A NUCLEAR GENE FOR HIGHER-LEVEL PHYLOGENETICS - PHOSPHOENOLPYRUVATE CARBOXYKINASE TRACKS MESOZOIC-AGE DIVERGENCES WITHIN LEPIDOPTERA (INSECTA)

The sequence of phosphoenolpyruvate carboxykinase (PEPCK) has been pre viously identified as a promising candidate for reconstructing Mesozoi c-age divergences (Friedlander, Regier, and Mitter 1992, 1994). To tes t this hypothesis more rigorously, 597 nucleotides of aligned PEPCK co ding sequence (similar to 30% of the coding region) were generated fro m 18 species representing Mesozoic-age lineages of moths (Insects: Lep idoptera) and outgroup taxa. Relationships among basal Lepidoptera are well established by morphological analysis, providing a strong test f or the utility of a gene which has not previously been used in systema tics. Parsimony and other phylogenetic analyses were conducted on nucl eotides by codon positions (nt1, nt2, nt3) separately and in combinati on, and on amino acids, for comparison to the test phylogeny. The high est concordance was achieved with nt1 + nt2, for which one of two most -parsimonious frees was identical to the test phylogeny, and with all nucleotides when nt3 was downweighted sevenfold or higher, for which a single most-parsimonious tree identical to the test phylogeny resulte d. Substitutions in nt3 approached saturation in many, but not all, pa irwise comparisons and their exclusion or severe downweighting greatly increased the degree of concordance with the test phylogeny. Neighbor -joining analysis confirms this finding. The utility of PEPCK for phyl ogenetics is demonstrated over a time span for which few other suitabl e genes are currently available.