Bee diversity along a forest regeneration gradient in Western Kenya
Mary Gikungu, Dieter Wittmann, David Irungu and Manfred Kraemer
Changes in bee species richness and diversity were studied along a forest regeneration gradient in seven sites in Buyangu Nature Reserve, Kakamega Forest, Kenya. At each site, 12 belt transects of 100 m length and 2 m width were established. The selected sites ranged from relatively undisturbed primary to late secondary forests, bush lands and the surrounding farming areas. A total of 4,485 individuals were identified out of 234 species of bee in four families. A Renyi Diversity Index was used to analyse bee diversity. One-way measures of ANOVA were calculated for bee diversity and species richness, with study sites and year as independent factors. The highest species richness and bee diversity were recorded in the open areas followed by secondary forests while evenness was higher in forested sites. There was a general similarity between sites in bee species composition, especially between those of almost similar vegetation structure. This similarity was suspected to have important implications in promoting current understanding of ecological resilience of bees in tropical ecosystems. The study concludes that the future of forest biodiversity and pollination services are dependent on strategic and holistic management of natural forests, secondary forests and the neighbouring agro-ecosystems.