Factors limiting the species richness of bees in Saharan Africa

Abstract

There is a severe shortage of knowledge of bee biogeography. Some former studies have highlighted a link between bee diversity and xeric ecosystems, but we know practically nothing of the macro-ecological factors driving bee diversity. The present study aims to analyse the main macro-ecological factors driving bee species-richness in the Saharan region. Our dataset includes 25,000+ records for localities in Africa, between 37 degrees and 10 degrees N. Maps and GIS were used to get a first overview of the distribution of the studied taxa. Partial least squares analysis (PLS) was used to study the impact of a set of ecological factors on the bee species richness (SR). The mapping highlighted the clustering of the highest bee SR values in some parts of the Saharan area (e.g. Maghreb, western Africa). In Central Sahara, there is an obvious topological coincidence of the high SR, the local mountain chains and the inland waters. The PLS helped to quantify the relationships between bee SR and a set of eco-climatic variables. It also highlighted a residual variance not explained by the considered descriptors. Our results recover the tight link between bee SR and xeric ecosystems. They also suggest that, within these ecosystems, bee SR is driven by an optimum of the energy-water balance (on which adjustment is allowed by the above gradients).

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

“…Variety of food sources represented by richness of vascular plants and centres of plant diversity was significant at all scales and appeared to be the strongest predictor of bee species richness as already presumed by Patiny et al (2009a). For example, the global Colletinae species richness hot-spot in the GCFR coincides with one of the most prominent centres of plant diversity and endemism (Kuhlmann 2009).…”

“…northern Atacama, Sahara) or are found in the moist tropics, both unfavourable for bees. Areas too xeric for optimal bee diversity are extensive in the Afrotropical and Palaearctic Realms where the relationship between growing degree days and species richness was significantly negative and where bee diversity appears to be driven by optimal (rather than maximal) ecosystem energy (Patiny et al 2009a). Irradiance of the warmest quarter, on the other hand, was positively related to bee richness on the global scale, and in the Neotropical, Nearctic and Palaearctic Realms.…”

“…This paucity of large-scale studies reflects a shortage of comprehensive, taxonomically reliable distribution data for most geographic regions. Large-scale patterns of bee diversity and distribution and their primary determinants have been only partly described for relatively small sub-continental regions (Patiny and Michez 2007;Kuhlmann 2009;Patiny et al 2009a) or on a coarse country scale (Patiny et al 2009b;Leonhardt et al 2013;Nieto et al 2014), but are essential for identifying target areas for conservation actions and developing effective global strategies for bee conservation. So far, global distribution data have been analyzed for only a few large and conspicuous taxa (e.g.…”

A survey and review of the status of wild bees in the West-Palaearctic region

“…Based on original datasets for duly chosen model taxa, patterns in the distribution of species richness in the southern WestPalaearctic have been described in a couple of papers Patiny et al, 2009). These latter studies have shown that (i) Maghreb and the Nile delta have remarkably high species richness; (ii); Morocco constitutes remarkable hotspot for bee species richness; (iii) The area between western Egypt and southeastern Tunisia is, by contrast, characterized by a very low level of species richness.…”

“…These latter studies have shown that (i) Maghreb and the Nile delta have remarkably high species richness; (ii); Morocco constitutes remarkable hotspot for bee species richness; (iii) The area between western Egypt and southeastern Tunisia is, by contrast, characterized by a very low level of species richness. Based on a multivariate analysis of the macroecological parameters of the species richness distribution in the southern West-Palaearctic, Patiny et al (2009) concluded that the patterns of species richness in Saharan Africa (northern and southern) are ruled by the water/energy balance within ecosystems, which impacts on bees through their feeding resources (i.e. flowering plants).…”