Toward Understanding the Genetic Basis of Mimetic Color Pattern in Limenitis lorquini

Grave Covell

Mimicry is a crucial antipredator defense in insects that involves the convergence of color pattern between unrelated species. Two classic examples of mimicry in North America involve the butterfly genus Limenitis. In Eastern North America, the well-defended distasteful species Danaus plexippus (Monarch) and Battus philenor (Pipevine swallowtail) are mimicked by the moderately defended L. archippus (Viceroy) and L. arthemis astyanax (Red-spotted purple) respectively. Additionally, in Western North America the palatable Limenitis lorquini (Lorquin’s admiral) mimics the unpalatable model Adelpha bredowii (California sister). The mimicry in L. lorquini involves an orange patch on the apex of the forewing. The genetic basis of this trait, including the number of loci involved, is currently unknown. We investigated this by taking advantage of a natural hybrid zone between L. lorquini and a species with a black forewing apex, L. weidemeyerii. These two species are known to hybridize and produce fertile offspring in eastern California. We crossed the orange-tipped L. lorquini with black- tipped L. weidemeyerii (parental generation) which produced an F1 hybrid generation that all displayed orange forewing coloration. We then self-crossed several of the F1 hybrids with the prediction that the F2 offspring would exhibit a 3:1 ratio of orange-tipped to black-tipped individuals. Our results are consistent with a 3:1 Mendelian ratio indicative of a trait controlled by a single locus with two alleles. In this case we conclude that the allele for orange color is dominant to the recessive black allele for forewing apex coloration.