Butterfly Diversity in a Sacred Kaya Forest in Southern Kenya

Habitat destruction and the deterioration of habitat quality are among the main drivers causing worldwide biodiversity loss. The lowland tropical dry forests of the East African coastal region, a hotspot of endemism, have been negatively affected by anthropogenic activities over the last few centuries. Today, only small remnants of these forests with their pristine flora and fauna still exist. It is questionable to what extent the original biodiversity can persist in such small and isolated habitat remnants. Butterflies respond highly sensitively to environmental changes. In this study, we analysed butterfly community structures across a habitat mosaic consisting of natural ecosystems and anthropogenic agro-environments in southern Kenya. Butterflies were counted along line-transects in dense forest, along the forest margin, and in neighbouring pastures and orchards; several biotic and abiotic parameters were assessed for all transect sections (e.g., addressing the vegetation structure). Data collection was conducted during the rainy and dry season, as well as during the transition between both seasons. We compiled species specific traits on the butterfly species ecology, distribution, and behaviour. The obtained results revealed significant differentiation among the butterfly communities in natural forest, forest margins, and in the anthropogenic ecosystems. Although both butterfly diversity and abundance were lowest inside the natural forest, vulnerable forest specialist species occurred restricted to the forest and were absent from anthropogenic ecosystems. The butterfly communities found in the agro-environments were species-rich if compared with the natural forest ecosystem, but dominated by generalist species. From the dry to the rainy season, species numbers increased in all habitat types, but the number of individuals increased only at forest margins and in pastures. This underlines the buffering effect against drought in forests but also in orchards. In general, our data underline that no surrogate habitat exists for typical forest butterflies. This underlines the high ecological relevance of such forest remnants and confirms the necessity of strict conservation of these last remnants of lowland dry forest.