Document: LEO-3-39-17

Safety in numbers: Evidence for Allee effects in rare and common species of Silene.

MOYLE, L.C.* ¹ and J.ANTONOVICS ²

Duke University, Durham, NC 27708, USA ¹
University of Virginia, Charlottesville, VA, USA ²

Abstract:
The biological consequences of rarity (i.e. small population size and/or patchy distribution) are thought to be contingent upon the evolutionary and ecological history of a given taxon. One specific consequence of numerical rarity may be reduced fitness resulting from insufficient cooperative interactions between conspecifics i.e., Allee effects. Species with a history of rarity may be expected to be less susceptible to Allee effects. We used a comparative approach to investigate differences in population demography and genetics of four species in the herbaceous plant genus Silene, two of which are common/widespread and two of which are geographically restricted. Multiple populations, spanning a range of sizes, were examined for each species. Demographic characters included survival and reproductive output in the field; genetic factors included susceptibility to inbreeding depression. One goal was to determine whether Allee effects differentially affected rare versus common species. Results suggest that while both rare and common species experience some negative consequences of small population size (for example, individual seed weight is positively correlated with population size), species with historically widespread distributions are no more susceptible to these effects than rare congeners. Thus, there is no evidence that historically rare species of Silene have developed adaptive strategies that mitigate the negative effects of small population size.

Keywords: Allee effect, rare species, Silene

This abstract is being presented at: 1:45 PM in session:
Oral Session #63: Evolutionary Ecology.