Meeting Abstract

P3.40  Wednesday, Jan. 6  Adaptive radiation in Eastern Pacific sea fans? TABIMA, J.F.*; GRANADOS, C.; MANRIQUE, N.; ARDILA, N.; SáNCHEZ, J.A.; Universidad de los Andes; Universidad de los Andes; Universidad de los Andes; Universidad de los Andes; Universidad de los Andes j-tabima@uniandes.edu.co

New environments and niches provide ecological opportunities facilitating adaptive radiations. Compelling evidence for a burst-like rapid adaptive radiation is found in the Eastern Pacific sea fans (Pacifigorgia: Gorgonidae: Octocorallia). With only one species in the Atlantic, it is suggestive that since the closure of the Isthmus of Panama a few ancestral species turned into about 30 morphological species. Up to one order of magnitude difference can be observed among the mesh sizes of these suspension-feeding corals. Mitochondrial trees using several coding genes (msh1, ND2 and ND6) indicated lack of phylogenetic resolution among species. Non-monophyletic relationships were also detected within the ITS2 intragenomic variation in the same species. Pacifigorgia firma, P. rubicunda and P. media had consistent signal for sharing ITS2 ancestors from disparate places in the phylogeny. Low phylogenetic resolution and divergence were observed with both nuclear and mitochondrial sequences. Mito-nuclear discordance was evident in contrast to very similar diversification times. Molecular clocks for ITS2 and msh1 genes showed that most radiations occurred after the rise of the Isthmus. The information gathered suggests a rapid adaptive radiation scenario for this group, which could involve reticulate evolution. The rise of the isthmus induced dramatic oceanographic changes at both sides, the Caribbean turned oligotrophic whereas the Eastern Pacific turned in a productive environment with a luxuriant diversity and biomass of plankton. The offer of new resources allowing new niches for suspension feeding organisms, such as sea fans, could drive an adaptive radiation for these corals.