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KERN RIVER
RESEARCH CENTER
Fieldnotes
Spring 1997
Vol. 6, No. 2
SALAMANDER DIVERSITY IN THE KERN VALLEY REGION
By Robert W. Hansen
Considering the
arid terrain that characterizes much of the Kern Valley Region, at first glance
salamanders would not appear to be an especially prominent feature of the local fauna.
However, not only does this region harbor salamanders, but the diversity of species here
is unmatched anywhere in California! Reconciling this apparent enigma is one of the most
fascinating and difficult challenges for California herpetologists.
For the uninitiated,
a good place to start is to shed preconceived notions about where salamanders live.
Contrary to what most popular books depict, the majority of the world's salamander species
do not breed in water, and thus are not dependent on surface water for any part of their
life cycle. The various species of American and European pond- and stream-breeding newts
and waterdogs, are actually in the minority. The salamander family Plethodontidae (the
lungless salamander) is the largest family with over 160 species. With few exceptions,
species in this family undergo terrestrial development. Their eggs are laid on land,
usually underground or in moist talus or logs, and the larval stage is completed within
the egg. Fully formed, miniature salamanders hatch directly from the eggs on land. Of
California's 25 described species of salamanders, only nine are stream or pond-breeders.
These include such familiar species as the California newt (Taricha torosa) and the California tiger
salamander (Ambystoma californiense).
In 1968, University
of Southern California-based herpetologist Arden Brame, Jr. and his colleague Keith Murray
described three new species of so-called "slender salamanders" of the genus Batrachoseps from Kern County. Batrachoseps is a genus of plethodontid salamanders, lungless and fully
independent of surface water. These species live in seasonally moist habitats, which for
foothill and mid-elevation mountain areas means north-facing slopes in protected canyons.
Brame and Murray described the Kern Canyon slender salamander (Batrachoseps simatus), as well as the Tehachapi
slender salamander (B. stebbinsi), both Kern
County endemics with small ranges and threatened status.
In the late 1970's, a
new laboratory technique (gel electrophoresis) was being used to assess genetic
differences between populations of salamanders. This was especially important because many
species of
Batrachoseps are confusingly
similar - small, wormlike with similar coloration. And yet, the lab studies revealed
hidden genetic diversity not previously imagined. For example, what we regarded as a
single species turned out to be several species with deep genetic differences, which
probably had not shared a common ancestor for several million years!
Increasing
sophistication of lab techniques was only part of the story. Beginning in 1979, I began a
collaboration with David Wake, Director of University of California, Berkeley's Museum of
Vertebrate Zoology, to explore many of the mountain populations of Batrachoseps. The field work continues, with new
discoveries still being made. What follows is a summary of our current understanding of
salamanders of the region.
Taricha torosa (California newt) -
The Sierran subspecies (T. t. sierrae) ranges
the length of the Sierra Nevada to the Kern River Canyon, where a healthy population
occurs at Mill Creek. Nearby Clear Creek looks as though it ought to harbor newts as well,
but it doesn't. Perhaps this is due to the more xeric conditions of the surrounding land.
This is a member of the family Salamandridae, and
is our only non-plethodontid of the region.
Ensatina
eschscholtzii
(Ensatina) - This
beautiful salamander is represented by two distinct subspecies in our area: E. e. platensis from the Greenhorn Mountains
northward; and E. e. croceater from the lower
Kern River Canyon, Piute Mountains, and Breckenridge Mountain south through the Tehachapis
and into Los Angeles and Ventura counties. Some individuals from the lower Kern River
Canyon appear to be intergrades between the two subspecies. The northern form (E. e. platensis) is a conifer forest dweller, most
often found under moist logs or bark. The southern form (E. e. croceater) has broader habitat tolerances
and occurs both in oak woodland and coniferous forest. Ensatina is unknown from
east of the Kern River, and thus is absent from the western part of the Kern Plateau where
appropriate habitat occurs.
Batrachoseps
nigriventris
(Black-bellied
slender salamander) - This species occurs mostly in oak woodland areas of the Sierran and
Tehachapi foothills. Although found at scattered sites in the western foothills of the
Greenhorns, it does not occur anywhere east of the mouth of the Kern River Canyon. It is
known from a few sites on the lower slopes of Breckenridge and on the northern slopes of
the Tehachapis.
