Abstract

MORALES, Carolina L. Introduction of no native bumblebees (Bombus): causes, ecological consequences and perspectives. Ecol. austral [online]. 2007, vol.17, n.1, pp.51-65. ISSN 1667-782X.

The invasion of non native pollinators might have considerable impacts on native pollinators, native and introduced plants. In this article I analyze the causes of introduction of bumblebees (Bombus), the factors favoring the invasion and the distribution of introduced species. I also review the studies about their ecological impact, discussing the limitations of those studies, and the main gaps in knowledge. Five bumblebee species are established outside their native ranges, as a consequence of intentional releases and the trade of colonies. Introduced bumblebees are highly polylecthic and could acquire high abundances in invaded areas, dominating in some cases the anthophyllous communities. In general, they gather resources more efficiently than natives, and despite a substantial overlap in the use of floral resources, in general both groups mutually exclude in time and space, suggesting the potential for competition; nevertheless no study has experimentally tested this hypothesis. The introduction of bumblebees could favor the introduction and transmission of pathogens. Non native bumblebees are less efficient pollinators of some native plants than natives and, in general, they prefer non native plant species, contributing to the pollination of important weeds, although their influence on weed invasion process has not been tested. Under experimental conditions some species of non native bumblebees can mate with native congeners; nevertheless no hybridization has been reported in the wild. The evidence of the impact of non native bumblebees on native ecosystems is scarce, fragmented and preliminary. In spite of them, considering the overall available evidence I strongly recommend the application of the precautionary principle to analyze potential future introductions.

Keywords : Biological invasions; Commercial rearing of bumblebees; Competitive displacement; Crop pollination; Exotic species; Hybridization; Pathogens.

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