Mitochondrial DNA sequence variation among populations and host races of Lambdina fiscellaria (Gn.) (Lepidoptera : Geometridae)

The hemlock looper, Lambdina fiscellaria (Gn.), is a recurring major forest pest that is widely distributed in North America. Three subspecies (L. f. fiscellaria, L, f. lugubrosa (Hulst) and L. f. somniaria (HuIst)) have been recognized based on larval host or adult pheromone differences, but no con sistent morphological differences have been reported. To clarify their taxo nomic status, we surveyed mitochondrial DNA (mtDNA) sequence and restrictio n site variation in two protein coding genes, cytochrome oxidase I and II ( COI and COII), in populations across the range of L. fiscellaria, In additi on to variation in COI and COII, we found an intergenic spacer region of 20 -23 bp located between the tRNA tyrosine gene and the start of COI, Of the 141 specimens of L, fiscellaria assayed, 137 were grouped into two distinct mtDNA lineages, one of which was disproportionately associated with easter n populations and one with western populations. However, single specimens a nd two populations in eastern Canada had mtDNA resembling that of western p opulations. Three divergent and rare haplotypes had basal affinities to the two common lineages. The two major lineages of L, fiscellaria were diverge d by approximately 2% from each other, as well as from the mtDNA of two out group species, L. athasaria (Walker) and L. pellucidaria (G. & R.). The two outgroup species had essentially the same mtDNA and may be conspecific, We interpret the pattern of mtDNA variation within L. fiscellaria as indicati ng genetic polymorphism within a single species without clear subspecific d ivisions, rather than evidence of multiple cryptic species.