Convergence in the leaf shape of vines: A test of the Carolina flora using phylogenetic comparative methods

An association between vine habit and cordate leaf shape in higher plants has been reported, but previous comparative analyses have not taken into account phylogenetic history. We surveyed the flora of the Carolinas and used phylogenetic comparative methods to test the hypothesized relationship. We found 25 phylogenetically independent vine taxa in the Carolina flora and, for each, attempted to identify its hypothesized non-vine sister taxon based upon recent phylogenetic studies. Using conservative criteria for vine habit and leaf shape determinations, a sign test revealed a significant association between the two traits. The addition of taxa for which information was slightly more ambiguous increased the strength of the association. Our findings suggest that convergence in leaf shape of vine taxa may result from a selective advantage of cordate leaves in plants with a climbing habit. We discuss possible adaptive explanations for the observed association