Environment drives color pattern polymorphism in sand lizards beyond the Gloger's rule

Abstract

Species color and color pattern vary geographically contributing to environmental tolerance of the species to the fluctuating climate. In a constantly changing environment, the population remains polymorphic, when individuals that are not acclimated to the current environment can survive adverse time periods. Factors influencing color morph frequencies in populations affect spatial variation through local adaptation, which is in turn linked to large‐scale environmental gradients. The influence of environmental factors has not been adequately studied in many polymorphic organisms where the influence of sexual selection on the persistence of polymorphisms is widely recognized. We hypothesized that different color morphs of sand lizard are distributed throughout the Palearctic depending on different environmental conditions. The goal of this study was to examine if the range of morph composition in a color polymorphic lizard can be explained by geographic and climatic variation in the Palearctic. We used publicly available data on sand lizard occurrence from the Global Biodiversity Information Facility and environmental variables from WorldClim and SEDAC databases. We categorized sand lizards' photos to 10 discrete color morphs based on color and color pattern variation. We predicted the color morph distribution using maximum entropy models. We found that variations in morph distributions were mostly related to temperature seasonality, precipitation, elevation, and anthropogenic activities. Our findings support the relationship between environmental conditions and color morph distribution, implying that environmental selection acts differently on color morphs, most likely in conjunction with sexual selection.

The Endangered Sardinian Grass Snake: Distribution Update, Bioclimatic Niche Modelling, Dorsal Pattern Characterisation, and Literature Review

“…The Sardinian grass snake is characterised by a high level of colour polymorphism (e.g., [ 15 , 25 , 28 ]). In reptiles, this interspecific colour variation may be correlated with geographic, bioclimatic, and environmental factors (e.g., [ 42 , 43 , 44 ]). Therefore, we carried out a tentative characterisation of the dorsal patterns, based on both personally acquired and citizen science photographs (the unavailability of photos taken in a standardized way for all snakes, has not allowed the use of computer-based colour assessment methods).…”