Biodiversity, connectivity and evolutionary history of specialist polychaetes in organic islands (whale falls) in the deep SW Atlantic

Abstract

Whale falls promote high biodiversity on the ocean floor, providing rigid substrates, organic enrichment and free sulphides in typically oligotrophic environments such as the deep sea. Current hypotheses suggest the "organic islands" may have served as hot spots of adaptive radiation for a specialized fauna; they have also provided evolutionary stepping stones for vent and seep taxa. This is corroborated by the typical co-occurrence of many species in reducing habitats, as hydrothermal vents or/and cold seeps. However, studies on the large scale patterns of biodiversity, biogeography and connectivity of the populations that exploit these islands are still scarce, as well as on the relationships between diversity and ecosystem function. The Hesionidae are an abundant polychaete family, with many specialized taxa and widely distributed in chemosynthetic environments, therefore they could serve as connectivity models of whale carcasses, as well as their evolutionary history could contribute to the advancement in knowledge about the evolution and diversification in chemosynthetic environments in the deep sea. This proposal will be conducted under the thematic project BioSuOr (FAPESP Biota Nº2011/50185-1), which aims to advance knowledge on hesionids biodiversity in organic islands in the deep sea, through whale carcasses implanted at different depths (1500 and 3300 m) and latitudes along the southwest Atlantic. For the characterization of specific composition, it is intended to use both conventional morphological taxonomy methods and molecular tools. Two mitochondrial markers (16S rRNA and COI) and two nuclear (28S rRNA and 18S rRNA) will be used to assess the genetic diversity of the dominant species and determine the degree of divergence among populations or cryptic species (connectivity). This will assess the gene flow among specific populations of hesionids of the carcasses. It is intended to also describe the reproductive aspects of specialist species, in order to understand their strategies for the development, fertilization and consequently on its dispersal in the seabed. For this, the animals will be studied under optical, scanning electron and transmission microscopes, as well as from the use of both conventional histology techniques and computed tomography through MicroCT scan. Finally, from the biogeographic and phylogenetic analysis of Hesionidae family also intends to discuss the evolutionary history of reducing environments on sea floor. This is a highly innovative scientific project in Brazil, with national and international partners of high scientific level, being one of the first studies involving aspects such as biodiversity, connectivity and reproductive biology to better understand the evolutionary history of experts organisms on islands organic in the deep sea. (AU)