[Federal Register Volume 76, Number 192 (Tuesday, October 4, 2011)]
[Proposed Rules]
[Pages 61321-61330]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-25561]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8-ES-2007-0023; MO 92210-0-0008-B2]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition to List the Amargosa River Population of the Mojave
Fringe-Toed Lizard as an Endangered or Threatened Distinct Population
Segment
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
12-month finding on a petition to list the Amargosa River population of
the Mojave fringe-toed lizard (Uma scoparia) located in San Bernardino
County, California, as an endangered or threatened distinct population
segment (DPS), under the Endangered Species Act of 1973, as amended
(Act). After a thorough review of all available scientific and
commercial information, we find that the Amargosa River population of
the Mojave fringe-toed lizard does not constitute a DPS under our 1996
policy and, therefore, is not a listable entity under the Act. We ask
the
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public to continue to submit to us any new information concerning the
status of, and threats to, the Amargosa River population of this
species and the species overall. This information will help us to
monitor and encourage the ongoing management of this species.
DATES: The finding announced in the document was made on October 4,
2011.
ADDRESSES: This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R8-ES-2007-0023 and at http://www.fws.gov/ventura/. Supporting documentation we used in preparing
this finding is available for public inspection, by appointment, during
normal business hours at the U.S. Fish and Wildlife Service, Ventura
Fish and Wildlife Office, 2493 Portola Road, Suite B, Ventura, CA
93003; telephone 805-644-1766, extension 372; facsimile 805-644-3958.
Please submit any new information, materials, comments, or questions
concerning this finding to the above street address.
FOR FURTHER INFORMATION CONTACT: Michael McCrary, Listing and Recovery
Coordinator, U.S. Fish and Wildlife Service, Ventura Fish and Wildlife
Office (see ADDRESSES section). Persons who use a telecommunications
device for the deaf (TDD) may call the Federal Information Relay
Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Endangered Species Act of 1973, as
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition
to revise the Lists of Endangered and Threatened Wildlife and Plants
that contains substantial scientific and commercial information that
the petitioned action may be warranted, we make a finding within 12
months of the date of our receipt of the petition. In this finding, we
determine that the petitioned action is: (1) Not warranted; (2)
warranted; or (3) warranted, but the immediate proposal of a regulation
implementing the petitioned action is precluded by other pending
proposals to determine whether species are endangered or threatened,
and expeditious progress is being made to add or remove qualified
species from the Lists of Endangered and Threatened Wildlife and
Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition
for which the requested action is found to be warranted but precluded
as though resubmitted on the date of such finding; that is, it requires
a subsequent finding to be made within 12 months. We must publish these
12-month findings in the Federal Register.
Previous Federal Actions
We received a petition dated April 10, 2006, from the Center for
Biological Diversity (CBD) and Ms. Sylvia Papadakos-Morafka requesting
that the Amargosa River population of the Mojave fringe-toed lizard
(Uma scoparia) located in San Bernardino County, California, be listed
as an endangered or threatened distinct population segment (DPS) under
the Act (CBD and Papadakos-Morafka 2006). According to the petition,
the Amargosa River population is limited to Ibex and Dumont dunes and
Coyote Holes, which are located at the northern end of the entire range
of the species. On January 10, 2008, the Service made its 90-day
finding (73 FR 1855), concluding that the petition did present
substantial scientific or commercial information to indicate that the
Amargosa River population of the Mojave fringe-toed lizard may be a DPS
based on genetic evidence, which may meet both the discreteness and
significance criteria of the DPS policy (61 FR 4722; February 7, 1996),
and, thus, may be a listable entity under the Act. Additionally, the
Service found the petition presented substantial scientific or
commercial information that listing the Amargosa River population of
the Mojave fringe-toed lizard as endangered or threatened may be
warranted. With publication of the 90-day finding, the Service
initiated a status review of the Amargosa River population of the
Mojave fringe-toed lizard and solicited scientific and commercial
information regarding this population.
