Biological Invasions (2011) 13, 2379-2389

Christina Alba, M. Deane Bowers, Dana Blumenthal and Ruth Hufbauer (2011)
Evolution of growth but not structural or chemical defense in Verbascum thapsus (common mullein) following introduction to North America
Biological Invasions 13 (10), 2379-2389
Abstract: Post-introduction evolution of increased growth or reproduction has been observed in many species of invasive plants; however, it is not consistently associated with a loss of defense, as predicted by the influential evolution of increased competitive ability (EICA) hypothesis. Inconsistent support for the EICA hypothesis likely reflects the fact that, although invasive plants are released from attack by some enemies, typically specialists, they often do not escape attack from generalists. Thus, different types of defense (e.g., structural versus chemical) may evolve in different directions following introduction. We used a common garden experiment to test whether a shift in allocation among defenses (as opposed to a simple increase or decrease in a single defense) is associated with increased growth in introduced Verbascum thapsus populations. Introduced populations had significantly greater shoot biomass than natives. However, root biomass was similar between ranges, and highly variable, resulting in only marginal differences in total biomass. Mean investment in all three defenses was remarkably similar between the native and introduced populations, providing no evidence for range-level, post-introduction evolution of defense. This finding was consistent with the fact that, despite significant population-level variability for all defenses, there was little evidence of trade-offs between growth and defense or among different types of defense. These results suggest that evolution of increased growth in V. thapsus is not fueled by decreased allocation to defense, and that selection on defense may vary more at the population scale than the continental scale.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Ruth A. Hufbauer, Dana M. Blumenthal

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Verbascum thapsus (weed)