Meeting Abstract

S10-2.3  Saturday, Jan. 7  Biogeography of the widespread intertidal barnacle Chthamalus malayensis in Indo-Pacific waters: the interplay of geological history, contemporary ocean circulation patterns and habitat specificity CHAN, B.K.K.*; TSANG, L.M.; NG, W.C.; WILLIAMS, G.A.; CHU, K.H.; Academia Sinica, Taiwan; The Chinese Univ. of Hong Kong, Hong Kong; Univ. of Hong Kong, Hong Kong; Univ. of Hong Kong, Hong Kong; The Chinese Univ. of Hong Kong, Hong Kong chankk@gate.sinica.edu.tw

Chthamalus malayensis is a widespread rocky shore barnacle in the Indo-Pacific. To examine the possible factors affecting the distribution of C. malayensis, samples were collected from the South China Sea to the West Indian Ocean. In each location, distribution patterns were scored and at least 30 barnacles were collected. COI genes were sequenced, revealing four distinct clades. The South China Sea Clade (SC) is widely distributed and occurs in high abundance (70% cover) in the South China Sea. In Taiwan, the SC clade is sparse but there is an endemic Taiwan Clade (TC) which occurs at low densities (10% cover). In the Gulf of Thailand, Malacca Strait, N Borneo, Bay of Bengal and Arabian Sea, the Indo-Malay Clade (IM) is present (60% cover). In Christmas Island, there is a South Indian Ocean Clade (SI). Separation of the IM and SC clades in the Indian and Pacific Ocean, respectively, is probably due to isolation of the two oceans during the Pleistocene glaciations. The distribution of the SC and IM clades does not appear to be explained by present day ocean currents, and their wide distributions may result from low habitat specificity as both are abundant on exposed to sheltered rocky shores. These clades, therefore, colonize a wide range of habitats, which act as stepping stones for larval dispersal across oceanographic systems. The TC clade appears to be specific to exposed rocky shores and its distribution may be limited by its low abundance. The endemism of the SI clade suggests that this clade cannot cross the distinct horizontal Hydrochemical Front around 10oS in the Indian Ocean.