Taxonomy and Evolutionary Biology of Cutthroat Trout

In 1979, the late R.J. Behnke proposed a classification scheme for Cutthroat Trout consisting of 14 subspecies - 12 extant and 2 extinct.  Behnke’s classification was based on an evolutionary history and sequence of geographical expansions first proposed by David Starr Jordan.  Jordan held that ancestors of modern Cutthroat Trout moved up the Columbia and Snake Rivers, and from there spread to many inland waters in western North America. Behnke hypothesized that the current subspecific diversity resulted from events that occurred during the last million years.  He utilized fossil records and early chromosome studies, but relied primarily on meristic and morphometric character differentiation as the basis for his Cutthroat Trout phylogeny.  Although differences of opinion occasionally arose, Behnke believed that the later allozyme electrophoresis studies by others largely corroborated his classification. However, recent investigations using mitochondrial and microsatellite DNA evidence have called the validity of his classification into question, and some management organizations, taking their cues from publications arguing for a more lumped classification of Cutthroat Trout subspecies, have concluded that unique subspecific recognition of certain populations may not be warranted. This has generated controversy when some of the populations in question have been ESA-listed. Not every alternative classification scheme has proposed lumping subspecies; at least one has suggested more splitting may be needed. To help focus on the key similarities and differences in the new classifications and to determine if taxonomists and evolutionary biologists are now able to agree on a revised Cutthroat Trout classification we will bring together authors of recent DNA investigations as well as experts in Cutthroat Trout biogeography and evolutionary biology to determine if it is possible to reach consensus on what a valid classification should be.
Patrick Trotter
Pete Bisson and Brett B. Roper
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