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

Abstract

We quantified functional traits (escape strategy, sprint speed and predatory performance) and population density across 10 lizard species representing morphotype stages in the acquisition of burrowing snake-like morphotypes (BSLM), from Brazil. We used phylogenetic mixed models to test if: (a) morphotype and substrate affects flight strategy and speed, (b) BSLM species more effectively access different potential prey types than lacertoid species, when in syntopy, and (c) morphotype is correlated with population abundance and habitat use in a way expected from the output of the previous experiments. BSLM rigidly relied on burrowing as flight strategy, while syntopic lacertoid species changed their strategy according to the substrate. In addition, sand had opposing effects on sprint speed depending on morphotype, making lacertoids run more slowly and BSLM faster. Even though BSLM were overall slower than lacertoids, they were equally effective hunters of challengingly fast prey, and better hunters of underground prey. In their shared habitats, prey is most abundant in the superficial layer of leaf litter, although a large fraction is found beneath this layer, under bushes. Experimental results support the observed higher importance of sand for BSLM’s density and the higher importance of vegetation for lacertoids’ density. Finally, although BSLM species reached the highest population densities among the studied species, a systematic effect of morphological evolution on the abundance of limbless lizards remains elusive.