7017

• UCREFRP Catalog Number: 7017
• Author: Starnes, W. C.
• Title: Colorado River Basin
• USFW Year: 1989.
• Copyright Material: NO

spp. was established because knowledge of variation of
numerous loci (45) in this species was gained in the study.
1989. Moretti, M., S. Cranney and B. Roberts. Distribution and
abundance of Gila spp. in Desolation and Gray canyons of the
Green River during 1985 and 1986. Utah Div. Wildlf. Res.
Rpt., Salt Lake City. 29 p.
Reports a study in which numerous Gila spp. were collected
in the Green River in Desolation and Gray canyons with
morphometric and meristic data taken and photographs for
later analysis by digitizer and computer. Fin tissue and
dead specimens were frozen for eletrophoretic analysis.
Morphometric and eletrophoretic analyses of this material
were performed by M.J. Rosenfeld (see below). In this
population, based on chromosomal analysis, "reproductive
isolation" was indicated between G. cypha and G. robusta;
the degree of isolation between G. cypha and G. elegans (if
present?) could not be determined. However this same
conclusion cannot be inferred from Rosenfeld and Wilkinson
(1989)(next) who stated that these taxa were
electrophoretically indistinguishable. Morphological
analysis indicated considerable variation among localities
within the canyon area, ranging from pure humpbacks to
"humpback intergrades" similar to some specimens encountered
from Black Rocks on the Colorado River. However, it was
felt that hybridization was rare or non-existent (but see
conflicting opinions below).
1989. Rosenfeld, M.J., and J.A. Wilkinson. Biochemical genetics
of the Colorado River Gila complex (Pisces: Cyprinidae).
Southwest. Nat. 34:232-244.
Presents results of a study performed on Gila specimens from
` scattered localities in the Colorado basin, including
presumed cypha from Colorado and Green river canyon areas
and the Little Colorado River, robusta from the Colorado
River and the San Raphael system (Green R. trib.), elegans
obtained from the hatchery stock derived from Lake Mohave
population, G. robusta seminuda from the Virgin River, and
known hybrids from hatchery stock. Fixed differences at
loci were not found but allelic variation was present,
though not necessarily in concordence with morphotypes.
Intra- and interspecific allelic variation was present. G.
cypha and G. robusta from the upper basin are
indistinguishable while differences exist between upper
basin and Little Colorado humpback samples. While
heterozygosity may have remained high in elegans (e.g.,
Minckley et al, 1989, above)(but no historic estimate of
this is available?), this attribute may have declined in
recent years in cypha and extensive hybridization with
robusta is inferred in upper basin populations. This is in
contrast to statements made in Moretti et al. above based on
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