Assessment Of Bee Diversity And Pollination Networks In Isecheno Forest And Surrounding Farmlands,in Kakamega Rainforest,kenya

The importance of bees to the ecosystem,particularly their contribution to pollination of many insect pollinator-dependent angiosperms is irrefutable.However,global reports on pollinator decline crisis in some parts of the world is a threat to food security,human health,agricultural services,and ecosystem balance.Kakamega forest is rich in pollinator diversity and endemism,however,given drastic environmental pressures alongside land use changes such as habitat fragmentation,deforestation and agricultural intensification,bee diversity,abundance,and bee-pollinator network is vulnerable.Therefore,awareness of the bee species composition and their interaction with domesticated and wild plants is significant in the conservation and survival of bees as well as maintenance of ecosystem services.This study was conducted in Isecheno forest block of Kakamega forest and the surrounding farmlands.The study was designed to assess bee diversity and abundance and to determine bee-plant interaction networks in Isecheno forest and surrounding farmlands.The study examined the diversity of bees and bee-plant mutualism across three habitats,forest,forest edges,and farmlands.The study was carried out between the month of May and July 2018.Six main transect each about 0.6 kilometer long were established,two transects in each habitat.Two sampling points were located along each transect at an interval of 0.5 km.A single belt transect,50 m long by 30 m wide were laid at each sampling point.The study was carried out in 12 sampling points(four in each habitat type located along the two transects).Each belt transect was sampled on four different days across the entire sampling period.Sweeping was executed at each site between 8.00-11.00 Am and 12.00-3.00 pm daily.Bee species were collected together with their respective plants.The bee specimens were then preserved in vials filled with Absolute ethanol and labelled with the date,site name,and collector.The specimens were later taken to the National Museum of Kenya Entomology laboratory for pinning,drying,and taxonomic identification.We recorded that majority of the flowering plants were visited by the bees on all the habitat sites.Data was analyzed using Microsoft Excel,Statistical Package for the Social Sciences(SPSS)and R software "bipartite package" to determine bee diversity,bee abundance,and bee-plant interaction networks.Bee species were identified using morphological features and bee-plant interaction webs determined using network properties such as connectance,nestedness,web asymmetry,link per species,number of shared hosts and degree distribution to describe habitat dissimilarities.In total,54 bee species and 35 plant species were recorded and also involved in the web networks.The highest bee diversity was recorded in the farmlands and the lowest was recorded on forest edges.A statistically significant difference in bee diversity was established across the study sites at P<0.05.Farmlands revealed the highest abundance of bees while forest edges recorded the least abundance.Relative abundance was highest in the forest interior at J=0.8396.We recorded a relatively high asymmetrical bee-plant interaction in the three habitats.The four key plant species were Justicia flava,Tithonia diversifolia,Bidens pilosa,and Aspilia mossambicensis,and were involved in about 30%of the total interactions.Key bee species in the network included,Apis mellifera,Seladonia sp,and Ceratina sp,involved in about 60%of the total interactions.Highest connectance was recorded at the forest edge at 22%while the least was recorded in farmlands at 15%,which implied that farmlands were more diverse in plants and bee species communities.In addition,web asymmetry in the forest and forest edges recorded negative values implying more bee species compared to plant species.Conversely,farmlands recorded a positive value signifying that more plant species were involved in the network compared to the flower visitors.The present findings confirm that Isecheno forest and surrounding farmlands are diverse in bee species forming about one-quarter of bee species previously recorded in Kakamega forest.High species diversity in both farmlands and forest is an indication of pollination activities in the area as well as a confirmation that cultivated and natural or semi natural habitats can complement one another in the conservation and management of bee diversity and abundance.In addition,information on bee-plant networks are limited in many natural ecosystems in Kenya,thus,this study contributes to our knowledge on bee-plant interaction network in Isecheno forest,potential food plants sources for bees and the importance of preservation and management of biological communities.