Dissertations, Theses, and Capstone Projects

Date of Degree

5-2018

Document Type

Dissertation

Degree Name

Ph.D.

Program

Biology

Advisor

Ana Carolina Carnaval

Committee Members

Robert P. Anderson

Michael Hickerson

Jose Anadon

Stephen Harris

Subject Categories

Biodiversity | Evolution

Keywords

biodiversity, thermophysiology, species distributions, environmental niche

Abstract

The environmental niche is a central organizing concept in the study of ecology and evolution, as the environmental conditions in which species can persist (their fundamental niches) and the conditions in which they occur (their realized niches) can shape spatial and temporal patterns of biodiversity at multiple scales. How organisms at different levels of biological organization are affected by environmental heterogeneity has consequences for the distribution of genetic and phenotypic diversity, yet the mechanisms through which this occurs are poorly studied. In this dissertation, I present three research chapters that explore how species’ traits and their microclimatic environments shape biodiversity patterns across geographic space and throughout evolutionary time. I focused on a group of Neotropical lizards distributed throughout Central and South America, the Gymnophthalminae clade of the Gymnophthalmidae family. First, I described spatial and temporal patterns of biodiversity in the Gymnophthalminae clade of Gymnophthalmidae lizards. By combining custom exon capture genetic data with environmental data, I found that the use of ecologically-informed microclimatic environmental variables uncovered more complex patterns of niche shifts throughout the history of this group than did more commonly used macroclimatic variables. Second, I explored the ecological mechanisms that shape species distributions for three montane species that occupy the Atlantic Forests of Brazil. To ask whether the physiological traits that delimit the species’ fundamental niches explain their present-day range limits, I created spatial models of thermophysiological suitability across the Atlantic Forest of Brazil for three species. I found that thermophysiological constraints in the warm edge of the distribution, while commonly inferred to drive range contractions and expansions in this system, do not restrict the ranges of these species to high elevations. Third, I investigated the ecological mechanisms through which species’ phenotypic traits interact with microclimatic conditions, resulting in the generation of genetic and genomic diversity in the cold edge of a species range. I found evidence that divergence in isolation has been an important driver of evolution in this system. In particular, poor thermophysiological performance in cool environments best predicted intraspecific patterns of genetic diversity. Common to all chapters is the use of novel, integrative approaches tied to empirical studies to investigate the many different ways environmental heterogeneity and species’ environmental niches shape species distributions and genetic diversity.

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