Molecular Systematics of the Lower Lepidoptera

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Phylogenetic relationships within insects, the most diverse class of organisms, are a major unsolved systematic problem. Nucleotide sequence characters could be a key part of the answer, but there have been only a few studies, based mostly on the same gene. One model system is the enormous order Lepidoptera (150,000 species), subject of innumerable comparative research programs whose well-studied basal relationships provide a strong test for the utility of new molecules. Prior to this project, computer search, Southern hybridization, and polymerase chain reaction (PCR) studies were used to identify five previously untested nuclear genes which appear suitable for higher-level phylogenetics (elongation factor-l (alpha), the largest subunit of RNA polymerase II, dopa decarboxylase, elongation factor-2, phosphoenolpyruvate carboxykinase). Oligonucleotide primers were synthesized for all five genes, plus the nuclear ribosomal RNA gene, and tested for successful genomic amplification in primitive Lepidoptera and related panorpoid orders. Portions of the elongation factor-1 (alpha) and ribosomal genes have been sequenced directly from PCR products for 6 and 11 taxa, respectively. The resulting trees, under several analytical methods, show concordance with morphology. Additional studies will complete evaluation of potentially informative nuclear genes by sequencing larger portions of elongation factor 1 (alpha), RNA polymerase II and the ribosomal gene in 15 species that together represent relationships strongly supported by morphology within basal Lepidoptera and closely related orders. Trees constructed by independent analyses of each gene will be tested for concordance with each other and with the morphological phylogeny. For genes showing strong concordance, the analysis will then be extended to an additional 20 moth species that sample, in duplicate, all major lower lepidopteran lineages, including problematic relationships; sufficiently conservative genes will additionally be used to initiate a broader study of relationships among panorpoid orders.