Diversity and Distribution of Octocorallia

Abstract

Octocorals are a group of striking presence in marine benthic communities. With approximately 3400 valid species the taxonomy of the group is still not resolved, mainly because of the variability of morphological characters and lack of optimization of molecular markers. Octocorals are distributed in all seas and oceans of the world, from shallow waters up to 6400 m deep, but with few cosmopolitan species (principally pennatulaceans). The Indo-Pacific is the region that holds the greatest diversity of octocorals, showing the highest level of endemism. However, endemism in octocorals as we know might be the reflex of a biased sampling effort, as several punctual sites present high level of endemism (e.g. Alaska, Antarctica, South Africa, Brazil, Gulf of Mexico). Since around 75 % of described octocoral species are found in waters deeper than 50 m, increasing knowledge on octocoral diversity and distribution is still limited by the availability of resources and technologies to access these environments. Furthermore, the limited number of octocoral taxonomists limits progress in this field. Integrative taxonomy (i.e. morphology, molecular biology, ecology and biogeography) appears to be the best way to try to better understand the taxonomy of such a diverse and important group in marine benthic communities.