Variabilidade genética e identificação de Talitrídeos (crustacea: amphipoda) ao longo do litoral brasileiro

Abstract

Talitridae is a family of terrestrial or semi-terrestrial crustaceans, of the order Amphipoda, understudied in Brazil and with high potential as indicator of environmental quality. They are abundant inhabitants of the supralittoral region, especially in sandy beaches. These areas most sensitive and threatened by human activities, the most profitable ecosystem for the world tourism industry, and at high risk of extinction due to increasing urbanization and climate changes. Given the urgency of actions to preserve its biodiversity, this study aimed to characterize the genetic structure of Talitridae species in beaches along the Brazilian coast. Partial sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene were used to perform analysis of genetic characterization diversity of the sampled talitrids. Among 397 individuals, 2 species were morphologically identified, Atlantorchestoidea brasiliensis (56%) and Talocherstia tucurauna (32%), while 12% were not conclusively identified. Of the 60 sequenced individual, distinct OTUs were spatially grouped; A. brasiliensis in Southeastern Brazil (SP, RJ e ES), T. tucurauna in the northeastern beaches (BA e AL), both OTUs in accordance with morphological identification, and 2 distinct OTUs, not identified morphologically and with no correspondence in the world genetic database (GenBank), one in PA (North Brazil) an 1 in AP and RS (furthest sampled points). The highest genetic diversity was within the species A. brasiliensis, specifically in RJ population, while individuals in north SP showed signs of high reproductive isolation from the other southeastern population, what is here ascribed to high levels of anthropogenic modification of the Guanabara Bay. Talorchestia. tucurauna showed moderated haplotipic diersity, similarly diverse at each sampling beaches, in BA and AL, but highly isolated from each other, between which the highest impacted area is Todos os Santos Bay. For AP and PA federal units, northernmost Brazil, the record of Talitridae is unprecedent. PA showed an exclusive OTU, without database correspondence, though close to Talorchestia. The isolation of this OTU is most likely natural features, as the area lies between a strong westward current flow and the Amazon river estuary. Individuals from AP and RS showed remarkable haplotipic similarity, of an exclusive OTU, without database correspondence in high hierarchical level. The beach in AP is the most pristine from all sampled beaches, and its individuals showed the highest within-group genetic distance and most complex haplotype network. A higher diversity of Talitridae than registered in the literature, new OTUs from distinct hierarchical taxonomic levels, the identification of intrinsic genetic OTU structures, and the high potential of indication of environmental quality of the group, through genetics, are emphasized contributions of this study.