Cytochrome b (cyt-b) is widely used in molecular phylogenetic studies of vertebrate, but not invertebrate, taxa. To determine whether this situation is an historical accident or reflects the utility of cyt-b, we compared the abilities of cyt-b, COI, and one nuclear ribosomal gene region (D1 of 28S) to recover intergeneric relationships within the tiger moth tribes Ctenuchini and Euchromiini. Additionally, we compared the rate of sequence and amino acid evolution of cyt-b across insects. Cytochrome b had the same level of sequence variation and A/T bias as COI, but was less useful for recovering intergeneric relationships. The total evidence tree casts doubt on the traditional taxonomy of the group. For the class Insecta, we found that functional conservation of amino acids occurs for the same regions as those found in vertebrates with the exception of Mallophaga (lice). Lice have an accelerated rate of nonsynonymous substitutions. Accelerated rate of cyt-b nucleotide and amino acid evolution in Apidae (bees) may be correlated with increased metabolic rates associated with facultative endothermy (= heterothermy).
Bibliographical noteFunding Information:
We thank the following for their comments: two anonymous reviewers, A. Kessen, A. Prather, S. Lanyon, and R. Zink. S. Farrell aided in laboratory work and data collection. J. Moe assisted with Fig. 1. We thank R. Holzenthal (University of Minnesota, Insect Collection) for providing museum material. Simmons’ fieldwork was funded by a Theodore Roosevelt grant (American Museum of Natural History) and a Dayton-Wilkie grant (Bell Museum of Natural History). Additional funding was provided by NSF Doctoral dissertation improvement grant, DEB-9706192 (R. Simmons) and NSF DEB-9306755 and Grant-in-Aid, University of Minnesota (S. Weller).
- Cytochrome b
- Metabolic rate hypothesis