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BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32
insularis
vestigium
bicinctores
reticularus
dickersonae
nebrius
collaris
Fig. 42.-The single tree discovered by Monfanucci et al. (1 975)
in their analysis of crotaphytid relationships.
netic analysis of Crotaphytus relationships (again
without considering Crotaphytus reticulatus). The
Ward's Minimum Variance Cluster Analysis (Wis-
hart, 1968) employed morphometric and color pat-
tern data. Their results were consistent with those
oftheir 1972 study, although they were more specific
in their assessment of relationships in this later anal-
ysis. They discussed the interspecific relationships
of the western complex species and recognized two
pairs ofsister taxa, (C. dickersonae + C. bicinctores)
and (C. vestigium + C. insularis). Their tree indi-
cates that they were unsure whether the western
complex was monophyletic or if (C. bicinctores +
C. dickersonae) was actually the sister taxon of C.
collaris (= the collaris complex). Their phyletic tree
suggested Gambelia (= G. wislizenii) to be the sister
taxon of Crotaphytus, and C. reticulatus to be the
sister taxon of the remainder of Crotaphytus. How-
ever, data were not presented for these species and
it is therefore unclear how these conclusions were
reached. The phylogenetic conclusions of this anal-
ysis agree in most respects with those of the present
study except in the placement of C. dickersonae.
which was found to be the sister taxon of C. grismeri,
C. bicinctores, C. vestigium, and C. insularis in this
analysis.
Montanucci et al. (1975) performed the first cla-
distic analysis of Crotaphytus, utilizing 12 allozyme,
discrete morphological, and morphometric char-
acters. Their analysis of these data (using the Wagner
program, Kluge and Fams, 1969) resulted in the
tree depicted in Figure 42. This tree is similar to
those discovered here in the placement of C. bi-
cinctores as the sister taxon of (C. vestigium + C.
insularis). However, their tree differs from the trees
discovered here in the placement of C. dickrsonae
as the sister taxon of (C. nebrius + C. collaris), in
the placement of C. reticulatus as the sister taxon
of this group, and in placing (C. bicinctores (C. ves-
tigium + C. insularis)) as the sister taxon of (C.
reticulatus (C. dickersonae (C. nebrius + C, collar-
is))). As with the previous analyses, several taxa
could not be included, such as C. grismeri (not yet
recognized as a distinct lineage) and C. antiquus (yet
to be discovered).
Few comparisons can be drawn between the re-
sults of this analysis and those of previous studies
regarding the phylogenetic relationships of Garn-
belia. Those previous workers who recognized G.
silus as a distinct species generally assumed it to be
the sister taxon of G. wislizenii. Only Norell (1989)
attempted to elucidate the phylogenetic relation-
ships of Gambelia and he was primarily interested
in the position of G. coronaf. Although Norell (1 989)
described a number of useful characters, he was un-
able to provide phylogenetic resolution. A distinc-
tion between this analysis and several others relates
to the evolution of G. silus. Some previous workers
suggested that G. silus may have evolved as recently
as 11,000 years ago by peripheral isolation (Mon-
tanucci, 1967, 1970; Tollestrup, 1979), although
Montanucci (1970) also entertained the possibility
that G. silus entered the valley much earlier. Re-
gardless of the timing of the event, Montanucci
(1 970) suggested that differences between G. silus
and G. wislizenii are examples of derived character
states in G. silus rather than derived characteristics
of G. wislizenii. However, most of these features,
such as the presence of territoriality, a truncated
snout, and sexual dimorphism wherein males are
larger than females, are more parsimoniously inter-
preted as plesiomorphic retentions in G. silus. This
interpretation is consistent with that of Tollestrup
(1983), at least with respect to the loss of territori-
ality in G. tvislizenii. Thus, it appears that G. silw
is a relatively plesiomorphic taxon and not a re-
cently derived offshoot of G. wislizenii.
It may seem counterintuitive that a narrowly dis-
tributed peripheral species such as Gambelia silus
would be relatively plesiomorphic in comparison
with a wide-ranging taxon such as G. wislizenii (plus
its sister taxon, G. copei). However, there are ex-