DATA: Selected EST sequences from Eytan et al. 2009

PRESENT:  
spawning coral
Sperm from a spawning coral.
Photo: Michael S. Taylor.
Trans-Pacific gene flow and species delimitation in Porites The reef-building Porites found in the Eastern Pacific are a subset of more diverse Central and Western Pacific coral assemblages. Are these faunal similarities the vestiges of past (pre-Pleistocene) connections, or the result of ongoing genetic exchange, perhaps aided by current reversals during El Nino events? In collaboration with Iliana Baums, we are completing an NSF-funded project that has generated nuclear sequence and microsatellite markers that will enable us to answer this and other questions.
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Planula Larva
Planula larva from Balanophyllia rarely move more than 40cm from the parental
polyp.
Photo: Richard Grosberg.
Large-scale (100-3000 km) genetic subdivision in a coral with limited larval dispersal potential was extensive, but not as great as predictedby stepping stone models. The discrepancy between observed levels of gene flow between populations of Balanophyllia elegans (estimated using allozyme markers) and computer simulations suggests nonequilibrium conditions prevail. Relatively low numbers of alleles per locus in parts of Balanophyllia's range recently covered by glaciers supports this idea (Hellberg 1994 Evolution 48: 1829-1854). To further test this idea, I looked at gene flow at a smaller spatial scale (1-50 km) and found gene flow matched equilibrium stepping stone expectations (Hellberg 1995 Marine Biology 123: 573-581). Gene flow in a coral with planktonically dispersed larvae was high, and did not decrease with geographic distance (Hellberg 1996 Evolution 50: 1167-1175).

 
Clonal reproduction and population connectivity in Acropora
Acropora palmata is a shallow water, branching hermatypic coral that is a gallmark of healthy Caribbean reefs. Because the geographic distribution of A. palmata spans many national boundaries, estimating levels of population connectivity is a critical first step to any management plan. As part of her Ph.D. thesis, Iliana Baums generated several microsatellite markers for A. palmata, verified that they were single-copy, coral-specific, and Mendelian using controlled crosses (Baums et al. 2005 MEPS 288:115-127). Analysis using STRUCTURE indicates a genetic break between A. palmata populations in the western and eastern Caribbean occurring near the Mona Passage (Baums et al. 2005 Mol Ecol. 14: 1377-1390). In part because of this work, A. palmata has now been listed as "threatened" under the U.S. Endangered Species Act, the first marine invertebrate to be so designated. Margaret Miller is a collaborator on this work, which was funded by NOAA.

Balanophyllia elegans
Balanophyllia elegans.
Photo: Michael E. Hellberg.
MtDNA variation (not) in Balanophyllia elegans A geographic survey of mtDNA sequences from B. elegans revealed greatly depressed mtDNA mutation rates, over 100x slower than those of most other animals (Hellberg 2006 BMC Evol Biol 6: 24). We would like to look for repair genes that might be responsible. We are also interested in resurveying the original B. elegans population samples for DNA sequence variation underlying observed allozyme differentiation.
 
Species status of Oculina varicosa
O. varicosa forms large deep water reefs off the eastern Florida coast that provide valuable nursery habitat for several fisheries. These fragile reefs have been much damaged by fishing dredges. Using sequence data from three nuclear markers, we showed that deep water populations of O. varicosa are distinct from congeners that occur along the southeastern US (Eytan et al. 2009). As part of work funded by NOAA and carried out in collaboration with Marshall Hayes, we have generated EST's for O. varicosa and have found a candidate gene that may be involved in defending corals against microbial pathogens (Hayes et al. 2010).

 

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