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McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS
tion of Crotapl~ytus ~vislizerti copei and described a
new subspecies, C. IV. neseotes, from Isla de Cedros
off the west coast of Mexico. They did not follow
Weiner and Smith (1965) with regard to the subgeneric
groupings.
In response to Weiner and Smith (1965), Montanucci
(1 969) entered the Gambelia-Crotaphyfus
debate. Based on an examination of the osteology
of C. wislizenii, C. silus, C. collaris, and C. reticulatus,
he concluded that there should be no generic
or subgeneric segregation within the group. He also
recognized C. silus as a species distinct from C. wislizenii,
based on unpublished data. Crotaphytus
dickersonae and C. insularis were again recognized
as full species distinct from C. collaris. In a paper
published the following year, Montanucci (1 970)
formally elevated Crotaphytus silus from a subspecies
of C. bvislizenii to a full species based on morphological,
ecological, and behavioral differences.
Ingram and Tanner (1 97 1) described Crotaphytus
collaris ficus from the Chihuahuan Desert region.
The subspecies could not be diagnosed by discrete
morphological characters and was proposed on the
basis of a distinctive discriminant function.
In 1972, Holman described Crotaphytus oligocenicus
on the basis of a right dentary from the early
Oligocene Cypress Hills Formation, Saskatchewan,
Canada.
Smith and Tanner (1972) were the first to rec-
ognize that there were additional distinct Crotaphyt
i taxa occurring primarily west of the Colorado
River. They described Crotaphytus collaris bicinctores
from the Great Basin region and C. insularis
rlestigiurn from the peninsular ranges of Baja California,
Mexico, and southern California. Using a
Ward's Minimum Variance Cluster Analysis, they
found that there were two phenotypically distinct
groups of collared lizards (excluding C. reticulatus),
each comprised of four named forms. The "western
complex" was found to include C. i. insularis, C. i.
vestigiurn, C. c. bicinctores, and C. c. dickersonae,
while the "collaris complex" was found to include
C. c. collaris, C. c. baileyi, C. c. auriceps, and C. c.
ficus. Despite these findings, they described bicinctores
as a subspecies of C. collaris and chose to
recognize C. dickersonae as a subspecies of C. collaris,
as well. Thus, their own classification did not
follow the phylogenetic relationships they had proposed.
Axtell (1 972) considered Crotaphytus collaris bicinctores
and C. c. baileyi to be distinct at the species
level based on morphological differences and a nar-
row hybrid zone between the two in the Cerbat
Mountains of Arizona. He tentatively placed bicinctores
as a subspecies of C. instrlaris.
Smith and Tanner ( 1974) again recognized bicinctores
as a subspecies of Crotaphytus collaris. They
based this taxonomic decision on intergrade specimens
between C. bicinctores and C. collaris in nonhwestern
Sonora, Mexico, and southwestern Arizona,
as well as the hybrid specimens identified by Axtell
(1972) from the Cerbat Mountains of Arizona.
However, the presumed intergrade specimens were
actually C. c. nebriics, subsequently described by
Axtell and Montanucci (1977), with the characteristic
features ofthis species. They substantiated their
previous recognition of C. dickersonae as a subspecies
of C. collaris on the basis of intergrades between
dickersonae and collaris from the Guaymas region.
However, these specimens are again C. nebrius.
Based on the results of their cluster, canonical, and
discriminant function analyses, they provided two
potential phylogenetic hypotheses for Crotaphytus
shown here in parenthetical form: (wislizenii (reticulatus
+ (fisctcs (collaris (baileyi + auriceps))) +
((dickersonae + bicinctores) + (insularis + vestigiurn)))))
or (~crislizetlii (reticulatus + ((insularis +
vestigiutn) + ((dickersonae + bicinctores) + (ficus
(collaris (baileji + auriceps))))))). These hypotheses
of relationship differ in that the first recognizes a
group that includes C. c. dickersonae, C. c. bicinctores,
C. i. insularis, and C. i. vesrigium, while the
second recognizes all of the C. collaris subspecies as
a group. In addition, Smith and Tanner (1 974) again
recognized silus as a subspecies of C. wislizenii.
Montanucci et al. (1975) made the first attempt
at a cladistic analysis of the group. As a result of
their electrophoretic study, they recommended the
recognition of Garnbelia as a valid genus, elevated
Crotaphytus tvislizeni silus and C. collaris dickersonae
to full specific status, and removed C. c. bicinctores
from C. collaris (again recognizing C. i.
bicinctores). They did not recognize C. c. auriceps,
considering it to be a junior synonym of C. c. baileyi.
They found the character states present in C. dickersonae
to be confounding and proposed a possible
hybrid origin for the species. Their proposed phylogeny
of the group was similar to those of Smith
and Tanner ( 1 972, 1 974), except that C. dickersonae
was included with Smith and Tanner's (1972) "collaris-complex."
The soon-to-be-described C. c. nebrius
(included as C. collaris ssp.) was also included
in this complex. Their data suggested the following
phylogenetic relationships: ((bicinctores (insularis +