Title: FITTING A PIECE IN THE SOUTH ATLANTIC PUZZLE: SEAMOUNTS AS STEPPING-STONES BETWEEN MAINLAND AND OCEANIC ISLANDS

Abstract: The puzzling pattern that arises from the disjunct distribution of tropical reef fishes in the South Atlantic indicates that stepping-stone habitats are not required for ocean-wide dispersal, but they may be important for short routes between oceanic islands and mainland. Trindade and Martin Vaz, 1,200 km off the Brazilian coast, are the only exposed peaks of a volcanic ridge, the Vitória-Trindade Chain (VTC), and show high species richness when compared to other remote islands of the Atlantic. The seamounts of the VTC, which summits today are in mesophotic depths (average 50 m), have been suggested to serve as stepping-stones between the continental shelf and the islands. A comparative phylogeographic approach was used to understand the role of seamounts for fish diversity on islands, helping solve the South Atlantic puzzle. Two reef fishes collected throughout the VTC were analyzed for both mtDNA (cytochrome b and control region) and nDNA (8-12 microsatellite loci) markers. Populations from the continental shelf and seamounts have undergone severe bottlenecks associated to habitat loss during glacial low sea level stands, while those from the islands apparently experienced more stable conditions. A clear signal of isolation by distance was found in the species with lower dispersal ability, evidencing that seamounts are important for increasing the reef fish richness on the remote islands. A biodiversity feedback, controlled by sea level fluctuations, was identified amongst islands, seamounts and mainland, showing that peripheral locations are not evolutionary graveyards.

Authors: Simon T, Pinheiro HT, Macieira RM, Rocha LA, Santos S, Joyeux JC

Presentation: Oral

Session: 28A

Date: 06/20/16

Time: 15:00

Location: 308 A/B

Back