ARS | Publication request: Testing for Evolution of Increased Competitive Ability Across Species and Functional Groups

Submitted to: Ecological Society Of America Proceedings
Publication Acceptance Date: December 31, 2003
Publication Date: August 2, 2004
Citation: Blumenthal, D.M., Hufbauer, R. 2004. Testing For Evolution Of Increased Competitive Ability Across Species And Functional Groups. P. 50. Ecological Society Of America Proceedings.

Technical Abstract: Although considerable evidence exists to suggest that release from natural enemies contributes to exotic species invasion, the relative importance of plastic vs. evolutionary responses to enemy release is poorly understood. The Evolution of Increased Competitive Ability hypothesis suggests that exotic species may need to evolve away defenses, and evolve traits that confer competitive ability, to benefit from natural enemy release. Early tests of this hypothesis have been inconclusive for two reasons. First, relatively few species have been examined, and results from those that have, have varied widely. Second, few experiments have examined competitive ability across multiple environments. Here we report the results of a common garden experiment comparing defensive traits and competitive ability among four populations (two from the native and two from the exotic range) of 25 invasive species. The species include invaders of both agricultural and natural systems, grasses and forbs, and annuals and perennials. Four individuals from each population were grown in a greenhouse from seed under three competition treatments: no competition, competition with Phalaris arundinaceae added as seed, and competition with established P. arundinaceae. Seed mass, an indicator of the potential importance of maternal effects, did not differ among populations from native and exotic ranges. Responses of plant size (height, stem diameter, leaf number), phenology (time to germination and flowering), leaf toughness, density of hairs and spines, and generalist herbivore (Trichoplusia ni) preference, will be compared across population origins, competition treatments and invader functional groups.