Sexually selected traits can be expected to increase in importance when the period of sexual behavior is constrained, such as in seasonally restricted breeders. Anolis lizard male dewlaps are classic examples of multifaceted signaling traits, with demonstrated intraspecific reproductive function reflected in courtship behavior. Fitch and Hillis found a correlation between dewlap size and seasonality in mainland Anolis using traditional statistical methods. Here, we present two tests of the Fitch-Hillis Hypothesis using new phylogenetic and morphological data sets for 44 species of Mexican Anolis. A significant relationship between dewlap size and seasonality is evident in phylogenetically uncorrected analyses but erodes once phylogeny is accounted for. This loss of strong statistical support for a relationship between a key aspect of dewlap morphology and seasonality also occurs within a species complex (A. sericeus group) that inhabits seasonal and aseasonal environments. Our results fail to support seasonality as a strong driver of evolution of Anolis dewlap size. We discuss the implications of our results and the difficulty of disentangling the strength of single mechanisms on trait evolution when multiple selection pressures are likely at play.

Standardized photos of animals were taken in the field, localities recorded via GPS, and dewlap size data extracted using ImageJ. Seasonality data (BIO15 from Bioclim) from collection localities were extracted using QGIS.

Data are very straight-forward and there are no missing values. There are two primary datasets. One (interspecies data) represents 41 species of Mexican anoles and another (silky anoles) represents only the Anolis sericeus complex.

Data files contain locality (latitude and longitude), values for head length (in mm), values for dewlap size (in mm2), and seasonality (BIO15 from Bioclim). For the interspecies analyses, data for head length and dewlap size were log-transformed and names for each species from the phylogenetic tree used (Poe et al. 2017) for PGLS. Information on date and season (Dry or Wet) of collection are also included.

Input files for calculating the intra-class correlation coefficients for dewlap size and seasonality are also included.