Meeting Abstract

P2.3  Friday, Jan. 4  Morphological variability of Lytechinus variegatus across its geographic range WISE, ML*; RITTSCHOF, D; Duke University Marine Laboratory mlw15@duke.edu

Morphological traits are an important diagnostic tool in species identification and classification. Recent genetic and molecular tools have shown that in many instances morphological differences correlate closely with genetic differences, while in other instances they don�t. Many morphologically similar species are genetically distinct. In the marine environment many organisms with broad geographical ranges have large intraspecific variability making identification and classification difficult. One highly variable species is the sea urchin Lytechinus variegatus, common along the western Atlantic from North Carolina to southern Brazil and throughout the Caribbean. As its name implies this urchin is variable in visual morphological features. Previous research on color patterns and test morphometric data indicated that the differences warranted subdivision into three subspecies. Recent genetic data reduce it to two subspecies. Here we examine test morphological traits from several sites throughout the geographical range to quantify differences between sites and determine how these differences relate to the current taxonomic subdivision. Morphological features of the test, such as weight versus diameter, mean thickness, H/D (height-diameter) ratio and spine thickness show striking differences among sites. The Caribbean populations have thinner, more rounded and fragile tests and longer and thinner spines while the northern and southern Atlantic populations have flatter, thicker and sturdier tests and thicker spines. The differences broadly correlate with current classification. These differences may signal important physiological adaptations to the heterogeneity of L. variegatus habitats. While morphology may not be the diagnostic tool it once was, it yields important information suitable for investigation of physiological differences between populations that may have important ecological and evolutionary implications.