Montes submarinos da Cadeia Vitória-Trindade como alpondras para peixes recifais
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Data
2014-09-09
Autores
Simon, Thiony Emanuel
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Universidade Federal do Espírito Santo
Resumo
Trindade Island and the Martin Vaz Archipelago, located about 1,200 km from the central coast of Brazil, constitute the most isolated reef environments of the Brazilian biogeographic province. These islands harbora reef fish faunacomparatively rich, and their composition are similar to that found at the western margin of the Atlantic Ocean. This pattern has been attributed to the presence of a linear series of seamounts, which, together with the islands, comprisethe Vitória-Trindade Chain. Hypothetically, the seamounts would be used as stepping-stones, allowing species with low dispersal ability to colonize adjacent environments, successively, until they reach the islands, located at the eastern end of the ridge.In the present work, this hypothesis is evaluated through a comparative phylogeographic approach. Two species of reef fish were selected to represent different scenarios of gene flow along the ridge. Molecular markers of the mitochondrial DNA (partial sequences of the Cytochrome B gene and of the Control Region) and of the nuclear DNA (8–12 microsatellite loci) were combined to investigate (1) the distribution of the genetic lineages, (2) the population structure, (3) the demographic history and (4) the historical and contemporary gene flow. The species selected to represent a scenario of high-dispersion, Cephalopholis fulva, showed low population structure, absence of isolation by distance and haplotypeswidely distributed. On the other hand, for the species selected to represent a scenario of limited dispersive ability, Stegastes pictus, the islands are isolated from other populations most of the time, and throughout the ridge it was found to show a pattern of isolation by distance. Apparently, the islandswere connected with Columbia, the closest seamount, only during glacial maxima. This seamount also appears to have exported genetic lineages to other populations during low sea level periods, functioning as an essential stepping-stone to connect the islands to the coast. During glacial maxima, when the sea level reached 130 m below present level, the continental shelf and the seamount summits emerged, reducing the reef area available and hence the size of somepopulations. In both species, it was found that historical gene flow occurs according to the stepping-stone model, where larval dispersal is limited to, or predominantly between, adjacent populations. At ecological times, the Trindade’s population of S. pictus is maintainedby self-recruitment. This scenario shows that seamounts are essential for many species to colonizeTrindade, which corroborates the biogeographical hypothesis. The biodiversity of the Vitória-Trindade Chain has been seriously threatened by commercial and recreational fisheriesand mining. As the continuity of ecosystem goods and services depend upon the maintenance of gene flowmediated by seamounts in some cases and by in situ conservation in others, it is recommended that urgent measures to manage the use of this region be taken
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Ridge , Phylogeography , Island biogeography , Gene flow , Cordilheira , Conservation , Fluxo gênico
Citação
SIMON, Thiony Emanuel. Montes submarinos da Cadeia Vitória-Trindade como alpondras para peixes recifais. 2014. 127 f. Tese (Doutorado em Biologia Animal) - Universidade Federal do Espírito Santo, Centro de Ciências Humanas e Naturais, Vitória, 2014.