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 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. To address this, I estimated population structure in the peacock grouper Cephalopholis argus using ~15,000 SNPs through ddRAD-seq and found three genetic populations: western Micronesia (Palau), eastern Micronesia (Pohnpei and Kwajalein), and the Mariana Archipelago. Within the unstudied Mariana Archipelago, I examined the fine-scale population structure of six fish species, including two shallow-water and four deep-water species. While all six species exhibited a lack of genetic structure based on F-statistics, three species showed isolation by distance. Finally, 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.
Pavithiran Amirthalingam
Dr. Michelle Gaither, Advisor
Read More