A METHOD FOR QUANTIFYING THE BUMPINESS IN COLONY SHAPE FOR THE REEF CORAL MONSTASTRAEA ANNULARIS AND RELATIVES

The reef coral species Montastraea annularis has been used in a wide range of investigations such as coral bleaching, symbiosis, paleoecology, and paleoclimatic reconstructions. Recently, Montastraea annularis has been recognized as a complex of three sibling species based on field observations of variation in colony shape. Historically, colony shape had been ignored as a discriminator of species based on the wide-spread viewpoint that it was controlled by ecophenotypy. However, new methods in molecular biology as well as morphometrics of corallites have confirmed field discriminations of the three sibling species.

Here I present a new quantitative method for measuring colony shape, which initiated re-evaluation of M. annularis, based on geostatistics. I gathered data from 17 total colonies collected from San Blas, Panama in 1995 and 1996. All of the specimens were collected from approximately 10 meters depth. I collected three-dimensional coordinates of the center of several hundred corallites of a colony using Polhemus 3SPACE FASTRAK system, which consists of a 3D-digitizing stylus. In order to understand the relative amount of bumpiness in colony shape better, I analyzed the three-dimensional data using geostatistic methods in two different ways: 1) variation in heights of corallites and 2) the compactness of the corallites. Both of these methods measure the larger bumps or “ridges” as well as the smaller bumps or “lumps” of the colonies. Next, I calculated variograms for all the specimens for both of the methods listed above. Last, I used the lag distances and the values of the variogram in a principal components analysis followed by a discriminant analysis.

Overall, this method indicates that M. annularis and M. faveolata overlap in their relative amount of bumpiness in colony shape while M. franksi is distinct from the other two species. In the future, work needs to be done to expand the sample size and to fine tune this method. This method has great implications for both the Recent and fossil record.