Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

The Neotropics contain several biodiversity hotspots and harbor the highest diversity of freshwater fishes globally. Yet, recognizing the patterns and processes driving this richness remains a challenge. Similarly, all groups and subregions have not received the same attention, especially in the genomics era. Addressing these knowledge gaps will help us to better understand the region’s evolutionary and biogeographic complexity. The goal of this dissertation is to examine phylogenetic and biogeographic patterns of Neotropical freshwater fishes, with emphasis on the Greater Antilles, across multiple taxonomic and geographic scales. To achieve this goal, I generated a genomic dataset of hundreds of ultraconserved loci (UCEs) at both the family (Poeciliidae) and generic (Girardinus) levels, and compiled the most comprehensive freshwater fish occurrence dataset for the Greater Antilles to date. First, a thorough investigation of the genealogical heterogeneity within Poeciliidae revealed that incomplete lineage sorting and reticulate evolution played a major role in shaping its diversity, likely because of rapid and successive speciation events. Secondly, hierarchical clustering and population genetic analyses uncovered that the Greater Antilles consist of multiple areas of endemism, and their boundaries align closely with the tectonic blocks that form these islands. These patterns of distribution also reflect the multifaceted mosaic of life-history traits, colonization events, and in-situ speciation events that compose the region’s freshwater ichthyofauna. Finally, a detailed examination of gene tree variation within Girardinus showed that the multiple in-situ speciation events leading to its radiation are related to biological processes such as incomplete lineage sorting and hybridization. Moreover, our biogeographic analysis estimated that western Cuba was the most likely area of origin for Girardinus and its sister genus Quintana and inferred that multidirectional dispersal events explain its distribution on the island. Overall, this dissertation not only refines phylogenetic hypotheses within Poeciliidae at the family and generic level but also offers a framework for future studies on systematics, diversification, and endemism in the Neotropics and a guide for potential biodiversity assessments and management efforts in the Greater Antilles.

Date

5-18-2025

Committee Chair

Prosanta Chakrabarty

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Available for download on Monday, May 18, 2026

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