RETICULATE EVOLUTION BY HYBRIDIZATION IN CORALS

Abstract

Hybrid speciation and adaptive introgression have been recognized as mechanisms promoting biodiversity in animals. For corals with high morphological variation, hybridization is being considered as a possible explanation of phylogenetic incongruences. For instance, in the Caribbean Sea, it has been shown that Acropora prolifera contains a haplotype from each of its parents (A. cervicornis and A. palmata) and intermediate morphology. Because of the polyphyly and paraphyly, in addition to crosses between species, it is suggested that hybridization has an important role in the evolution of Acropora and other corals. Moreover, it has been proposed that the evolution of Acropora is in a reticulate pattern owing to a syngameon. Nevertheless, in some cases it has not been possible to state the reason of morphological and genetic variation since it was not possible to differentiate between introgressive hybridization and other process such as incomplete linage sorting, convergence and ancestral polymorphism selectively maintained. To review the empiric evidence of reticulate evolution by hybridization in corals, here, I reviewed published research on the morphologic and phylogenetic evidence of possible events of hybridization. Additionally, I analyzed the reproductive barriers and the results of interspecifi crosses of species that synchronically spawn their gametes. Moreover, I reviewed the effect of hybridization on coral biodiversity and a possible adaptation of corals under climate change. In conclusion, up today, there is no evidence of hybrid speciation in corals. Thus, the use of new methodologies of next generation is needed as a way to looking for hybridization or introgression signals in order to state whether hybrid speciation and/or adaptive introgression are forces driving the great coral diversity.