Environmental drivers of scale morphology in a Canary Island lizard across 3700 m of elevation

Abstract

The skin serves as the outermost barrier between an organism and its environment and fulfills numerous physiological and ecological functions. In lizards, scale morphology is an important adaptive trait that mediates responses to environmental influences such as extreme temperatures, ultraviolet radiation, drought and anthropogenic disturbances. Our study provides an analysis of the environmental drivers influencing intraspecific variation in the scale ecomorphology of the island lizard Gallotia galloti across 3700 m of elevation, taking into account different macro- and microclimatic conditions and varying degrees of anthropogenic influences and across three body regions: dorsal, ventral and tail. We found several correlations suggesting multiple dependencies of scale morphology on environmental variation. The positive correlation between July temperature and wind speed at 3 cm above the ground and dorsal scale density showed that more densely packed scales are associated with hotter and drier environments. This could possibly be related to the thermoregulatory and hydroregulatory function of the skin, since the dorsal side of the body is most exposed. Higher sun exposure was associated with larger dorsal and tail scales, indicating a possible photoprotective function. Ventral scales are not exposed to the pressure of solar radiation and wind. Accordingly, ventral scales showed no correlation with these factors, but we found that a higher ratio of day-to-night temperature variation relative to seasonal changes (isothermality) was associated with a higher density of ventral scales. The human footprint index positively correlated with larger and denser ventral (and not dorsal or tail) scales. Overall, our results illustrate the complexity of responses of scale morphology to different environmental variations. Evidently, G. galloti exhibits morphological diversity in response to climatic conditions and urbanization, highlighting the potential ecological significance of scale size variation. Future research should investigate the genetic basis and possible effects of climate change on scale morphology.