Document: BER-3-16-5

Can a decrease in herbivore defense explain the increased competitive ability of invasive non-indigenous plants?

BLOSSEY, B.*, V.VASQUEZ and B.MONTGOMERY

Cornell University, Ithaca, NY 14853 USA ¹

Abstract:
Blossey and Ntzold (1995) developed a hypothesis explaining the success of plant invaders as a result of shifts in biomass allocation. In the absence of herbivores, selection favors genotypes with improved competitive abilities and reduced herbivore defense. The resulting predictions that (1) genotypes from the native range grow smaller and produce less biomass compared to genotypes from the introduced range, and (2) herbivores show improved performance on plants from the introduction area have been tested for purple loosestrife (Lythrum salicaria). North American plants consistently outperform their European ancestors during germination, grow taller, and show increased seed and biomass production. These results are independent of growing location (Europe or North America), confirming prediction 1. Contrary to prediction 2, the resistance of North American genotypes to herbivore attack was not reduced, and larval performance of a specialized leaf beetle (Galerucella calmariensis), and a generalist leaf feeder (Spodoptera exigua) was similar on all genotypes. However, tannin content of European genotypes was higher compared to North American genotypes. Currently available evidence is therefore contradictory. Although invasive plants show improved competitive ability, reductions in allocation to herbivore defense alone, may not explain this pattern. The high variability among individuals from test populations together with limitations in the power of the statistical analyses may have contributed to the failure of detecting differences among genotypes from the introduced and native range.

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This abstract is being presented at: 1:05 PM in session:
Symposium #6: Ecological Consequences of Adaptive Evolution Among Invasive Species in Terrestrial and Marine Systems.