Revealing the hidden niches of cryptic bumblebees in Great Britain: Implications for conservation

Abstract

a b s t r a c tBumblebees are ecologically and economically important, and some species have suffered dramatic population declines. The absence of morphological diagnostic characters for the identification of some species creates difficulties for basic ecological studies, and for conservation management. The widespread and commercially exploited bumblebee subgenus Bombus sensu stricto contains a cryptic species complex, known as the lucorum complex, which in Europe comprises B. lucorum, B. cryptarum and B. magnus. Little is known about these species and much of what has been reported is likely to have suffered from incorrect identification. Although the lucorum complex as a whole is common in Great Britain, we aimed to determine whether the populations of the individual species are vulnerable and require conservation action. Using genetic methods to distinguish them, we determined the geographic distribution and abundance of the lucorum complex species in Great Britain, and assessed the extent of niche differentiation between these species. We detected major differences in the geographic range, forage use and sensitivity to summer temperatures of the three species. Bombus lucorum was found to have the broadest distribution and diet, being present throughout mainland Great Britain, whereas B. cryptarum and B. magnus were absent from large areas of central and southern England. Bombus cryptarum and B. magnus were more likely to be found at sites with lower summer temperatures. Bombus magnus, the least abundant species, was found to exhibit an unusually tight biotope association with heathland habitat. This has conservation implications for B. magnus given the current threats to this habitat type.

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

“…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). Further, the directionality and relative importance of various climatic variables appears to be consistent across different scales and geographic regions; however area-specific differences cannot be ruled out.…”

Niche partitioning in a sympatric cryptic species complex

“…All three species co‐occur at many locations in Great Britain and Ireland; additionally, Scriven et al. (), Murray et al. (), and Stanley et al.…”

“…; Scriven et al. ). All three species co‐occur at many locations in Great Britain and Ireland; additionally, Scriven et al.…”

“…Furthermore, Scriven et al. () and Waters et al. () found that B. magnus was strongly associated with the forage plants Calluna vulgaris and Erica spp.…”

“…; Scriven et al. ): Unlike B. lucorum , both B. cryptarum and B. magnus occurred most commonly at sites with lower summer temperatures (Scriven et al. ).…”