Patterns of genetic diversity and structure of three nymphalid butterfly species in Ghana: The role of forest fragmentation

The genetic effects of forest habitat fragmentation strongly depend on a species' ecological requirements and dispersal ability. Genetic diversity and structure of three forest butterfly species with differing dispersal abilities and habitat fidelities were quantified. Aterica galene has high habitat fidelity, but low dispersal ability. Euphaedra medon has high habitat fidelity and is the strongest disperser among the three. Gnophodes betsimena is a low disperser, but utilizes habitats outside the forest. A total of 291 individuals were collected from seven forest fragments (two large Forest Reserves and five small Sacred Groves) in Ghana, West Africa. Individuals were sequenced for the mtDNA cytochrome oxidase I (COI) gene. The genetic diversity of both A. galene and E. medon was significantly higher than that of G. betsimena. Genetic differentiation was relatively high among A. galene populations, low among E. medon, and absent among G. betsimena populations. There was no evidence of isolation by distance among populations in any of the species which suggests that isolation of these forest butterflies is relatively recent and that populations have not yet reached a migration-drift equilibrium. Alternatively, straight line distance may not be an adequate measure of gene flow and connectivity among populations. The divergence among A. galene populations, especially the population at the smallest forest fragment, which is located in a densely populated area, indicates that human modifications such as urbanization present barriers to gene flow among low dispersing, forest-dependent species.