MULTIPLE ORIGINS OF A SPIDER RADIATION IN HAWAII

The Hawaiian Islands are renowned for some of the most spectacular spe cies radiations in the world. Most of these radiations have been attri buted to single colonization events, although the evidence supporting monophyletic origins is often poorly resolved and/or ambiguous. Withou t a concrete understanding of the origins of species radiations, it is impossible to understand the phylogenetic pattern of species prolifer ation or the spectrum of morphological, ecological, and behavioral mod ifications attributable to a single colonist. In this study we examine d the species radiation of the spider genus Tetragnatha in Hawaii. Unl ike their mainland congeners, the Hawaiian Tetragnatha are extremely d iverse in morphology, ecology, and behavior. We tested whether this di versity arose from a single or multiple colonization events. We couple d morphological (37 characters) and molecular (sequence from the 12S r ibosomal subunit of mitochondrial DNA) approaches to assess the phylog enetic position of the Hawaiian Tetragnatha relative to continental co ngeners and to examine evidence for monophyly. We provide evidence tha t the Hawaiian Tetragnatha emanate from multiple origins. At least two independent species radiations, the ''spiny-leg'' clade and the web-b uilding species Tetragnatha stelarobusta and Tetragnatha acuta, have a risen from one or more founder events. Two additional natural coloniza tions have resulted in the establishment of non-speciose lineages, as represented by Tetragnatha hawaiensis and Doryonychus raptor.