Griffin, Nicholas , Templeton, Alan , Knight, Tiffany .
Competition and inbreeding depression: invasive purple loosestrife alters inbreeding depression in Mimulus ringens.
Inbreeding depression is often thought to increase in magnitude with environmental stress. Several studies of ecological interactions involving plants support this hypothesis, particularly in the case of herbivory, but the relationship between inbreeding depression and competitive stress remains unclear. We investigated the effects of interspecific competition with the invasive purple loosestrife (Lythrum salicaria) on inbreeding depression in the square-stemmed monkeyflower (Mimulus ringens). We grew selfed and outcrossed M. ringens individuals in pots under three competitive regimes: intraspecific competition, interspecific competition with the native Lythrum alatum, and interspecific competition with the invasive L. salicaria, and measured both aboveground and belowground performance. The magnitude of competitive stress induced by each environment was determined by the average performance of M. ringens in that environment and progressed in the following order: intraspecific competition < L. alatum < L. salicaria. However, the magnitude of inbreeding depression was least in those M. ringens competing against L. salicaria. This pattern was consistent for both aboveground and belowground performance measures, including total biomass and the production of fruits and rhizomes. Our results support the hypothesis that the magnitude of inbreeding depression is dependent upon levels of environmental stress, but are not consistent with the commonly found positive relationship between the two. This suggests that this relationship may be more complex in the context of competition. Our results also suggest that novel stressors, such as invasive species, may alter the magnitude of inbreeding depression in native plant populations, potentially affecting their population growth, maintenance of mating systems, and other important population properties.
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1 - Washington University, Biology, One Brookings Dr, Box 1137, St. Louis, MO, 63130, USA
2 - Washington University in St. Louis, Department of Biology, One Brookings Dr. Box 1229, McDonnell 407, St. Louis, Missouri, 63130, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Council Chambers/SUB
Date: Monday, July 28th, 2008
Time: 8:45 AM