Utility and evolution of cytochrome b in insects

Cytochrome b (cyt-b) is widely used in molecular phylogenetic studies of ve rtebrate, but not invertebrate, taxa. To determine whether this situation i s 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 Ctenuchi ni and Euchromiini. Additionally, we compared the rate of sequence and amin o acid evolution of cyt-b across insects. Cytochrome b had the same level o f sequence variation and A/T bias as COI, but was less useful for recoverin g intergeneric relationships. The total evidence tree casts doubt on the tr aditional taxonomy of the group. For the class Insecta, we found that funct ional conservation of amino acids occurs for the same regions as those foun d in vertebrates with the exception of Mallophaga (lice). Lice have an acce lerated rate of nonsynonymous substitutions. Accelerated rate of cyt-b nucl eotide and amino acid evolution in Apidae (bees) may be correlated with inc reased metabolic rates associated with facultative endothermy (= heterother my). (C) 2001 Academic Press.