Tubastraea micranthus, comments on the population genetics of a new invasive coral in the western Atlantic and a possible secondary invasion

The Indo-Pacific azooxanthellate coral Tubastraea micranthus (Cairns and Zibrowius, 1997) has successfully invaded offshore oil/gas production platforms in the Gulf of Mexico. The genetic structure of these populations has been unknown. A question has arisen regarding whether there have been multiple invasions of this species. Five platforms were surveyed; only two were found to possess populations large enough to sample – GI-93C and MC-280A. Tissue samples were collected and analyzed via Amplified Fragment Length Polymorphisms (AFLPs). STRUCTURE analysis identified four genetically distinct clusters or groups among the two platforms. The MC-280A population exhibited an overwhelming association with only one genetic group. Although the three other groups were represented, they were present in small proportions – 1–5%. By contrast, the GI-93C population showed high genetic diversity, with colonies exhibiting association with all four groups in widely varying proportions. The lack of genetic variability on MC-280A most likely resulted from a single recruitment event on this more isolated platform. It is possible that this event could have been derived from a second invasion of this species. In that case, treatment of the invasive would best be focused on the species at the vector point (e.g., treating the hull or ballast water of a ship prior to reaching its destination) rather than in the already infected environment, to avoid repeated replacement invasions. On GI-93-C, the genetic variability was most likely the result of multiple recruitment events. Other possible factors causing the observed pattern could include recruitment from genetically diverse populations in the region and sampling from an older age population where reproduction could result in admixture.