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Meeting Abstract

45-5   14:30 - 14:45  Genomic analyses suggest incipient speciation in a widespread Tropical Atlantic swimming crab Peres, PA*; Bracken-Grissom, H; Timm, L; Mantelatto, FL; Florida International University (FIU), Institute of Environment, Miami, FL, USA/University of São Paulo (USP), Faculty of Philosophy, Sciences and Letters at Ribeirão Preto (FFCLRP), Riberão Preto, SP, Brazil; Florida International University (FIU), Institute of Environment, Miami, FL, USA; University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, Fairbanks, AK, USA/NOAA National Marine Fisheries Service, Alaska Fisheries Science Center, Auke Bay Laboratories, Juneau, AK, USA; University of São Paulo (USP), Faculty of Philosophy, Sciences and Letters at Ribeirão Preto (FFCLRP), Riberão Preto, SP, Brazil pedro.peres27@gmail.com

The patterns and drivers of marine species diversification remain a challenge for ecologists and evolutionary biologists. In the tropical Western Atlantic, we find the world's largest freshwater and sediment discharge into the ocean: The Amazon-Orinoco plume (AOP). Previous studies limited to mtDNA showed that the swimming crab Callinectes ornatus show two distinct genetic clusters separated by the AOP (Brazilian – BR; Caribbean – CR), despite its high dispersal potential. Here, we combined mtDNA data with ddRAD-seq to explore the diversification patterns and processes within the swimming crab C. ornatus. We investigated 1) the existence of fine-scale structure across BR groups; 2) the differentiation level between individuals from both sides of the AOP (BR and CR) 3) the occurrence of loci under selection and adaptive structure; 4) the potential existence of recently diverged species. Our results show a lack of genetic structure among BR groups, divergence between BR and CR, and signs of hybridization between BR and CR. We find asymmetrical migration between both groups (higher migration in the BR to CR direction) congruent to local currents, and divergence estimates congruent to a further uplift of the Andes Mountains (~2MYA) that intensified the AOP. We also show adaptive structure between Caribbean and Brazil. Overall, mtDNA and ddRAD-seq indicate the same patterns but the latter gives us a better resolution. We propose an incipient speciation with gene flow scenario process driven by disruptive selection coupled with a permeable barrier (the Amazon-Orinoco plume), differences in effective population size, and oceanographic currents acting together. The work we present here represents the first investigation employing ddRAD-seq in a marine invertebrate species with distribution encompassing tropical north and south Western Atlantic.