). We collected body temperature data and dorsal colouration measurements from two populations in Czechia and used structural equation modelling to disentangle direct and indirect effects. Environmental temperature was the strongest predictor of body temperature, showing a positive effect, whereas body size and site had negative effects. Colouration did not directly affect body temperature but significantly influenced activity timing, with darker and more saturated individuals emerging earlier in the day. This result suggests that colour-mediated thermoregulation in sand lizards is primarily behavioural, shaping basking opportunities rather than passively dictating heat gain. Our findings demonstrate how environmental, morphological, and behavioural factors collectively shape lizard thermoregulation, with colour primarily influencing activity timing rather than directly affecting body temperature.

The house mouse, Mus musculus, is a widely used animal model in biomedical research, with classical laboratory strains (CLS) being the most frequently employed. However, the limited genetic variability in CLS hinders their applicability in evolutionary studies. Wild-derived strains (WDS), on the other hand, provide a suitable resource for such investigations. This study quantifies genetic and phenotypic data of 101 WDS representing 5 species, 3 subspecies, and 8 natural Y consomic strains and compares them with CLS. Genetic variability was estimated using whole mtDNA sequences, the Prdm9 gene, and copy number variation at two sex chromosome-linked genes. WDS exhibit a large natural variation with up to 2173 polymorphic sites in mitogenomes, whereas CLS display 92 sites. Moreover, while CLS have two Prdm9 alleles, WDS harbour 46 different alleles. Although CLS resemble M. m. domesticus and M. m. musculus WDS, they differ from them in 10 and 14 out of 16 phenotypic traits, respectively. The results suggest that WDS can be a useful tool in evolutionary and biomedical studies with great potential for medical applications.

The gut microbiota of vertebrates is acquired from the environment and other individuals, including parents and unrelated conspecifics. In the laboratory mouse, a key animal model, inter-individual interactions are severely limited and its gut microbiota is abnormal. Surprisingly, our understanding of how inter-individual transmission impacts house mouse gut microbiota is solely derived from laboratory experiments. We investigated the effects of inter-individual transmission on gut microbiota in two subspecies of house mice (Mus musculus musculus and M. m. domesticus) raised in a semi-natural environment without social or mating restrictions. We assessed the correlation between microbiota composition (16S rRNA profiles), social contact intensity (microtransponder-based social networks), and mouse relatedness (microsatellite-based pedigrees). Inter-individual transmission had a greater impact on the lower gut (colon and cecum) than on the small intestine (ileum). In the lower gut, relatedness and social contact independently influenced microbiota similarity. Despite female-biased parental care, both parents exerted a similar influence on their offspring’s microbiota, diminishing with the offspring’s age in adulthood. Inter-individual transmission was more pronounced in M. m. domesticus, a subspecies, with a social and reproductive network divided into more closed modules. This suggests that the transmission magnitude depends on the social and genetic structure of the studied population.

Predators attack conspicuous prey phenotypes that are present in the environment. Male display behaviour of conspicuous nuptial colouration becomes risky in the presence of a predator, and adult males face higher predation risk. High predation risk in one sex will lead to low survival and sex ratio bias in adult cohorts, unless the increased predation risk is compensated by higher escape rate. Here, we tested the hypothesis that sand lizards ( Lacerta agilis ) have sex-specific predation risk and escape rate. We expected the differences to manifest in changes in sex ratio with age, differences in frequency of tail autotomy, and in sex-specific survival rate. We developed a statistical model to estimate predation risk and escape rate, combining the observed sex ratio and frequency of tail autotomy with likelihood-based survival rate. Using Bayesian framework, we estimated the model parameters. We projected the date of the tail autotomy events from growth rates derived from capturerecapture data measurements. We found statistically stable sex ratio in age groups, equal frequency of tail regenerates between sexes, and similar survival rate. Predation risk is similar between sexes, and escape rate increases survival by about 5%. We found low survival rate and a low number of tail autotomy events in females during months when sand lizards mate and lay eggs, indicating high predator pressure throughout reproduction. Our data show that gravid females fail to escape predation. The risks of reproduction season in an ectotherm are a convolution of morphological changes (conspicuous colouration in males, body allometry changes in gravid females), behaviour (nuptial displays), and environmental conditions which challenge lizard thermal performance. Performance of endotherm predators in cold spring months endangers gravid females more than displaying males in bright nuptial colouration.

Colour pattern influences behaviour and modifies survival of organisms through perception of light reflectance. Spectrophotometric methods used to study colour navigate between precision and accuracy of reflectance across wavelengths, while photographic methods are generally used to assess the complexity of colour patterns. Here, we compare how colours characterised using point measurements (simulating spectrophotometry) on the skin of a sand lizard (Lacerta agilis) differ from colours estimated by clustering pixels in a photograph of the lizard’s body. We found that point measurements adequately represented the dominant colour of the lizard; however, where colour patterning influenced measurement geometry, image analysis outper-formed point measurement as regards stability between technical replicates on the same animal. The greater colour variation established from point measurements increased further under controlled laboratory illumination. Both methods revealed lateral colour asymmetry in sand lizards. We conclude that studies assessing the impact of colour on animal ecology and behaviour should utilise hyperspectral imaging, followed by image analysis that encompasses the whole colour pattern.