Habitat specialisation and resource availability determine dispersal behaviour in four afro-tropical butterflies

Abstract

Ecological demands, such as sex and environmental conditions, determine species' behaviour, such as dispersal, and shape local population structures. However, only marginal knowledge of these factors exists for afro-tropical insects so far. Therefore, we performed a mark–release–recapture study in the coastal region of Kenya over a period of 2 months, covering the dry and the rainy seasons. As study species, we used four co-occurring but ecologically diverging butterfly species, the forest species Bicyclus safitza and Junonia natalica and the savannah species Junonia oenone and Byblia ilithyia. The study area represents an ecosystem mosaic consisting of anthropogenic habitats as well as natural forest and savannah, assessed by detailed landscape mapping. We obtained 1701 capture events, comprising 1224 individuals with an overall recapture rate of 24% (ranging from 15% to 48%). The analyses based on these results allowed an assessment of the population ecology, dispersal behaviour and habitat preferences of these species. Demographic models inferred different patterns of population dynamics among species. All species preferred the habitats they were known for. The observed dispersal distances were rather low ranging from a mean of 25 to 72 m, referring to taxa and sexes. The dispersal extrapolations were unreliably low for the negative exponential function, while the values for inverse power function were credible. The latter predicted a considerably higher long-distance dispersal capacity in males than in females of the forest species B. safitza and J. natalica, while females dispersed more than males in the savannah species J. oenone and B. ilithyia. Our results obtained from these four ecologically diverging afro-tropical butterfly species underline that species’ behaviour, such as dispersal, is strongly determined by habitat preferences, sex and the availability of resources.