Research on animal colouration has grown exponentially in the last decade thanks to multidisciplinary approaches. Most studies were focused on trade-offs between communication and mimicry, which represent the two main constraints and drivers of the evolution of body colourations. Reptiles are excellent model species in order to investigate such field of study and lizards in particular show great variability of body colourations and their functions. We studied the lizard Podarcis siculus analysing the variations of dorsal colour of three populations and we obtained clear patterns of seasonal and ontogenetical variation of dorsal colour. According to baseline colour, males were greener and brighter than females, although no difference in saturation was recorded. According to seasonal variations, analyses showed that both sexes significantly vary in colour during the year: males reached higher peaks of hue and saturation later than females during spring; contrastingly, females showed higher peaks of brightness, reached earlier similarly to hue and saturation. Ontogenetic variations were recorded only in males, which become greener, less bright and saturated with growing size. Therefore, our results suggest the occurrence of two opposed strategies in colour expression between sexes: males' dorsal colouration plays a major role in communication, while females are more crypsis-oriented.

Colour variability is largely widespread in the animal world as it is tightly associated with fitness and survivorship. Therefore, the drivers and implications of such variability have been of great interest for zoologists in the past decades. Reptiles are excellent models to investigate colour variations and expression under different conditions. Here, we focused on melanism occurrence in the two main lineages of Hierophis viridiflavus at the scale of the species distribution, by extracting available data from iNaturalist, a citizen science network, with the aim of detecting any pure effect of climate or local habitat on colour expression. Our analyses highlighted that habitat does not explain differences in phenotypes, whereas marked effects of geographic and climatic variables were detected. However, the observed climatic effects could be a proxy of the geographical distribution of the two groups, and thus the high occurrence of bright colourations in western populations of the eastern lineage could be addressed to an ongoing event of asymmetric gene flow in contact zones. The current distribution of phenotypes could be the outcome of the evolutionary history of the species combined with the geological history of the Mediterranean region. This investigation, though, is only preliminary and molecular analyses on highly variable regions of the genome are mandatory to address this issue.

Melanin-based dorsal pattern polymorphisms are common in reptiles and generally evolve under the interaction between opposite selective pressures, notably thermal advantage in cold environments and background matching to avoid predation. When those pressures change over space and time, the relative frequencies of morphs can vary across the species range. However, no previous study has analysed the spatial patterns of variation of morphs under a phylogenetic perspective in addition to the adaptive responses to natural selection. In this study, we focused on the distributional patterns of the three dorsal morphs of Podarcis muralis at wide-range scale to assess how they associate with geography, climate, microhabitat, phylogeny and sexual dimorphism. By using open access data from iNaturalist, we assembled a dataset of 4096 georeferenced points with information on sex and morph. Data were analysed through Bayesian GLMs, and four alternative models were formulated depending on the specific factors affecting morphs’ frequency. The dorsal morphs are not randomly distributed in Europe, but follow clear geographic patterns, vary with altitude and habitats, show sex-specific trends, and correlate with the phylogenetic history of the species. When comparing models, the phylogenetic model always obtained the best performance, and no overlap with other models occurred, thus best explaining the distributional patterns of dorsal morphs. The evolutionary processes, in addition to present environmental pressures, can significantly affect local-scale microevolutionary adaptations, influencing the current distribution of dorsal phenotypes across the species range. More generally, results point out the importance of considering the evolutionary processes when analysing distributional patterns of polymorphisms.

We analysed a snake species community of a Mediterranean 0.2 ha ecotonal area during a 21 year time span, monitoring two colubrid and one viperid snake species. We carried out analyses in seven years (1997, 1999, 2002, 2004–2005, 2016–2017) that had similar sampling efforts and, in the last two years of short-term monitoring, we applied a recently proposed monitoring protocol of the Italian Environment Ministry. In total, we captured 172 distinct individuals, 61 whip snakes (Hierophisviridiflavus), 26 barred grass snakes (Natrixhelvetica) and 85 asp vipers (Viperaaspis). Regarding the long-term monitoring period, whip snakes were captured on average about nine times per year, grass snakes were captured four times per year and asp vipers were found 12 times per year. Captures decreased in whip snakes, while increased in grass snakes and remained constant in asp vipers. In 2016 and 2017, we captured 10 whip snakes, 19 grass snakes and 31 asp vipers. Density estimates of snake species (0.5 H.viridiflavus/ha, 0.3 N.helvetica/ha and 0.7 V.aspis/ha) differ, to a certain extent, from published results for some other areas of central, northern and western Europe, perhaps depending on the approach applied for habitat suitability estimation. The average body size between two years differed neither for whip snakes nor for grass snakes, but it decreased significantly in asp vipers.