Halictines at the Mt Kilimanjaro. Cryptic species and hidden ecological interactions of halictine bees along an elevational gradient

Changes of abiotic and biotic conditions along elevational gradients represent serious challenges to organisms that require evolutionary and ecological adaptations. Information on such adaptations beyond morphological features are currently sparse for insects, and especially bees. Here, we used molecular methods to study hidden traits, biotic interactions and phylogenetic relationships of halictid bees of the genus Lasioglossum along a 2,900 m elevational gradient at Mt. Kilimanjaro, Tanzania. We detected a strong phylogenetic species turnover of morphologically undistinguishable taxa, changes in cuticular hydrocarbon (CHC) profiles, pollen resource diversity and the gut and body surface microbiome of bees. At high elevations increased proportions of saturated compounds in CHC profiles indicate physiological adaptations to prevent desiccation. More specialised diets with higher proportions of Asteraceae pollen imply constraints by food resources. Interactive effects of climatic conditions on gut and surface microbiomes, CHC profiles and pollen diet suggest complex feedbacks among abiotic conditions, ecological interactions, physiological adaptations and phylogentic constraints as drivers of halictid bee communities at Mt. Kilimanjaro.