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Background: Brazil's Atlantic Forest is a biodiversity hotspot endangered by severe habitat degradation and fragmentation. Habitat fragmentation is expected to reduce dispersal among habitat patches resulting in increased genetic differentiation among populations. Here we examined genetic diversity and differentiation among populations of two Heliconius butterfly species in the northern portion of Brazil's Atlantic Forest to estimate the potential impact of habitat fragmentation on population connectivity in butterflies with home-range behavior. Results: We generated microsatellite, AFLP and mtDNA sequence data for 136 Heliconius erato specimens from eight collecting locations and 146 H. melpomene specimens from seven locations. Population genetic analyses of the data revealed high levels of genetic diversity in H. erato relative to H. melpomene, widespread genetic differentiation among populations of both species, and no evidence for isolation-by-distance. Conclusions: These results are consistent with the hypothesis that the extensive habitat fragmentation along Brazil's Atlantic Forest has reduced dispersal of Heliconius butterflies among neighboring habitat patches. The results also lend support to the observation that fine-scale population genetic structure may be common in Heliconius. If such population structure also exists independent of human activity, and has been common over the evolutionary history of Heliconius butterflies, it may have contributed to the evolution of wing pattern diversity in the genus. [ABSTRACT FROM AUTHOR]

I described the development of degenerate polymerase chain reaction (PCR) primers for intron-containing regions of nine candidate wing patterning and pigmentation genes in Heliconius butterflies. Primers were developed by comparing sequence data from Drosophila melanogaster, Precis coenia, and a variety of other insects so they are likely to be applicable widely among the butterfly family Nymphalidae and perhaps Lepidoptera in general. The amplified regions are highly variable and should be useful for inferring relationships among closely related species and estimating the phylogeographical and population genetic structure of individual species. [ABSTRACT FROM AUTHOR]

North American Speyeria butterflies are a group of conservation concern and a challenge to butterfly systematists. Establishing species delimitation and evolutionary relationships among Speyeria has proven difficult due to the polytypic nature of many species, coupled with the similarity of wing patterns of sympatric species. Recent molecular work has found not all Speyeria species to be monophyletic, which could be explained by improper species definitions, incomplete lineage sorting, or ongoing hybridization and introgression. However, these studies involved broad geographic sampling where molecular markers such as the DNA barcode may be especially subject to incomplete lineage sorting. Here we focus on a more local scale, analyzing the mitochondrial gene cytochrome oxidase subunit I (CoI) to test whether this marker recovers four sympatric Speyeria species: adiaste (W. H. Edwards, 1864), callippe (Boisduval, 1852), coronis (Behr, 1864), and zerene (Boisduval, 1852), in the greater San Francisco Bay Area. We found that CoI works well to separate all four species. Subspecies were less well-defined, with the S. adiaste subspecies clustering separately, but more mixed for the S. zerene and S. callippe subspecies. Overall, our analyses illustrate the utility of the DNA barcode for separating the Speyeria species and suggest further studies to investigate different geographic scales in order to elucidate genetic diversity patterns in this genus in North America. [ABSTRACT FROM AUTHOR]

Sexual dimorphism is a major component of morphological variation across the tree of life, but the mechanisms underlying phenotypic differences between sexes of a single species are poorly understood. We examined the population genomics and biogeography of the common palmfly Elymnias hypermnestra , a dual mimic in which female wing colour patterns are either dark brown (melanic) or bright orange, mimicking toxic Euploea and Danaus species, respectively. As males always have a melanic wing colour pattern, this makes E. hypermnestra a fascinating model organism in which populations vary in sexual dimorphism. Population structure analysis revealed that there were three genetically distinct E. hypermnestra populations, which we further validated by creating a phylogenomic species tree and inferring historical barriers to gene flow. This species tree demonstrated that multiple lineages with orange females do not form a monophyletic group, and the same is true of clades with melanic females. We identified two single nucleotide polymorphisms (SNPs) near the colour patterning gene WntA that were significantly associated with the female colour pattern polymorphism, suggesting that this gene affects sexual dimorphism. Given WntA 's role in colour patterning across Nymphalidae, E. hypermnestra females demonstrate the repeatability of the evolution of sexual dimorphism.