AOBPreview originally published online on June 30, 2008
Annals of Botany 2008 102(3):417-424; doi:10.1093/aob/mcn109
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High Invasive Pollen Transfer, Yet Low Deposition on Native Stigmas in a Carpobrotus-invaded Community
1 Center for Ecological Research and Forestry Applications (CREAF)
2 Ecology Unit, Department of Animal and Plant Biology and Ecology, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia, Spain
3 Estación Biológica de Doñana (EBD-CSIC), Avda/María Luisa s/n, Pabellón del Perú, 41013 Sevilla, Spain
* For correspondence. E-mail montse.vila{at}ebd.csic.es
Received: 10 March 2008 Returned for revision: 6 May 2008 Accepted: 5 June 2008 Published electronically: 30 June 2008
Background and Aims: Invasive plants are potential agents of disruption in plant–pollinator interactions. They may affect pollinator visitation rates to native plants and modify the plant–pollinator interaction network. However, there is little information about the extent to which invasive pollen is incorporated into the pollination network and about the rates of invasive pollen deposition on the stigmas of native plants.
Methods: The degree of pollinator sharing between the invasive plant Carpobrotus affine acinaciformis and the main co-flowering native plants was tested in a Mediterranean coastal shrubland. Pollen loads were identified from the bodies of the ten most common pollinator species and stigmatic pollen deposition in the five most common native plant species.
Key Results: It was found that pollinators visited Carpobrotus extensively. Seventy-three per cent of pollinator specimens collected on native plants carried Carpobrotus pollen. On average 23 % of the pollen on the bodies of pollinators visiting native plants was Carpobrotus. However, most of the pollen found on the body of pollinators belonged to the species on which they were collected. Similarly, most pollen on native plant stigmas was conspecific. Invasive pollen was present on native plant stigmas, but in low quantity.
Conclusions Carpobrotus: is highly integrated in the pollen transport network. However, the plant-pollination network in the invaded community seems to be sufficiently robust to withstand the impacts of the presence of alien pollen on native plant pollination, as shown by the low levels of heterospecific pollen deposition on native stigmas. Several mechanisms are discussed for the low invasive pollen deposition on native stigmas.
Key words: Alien plant, Carpobrotus aff. acinaciformis, competition for pollinators, invasion, Mediterranean shrubland, plant-pollinator network, pollen loads, pollinator visits, stigma
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