Genetic population structure of buckeye butterflies (Junonia) fromArgentina

Abstract

AbstractThere are nine named species of buckeye butterflies (genusJunoniaHübner) in theWesternHemisphere. There is considerable geographic variation withinJunoniaspecies, and possible ongoing hybridization between species, suggesting thatJunoniamay be a ring species, but also making this a very difficult group to define taxonomically. We tried to determine whether two forms ofJunoniafromArgentina – conventionally referred to asJunonia genoveva hilarisC. &R. Felder, the light buckeye butterfly, andJunonia evarete flirtea(Fabricius), the dark buckeye butterfly – were genetically distinct species or simply colour forms of a single species using morphological characters, mitochondrialcytochrome oxidase I(COI)DNAbarcodes, nuclearwingless(wg) locusDNAsequences, and anonymous nuclearRandomlyAmplifiedFingerprints (RAF). Phylogenetic analysis ofCOIidentified two distinct mitochondrial haplotypes that differ by about 4% sequence divergence; one confined to light‐colouredJunoniaspecimens and one shared between some light‐colouredJunoniaand all of dark‐colouredJunoniaspecimens. Analysis of nuclearwinglesssequences revealed 32 alleles among 22Junoniaspecimens and showed significant genetic differentiation between light‐coloured and dark‐colouredJunonia. Analysis ofRAFgenotypes suggests that there are actually three genetically distinctJunoniapopulations inArgentina: two with light wing coloration, and one with dark wing coloration. Genetic evidence of recent hybridization among these populations was also observed, consistent with the ring species hypothesis. Careful comparisons of morphological characters betweenArgentinianJunoniaandJunoniaspecies from elsewhere inSouthAmerica suggests that the two light‐coloured populations correspond toJ. genovevaand either a genetically disparate population of the same species or an undescribed crypticJunoniaspecies, The dark‐coloured population may correspond toJ. wahlbergiBrévignon. Our data suggest thatCOI DNAbarcodes by themselves are not very useful for studyingJunoniataxonomy, population structure or evolution.