Variation and Evolution in Plants and Microorganisms Toward a New Synthesis 50 Years After Stebbins (2000) / Chapter Skim
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16 Hybridization as a Stimulus for the Evolution of Invasiveness in Plants?
16 Hybridization as a Stimulus for the Evolution of Invasiveness in Plants?
Pages 289-309
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From page 289... ...
Progeny with a history of hybridization may enjoy one or more potential genetic benefits relative to their progenitors. The observed lag times and multiple introductions that seem a prerequisite for certain species to evolve invasiveness may be a correlate of the time *
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From page 290... ...
In the United States alone, the damage wrought by invasive species totals approximately $122 billion per year (Pimentel et al., 2000~. Only a tiny fraction of introduced species become successful invasives (Williamson, 1993~.
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From page 291... ...
For example, North America's most successful invasive birds, the European Starling and the House Sparrow, both became invasive only after repeated introduction (Ehrlich et al., 1988~. Collectively considered, these observations suggest genetic change and adaptive response play a role in the ultimate establishment of some invasive species.
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From page 292... ...
Finally, we examine how our model for interspecific hybridization could work equally well for hybridization between previously isolated populations of the same species. MATERIALS AND METHODS We sought at least 25 well documented examples of the evolution of invasiveness in plants after a spontaneous hybridization event.
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From page 293... ...
We define invasive populations as those that are capable of colonizing and persisting in one or more ecosystems in which they were previously absent. The minimal criterion of invasiveness for our hybrid derivative is that it must replace at least one of its parental taxa or invade a habitat in which neither parent is present.
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From page 294... ...
Schierenbeck TABLE 1. Invasive taxa that evolved after intertaxon hybridization Habit of Site of Evidence hybrid taxon's beyond Derived taxon Parent taxa Family lineage origin morpholc Amelanchier erecta A
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From page 295... ...
Clonal growth Noxious weed Yes (1995) .urope s Stace (1975)
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From page 296... ...
. In many cases, the new hybrid lineage is a coalescent complex that absorbs one or both parental types, especially among the unnamed cases in Table 2.
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From page 297... ...
Coalescent complex Noxious weed Yes ,, i Gallagher et al. (1997~; Clonal growth Replacing one Yes Vita and D'Antonio (1998)
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From page 298... ...
Anderson and Stebbins (1954) predicted that human disturbance should both mix previously isolated floras as well as create novel niches well suited to novel hybrid-derived genotypes, that is, to create niches better suited to intermediates or segregants than to the parental species.
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From page 299... ...
The resulting hybrid plants are morphologically similar to the crop but are annuals, bolting, flowering, and setting seed, leaving a woody root that cannot be sold, that in fact damages harvesting and processing machinery (Parker and Bartsch, 1996~. These beet hybrids have given rise to weedy lineages, whose evolutionary novelty of annuality preadapts them for invasive success in cultivated beet fields.
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From page 300... ...
Genetic variation Recombination in hybrids generates both novelty and variation. A hypothesis related to the one just discussed is that the increase in genetic variation produced in a hybrid lineage can, in itself, be responsible for the evolutionary success of that lineage (Stebbins, 1969~.
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From page 301... ...
also will fix heterotic genotypes. It may well be that the fitness boost afforded by fixed heterozygosity is all that is necessary to make a hybrid lineage invasive.
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From page 302... ...
Modern transportation has accelerated that process, including bringing together cross-compatible species that previously were geographically isolated. More than one-third of our invasive hybrid derivatives involves cases in which both parental species were introduced to the location where the initial hybridization event occurred.
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From page 303... ...
Introduction of distantly related individuals of the same species from different parts of its range may yield an evolutionary stimulus that is essentially the same as is the introduction of different species. lust as with interspecific hybridization, we do not expect all intraspecific hybridization events to lead to invasiveness.
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From page 304... ...
This suggestion may seem surprising because of the commonly held view that invasives should be relatively genetically depauperate as a result of the bottlenecks associated with their colonization dynamics (Barrett and Husband, 1990~. On the other hand, hybridization between well differentiated populations resulting from introductions from different sources ought to leave relatively high levels of within-population polymorphism as a "signature." We have found two such examples.
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From page 305... ...
Similarly, North American populations of the introduced weed cheatgrass, Bromus tectorum, were found to have increased within-population genetic variation as compared with populations from its source range in Europe and northern Africa (Novak and Mack, 1993~. Again, there is ample evidence of multiple introductions (Novak et al., 1993~.
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From page 306... ...
(1992) Plant invasions, interspecific hybridization, and the evolution of new plant taxa.
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From page 307... ...
(1997) Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)
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(1959) A 10 year study of vegetational changes associated with biological control of Klamath weed species.
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From page 309... ...
(1990) Helianthus-annuus ssp texanus has chloroplast DNA and nuclear ribosomal RNA genes of Helianthus-debilis ssp cucumerifolius.
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