Does specialized pollination impede plant invasions?
van Kleunen, M.
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Generalized pollination systems and aotonomous self-fertilization are traits that have been linkes with lplant invasiveness. However, whether specialized pollination requirements pose a significant barrier to plant invasions is not yet clear. Likewise, the contribution of pollinators to the fecundity of facultatively self-pollinating invasive plant species is poorly understood. We addressed these issues using the self-compatible and autonomous self-pollinating, Liliton formosarium, which also has large, showy flowers that are adapted for pollination by hawk moths. We investigated the pollination of this lily - which is indigenous to Taiwan - in KwaZulu-Natal, South Africa, where it is invasive. The long-tongued hawk moth Agrius convolvuli was identified as the primary pollinator on the basis of field observations, pollen load analysis, presence of lepidopteran scales on stigmas, and higher seed production in emasculated flowers exposed at night than in those exposed during the day. Remarkably, this moths is native to much of the Old World, including Taiwan and South Africa. Autonomous self-pollination resulted in seed production, but at a reduced level relative to the seed production of open- and hand-pollinated flowers, which was significant in one out of two populations examined. Thus, pollinatiors potentially contribute to invasion by increasing seed production and genetic variability through cross-pollination, although contributions of pollinators to seed set versus that of autonomous self-pollination may vary between populations. We conclude that specialized pollination requirements do no present a barrier to invasions when plants are specialized to pollinatiors or pollinatior functional groups with very wide distributions.
- RESEARCH: Johnson S