Consequences of warming up a hotspot: species range shifts within a centre of bee diversity

Abstract

Aim Bees are the most important pollinators of flowering plants and essential ecological keystone species contributing to the integrity of most terrestrial ecosystems. Here, we examine the potential impact of climate change on bees’ geographic range in a global biodiversity hotspot. Location South Africa with a focus on the Cape Floristic Region (CFR) diversity hotspot. Methods Geographic ranges of 12 South African bee species representing dominant distribution types were studied, and the climate change impacts upon bees were examined with A2 and B2 climate scenarios of HadCM3 model, using MaxEnt for species distribution modelling. Results The predicted levels of climate change‐induced impacts on species ranges varied from little shifts and range expansion of 5–50% for two species to substantial range contractions between 32% and 99% in another six species. Four species show considerable range shifts. Bees of the winter rainfall area in the west of South Africa generally have smaller range sizes than in the summer rainfall area and generally show eastward range contractions toward the dry interior. Bee species prevalent in summer rainfall regions show a tendency for a south‐easterly shift in geographic range. Main conclusions The bee fauna of the CFR is identified as the most vulnerable to climate change due to the high level of endemism, the small range sizes and the island‐like isolation of the Mediterranean‐type climate region at the SW tip of Africa. For monitoring climate change impact on bees, we suggest to establish observatories in the coastal plains of the west coast that are predicted to be worst affected and areas where persistence of populations is most likely. Likely impacts of climate change on life history traits of bees (phenology, sociality, bee‐host plant synchronization) are discussed but require further investigation.

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

“…As climatic factors clearly have an influence on bee distribution, climate change can be expected to affect many bee species by causing spatial and/or temporal mismatch between plants and pollinators, and impact them through extreme weather events and shifts in distributional ranges (Memmott et al 2007;Goulson et al 2015). Roberts et al (2011) demonstrated that three generalists and three specialist species of Colletes might be threatened by climate change, and for the global bee diversity hotspot of the GCFR, substantial range contraction for most bee species under a scenario of warming climate is predicted (Kuhlmann et al 2012). In our study, the significant association of a number of climatic variables (precipitation of the wettest month, irradiance of the warmest quarter and growing degree days) with species richness estimates corroborates the results of the earlier studies and suggests that changing climate might have a direct effect on bee diversity at the global to regional scales (Williams et al 2009;Pradervand et al 2014;Scriven et al 2015).…”

“…Multiple drivers of wild bee decline can act on various spatial scales ranging from local land-use change and unsustainable agricultural practices (Quintero et al 2009;Brittain and Potts 2011;Rollin et al 2015) to regional biological invasions of pathogens (Cameron et al 2011) and non-native species (Ghazoul 2004), and continental-scale climate change (Hegland et al 2009). While local factors of bee decline are relatively well known and potential mitigation strategies at a landscape scale have been outlined (Zurbuchen and Müller 2012), regional and continental-scale threats to bee diversity have only been marginally explored (Roberts et al 2011;Kuhlmann et al 2012). This paucity of large-scale studies reflects a shortage of comprehensive, taxonomically reliable distribution data for most geographic regions.…”

Climatic Risk and Distribution Atlas of European Bumblebees

“…Indeed, bumblebee populations seem to be more sensitive to other threats when they reach their climatic limits (Williams & Osborne, 2009). Further, there is some indication that future climate change could have severe impacts on wild bee faunas (Kuhlmann et al, 2012) including bumblebees (Kirilenko & Hanley, 2007;Herrera et al, 2014).…”

“…Parmesan & Yohe, 2003;Chen et al, 2011) including bees (e.g. Kuhlmann et al, 2012). On the other hand, the gradual changes can lead to modification of species' phenology (Polgar et al, 2013;Kharouba et al, 2014; for wild bees see Bartomeus et al, 2011).…”

Hydrological Niche of Restionaceae Species in Silvermine South Africa

“…Should there be any climate change (for example, less rainfall) resulting in a higher water table depth, it could result in a reduction of species richness, as some species might not survive with the changed conditions. Accounting for South Africa's semi-arid environment, urbanization, groundwater extraction and the creation of more bore holes will ultimately cause a change in hydrology and therefore impact the Restionaceae species niche [21,22].…”