Biology Reference
In-Depth Information
these species that occur in North America. The hybrid also shows sub-
stantial genetic variation (Newcombe et al. 2001).Whether or not it will
prove to be a more virulent pathogen than its parents remains to be seen.
Overall Significance of Hybridization
Thus, hybridization between and among alien species and between alien
and native species has proven ability to give rise to new invasive forms,
especially in the case of plants and plant disease agents. As the last exam-
ple of cottonwoods and their rusts shows, deliberate hybridizations by
plant and animal breeders are likely to increase the complexity of unin-
tended hybridizations by their parasites and diseases.
The invasive forms resulting from some hybridizations have the capac-
ity to transform habitats and biotic communities. Hybrid cordgrasses and
willows can modify the physical habitats that they tend to dominate.
Hybrid parasitic fungi have greatly altered the biotic structure of the
communities they have invaded.The risk of origin of new, highly invasive
organisms by hybridization is enormous, especially among fungi and
other microorganisms about which our knowledge of introductions to
new areas is fragmentary.
Issues involving hybridization are not limited, however, to those of the
origin of invasive forms as considered in this chapter. In the next chapter
we shall examine a special issue related to hybridization: the risks of trans-
fer of engineered genes from crop plants and domestic animals to their
wild relatives.
