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Positive allometry of signalling traits has often been taken as evidence for sexual selection. However, few studies have explored interspecific differences in allometric scaling relationships among closely related species that vary in their degree of ecological similarity. Anolis lizards possess an elaborate retractable throat fan called a dewlap that is used for visual communication and differs greatly in size and colour among species. We observed that Anolis dewlaps demonstrate positive allometry: relative dewlap size increases with body size. We also observed that coexisting species are divergent in signal size allometries, while convergent species—similar in other aspects of ecology, morphology and behaviour—typically share similar dewlap allometric scaling relationships. These patterns suggest that dewlap scaling relationships may follow the same pattern as other traits in the anole radiation, where ecologically different sympatric species have evolved a suite of divergent traits.

Supplementary information and analyses, including: addiional methods on thermal trait trials, additional statistical methods, sources of climate data, summary statistics of body sizes for all study species, taxonomic classifications and native geographic distributions of all study species, local and regional media news stories about the extreme cold event on which the study is based, local social media evidence of lizard responses to the extreme cold event (including photos).

Supplementary Methods, Analyses, Figures, and Tables

Supplementary tables: Table S1 (a list of specimens) and Tables S2-6 (additional statistical results)

Additional information about data extraction and processing, analyses using absolute dewlap size, and the implementation and validation of the multi-psi model.

How individuals move through their environment dictates which other individuals they encounter, determining their social and reproductive interactions and the extent to which they experience sexual selection. Specifically, females rarely have the option of mating with all males in a population—they can only choose among the males they encounter. Further, quantifying phenotypic differences between the males that females encounter and those that sire females’ offspring lends insight into how social and reproductive interactions shape male phenotypes. We used an explicitly spatiotemporal Markov chain model to estimate the number of potential mates ofAnolis sagreilizards from their movement behavior, and used genetic paternity assignments to quantify sexual selection on males. Females frequently encountered and mated with multiple males, offering ample opportunity for female mate choice. Sexual selection favored males that were bigger and moved over larger areas, though the effect of body size cannot be disentangled from last-male precedence. Our approach corroborates some patterns of sexual selection previously hypothesized in anoles based on describing them as territorial, whereas other results, including female multiple mating itself, are at odds with territorial polygyny, offering insight into discrepancies in other taxa between behavioral and genetic descriptions of mating systems.