Go with the flow: patterns of connectivity in low dispersal coral reef gobies (Coryphopterus spp.) throughout the western Atlantic

Masters thesis

Gene flow is an integral biological process that can mediate speciation. While many consider the ocean to be an open environment, there are many barriers that limit gene flow, particularly in the western Atlantic. I analyzed data from two widespread, coral reef fishes, the bridled goby (Coryphopterus glaucofraenum) and sand-canyon goby (C. venezuelae), throughout their range in the western Atlantic. Using two genetic datasets, mitochondrial DNA (mtDNA) and genomic SNPs, I investigated the evolutionary history of these species and inferred the location and strength of putative barriers. My results suggest that several unique lineages have genetically diverged from one another in the presence of two major barriers. First, the Amazon River has isolated Brazil from the Caribbean and second, a unique lineage was found at an isolated oceanic island, Atol das Rocas, off the northeast coast of Brazil. Furthermore, minor barriers have caused slight genetic differentiation in each of the Caribbean species off the coast of Venezuela, while on the Brazilian coast, there are up to two barriers that separate three genetically unique areas. The stronger of the two barriers is located at Cabo Frio near an upwelling system and the weaker barrier coincides with the outflow of the São Francisco River. Overall, this research highlights how barriers impact speciation and genetic structure within these gobies in the western Atlantic and more broadly, deepens our understanding about the role of oceanographic features in the speciation process.