Amphibian and Reptile Biogeography

The amphibians and reptiles that occur in the White-Inyo mountains region show several different distributional patterns. This is due in part to changes in desert vegetation in the area. The southern valleys, which are relatively low in elevation, have Creosote Bush (Larrea tridentata ) as the dominant plant. This is typical of the Mojave Desert as well as other southern deserts in North America. Panamint Valley, Saline Valley, Eureka Valley, and the western slopes of the Inyo Mountains in southern Owens Valley all have Creosote Bush Scrub. The higher, northern valleys, where Creosote Bush is absent, have other dominant plants, such as Shadscale (Atriplex confertifolia ). Fish Lake Valley, Deep Springs Valley, Owens Valley (except the southwestern part), Chalfant Valley, Hammil Valley, Benton Valley, and Queen Valley all feature this Great Basin Scrub desert. The change in desert foliation causes a south-to-north transition in species of amphibians and reptiles.

The amphibians and reptiles can be grouped into five distributional patterns (see Table 10.1). The southern group consists of species whose ranges are primarily south of the area in Creosote Bush Scrub; these species typically occur in the Mojave Desert. In the White-Inyo mountains region, two species appear to follow the distribution

of Creosote Bush closely: the Desert Iguana (Dipsosaurus dorsalis ) and the Western Blind Snake (Leptotyphlops humilis ). However, the Western Banded Gecko (Coleonyx variegatus ), Common Chuckwalla (Sauromalus obesus ), Desert Night Lizard (Xantusia vigilis ), Southwestern Black-headed Snake (Tantilla hobartsmithi ), Sidewinder (Crotalus cerastes ), and Speckled Rattlesnake (Crotalus mitchellii ), extend north of the Creosote Bush Scrub into Great Basin Scrub. The Red-spotted Toad (Bufo punctatus ), the only southern amphibian in the area, requires a moist habitat with permanent water. It is absent from the Eureka and southern Owens valleys. The Glossy Snake (Arizona elegans ) and Sidewinder (Crotalus cerastes ) seem to be absent from the Saline and Eureka valleys. The Western Shovel-nosed Snake (Chionactis occipitalis ) has not been found in the Eureka Valley. The Rosy Boa (Lichanura trivirgata ), Spotted Leaf-nosed Snake (Phyllorhynchus decurtatus ), and Lyre Snake (Trimorphodon biscutatus ) have yet to be recorded from any valley except the Panamint.

The wide-ranging species have distributions in both the Mojave Desert and the Great Basin Desert. These species occur in every valley, with the exception of the Zebra-tailed Lizard (Callisaurus draconoides ), which appears to be absent from Deep Springs Valley.

Species in the northern group generally avoid Creosote Bush Scrub. They have distributions to the north in the Great Basin Desert. Many of these species also occur to the west of the Sierra Nevada, and some are found isolated on high mountains in the Mojave Desert. The Northern Leopard Frog (Rana pipiens ) is restricted to the Owens River and its tributaries in the northern Owens Valley, and apparently along creeks draining the eastern White Mountains, since there is one record from 7,100 ft (2,160 m). The Western Toad (Bufo boreas ), Pacific Treefrog (Pseudacris regilla ), and Great Basin Spadefoot Toad (Spea intermontana ), which tend to be near water, each have one record in the range of Creosote Bush. The Western Skink (Eumeces skiltonianus ) is mainly distributed in mountain areas in the vicinity of water and avoids Creosote Bush Scrub in this area. The Sagebrush Lizard (Sceloporus graciosus ) mainly occurs in high mountain areas but it also occurs on the valley floors of the southern Owens, northern Owens, Chalfant, Hammil, Benton, Queen, and Fish Lake valleys. The Western Fence Lizard (Sceloporus occidentalis ) occurs in or around all valleys, but at higher elevations around the Panamint Valley. The Western Rattlesnake (Crotalus viridis ) is present only in the Queen and Fish Lake valleys, where it may be hybridizing with the Speckled Rattlesnake (Crotalus mitchellii ). The Striped Whipsnake (Masticophis taeniatus ) is present in all northern valleys, as is the Western Terrestrial Garter Snake (Thamnophis elegans ). The latter is also in the southern Owens Valley.

The five endemic species occur only in the White-Inyo mountains region and directly adjacent areas. The Inyo Mountains Salamander (Batrachoseps campi ) occurs at 13 springs in the Inyo Mountains, and is in the Saline Valley and southern and northern portions of the Owens Valley. The Kern Plateau Salamander (Batrachoseps sp.) occurs along creeks draining the Sierra Nevada in the southern Owens Valley. The Owens Valley Web-toed Salamander (Hydromantes sp.) is present along creeks draining the Sierra Nevada in the southern and northern portions of the Owens Valley. The Black Toad (Bufo exsul ), a close relative of the Western Toad (Bufo boreas ), occurs

only in the Deep Springs Valley, where the Western Toad (Bufo boreas ) is absent. The Panamint Alligator Lizard (Elgaria panamintina ) is recorded from the Panamint and Saline valleys and throughout the eastern portion of the Owens valley. A site record for the west side of the White Mountains in the Hammil Valley also exists.

