Abstract

Acrodipsas cuprea is the only polymorphic species in an uncommon myrmecophagous radiation within the Lycaenidae in Australia. A small cryptic butterfly, it is found almost exclusively on hilltop sites in eastern Australia where several geographically localised morphotypes are recognised. This study used mitochondrial DNA sequences extracted from museum specimens to reveal whether A. cuprea morphotypes evolved in isolation, such that intermediate populations resulted from secondary contact, or whether the distribution of morphotypes was maintained solely by selection across a primary contact zone. Genetic data were also used to assess the species' dispersal ability and to explain the historical processes resulting in its extant distribution. Analysis of molecular variance found that 81% of genetic variation was distributed among colour morphs, suggesting that different wing colours had evolved in isolation. Mixed haplotypes and morphotypes in a zone separating the otherwise discrete morphological populations, particularly along the Great Dividing Range in south-east Queensland, suggests a more recent secondary admixture. Isolation by distance detected by nested clade analysis and pairwise comparisons confirmed the limited dispersal ability of A. cuprea, which was more evident in the southern part of its range. Genetic relationships among haplotypes suggest that the species originated in the drier inland areas of central Queensland, before expanding to the coast and south to Victoria.