Heather Driscoll, Botany & Mycology 2009 Poster Interviews

Molecular phylogeny of the genus Costus (Costaceae). Co-authors: Irene T. Liao, Yizhuo Wang and Chelsea Specht The genus Costus (Costaceae) is a large group of perennial herbs distributed in the moist rainforests of both the New and Old World tropics with its center of species diversity in the neotropics. A genus-wide molecular phylogeny for Costus, including 84 ingroup taxa and two outgroup taxa (Monocostus uniflorus and Chamaecostus lanceolatus), was reconstructed to explore evolutionary trends in floral morphology, pollination biology, and biogeography of the group. The phylogenetic analysis is based on two nuclear ribosomal sequences — the internal and external transcribed spacers (ITS and ETS) —and the 23rd intron of the low copy nuclear gene RNA polymerase II (RPB2) from a taxonomically and geographically diverse sample. Parsimony and Bayesian phylogenetic analyses of the combined data support a monophyletic Costus and corroborate recent hypotheses as to membership and sequence of origin of the major groups within the genus. Neotropical Costus represents a rapidly evolving, monophyletic group, which remains inadequately resolved, while African Costus form a paraphyletic group comprised of several early-diverging lineages each comprised of a few closely related species.