UC Berkeley

This dissertation is primarily focused on closely-related species’ coexistence and how it is both a function and a driver of phenotypic evolution. To understand how phenotypic diversity evolves in relation to a species’ interactions and evolutionary history, I focus on ecomorphology—an organisms’ ecological role and morphological adaptations. My dissertation uses field and museum-based methods to quantify the dynamics of ecomorphological evolution within the genus Sceloporus lizards, a radiation of ~100 species, and how it influences species’ resource use and distributions, from sites to landscapes to continents, and from populations to communities to the entire genus.Chapter I of my dissertation examines the relationship between resource use and phenotypic variation among four species of co-occurring lizards in a sky island system, the Chiricahua Mountains of southeastern Arizona. This isolated environment provides an opportunity to quantify resource use where forces of selection are expected to be strong. I quantified niche use of 300+ co-occurring lizards across multiple axes to determine their relative importance and found that perch height and type explained most variance between species, but also uncovered variation in the temporal and thermal activity of these interacting species. By measuring phenotypic traits for all individuals, I found that species differed in traits associated with climbing ability, thus suggesting a coevolved relationship between physical traits and divergent niches.

In Chapter II, I explored another resource axis along which many co-occurring species differentiate by quantifying the trophic ecology of the Sceloporus species in the Chiricahua Mountains. Using DNA metabarcoding, I found significant differences in species’ diets concomitant with their respective ecologies as uncovered in Chapter 1. As sit-and-wait predators, diet is a function of microhabitat, underscoring the importance of spatial niche partitioning in allowing co-occurrence in this system.

In Chapter III, I examined the dynamics of ecomorphological evolution Sceloporus and its role in facilitating coexistence between congeners. By collecting ecological and morphological data for 80 taxa from 300+ specimens at 5 museums, I found that multivariate morphology is a good predictor of ecology and that Sceloporus species occur in six ecological modes with associated morphologies (ecomorphs). I show that the evolution of arboreality at the base of a rapid radiation led to further ecological and morphological evolution. Examination of the spatial distribution of ecomorphology revealed a pattern of spatial overdispersion: across their range Sceloporus assemblages are comprised of more ecomorphs than expected by chance, suggesting ecological and morphological diversity play a key role in spatial sorting.

Together, the results of my dissertation suggest that across the Sceloporus radiation, ecology andmorphology have evolved in concert and these traits influence the spatial distribution of populations, species, and assemblages.