The ground beetle tribe Platynini (Coleoptera: Carabidae) is endemic to the Hawaiian archipelago. The three commonly accepted divisions among Hawaiian Platynini (Liebherr and Zimmerman 1998) are: Division 0, the Copocaccus species-group, Division 1, the Blackburnia species-group, and Division 2, the Metromenus species-group. Cryan et al. (2001) presented a phylogenetic tree for Hawaiian Platynini beetles, based on analysis of the ribosomal gene 28S (668 bp), the mitochondrial protein-coding genes cytochrome b (cyt-b) and cytochrome oxidase subunit II (COII), the nuclear protein-coding gene "wingless" (Wg), and 206 morphological characters for 69 species, indicating that all three Divisions are monophyletic but Division 2 is completely unresolved. Although the dynamics of molecular evolution in the Wg and COII genes of Hawaiian Platynini beetles has been described (McClellan pers. Comm.), the molecular evolution of the cyt-b gene in these beetles has not been described.
Most models used to determine the effect of selection on the molecular evolution of genes are based on the ratio of nonsynonymous to synonymous changes (ns/syn). The molecular evolution of cyt-b is usually conservative and such protein-coding genes usually have small ns/syn ratios. Therefore, the ns/syn ratio of amino acid changes is inappropriate for describing selective influences on the variable amino acid sites in conservative protein-coding genes. McClellan and McCracken (2001), however, presented a model that allows the selective influences on conservative protein-coding genes to be described. Based on this study, we predicted the dynamics of molecular evolution relative to the functional domains of cyt-b of Division 1 beetles. We tested these predictions and found that the matrix domain evolves in a nearly neutral manner, while the evolution of the transmembrane domain is constrained by a purifying selective gradient. We found little selection influencing most amino acid properties in the intermembrane domain.
Species 1: Coleoptera Carabidae Blackburnia punticeps
Keywords: nonsynonymous, functional domains
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA