Molecular Analysis of Morphologically Defined Taxa in the Montastraea Annularis Complex

点击翻译按钮获取中文摘要

Failure to accurately define and identify species fundamentally compromises our ability to understand and manage marine ecosystems. The problem is particularly acute on reefs, where there is no consensus on the species status of the numerous ecologically and morphologically distinct `forms` that comprise many important groups of corals. While the problematic nature of coral species is widely recognized, there is no consensus as to why this problem exists. Some scientists argue that extensive and complex patterns of hybridization make species boundaries arbitrary in corals, but the data to test this assertion are largely lacking, particularly for Caribbean corals. In this project, Dr. Knowlton and collaborators will tackle this problem using the star coral, Montastraea annularis, as a model system. This coral is the most abundant coral of the Caribbean, and has been for millions of years. It has been extensively studied by biologists and geologists as a kind of `lab rat` for a wide variety of studies (e.g. coral bleaching, paleoclimatology), but recent results suggest that what had been viewed as a single polymorphic species may represent a complex of at least three reproductively isolated forms that can be identified by their colony morphologies. Previous work was on coral genetics, symbiosis, morphometrics and reproductive biology but the genetic patterns on wide geographic scales are of fundamental importance. If the three taxa comprising Montastraea annularis do not routinely interbreed, then fixed diagnostic differences should in principle be detectable. Dr. Knowlton has already uncovered a few fixed or nearly fixed differences using amplified fragment length polyinorphism (AFLP) and restriction fragment length polymorphism (RFLP) between M. faveolata and the other two taxa. She has as yet found no fixed genetic differences between M. annularis and M. franksi, but they appear to spawn at distinct times throughout their range, suggesting that they are not genetically identical. In this project, she will continue to screen for genetic differences among these taxa, in order to determine if hybrids between M. faveolata and the other taxa can be detected and to see if more extensive searches will reveal differences between M. annularis and M. franksi. She will also extend the genetic analyses from Panama to other sites in the Caribbean, to determine if the patterns observed here are also seen elsewhere. This will be the first such genetic analysis of a reef coral species complex throughout its geographic range.