. "16 Hybridization as a Stimulus for the Evolution of Invasiveness in Plants?." Variation and Evolution in Plants and Microorganisms: Toward a New Synthesis 50 Years after Stebbins. Washington, DC: The National Academies Press, 2000.
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Variation and Evolution in Plants and Microorganisms: TOWARD A NEW SYNTHESIS 50 YEARS AFTER STEBBINS
Reference
How stabilized?
Invasiveness
Occurs in human-disturbed areas?
M. Blumler, personal communication
Selfing genotype
Spreading rapidly
Yes
Parker and Bartsch (1996)
Coalescent complex
Noxious weed
Yes
Gallagher et al. (1997); Vilà and D'Antonio (1998)
Clonal growth
Replacing one parent
Yes
Strefeler et al. (1996)
Clonal growth
Noxious weed
Yes
O'Hanlon et al. (1999)
Coalescent complex
Weed
Yes
Panetsos and Baker (1967)
Coalescent complex
Weed
Yes
Abbott and Milne (1995); Milne and Abbott (2000)
Coalescent complex
Noxious weed
Yes
Sun and Corke (1992)
Coalescent complex
Weed
Yes
Ayres et al. (1999); Daehler and Strong (1997)
Clonal growth
Replacing one parent
Yes
Neuffer et al. (1999)
Coalescent complex
Invading polluted forests
Yes
traits tend to be concentrated within a narrow subset of those traits possible. Almost all of our examples are herbaceous (24 of 28). However, the majority of the cases involve perennial species (19 of 28). Interestingly, these characteristics also are found to be frequent among cases of spontaneous hybridization. For example, Ellstrand et al. (1996) examined the 10 genera in the British flora with the highest number of different spontaneous hybrids. They found that most were perennial herbs.
These trends make sense. Perennial hybrids will persist longer than will annuals, giving more time for stabilization opportunities to occur, especially if clonal reproduction is available (as it is in about half of our examples). The predominance of herbaceous over woody examples in our Tables is consistent with Harper's (1977) prediction that colonizing plants allocate more resources to reproductive rather than to vegetative growth. Iteroparous perennial herbs appear to maximize fitness by investing in sexual structures and vegetative spread instead of investing in permanent structures (Crawley, 1986).
