Part 11

Distribution.--Low elevations in coastal Nayarit and on Islas Tres Marias (Fig. 20).

Specimens examined.--(12) MEXICO, Nayarit: 18.8 mi. NW Ahuacatlan, UIMNH 7808; San Blas, UMMZ 115452 (holotype), 115453-57; 17 km. NE San Blas, 150 m., MSU 5085; 12.8 km. E San Blas, UIMNH 71979; 31 km. E San Blas, UIMNH 71978; 13.5 km. N Tepic, UIMNH 71980-81.

=Syrrhophus teretistes= Duellman

Syrrhophus teretistes Duellman, 1958:2-3, 10-14, pl. 2, fig. 2 [Holotype.--UMMZ 115451, from 4.8 km. NW Tepic, Nayarit, Mexico, 840 m.; collected on August 12, 1956, by William E. Duellman]. Gorham, 1966:167.

Diagnosis.--Medium-sized frogs, males 19.2-23.2 mm. snout-vent length, single known female 24.8 mm. snout-vent; vocal slits in males; finger tips widely expanded; first finger shorter than second; inner metatarsal tubercle about three times size of outer; skin of dorsum shagreened, that of venter smooth; tympanum partially concealed, its diameter 28.6-43.8 per cent of eye in males; ground color brown vermiculated with dark brown to nearly black; upper arm and thigh banded; interorbital light bar absent.

Remarks.--S. teretistes appears to be most closely related to S. pallidus; I consider it to be an upland derivative of pallidus. Morphologically, the differences between the two are few, but lacking evidence of genetic exchange they are retained as species.

Etymology.--Greek, in reference to the whistle-like nature of the call.

Distribution.--Moderate elevations (840-1200 meters) in the Sierra Occidental of Nayarit, Sinaloa, and Durango, Mexico (Fig. 20).

Specimens examined.--(13) MEXICO, Nayarit: 4.8 km. NW Tepic, 840 m., UMMZ 115451 (holotype). Sinaloa: Santa Lucia, 1090 m., KU 75263-72; 1 km. NE Santa Lucia, 1156 m., KU 78257; 2.2 km. NE Santa Lucia, 1156 m., KU 78258.

DISCUSSION

There are relatively few clear-cut morphological differences among the fourteen species now assigned to Syrrhophus. The majority of the species are allopatric and differ primarily in color patterns. Sympatric occurrence serves as an indicator of specific distinctness and is one of the more practical tests of species validity when cross-breeding experiments are not possible. Two cases of sympatric occurrence are known for the species of Syrrhophus in western Mexico: modestus and nivocolimae are sympatric in southern Jalisco and pipilans nebulosus and rubrimaculatus are sympatric in southeastern Chiapas. In eastern Mexico, longipes and verrucipes are sympatric in southern Hidalgo, and longipes is sympatric with cystignathoides, dennisi, and guttilatus in southern Tamaulipas. Syrrhophus cystignathoides and leprus are apparently sympatric in central Veracruz.

Subspecific assignments have been made only when there is evidence of intergradation. The sympatric occurrence of morphologically similar species in this genus has led me to adopt a conservative approach to the degree of difference philosophy. I have therefore recognized all morphologically distinct allopatric populations as species.

Syrrhophus is closely allied to another Mexican leptodactylid genus, Tomodactylus, which was revised by Dixon (1957), who along with numerous other authors noted the close relationship between the two genera. There is an almost complete lack of sympatry between the two genera; in very few places in Mexico do they coexist (Fig. 21). Tomodactylus has its greatest diversity in the Cordillera Volcanica and Sierra Madre del Sur, whereas Syrrhophus reaches its greatest diversity in the Sierra Madre Oriental and eastern foothills. The species of both genera are about the same size and presumably have similar requirements insofar as food, breeding sites, and habitat selection.

Four cases of intergeneric sympatry are known for the two genera: 1) the Chilpancingo region of Guerrero, 2) the lowlands of Colima and the mountains just inland in Jalisco, 3) the lowlands of central Nayarit, and 4) the Sierra Madre Occidental on the Durango-Sinaloan border. The apparent sympatry in the Chilpancingo region involves four species: S. pipilans, T. albolabris, T. dilatus, and T. nitidus. Of the four, T. dilatus appears to be completely allopatric in that it occurs at higher altitudes (above 2000 meters), whereas the other three occur below 1800 meters in the region (Davis and Dixon, 1965). In the Colima-Jalisco region, Tomodactylus tends to occur higher (Dixon and Webb, 1966) than some of the Syrrhophus, but one subspecies of Tomodactylus nitidus is a lowland frog, occurring sympatrically with the lowland Syrrhophus modestus. A similar situation is observed in Nayarit; the lowland Tomodactylus occurs sympatrically with the small Syrrhophus pallidus. In both cases the Syrrhophus is smaller than the Tomodactylus.

Frogs of the genus Syrrhophus tend to occur at lower elevations than do their close relatives of the genus Tomodactylus (Fig. 22). This generalization is complicated by the occurrence in the Sierra Madre Oriental in relatively high altitude Syrrhophus (up to 2000 m.) and the occurrence in Michoacan of low altitude Tomodactylus (to sea level). There are no Tomodactylus in the Sierra Madre Oriental, whereas the genus Syrrhophus is represented in the lowlands of western Mexico (modestus group). Syrrhophus and Tomodactylus exhibit essentially parapatric distributions. The two genera as now composed can be characterized as low to moderate elevation frogs (Syrrhophus) and moderate to intermediate elevation frogs (Tomodactylus).

LITERATURE CITED

BAIRD, S. F.

1859. Reptiles of the Boundary. United States and Mexican Boundary Survey, pp. 1-35, pls. 1-41.

BARBOUR, T.

1923. The reappearance of Batrachyla longipes. Proc. New England Zool. Club, 8:81-83.

BARBOUR, T., and A. LOVERIDGE

1946. Typical reptiles and amphibians; supplement. Bull. Mus. Comp. Zool., 96:59-214.

BOULENGER, G. A.

1882. Catalogue of the Batrachia Salientia ... British Museum., 2nd ed.

1888. Note on the classification of the Ranidae. Proc. Zool. Soc. London, 1888, pt. 2:204-06.

CAMPBELL, H. W., and R. S. SIMMONS

1962. Notes on some reptiles and amphibians from western Mexico. Bull. So. California Acad. Sci., 61:193-203.

CONANT, R.