Going against the flow: Barriers to gene flow impact patterns of connectivity in cryptic coral reef gobies throughout the western Atlantic
Daniel Volk, John D. Konvalina, Sergio R. Floeter, Carlos Eduardo Leite Ferreira, Eric A. Hoffman
Abstract
Abstract Aim Complex oceanographic features have historically caused difficulty in understanding gene flow in marine taxa. Here, we evaluate the impact of potential phylogeographic barriers to gene flow and assess demography and evolutionary history of a coral reef goby species complex. Specifically, we test how the Amazon River outflow and ocean currents impact gene flow. Location Western Atlantic. Taxon The bridled goby ( Coryphopterus glaucofraenum ) and sand‐canyon goby ( C. venezuelae ) species complex. Methods We used mitochondrial DNA and 2,401 genomic SNPs to investigate evolutionary history and test hypotheses of how major barriers impact species‐level differentiation. We used clustering algorithms and pairwise F ST to assess population differentiation caused by minor barriers within and among regions. Finally, we tested alternate hypotheses of demographic history via coalescent simulations to determine the most plausible spread across the Western Atlantic. Results We found two unique clades of C. glaucofraenum along the Brazilian coast and the oceanic island Atol das Rocas (AR) that are more closely related to C. venzuelae . Further genetic structure within the Caribbean and separately along the Brazilian coast led to at least two distinct populations in each Province. Coalescent simulations indicated that an ancestral population of C. venezuelae split from C. glaucofraenum in the Caribbean, dispersed to Brazil, then spread to AR. Main conclusions Species‐level genetic differentiation has resulted from the Amazon River outflow and isolation of AR. Population differentiation within the Caribbean matched previous studies indicating an east‐west pattern of divergence. Brazilian population differentiation was impacted by the cold‐water upwelling filter at Cabo Frio. Overall, this research highlights how barriers to gene flow impact speciation and genetic structure within western Atlantic gobies and provides insight into the role oceanographic features have in the speciation process of fishes.