The Amphibians and Reptiles of Sinaloa, Mexico - Smithsonian ...

AMPHIBIANS AND REPTILES OF SINALOA, MEXICO 167
may be due to a single gene as suggested by Dixon and Fugler
(1959:163).
The ratio of tail length/total length shows a clinal trend. The
longest tails are those of males in the north (15.2, 15.3% for two
specimens from southern Arizona). In males, the shortest tails are
from southern Sinaloa (12.9%, south of Rosario); however, the
shortest tails in females are from northern Sinaloa (12.4, 13.2, 13.3
and 13.5%).
In general, the lateral interblotches are absent in the south and
present in the north. With one exception (LACM 6838 from 36.1
miles south of Coyotitan) all specimens south of El Dorado lack
lateral interblotches. With one exception (ASDM 1925 from five
miles north of Navojoa, Sonora) all specimens north of Terreros
have lateral interblotches. The southernmost specimen with lateral
interblotches has only a few blotches (LACM 6838); the next
southernmost specimen with lateral interblotches is AMNH 79916
from El Dorado. A specimen from 0.8 miles south of Guamuchil
(LACM 6857) has lateral interblotches that include the tips of
the ventrals. To the south, at 46.4 miles north of Culiacan (LACM
6848), the lateral interblotches do not include the ventrals; the
lateral interblotches decrease in number at 43 miles north of Culiacan
(LACM 6847) and are absent at 9 miles north of Culiacan
(LACM 6844). At least some lateral interblotch pigment is indicated
in specimens from southern Sinaloa, but is infrequent in
occurrence. In general, there is a gradual decrease in lateral interblotch
pigment from the north to the south.
The amount of blade pigment on the ventrals increases from
south to north (Table 5). The subcaudal black spots also vary
clinally; the number of specimens with black subcaudal spots increases
from south to north (Table 5).
The lateral extent of the black dorsal body blotches can be
measured by counting the scales separating the lateral margins of
the dorsal blotches and the lateral margins of the ventrals. This
separation varies from zero (dorsal blotch in contact with ventrals)
at the northern limit of the distribution of the species (ASDM 1681
in southern Arizona) to eight in southern Sinaloa (KU 87449).
The dorsal blotch contacts the ventrals in four specimens from
Arizona, two specimens from Sonora and in several specimens in
Sinaloa southward to Mazatlan. The dorsal blotches become smaller
from north to south, being separated by a maximum of two scale
rows in Arizona, three scale rows in Sonora, four scale rows in