7612

• UCREFRP Catalog Number: 7612
• Author: Roberts, B. and M. Moretti.
• Title: Final Fisheries Survey of the San Juan River, Utah 1988.
• USFW Year: 1988.
• USFW - Doc Type: Salt Lake City, Utah.
• Copyright Material: NO

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Brown and Wilson (1956) suggested that suspected hybrid systems
be analyzed within the geographical limits of the parents
contributing directly to the hybridization to prevent con-
fusion of the products of character displacement with those
of hybridization. They defined character displacement as
i
accentuation of differences between two species in a zone
of sympatry and the reduction of differences in allopatry.
The resultant changes may be divergent from both species or
convergent, seemingly toward an intermediate form. In this
way, the sympatric populations may contain individuals which
mimic hybrids but are actually within the normal distribu-
tion of intra-specific variation. Although the authors
invoke this phenomenon as an explanation of certain taxo-
nomic problems in the centrarchid genus Micro terus (Hubbs
and Bail), 1940), they based the original establishment of
character displacement upon a reinforcement of isolating me-
chanisms in the sympatric zone, and such reinforcement is
not always the case in fish systems. Hybridization may
readily occur in fish systems and is normally detectable
by intermediacy of the hybrid characters. The morphometric
and meristic intermediacy of the Yampa River hybrid suckers,
taken with the phenomena of exotic fish introduction and
environmental alteration, almost completely preclude the
possibility that the "intermediate" Yampa River catostomids
arose from character displacement.
Hybridization in fish may result in either sterile or
reproductive offspring, and the dynamics of the hybrid