7717

• UCREFRP Catalog Number: 7717
• Author: Rosenfeld, M. J.
• Title: Genetic Analysis of the Colorado River Gila
• USFW Year: n.d.
• USFW - Doc Type: Non-fatal Sampling, Cell Culture, Chromosomal Analysis and Electrophoresis.
• Copyright Material: NO

INTRODUCTION

The Colorado River drainage is naturally-inhabited by a

comple:<

of cyprinids within the genus GiJ.a.

Currently~ three

species are recognized on the basis of external

morpholoqy:

the

humpback chub~

cypha Miller; the bony tail chub~ ~. eleQans

Q.

Baird and Girard; and the roundtail

chub~ ~. robusta Baird and

Girard.

Changes in water quality have so inhibited reproductive

success

(Valdez

and Clemmer~

that the bony tail

1982)~

humpback chubs are now protected under the Endangered Species

Act.

Competition from introduced fishes may also have influenced

population declines

(Holden and Stalnaker~ 1975; Tyus et al.,

1982) .

,
We have little understanding of the phylogenetic relation-
ships among the Colorado River Gila. The three recogni~ed
!
i
species comprise closely-related (Uyeno, 1960; Holden i
a group ~nd

Stalnaker~

species status is not clear.

1970) ,

but biological

The Colorado River Gila complex

is notable for its varia~le

morphology in relation to ecology (Miller, 1946) and intergr~de

forms are numerous (Holden,

1968; Holden and Stalnaker, 1970>.

In order to understand species relationships with respect to

this morphological variability as well as to provide a foundat on

for sound management~ certain questions must be addressed:

1.

Are the three described s~ecies also true biologi~al

onE'S':'

2. Are species hybridizing
are speC1es so variable as
SE'('n in Natur-.er:>

1n the wild or, alternate~y,
to give the range of body fo~ms

and

i

~.
t