On-going genetic
studies strongly suggest that this is actually a species complex, consisting of several
distinct species.
Batrachoseps relictus
(Relictual
slender salamander) - Although originally described from several seepage areas in the
lower Kern River Canyon, it has not been found there since the early 1970s and may well be
extirpated from that area. Repeated and thorough searches for it at various wet places
along Highway 178 in the Kern Canyon have failed to turn up specimens of relictus. However, populations presently included
in this species are widespread in moist places in the upper Greenhorns, for example at
Greenhorn Summit on Highway 155. A single seepage-associated population is known from east
of the Kern River on the Kern Plateau at 7900 ft along the Sherman Pass Road. Undoubtedly
there are other small populations awaiting discovery here. Our inability to find relictus in the lower Kern River Canyon has made it
impossible to genetically compare material from this area with animals in the Greenhorns;
there are definite morphological differences and thus we could be dealing with different
species.
Batrachoseps simatus (Kern Canyon
slender salamander) - This large (for a Batrachoseps)
species is known only from a few sites in the lower Kern River Canyon, at elevations
of 1500 ft. (Stork Creek) to almost 4000 ft. (Erskine Creek Canyon in the Piutes).
Batrachoseps "Breckenridge"
(Breckenridge Mountain slender salamander) - This is an undescribed species known only
from a single seepage on the southeastern flank of Breckenridge Mountain at 6300 ft. First
collected in 1979, the site was severely damaged by the re-routing of a logging road
through the seep area. Recent attempts to find additional specimens have been unsuccessful
and it is possible this species may already be extinct.
Batrachoseps robustus (Kern Plateau slender salamander) - This species,
first collected in the late 1970s, and now known from over 20 sites on the Plateau, two
sites in the Scodie Mountains (just south of Walker Pass), and from several places on the
eastern slopes of the Sierra Nevada in Inyo Co. This is a large species that occupies a
range of habitats, from pinyon-juniper woodland to red fir forest, at elevations from 5500
to 9000 ft.
(Newly described per journal article in 2002. editor)
Wake, D.B., K.P. Yanev, and R.W. Hansen. 2002. New species of slender
salamander, Genus Batrachoseps, from the southern Sierra Nevada of
California. Copeia 2002(4): 1016-1028.)
Batrachoseps
"Fairview"
(Fairview slender
salamander) - Still another undescribed species, occurring in the vicinity of Fairview
along the North Fork Kern River in Tulare County. It occupies metamorphic outcroppings in
areas of seasonally moist talus in an otherwise xeric area.
The presence of so
many kinds of salamanders in this area is puzzling. Part of the explanation lies with the
extreme topographic diversity of the area, islands of habitat bordered by uninhabitable
"oceans". Certainly this has promoted isolation and genetic divergence. However,
the region's complex geologic history, including fault movements and uplifts, will likely
prove to be the major factor in lineage separation within
Batrachoseps - Although
Pleistocene climate shifts had considerable effects on the distribution of many plants and
animals in the American southwest, their role in explaining slender salamander
distribution is probably minor. The levels of genetic differentiation that we find with
this group, indicate that divergence considerably predates the Pleistocene, corresponding
to separations of millions rather than hundreds of thousands of years.
We are presently
working on the species descriptions for the above-mentioned forms, and still others will
be recognized once genetic studies are completed. Much remains to be done, however. As
with plants, butterflies, and other groups, there are areas yet to be explored. It is of
particular interest that the Piute Mountains have yet to yield a Batrachoseps, with the exception of B. simatus in Erskine Creek Canyon. There is
abundant habitat at upper elevations, but so far only Ensatina has been found.
Also, Breckenridge Mountain has not been adequately explored for Batrachoseps, both at
upper elevations and in some of the moist canyons on the lower eastern and southern slopes
- surely salamanders are in there somewhere!
Robert W. Hansen is a herpetologist living in Clovis,
California. He is the editor of the Herpetological Review and is the expert on reptile and
amphibian distribution in the southern Sierra Nevada.
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