Species in the western group have distributions mainly to the west of the Sierra Nevada. The Southern Alligator Lizard (Elgaria multicarinata ) is distributed along the east side of the Sierra Nevada at least from Olancha to Grant Lake, Mono County. The Gilbert Skink (Eumeces gilberti ) is present in springs at low elevations and in a variety of habitats at higher elevations. It occurs in many mountain ranges throughout the Mojave Desert and in all Creosote Bush Scrub valleys, but it appears to be absent from the western slopes of the Inyo Mountains in the southern Owens Valley. It also occurs on the western slopes of the White Mountains in the northern Owens Valley and in the southeastern slopes of the White Mountains in the Deep Springs and Fish Lake valleys. The Sierra Garter Snake (Thamnophis couchii ) is present in the southern Owens, northern Owens, and Chalfant valleys.

Figures 10.1 and 10.2 show the percentages of southern, wide-ranging, northern, endemic, and western species in each of the valleys. In general, as southern species decline in number, northern species increase. The valleys to the east of the White-Inyo Range show an abrupt transition between the northern fauna of the Great Basin Desert and the southern fauna of the Mojave Desert. In the Panamint, Saline, and Eureka valleys, which contain Creosote Bush, a few northern species occur. In contrast, the Fish Lake Valley to the north, in which no Creosote Bush is present, has 8 northern species. Additionally, the only southern species in the Fish Lake Valley is the Speckled Rattlesnake (Crotalus mitchellii ). To the south in the Eureka Valley there are 6 southern species, in the Saline Valley 9, and in the Panamint Valley 14.

On the west side of the White-Inyo Range a more gradual transition between the two desert fauna exists. The southern Owens Valley has 7 northern species, although it contains Creosote Bush desert. The northern Owens Valley contains 8, and the Chalfant, Hammil, Benton and Queen valleys together have 9 northern species. In the latter grouping of valleys only 3 southern species — the Desert Night Lizard (Xantusia vigilis ), Sidewinder (Crotalus cerastes ), and Speckled Rattlesnake (Crotalus mitchellii ) — occur, yet the northern Owens Valley, which lacks Creosote Bush, has 6 species. In the southern Owens Valley there are 10 southern species.

The Deep Springs Valley between the Inyo and White mountains contains Great Basin Scrub desert. The Speckled Rattlesnake (Crotalus mitchellii ) is the only southern species present in the valley. The wide ranging Zebra-tailed Lizard (Callisaurus draconoides ) appears to be absent from this valley. In addition, only four northern species occur here, along with one western species and one endemic.

To illustrate the relationships among valleys, two trees are included. These trees were derived from two formulas, called faunal resemblance factors. The Braun-Blanquet faunal resemblance factor (BFRF) emphasizes the differences between the species compositions of different geographic regions (Braun-Blanquet, 1932). It is calculated by taking the number of species in common (C ) to two sites and dividing it by the total number present at the site with the larger number of species (N_L ).

Figure 10.1
Amphibian and reptile distributional patterns on the two sides of the White-Inyo Range. Above are the valleys to the east
of the White-Inyo Range. Below are the valleys to the west of the White-Inyo Range. Note that the Chalfant Valley is
included with Hammil, Benton, and Queen valleys.

Figure 10.2
Amphibian and reptile distributional patterns across the White-Inyo Range.

The resulting value is multiplied by 100 to take the form of a percentage.

BFRF = (C/N_L )100

Alternatively, the Simpson faunal resemblance factor (SFRF) emphasizes the similarities between the species compositions of different geographic regions (Simpson, 1960). It is calculated by taking the number of species in common (C ) to two sites and dividing it by the total number present at the site with the smaller number of species (N _S ).

SFRF = (C/N_S )100

The numbers that were derived are presented in Table 10.2. To show the relation between the valleys in the White-Inyo mountains region, two sites outside the area were included. In the Mojave Desert, the Granite Mountains south of Kelso, San

Figure 10.3
The Baun-Blanquet faunal resemblance factor (BFRF) percent similarity tree, which
emphasizes differences.

Bernardino County, California, was used. In the Great Basin Desert, Pyramid Lake, Washoe County, Nevada, was used.

The trees are presented in Figs. 10.3 and 10.4. They illustrate the abrupt transition between the two desert fauna present on the east side of the White-Inyo Range. Both trees cluster the Panamint, Saline, and Eureka valleys with the Granite Mountains in the Mojave Desert. Both trees also cluster the Chalfant (including the Hammil, Benton, and Queen valleys), Deep Springs, and Fish Lake valleys with Pyramid Lake

Figure 10.4
The Simpson faunal resemblance factor (SFRF) percent similarity tree, which
emphasizes similarities.

in the Great Basin Desert. The two trees differ on the positioning of the southern Owens and northern Owens valleys. The BFRF, emphasizing differences, places the southern and northern portions of the Owens Valley together in a subcluster of the Mojave desert cluster. The SFRF, emphasizing similarities, places the southern Owens Valley furthest out from the Great Basin Desert cluster and puts the northern Owens Valley with the Fish Lake Valley. This illustrates a more gradual and broad transition between the two fauna in the Owens Valley to the west of the White-Inyo Range. This is due to a wider range of habitats present in the Owens Valley. The Owens River and the creeks that drain the eastern Sierra Nevada provide riparian habitat and cooler conditions for northern species. The Creosote Bush Scrub in the southern Owens Valley and the gradual elevational increase from Owens Lake to the Queen Valley provide a corridor for southern species to range further north (Macey, 1986; Murphy, 1983).