Bumblebees, humble pollinators or assiduous invaders? A population comparison of foraging performance in Bombus terrestris

Abstract

Worldwide trade in non-native bumblebees remains largely unrestricted despite well-documented cases where introductions of non-native bees have gone dramatically wrong. Within Europe, indiscriminate importation of non-native populations of bumblebees (Bombus terrestris) for the pollination of glasshouse crops continues on a massive scale. However, no risk assessment has been conducted for these introductions, perhaps because B. terrestris is considered a native species, so shipping populations from one region to another has been implicitly assumed to present no risk. This view is clearly unjustified because Bombus terrestris populations differ significantly in their genetic makeup as demonstrated by strong differences in coat colour and behavioural traits. Therefore, for the first time we compare an important competitive trait, namely foraging performance, between commercially available B. terrestris populations in contrasting environments. We test whether commercially reared populations differ in their nectar foraging performance and whether this is influenced by both their source environment and the one they are introduced into. We do this by means of a reciprocal transplant experiment. Strong, consistent inter-population differences in performance occurred irrespective of test location: Canary Island bees (B. t. canariensis) were superior to Sardinian bees (B. t. sassaricus), which were generally superior to mainland European bees (B. t. terrestris). These inter-population differences in performance were largely explained by inter-population variation in forager size, with larger bees being superior foragers. However, even when body size was accounted for, "native" bees were not superior to transplanted non-native bees in all but one case. We conclude that non-native populations, especially those with large foragers, can be highly competitive foragers. This could lead to their establishment and displacement of native bees. Therefore, we recommend that unregulated movements of non-native B. terrestris populations within Europe should not be carried out without a full risk assessment.

Herbivore Defence Compounds Occur in Pollen and Reduce Bumblebee Colony Fitness

“…for months, particularly as many common generalist bumblebee species have long nesting seasons and some are bivoltine (Ings et al 2005). There is potential for overlapping phenology of bumblebee male production and lupin flowering periods; the acceptability of Lupinus pollen combined with the potentially long period of availability means the possibility of bumblebees feeding lupin pollen, where available, to their offspring is high -particularly where it is cultivated as a large-scale crop.…”

The correlation of learning speed and natural foraging success in bumble-bees

“…We determined the foraging rate by dividing the difference in the forager's body mass (i.e. return minus outgoing mass) by the foraging trip duration (Ings et al 2005(Ings et al , 2006. Nectar foraging rate was calculated on a per bout basis for each colony.…”

Effects of aposematic coloration on predation risk in bumblebees? A comparison between differently coloured populations, with consideration of the ultraviolet

“…Nonetheless, we are confident in the power of our data. First, there is no risk of subconscious experimenter bias: the data were collected with an objective that was entirely different from the study subject here (Chittka, Ings & Raine, 2004;Ings et al, 2005b). Second, our sample sizes of almost 1000 foragers completing more than 8258 h of foraging flights (Table 1) are considerably larger than all other transplant or release/recapture studies of which we are aware.…”

“…In experiments conducted in Sardinia and Germany in 2001, three sets (blocks) of observations were carried out consecutively (for further details see Ings et al, 2005b). Each block consisted of one colony from each of the three populations: B. t. sassaricus, B. t. terrestris and B. t. canariensis (an additional block, i.e.…”

“…They were carried out in two separate locations on the island of Sardinia (Costa Rei, autumn 2000, and Monte Padru, spring 2001), one in Germany (W¨urzburg, summer 2001: for details see Ings, Schikora & Chittka, 2005b) …”