SICB Division of Invertebrate Zoology (DIZ)

DIZ Researchers Database Entry

Robert Thacker

Sponge-Microbe Symbioses
My research program integrates molecular and chemical ecology to examine the evolution and ecology of sponge-microbe symbioses. Symbiotic microbial communities provide model systems for studying the evolution of community structure. A fundamental question concerns whether symbionts are (1) distributed independently among host organisms (or communities); (2) distributed as functional groups, with one representative of each functional group in each community; or (3) distributed as strictly coevolved lineages. The three species of Dysideid sponges pictured above (Dysidea granulosa, Lamellodysidea herbacea and L. chlorea) each host a genetically distinct strain of the cyanobacterial symbiont Oscillatoria spongeliae, providing preliminary evidence for host-symbiont cospeciation (Thacker and Starnes 2003). I am currently conducting an expanded analysis of Dysidea-Oscillatoria cospeciation as well as analyses of bacterial community structure across large geographic and phylogenetic scales. Since many interactions within sponges can be regulated by secondary metabolites, these communities provide an opportunity to explore the impact of chemical signals on the evolution of community structure. In addition, sponge-microbe associations serve as model systems for examining the evolution of a full range of symbiotic interactions, including mutualism, commensalism, and parasitism (Thacker 2005).

Thacker, R. W., and S. Starnes. 2003. Host specificity of symbiotic cyanobacteria, Oscillatoria spongeliae, in marine sponges, Dysidea spp. Marine Biology 142: 643-648.
Thacker, R. W. 2005. Impacts of shading on sponge-cyanobacteria symbioses: a comparison between host-specific and generalist associations. Integrative and Comparative Biology 45(2): In press.