Abstract
BackgroundBrazil'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.ResultsWe 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.ConclusionsThese 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.
Highlights
Brazil’s Atlantic Forest is a biodiversity hotspot endangered by severe habitat degradation and fragmentation
Genetic Diversity Across all marker types, H. erato displayed greater genetic diversity than H. melpomene (Table 1), which is consistent with previous genetic comparisons between the two species [43,45,47,54]
Elevated genetic diversity in H. erato, relative to H. melpomene, is commonly attributed to the fact that H. erato is generally more abundant than H. melpomene [26,48,55,56], which could result in a larger effective population size
Summary
Brazil’s Atlantic Forest is a biodiversity hotspot endangered by severe habitat degradation and fragmentation. 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. Some populations may be found continuously distributed while others are patchily distributed across their range, both of which may lead to some degree of genetic differentiation. Such geographic patterns of genetic variation reflect both historical processes, such as natural selection, and contemporary gene flow [2]. Gene flow may be affected by a variety of ecological factors such as mating habits, gender-biased dispersal, diet specialization, habitat and population persistence, environmental factors and geographic distance [12]
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