Environmental Complexity and Species Diversity in the Gastropod Genus Conus on Indo-West Pacific Reef Platforms

Species diversity of assemblages of the gastropod genus Conus occurring on tropical Indo-West Pacific reef platforms increases in the following order of habitat types: (1) extensive regions of sand substrate (mean number of species N = 3.0; mean species diversity H = 0.5); (2) intertidal smooth limestone plantforms (mean N = 7.6; mean H = 1.3); (3) topographically complex subtidal coral reefs (mean N = 13.7; mean H = 2.1). The census data show a close correlation between N and H (Spearman r = 0.93). The absence of a longitudinal gradient of species number and diversity in the uniform Type II habitats over 160⚬ of longitude, despite reports of larger total numbers of species near the "faunistic center" of the Indo- West Pacific region, also supports the conclusion that habitat complexity is an important determinant of species diversity. Type III habitats near the "faunistic center" have more diverse assemblages than those of outlying areas east and west, but it has not been possible to distinguish the roles of habitat complexity and other possible determinants of species diversity gradients.