Alien Bumble Bee Affects Native Plant Reproduction Through Interactions With Native Bumble Bees

Abstract

Abstract. The invasive alien bumble bee Bombus terrestris may hinder the reproduction of native plants that have established specialized pollination systems with native bumble bees. To test this hypothesis, we examined the visitation frequency and behavior of native and alien bumble bee species and resultant seed production in Corydalis ambigua, a native plant in Hokkaido, Japan. This species is self-incompatible: the flower has a spur and requires visitation by bumble bees for effective seed production. We compared visitation frequency as well as fruit and seed set after cross-and open pollination at five sites of C. ambigua. Four of these sites occurred near a residential district and included naturalized populations of B. terrestris, and the fifth site was located in a forested habitat with no B. terrestris. The native species B. ardens and B. hypocrita and the alien B. terrestris frequently visited C. ambigua. Bombus ardens legitimately consumed nectar, whereas B. hypocrita and B. terrestris rob nectar by perforating spurs. The legitimate pollinator B. ardens produced fruits and seeds more efficiently than the nectar robbers. At three sites, the proportion of robbed flowers per inflorescence gradually increased through the flowering period, which may be caused by the intrusion of alien B. terrestris into the native plant-pollinator interactions. At these sites, C. ambigua suffered from pollen limitation, as seed production from open pollination was lower than from cross-pollination, despite the fact that the total abundance of three bumble bees was higher than in the other two sites. Legitimate B. ardens visited fewer flowers within inflorescences with more robbed flowers, suggesting that nectar robbing may reduce the frequency of visitations by B. ardens within inflorescences, and resulting in decreased fruit set. Furthermore, reduced seed set implies a reduction in the pollination quality by B. ardens, probably due to decreases in visiting time per flower. Thus, introduction of alien B. terrestris may alter the native plant-pollinator mutualism: C. ambigua could establish a novel pollination relationship with B. terrestris because of its nonzero pollination efficiency, similar to the native robber B. hypocrita.

Bombus terrestris, pollinator, invasive and pest: An assessment of problems associated with its widespread introductions for commercial purposes

“…It may use simple flowers but can learn to manipulate and exploit complex flowers (Stout et al, 1998). Moreover, it can take advantage of deep tubular flowers by piercing corollas to illegitimately obtain nectar that (Free, 1993;Matsumura et al, 2004;Dohzono et al, 2008).…”

Impacts of alien bees on native plant-pollinator relationships: A review with special emphasis on plant reproduction

“…Introduced honeybees and bumblebees compete with native pollinators and reduce the fitness of some native plant species (Gross and Mackay, 1998;Celebrezze and Paton, 2004;Dupont et al, 2004;Dohzono et al, 2008). However, in other cases, plant reproduction is unaffected (Vaughton, 1992;Dupont et al, 2004) or even enhanced by the presence of introduced honeybees and bumblebees (Gross, 2001;Madjidian et al, 2008).…”

Combining citizen science, bioclimatic envelope models and observed habitat preferences to determine the distribution of an inconspicuous, recently detected introduced bee (Halictus smaragdulus Vachal Hymenoptera: Halictidae) in Australia

“…4), and therefore it is likely to be having a larger impact in this area (Yokomizo et al 2009). Potential impacts of introduced bees include increased competition for nest sites and floral resources, the introduction and spread of pathogens and parasites, increased pollination and spread of introduced weeds, and the disruption of pollination of native plants (Barthell et al 2001;Cook et al 2007;Dohzono et al 2008;Goulson 2003;Kenis et al 2009;Stout et al 2002;Traveset and Richardson 2006 (Gollan et al 2008;Gollan, Batley and Pauly, unpublished data;Herrera 1988;Petanidou and Vokou 1993).…”