Ecological, Behavioural and Biochemical traits of African Meliponine bee species (apidae:meliponini) in a Biodiverse hotspot of Kenya

Abstract

This study was carried out with the aim of assessing habitat ecology and behavioral mechanisms critical for the survival of African meliponine bee species. This will help to fully decipher how they effectively communicate information amongst colony members during two vital ecological processes (colony defense and foraging). Surveys of the floral phenology of potential food plants of African meliponine bees (Apidae: meliponini) in six diverse habitat gradients, observed that most flowering plants overlapped across seasons, which could potentially provide both floral resources (nectar and pollen) to foraging; meliponine bee species. Approximately 80 different plant species belonging to 34 families were recorded, with high proportions from Fabaceae and Asteraceae families dominating flowering plants in both lowland and highland habitats. This indicates that such diverse vegetation found in these habitats could invariably sustain nutritional requirements essential for the survival of insect pollinators such as native meliponine bee species.

Further surveys conducted in these habitats confirmed the natural occurrence of four different meliponine bee species; Hypotrigona gribodoi, Hypotrigona ruspolii, Meliponula ferruginea (black) and Plebeina hildebrandti. The abundance of feral colonies were observed to be dissimilar across the habitats, with Hypotrigona gribodoi exhibiting the highest level of plasticity (abundance and diversity) in nesting preferences across the six habitats sampled, while Plebeina hildbrandti demonstrated the lowest level of plasticity, which may be attributed to their flexibility in nesting in varying habitat types. Diversity profiles indicates that MDW (mixed deciduous wood lands) presented itself as a much preferred habitat for nesting and trees as a preferred nesting substrate, as profile curves indicated that more species from all four species could be identified with increased sampling transects in this habitat and on more tree nesting substrates compared to other sampled habitats, it unmistakably signifies the negative effects that disturbed habitats play in predicting the diversity of bee species within an ecosystem. Discrimination of the meliponine bee species was further demonstrated by the analysis of their mitochondrial cytochrome oxidase 1(mtCOI) gene and wing venation patterns. Sequence analysis demonstrated high divergence enough to characterize bee specimens according to their species, while the wing venation pattern provided sufficient proof to support the level of phylogenetic segregation. Discrimination between nest-mates from non-nest mates from the four African meliponine bee species is facilitated through olfactory cues. Behavioral and electrophysiological assays together with coupled GC-MS analyses revealed that these species correctly detect members of their own colony based on the existence of a signature odor (alkanes, alkenes and methyl- branched alkenes), but were significantly defensive when exposed to the extract of a non-nest mate. This may imply that surface CHCs amongst other exogenous acquisition channels (nest entrance and nest construction materials) could play additional roles as recognition cues for individuals to locate con-specifics and discriminate hetero-specifics. Behavioral assays on foraging patterns of the four meliponine bee species showed insignificant differences between them. In trail laying bioassays, components of the volatiles from nasonov glands were twice more attractive to foragers compared to tarsal glands. Coupled GC-MS analyses identified the biological active peaks to be dominantly terpenes and esters. Additional trail laying bioassays with the dominant volatile compound (E)-β Farnesene identified from both the tarsal and nasonov glands showed that these bees may potentially produce trail pheromones from the nasonov glands, but deposit and disperse them via the openings located in the tarsal glands.In conclusion, this study has revealed how natural habitats converted to agro-ecosystems shape the diversity of African meliponine bee species in this biodiverse hotspot in Kenya. It also shows the use of olfactory cues by individual foragers to discriminate nest mates from non nest mates, which similarly occurs in honey bees during colony defense. It also implicates the nasonov gland as a likely source of trail pheromone production, while the tarsal glands facilitate the deposition and distribution of these essential compounds during foraging.