SICB 2016: Evolution of Lizard Jaw Morphology in Association with Diet and Social Behavior

Leah Selznick presents her poster at SICB 2016.

Muscle and jaw morphology is highly variable among lizards, which could be driven, at least in, part by a species’ diet, intraspecific combat, or both. Leah Selznick of the Johnson lab at Trinity University collected data on the head dimensions, jaw muscle mass, diet data (prey count), and estimates of sexual dimorphism (SSD) for seven species of lizards. Four of the species she examined – the leopard gecko, Northern curly tail, Texas spiny lizard, and the Carolina green anole – are saurophagous, meaning that they eat other lizards. The other three species – the Mediterranean house gecko, little brown skink, and spotted whiptail – do not eat other lizards. Leah predicted that saurophagous species and those with a higher variance in prey diet would also have larger heads and larger jaw muscles. Additionally, she predicted that species with higher sexual size dimorphism (SSD), a proxy for the strength of pre-copulatory selection on male body size, would be associated with larger jaw morphologies. First, she tested for phylogenetic signal in all of her traits and found strong signal for jaw muscle mass (λ = 0.99) and head size (λ = 0.65). She then tested for an association between both head size and jaw muscle mass (standardized by body mass) with species prey count and SSD. She found no correlation between any of the jaw morphologies and SSD or species prey count. Leah suggests that (1) there may be other traits that are experiencing selection due to prey size and combat and/or that (2) these traits may be experiencing evolutionary constraint. Leah is going to continue exploring the evolution of jaw morphology by examining the histology of the jaw muscle in these species to test for an association between muscle fiber composition and type with prey count and SSD.

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Selznick compared two groups of lizard species: four saurophagous species, and three exclusively insectivorous species. Here, she shows the prey count, and SSD for each species used in her analysis.