Date of Award

Spring 1-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology & Evolutionary Biology

First Advisor

Alexander Cruz

Second Advisor

Robert Guralnick

Third Advisor

Andrew Martin

Fourth Advisor

Dena M. Smith

Fifth Advisor

David Stock

Abstract

In the course of my dissertation work, I examined the evolution of Limia (Poeciliidae) in the context of their biogeography, adaptability, and diversity. Chapter one is a review of West Indian colonization, evaluating the historic and new evidence supporting land bridges, dispersal, and late Cretaceous vicariance. Chapter two is an updated phylogeny of Limia, based on multiple genes and the broadest sampling of Limia populations to date. I focus on the relationships between species of Limia, as well their relationships to mainland taxa, while evaluating their potential mechanisms of colonization. Chapter three investigates the role of salinity in driving the evolution of physiological and morphological traits in divergent populations of L. perugiae. While tolerance to salinity may play a vital role in their colonization of the West Indies, it may also be a driving force for diversification in Limia. Finally, chapter four evaluates the status of a potentially new species of Limia from the Haitian Lake Miragoane, providing evidence of reciprocal monophyly, as well as behavioral distinctness.

Overall, my results support a colonization model for Limia that is concordant with the Eocene/Oligocene timing of the GAARlandia model, a controversial land bridge hypothesis that may have connected South America to the Greater Antilles. Although little evidence exists for a true land bridge connection, global climate change during the Eocene/Oligocene boundary most likely facilitated dispersal for Limia and other groups able to travel along shorelines and cross over shorter seawater barriers. Our physiological data show that Limia are tolerant to saltwater, able to adapt by altering their osmoregulatory mechanisms, including active ion transport proteins, and mitochondrial remodeling within the gills to support the energy demands of a hypertonic environment. The energetic consequences to Limia living in saline and hypersaline environments may also be a driver for phenotypic diversity, altering the relative size and shape of the head, and impeding the growth of secondary sex features. Finally, as a group, Limia are remarkably successful in their overall diversity and distribution; there are eighteen species on Hispaniola alone, including the newly described Limia isla.

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