To ensure that this finding is based on the latest information and
incorporates the opinions of the scientific community, the Service
considered information provided by the public and additional
information and data in our files that, combined, provided the basis
for the status review for the Amargosa River population of the Mojave
fringe-toed lizard.
Species Information
Species Biology
The Mojave fringe-toed lizard is in the North American spiny lizard
family (Phrynosomatidae). This medium-sized lizard, which may reach a
snout-to-vent length of up to 4.5 inches (112 millimeters), is highly
adapted to a sand-dwelling existence (Norris 1958, p. 253). As part of
its adaptation to living in sand, the Mojave fringe-toed lizard's body
and tail are dorsoventrally (top to bottom) compressed, which
facilitates sand self-burial (Hollingsworth and Beaman 1999, p. 1). The
hind feet have a series of elongated scales fringing the lateral edges
of the third and fourth digits; these fringes widen the toes, giving
the lizard additional support for locomotion on sand, and serve as
``sand shoes.'' The fringes also assist in the lizard's movements
beneath the surface of the sand (Norris 1958, p. 253). Self-burial by
fringe-toed lizards is presumed to be defensive; there is no evidence
to suggest that self-burial is thermoregulatory or used for subsurface
hunting as exhibited by other genera of sand lizards (Pough 1970, p.
153). Nasal valves restrict the entrance of sand into the lizard's
nasal passages. The nasal passages are also specialized for desert
living; they are convoluted and have absorbing surfaces that reduce
moisture loss through the nasal openings (Stebbins 1944, p. 316). Other
adaptations to a sand environment include smooth skin surface, a wedge-
shaped head, and well-developed eye and ear flaps (Pough 1970, p. 145).
The Mojave fringe-toed lizard's smooth skin is patterned with
small, black circles and flecks. Both sides of the belly have a
conspicuous black spot, the underside of the tail has black bars, and
both sides of the throat have crescent-shaped markings. The concealing
coloration of fringe-toed lizards is striking and is one of the best
examples of this phenomenon among North American vertebrates. Adults of
the species have a yellow-green wash on the belly and pink on the sides
during breeding periods, but during other times of year, the Mojave
fringe-toed lizard's color mimics the sand dunes on which they dwell
(Norris 1958, p. 253). The Mojave fringe-toed lizard is distinguished
from other fringe-toed lizard species by the dark black spot on each
side of the belly and the crescent-shaped markings present on the sides
of the throat. The small black circles over the shoulders do not unite
to form lines as they do in the very closely related species, Uma
notata.
Mojave fringe-toed lizards are omnivorous throughout their lives.
They primarily feed on insects but will also eat seeds and flowers
(Stebbins 1944, p. 329). Annual plants provide forage during the
springtime; however, their availability diminishes during the summer as
vegetation dries up (Stebbins 1944, p. 329). Mojave fringe-toed lizards
derive most of their water from arthropods and plants they ingest.
The Mojave fringe-toed lizard is diurnal (active during the day)
and has daily activity patterns that are temperature-dependent. The
actual ambient temperature range in which the
[[Page 61323]]
Mojave fringe-toed lizard is active has not been documented. However,
it is documented that the Mojave fringe-toed lizard is likely active
when its internal body temperature is between 79 and 112 degrees
Fahrenheit (26 and 44 degrees Celsius) (Hollingsworth and Beaman 1999,
p. 3). In March and April, Mojave fringe-toed lizards are active fewer
hours than other species of fringe-toed lizards due to cooler
temperatures in the Mojave Desert. From May to September, they move
about in the mornings and late afternoons but retreat underground when
temperatures are high. Hibernation occurs from November to February
(Mayhew 1966, pp. 120-121).
