Macroevolution Meets Community Ecology: Does Species Interaction Influence Tempo and Mode of Diversification in Fishes That Cross the Marine/Freshwater Boundary?

Date of Award

6-2024

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Devin D. Bloom, Ph.D.

Second Advisor

Kathryn Docherty, Ph.D.

Third Advisor

Sharon Gill, Ph.D.

Fourth Advisor

Hernán López-Fernández, Ph.D.

Keywords

Adaptive radiation, ecological opportunity, macroecology, macroevolution, species interaction, trans-marine/freshwater fishes

Abstract

Evolutionary transitions between marine and freshwater ecosystems are an extreme ecological shift and expose fish lineages to novel abiotic and biotic settings. Yet, it remains unclear how those habitat transitions and the interaction with the newly invaded communities have altered the macroevolutionary dynamics of fish clades. The theory of ecological opportunity predicts that lineages that colonize species-poor regions will have greater potential for phenotypic diversification and speciation than lineages invading species-rich regions. Thus, transitions between marine and freshwaters in depauperate regions may promote adaptive radiation. While most major fish clades are restricted to either marine or freshwaters, so called transmarine/ freshwater clades have crossed this boundary, often multiple times. In this doctoral dissertation, I explored the effects of marine/freshwater transitions on the evolution of fishes and how varying species richness in fish communities can influence morphological diversification and speciation patterns. This study can help elucidate the effect of species interaction and the role of ecological opportunity over deep evolutionary timescales following the successful colonization of novel habitats in fishes. I used phylogenetic comparative methods to: (1) explore the effect of marine/freshwater transitions, species richness of incumbent community, and diversity of invading lineages on the evolution of body size in nine major transmarine/ freshwater clades; (2) investigate patterns of diversification of phenotypic traits in New World Silversides (Menidiinae) that invaded freshwater habitats in varying community context across Central and North America and test for adaptive radiation in Central Mexican Silversides; and (3) investigate whether the invasion of freshwater regions with low incumbent species richness across the globe increased phenotypic diversification of Silversides + Rainbowfishes (Atheriniformes). My results indicate that: (1) transitions to freshwater habitats do not lead to consistent morphological changes, but phenotypic disparity in freshwaters can be linked to the diversity of incumbent freshwater species and the diversity of closely related taxa; (2) transitions between marine and freshwater habitats are not the primary cause of exceptional morphological diversification in Menidiinae, but ecological opportunity in depauperate lakes lead to adaptive radiation in Central Mexican Silversides; (3) ecological opportunity in freshwater regions with lower diversity of incumbent fishes led to elevated morphological diversification in Atheriniformes. Altogether, I demonstrated that varying community compositions in freshwater habitats can lead to different macroevolutionary patterns, consistent with the theory of ecological opportunity.

Access Setting

Dissertation-Abstract Only

Restricted to Campus until

6-1-2026

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