Climate-related environmental variation in a visual signalling device: the male and female dewlap in Anolis sagrei lizards.

Animals communicate using a variety of signals that differ dramatically among and within species. The astonishing dewlap diversity in anoles has attracted considerable attention in this respect. Yet, the evolutionary processes behind it remain elusive and have mostly been explored for males only. Here, we considered Anolis sagrei males and females to study signal divergence among populations. First, we assessed the degree of variation in dewlap design (size, pattern and colour) and displays by comparing 17 populations distributed across the Caribbean. Second, we assessed whether the observed dewlap diversity is associated with variation in climate-related environmental conditions. Results showed that populations differed in all dewlap characteristics, with the exception of display rate in females. We further found that males and females occurring in 'xeric' environments had a higher proportion of solid dewlaps with higher UV reflectance. In addition, lizards inhabiting 'mesic' environments had primarily marginal dewlaps showing high reflectance in red. For dewlap display, a correlation with environment was only observed in males. Our study provides evidence for a strong relationship between signal design and prevailing environmental conditions, which may result from differential selection on signal efficacy. Moreover, our study highlights the importance of including females when studying dewlaps in an evolutionary context.