A test for Allee effects in the self-incompatible wasp-pollinated milkweed Gomphocarpus physocarpus

Coombs, Gareth; Peter, Craig I; Johnson, Steven D

Title: A test for Allee effects in the self-incompatible wasp-pollinated milkweed Gomphocarpus physocarpus
Creator: Coombs, Gareth
Creator: Peter, Craig I
Creator: Johnson, Steven D
Date Issued: 2009
Date: 2009
Type: Article
Identifier: vital:6511
Identifier: http://hdl.handle.net/10962/d1005938
Identifier: http://dx.doi.org/10.1111/j.1442-9993.2009.01976.x
Description: It has been suggested that plants which are good colonizers will generally have either an ability to self-fertilize or a generalist pollination system. This prediction is based on the idea that these reproductive traits should confer resistance to Allee effects in founder populations and was tested using Gomphocarpus physocarpus (Asclepiadoideae; Apocynaceae), a species native to South Africa that is invasive in other parts of the world. We found no significant relationships between the size of G. physocarpus populations and various measures of pollination success (pollen deposition, pollen removal, and pollen transfer efficiency) and fruit set. A breeding system experiment showed that plants in a South African population are genetically self-incompatible and thus obligate outcrossers. Out-crossing is further enhanced by mechanical reconfiguration of removed pollinaria before the pollinia can be deposited. Selfpollination is reduced when such reconfiguration exceeds the average duration of pollinator visits to a plant. Observations suggest that a wide variety of wasp species in the genera Belonogaster and Polistes (Vespidae) are the primary pollinators. We conclude that efficient pollination of plants in small founding populations, resulting from their generalist wasp-pollination system, contributes in part to the colonizing success of G. physocarpus. The presence of similar wasps in other parts of the world has evidently facilitated the expansion of the range of this milkweed.
Format: 13 pages
Format: pdf
Language: English
Relation: Coombs, G. and Peter, C.I. and Johnson, S.D. (2009) A test for Allee effects in the self-incompatible wasp-pollinated milkweed Gomphocarpus physocarpus. Austral Ecology, 34 (6). pp. 688-697. Available: http://dx.doi.org/10.1111/j.1442-9993.2009.01976.x

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Coombs, Gareth (Dr)

Peter, Craig (Assoc Prof)

RU Department of Botany

SDG 15. Life On Land

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