Living Reference Work Entry

Marine Animal Forests

pp 1-33

Date: Latest Version

Diversity and Evolution of Octocoral Animal Forests at Both Sides of Tropical America

  • Juan Armando SánchezAffiliated withDepartamento de Ciencias Biológicas-Facultad de Ciencias, Laboratorio de Biología Molecular Marina (BIOMMAR), Universidad de los Andes Email author 

Abstract

Octocoral animal forests (Gorgoniidae and Plexauridae: Octocorallia) at both sides of tropical America provide a unique and characteristic seascape. They can reach over 2 m in height and even form a closed “canopy” in the densest communities. As a functional forest, gorgonian corals provide feeding substrate and habitat for diverse associated biota. This shallow-water fauna was evidently affected by the closure of the Isthmus of Panama, which provided new and different ecological opportunities at both sides. The different ecological settings provided opportunities for these groups to undergo separate adaptive radiations. New ecological conditions could lead to diversification in this group. At the Tropical Eastern Pacific (TEP), new planktonic resources provided new niches for suspension-feeding organisms, such as azooxanthellated gorgonian corals, and could have driven an adaptive radiation to exploit the new food sources. In the Caribbean, there is evidence of ecological speciation in some genera, and the scenario of ecological divergence as a major driver of gorgonian coral diversification is very likely. Thus far, the developmental phenotypic plasticity that we see today in transisthmian gorgonian corals is not just the product of speciation but adaptive developmental plasticity, and it needs further study. Gorgonian corals are today affected by many of the stressors predicted by global change, such as an increase in the frequency and intensity of tropical storms, rising seawater temperatures, and invasive species, yet these cnidarians seem highly resilient to bleaching and ocean acidification conditions. However, there is a link between high thermal anomalies and gorgonian coral immunity, which is associated to disease outbreaks and mass mortalities in sea fans in the Caribbean since the 1980s and more recently in the TEP.

Keywords

Octocorals Gorgonian corals Ecological speciation Adaptive radiation Ocean acidification Octocorallia Zooxanthellae Global climate change Emerging marine diseases Aspergillosis