A NEW NUCLEAR GENE FOR INSECT PHYLOGENETICS - DOPA DECARBOXYLASE IS INFORMATIVE OF RELATIONSHIPS WITHIN HELIOTHINAE (LEPIDOPTERA, NOCTUIDAE)

The lack of a readily accessible roster of nuclear genes informative a t various taxonomic levels is a bottleneck for molecular systematics. In this report, we describe the first phylogenetic application of the sequence that encodes the enzyme dopa decarboxylase (DDC). For 14 test species within the noctuid moth subfamily Heliothinae that represent the previously best-supported groupings, a 690-bp fragment of DDC reso lved relationships that are largely concordant with prior evidence fro m elongation factor-1 alpha (EF-1 alpha), morphology, and allozymes. A lthough both synonymous and nonsynonymous changes occur in DDC substan tially more rapidly than they do in EF-1 alpha, DDC divergences within Heliothinae are below saturation at all codon positions. Analysis of DDC and EF-1 alpha in combination resulted in increased bootstrap supp ort for several groupings. As a first estimate of previously unresolve d relationships, DDC sequences were analyzed from 16 additional heliot hines, for a total of 30 heliothine species plus outgroups. Previous r elationships based on DDC were generally stable with increased taxon s ampling, although a two- to eightfold downweighting of codon position 3 was required for complete concordance with the 14-species result. Th e weighted strict consensus trees were largely resolved and were congr uent with most although not all previous hypotheses based on either mo rphology or EF-1 alpha. The proposed phylogeny suggests that the major agricultural pest heliothines belong to a single clade, characterized by polyphagy and associated life history traits, within this largely host-specific moth subfamily. DDC holds much promise for phylogenetic analysis of Tertiary-age animal groups.