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KERN RIVER
RESEARCH CENTER
Fieldnotes
Spring 1997 Vol. 6, No. 2
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 (see note) (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.
(NOTE:
The webmaster added the specific epithet after this article was
written with review of the following journal article)
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. |
