Since their introduction to Lake Washington in 1937, the salmon differentiated genetically and morphologically according to the nature of their breeding environments, Hendry reports. Fish associated with the river or lake breeding areas bred successfully when in their respective habitats. Although fish swam between the sites, the rate of gene flow did not correspond to immigration. Morphologically, fish that breed in the river consist of larger females that dig deeper nests, and river males have shallower bodies that allow them to cut through stronger currents than in the lake beach.
Recently introduced populations of organisms, in different environments, offer an opportunity to study the processes of rapid speciation in nature, because much of the observable reproductive isolation can arise soon after a population's initial divergence, or deviation from the ancestral form, notes Hendry.
Considering the short evolution time for reproductive isolation, many questions still remain, such as, why don't more species exist? The studies of Higgie and Hendry provide a basis for conducting more detailed ecological and genetic experimentation that examines how speciation may occur naturally across taxonomic groups.
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Contact: Ginger Pinholster
gpinhols@aaas.org
202-326-6421
American Association for the Advancement of Science
19-Oct-2000