Mitochondrial DNA sequence variation among pheromotypes of the dingy cutworm, Feltia jaculifera (Gn.) (Lepidoptera: Noctuidae)

Abstract

The dingy cutworm, Feltia jaculifera, is a complex of at least four pheromonal races (pheromotypes). We examined mitochondrial DNA (mtDNA) sequence and restriction-site variation in the cytochrome oxidase subunit I and II genes. Among 74 specimens representing the four pheromotypes, we found three discrete mitochondrial lineages. The most divergent mtDNA within F. jaculifera, the γ lineage, was associated with pheromotype C. This result confirms an earlier allozyme survey, which also found that pheromotype C was the most genetically distinct race. Thus, pheromotype C probably represents a classic sibling species. Of the two most similar mitochondrial lineages, the α lineage was disproportionately associated with pheromotype A and the β lineage was disproportionately associated with pheromotypes B and D. Although the correspondence between mitochondrial lineages and pheromotypes was incomplete, mtDNA variation provides strong nonbehavioral evidence for genetic divergence between pheromotypes A and B + D. Allozymes revealed more minor differentiation among the A, B, and D races. For pheromotypes A and B, the presence of distinct mtDNA lineages within populations without perfect correspondence to pheromone polymorphism has several possible explanations. It may be due to retained ancestral mtDNA polymorphism, whether initial divergence of pheromone races occurred in allopatry or sympatry, or to divergence in isolation with introgression following secondary contact. The greater differences in allele frequencies of mtDNA than of allozymes may be due either to the susceptibility of mtDNA to bottleneck effects or to asymmetric selection against hybrid females.