ORCID

0000-0003-0517-458X

Keywords

Fish, Mariana Islands, RADSeq, SNPs, divMigrate, TreeMix, phylogeography, Stairway plots

Abstract

Most marine species exist as metapopulations, composed of subpopulations inhabiting patchily distributed habitat. Connectivity among these subpopulations is primarily facilitated by larval dispersal via ocean currents. Understanding patterns of population connectivity is crucial for evaluating metapopulation dynamics and ensuring long-term population stability in managed species. Micronesia, a vast region in the North Pacific with hundreds of islands, is the northern extent for many tropical species and is thought to function as vital stepping-stones between the central and western Pacific. However, limited phylogeographic studies in the region have left significant knowledge gaps regarding metapopulation dynamics. Here I address this knowledge gap by examining population structure and estimate patterns of dispersal in six species of fish across the region. In Chapter II, I estimate population structure in the peacock grouper Cephalopholis argus using samples collected from across Micronesia. For this work I developed ~15,000 SNPs through ddRAD-seq and find three genetic populations: western Micronesia (Palau), eastern Micronesia (Pohnpei and Kwajalein), and the Mariana Archipelago. While western and eastern Micronesian populations are highly connected, subpopulations in the Mariana Islands are isolated. In Chapters III and IV, I focus on the Mariana Archipelago, which prior to my dissertation had not been examined in any published genetic studies. There, leveraging sampling from six fish species co-sampled across 8-10 of the Mariana Islands I examine fine-scale population structure in two shallow-water and four deep-water species. While all six species exhibited a lack of genetic structure based on tens of thousands of neutral loci, two species showed evidence of isolation by distance. This suggests that geographic distance may influence genetic differentiation across the archipelago in some species, with neighboring islands acting as stepping-stones for intra-archipelago processes. In Chapter IV, I inferred historic effective population size of the Marianas populations for all six species. All species except for the shallow water peacock grouper C. argus, showed population expansions following the last glacial maximum. These expansions may be attributed to the warmer climate of the interglacial period. Overall, the findings from Chapters II and III improve our understanding of population connectivity across the broader region (Chapter II), as well as in the under studied Mariana Islands (Chapter III), helping to inform management decisions in the latter. Meanwhile, the results from Chapter IV highlight the influence of historical sea-level fluctuations on the demographic history of marine fishes across the region.

Completion Date

2025

Semester

Fall

Committee Chair

Gaither, Michelle

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Biology

Format

PDF

Identifier

DP0029775

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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