Meeting Abstract

S8.3  Wednesday, Jan. 6  Intragenomic ITS2 (rDNA) variation in octocorals: ancestral polymorphisms or footprints of reticulate evolution? SANCHEZ, Juan A.; Universidad de los Andes, Bogotá, Colombia juansanc@uniandes.edu.co

Ribosomal DNA is supposed to evolve via concerted evolution resulting in the homogenization of its copies. However, variations within individuals have been reported in diverse eukaryotes. Regrettably, there is no proper way to evaluate if the IntraGenomic Variation (IGV) is the result of recent hybridization or incomplete lineage sorting. Here we tested, examining several groups of octocorals, if IGV has reticulate evolution signals. The ITS2 variation was assessed with DGGE, sequencing, secondary structure prediction, and phylogenetic approaches. Results were compared against mitochondrial phylogenies. Little IGV was found in deep-sea genera such as Paragorgia and Corallium, and shallow-water genera such as Plexaurella and Leptogorgia. In contrast, extensive IGV was detected in the deep-sea family Isididae and the shallow-water genera Gorgonia, Pseudopterogorgia, Eunicea, Muricea and Pacifigorgia. Phylogenetic analyses among the recovered intragenomic variants exhibited polyphyletic patterns. Most groups involving IGV exhibited mito-nuclear discordance. An interpretation of reticulate evolution is suggested for the origin of Gorgonia mariae (a brooder) as hybrid between Pseudopterogorgia (brooder) and Gorgonia (broadcast spawner) ancestors. Other cases, such as Eunicea, Muricea and Pacifigorgia with low divergence among species, suggest patterns related to recent burst-like adaptive radiations. Another approach is being tested to corroborate these results: Nucleolar Dominance, a potentially useful tool for assessing hybridization thanks to the epigenetics of rDNA transcription.