Consequences of Evolving Limbless, Burrowing Forms for the Behavior and Population Density of Tropical Lizards

Evolutionary ecologists seek to understand how phenotypic evolution relates to population level traits. To document that, we quantified functional traits (escape strategy, sprint speed and predatory performance) and population density across 10 lizard species representing the acquisition of burrowing snake-like morphs (BSLM), from Brazil. We used phylogenetic mixed models to test if: a) morph and substrate affects lizards’ flight strategy and speed, b) BSLM species get more access to different potential prey types than lacertoid ones, when in syntopy, and d) morph is correlated with population abundance and habitat use in a way expected from the output of the previous experiments. We found that BSLM rigidly relied on burrowing as flight strategy, while syntopic lacertoid species changed their strategy according to the substrate. Also, sand has opposite effects on sprint speed depending on morph, making lacertoids run slower and BSLM faster. Despite BSLM were overall slower than lacertoids, they were as good hunters of challengingly fast prey, and better hunters of underground prey. Further, in the sandy habitats where these morphs are syntopic, prey is most available at superficial leaf litter under vegetation, although there is a large stock of underground prey, under the vegetation, too. These results support our observed higher importance of sand for BSLM’s populations and the higher importance of vegetation for lacertoids’ population density. Finally, although BSLM species reached the highest populational densities among the studied species, a systematic effect of morphological evolution on abundance remains elusive.