Meeting Abstract

6.2  Sunday, Jan. 4  Population genetic structure of symbiotic dinoflagellates associated with Caribbean reef-building corals, Montastraea annularis and M. faveolata. THORNHILL, D.J.*; SANTOS, S.R.; Bowdoin College; Auburn University thornhill.dan@gmail.com

Symbiodinium is a highly diverse genus of unicellular dinoflagellate symbionts that associate with a variety of marine protists and invertebrates, including reef-building corals. Although the diversity and phylogenetics of the Symbiodinium complex is now well-established, there has been surprisingly few data on fine-scale population structure and biogeography in these symbionts. Here, we present data regarding the population structure of Symbiodinium hosted by the Caribbean reef-building corals Monastraea annularis and M. faveolata. Tagged coral colonies were sampled from reefs in the Florida Keys and Bahamas from 2002 – 2006 and Symbiodinium diversity was assessed using denaturing gradient gel electrophoresis of the internal transcribed spacer 2 (ITS2) rDNA and three microsatellite loci specific for Symbiodinium belonging to Clade B. The majority of individuals at a site harbor were found to harbor an identical Symbiodinium ITS2 type and clone, suggesting low symbiont population diversity per host species per site. Additionally, Symbiodinium populations within a colony remained homogeneous through time, including a prolonged 2005 high-temperature bleaching event. Notably, symbiont populations were unique to each site, suggesting low genetic connectivity between them due to Symbiodinium having a limited dispersal capability in the environment. Interestingly, neighboring colonies of M. annularis and M. faveolata harbored differing Symbiodinium populations in the Florida Keys while, adjacent M. annularis and M. faveolata colonies in the Bahamas harbored indistinguishable symbiont populations. We hypothesize that this is due to differences in the genetics of the host corals between these two regions.