The impact of alien mutualists on the pollination mutualism

AIZEN, M.A.

Buenos Aires

Simposio; 32nd New Phytologist Symposium; Plant interactions with other organisms: molecules, ecology and evolution; 2013

New Phytologist

Alien flowering plants and flower visitors can integrate into native pollination webs with little impact on existing plant-pollinator interactions and network structure. However, as the invasion process proceeds, many aliens, free from natural enemies, can become superabundant and disrupt original pollination mutualisms. Aliens can also change the nature, from mutualistic to antagonistic, of many of the flower-pollinator interactions they usurp, with consequences even for crop pollination. This is exemplified with a recent study of the effect of European Bombus terrestris on raspberry pollination in southern South America. Along with its congener B. ruderatus, these alien bumble bees displaced via resource competition and/or pathogen transmission the only native bumble bee, the giant B. dahlbomii, the main former pollinator of most large-flowered plant species in the region, including many crops. Although the consequences of these invaders for the pollination of the native flora is mostly unknown, we found that the extremely high abundances reached by B. terrestris in N.W. Patagonia are detrimental to raspberry yield because of increasing flower damage during visitation. On the other hand, alien bumble-bees could be facilitating the spread of some alien plant species whose seed production is highly pollination-limited. We conclude that alien mutualists can have several direct and indirect negative effects on the pollination mutualism, and further introductions should be discouraged.