Key environmental determinants of global and regional richness patterns for a wild bee subfamily

Authors: BYSTRIAKOVA, NADIA - Natural History Museum - London; Griswold, Terry; ASCHER, JOHN - National University Of Singapore; KUHLMANN, MICHAEL - University Of Kiel

Submitted to: Biodiversity and Conservation Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2017
Publication Date: 9/16/2017
Citation: Bystriakova, N., Griswold, T.L., Ascher, J.S., Kuhlmann, M. 2017. Key environmental determinants of global and regional richness patterns for a wild bee subfamily. Biodiversity and Conservation Journal. https://doi.org/10.1007/s10531-017-1432-7.

Interpretive Summary: There is concern that there is a world-wide decline in bee pollinators that may affect our ability to produce some crops. Local bee declines have been shown, but whether these are representative of regional or continental declines is not known, nor do we have a good understanding of what is causing the declines. In this article we document continental and world-wide patterns of distribution for one whole subfamily of bees, the cellophane bees, formally called the Colletinae. Results show that these bees are most diverse, not in the tropics like many other kinds of life, but in the more temperate bands between 30 to 50 degrees north and south of the equater. Places that had the most species were also the places that had the most species with very limited distributions that might be more prone to extinction. Present day climate was a strong predictor of where bees were most diverse. Climate change is thus a potential threat to bee diversity. Areas with high bee diversity were also areas with high plant diversity, so conservation strategies that benefit plants in these areas would also benefit bees.

Technical Abstract: Reports of world-wide decline of pollinators, and of bees in particular, raise increasing concerns about food security. While local factors of bee decline are relatively well known and potential mitigation strategies on landscape scale have been outlined, the regional and continental-scale threats to bee diversity have been only marginally explored. Here we document large-scale spatial patterns for a representative bee subfamily, the determinants of its species diversity, and assess major threats to these pollinators. Using a unique comprehensive global dataset of Colletinae (genera Colletes and Mourecotelles), a species-rich subfamily whose organismal and physiological ecology is representative of many bees, we measured species richness and endemism on global to continental scales. We explored the relationships between bee species richness and potential environmental stress factors grouped into three categories: contemporary climate, habitat heterogeneity, and anthropogenic pressure. Bees of the subfamily Colletinae demonstrate the reversed latitudinal gradient in species richness and endemism suggested for bees; the highest species richness of Colletinae was found between 30 and 50 degrees latitude in both the northern and southern hemispheres. Centres of endemism largely overlapped with those of species richness. The importance of the Cape Region, previously identified as a centre of richness and endemism of bees, was confirmed for Colletinae. On the global scale, present-day climate was a significant predictor of species richness as was flowering plant diversity represented by vascular plant species richness and centres of plant diversity. Climate change constitutes a potential threat to bee diversity. Declining diversity of vascular plants is also a potential threat to bee diversity. However, a significant overlap between centres of bee and plant diversity might increase chances for developing conservation strategies.