The Mojave fringe-toed lizard generally reaches sexual maturity
during the second summer following hatching. Reproductive activity in
both sexes varies from year-to-year and tends to increase with higher
rainfall; winter rainfall (October to March) in particular seems to be
the critical reason for the increased reproductive activity. The
moisture promotes germination in sand-dwelling plants and production of
leaves and flowers that provide nutrients, moisture, and protective
cover to the lizards, and thus enhances reproductive activity (Mayhew
1966, pp. 119-120). Breeding coloration and increase in testis size
indicate the male breeding period, which typically occurs between April
and late June. Female breeding colors are displayed between April and
September (Mayhew 1966, pp. 115-117). Ovarian egg counts also fluctuate
in response to rainfall and food availability, with reduced egg counts
and fewer juveniles following dry winters. There is also evidence to
suggest that female lizards may have more than one brood per year
(Mayhew 1966, p. 118).
Species Range, Habitat, and Dispersal
The Mojave fringe-toed lizard is endemic to the deserts of southern
California and a small area across the Colorado River in western
Arizona. The Mojave fringe-toed lizard occurs in the lower Sonoran life
zones of the Mojave Desert and the northwestern reaches of the Sonoran
Desert characterized by palo verde (Cercidium floridum), mesquite
(Prosopis chilensis), creosote bush (Larrea tridentata), white bur sage
(Franseria sp.), indigo bush (Dalea sp.), and numerous species of
annuals. The Mojave fringe-toed lizard inhabits areas of wind-blown
sand, including dunes, washes, hillsides, margins of dry lakes, and
flats with sandy hummocks that form around bases of vegetation
(Hollingsworth and Beaman 1999, p. 8). Fringe-toed lizards (Uma spp.),
including the Mojave fringe-toed lizard, likely select active sand dune
areas and other areas of wind-blown, intermediate-sized grains of sand,
because those conditions facilitate self-burying and respiration while
under the sand (Pough 1970, p. 154). Based on the scientific
literature, the Mojave fringe-toed lizard is currently known to occur
at more than 35 sand dunes localities in southern California and one
dune in western Arizona (Figure 1).
BILLING CODE 4310-55-P
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[GRAPHIC] [TIFF OMITTED] TP04OC11.016
BILLING CODE 4310-55-C
[[Page 61325]]
On April 10, 2006, we received a petition to list the Amargosa
River population of Mojave fringe-toed lizard as an endangered or
threatened DPS under the Act. The petition defined the Amargosa River
population as Mojave fringe-toed lizards occurring at Ibex Dunes,
Dumont Dunes, and Coyote Holes (Figure 1). Subsequent to the submittal
of the petition, and as part of the status review conducted for this
finding, Mojave fringe-toed lizards were found in new locations for
which there are no historical records of occurrence. Based on their
proximity to the three petitioned dunes, several of the new locations
are part of the Amargosa River population and, as hereafter described
in this finding, the Amargosa River population includes the following
newly discovered occupied dunes: Little Dumont Dunes, located about 3
miles (mi) (4.8 kilometers (km)) southwest of Dumont Dunes (Glenn 2008,
in litt.); Valjean Dunes, located about 4 mi (6.4 km) southeast of
Dumont Dunes (Encinas 2008, in litt.); the sandy area between Dumont
and Valjean dunes (Encinas 2008, in litt.); and three unnamed dunes
located roughly midway between Valjean Dunes and Coyote Holes (Encinas
2008, in litt.) (Figure 1).
Additionally, new records of Mojave fringe-toed lizards have also
expanded the areas known to be occupied at Ibex Dunes, Dumont Dunes,
and Coyote Holes (Glenn 2008, in litt.). Although not part of the
Amargosa River population, Mojave fringe-toed lizards have also been
recently found at an unnamed dune between Red Pass Dune and Silver Lake
(Glenn 2008, in litt.) (Figure 1). In aerial photographs, we also noted
the presence of other dune formations and wind-blown sand areas
southeast of Ibex Dune, northwest of Valjean Dunes, between Silver Lake
and Red Pass Dune, and between Red Pass Dune and Cronese Lakes. The
physical characteristics and structure of these areas appear to be
similar to habitat known to be occupied by the Mojave fringe-toed
lizard. However, these areas have not yet been surveyed for the
presence of Mojave fringe-toed lizards.
Dispersal of Mojave fringe-toed lizards between populations is
poorly studied. No specimen of fringe-toed lizard has been captured
more than approximately 150 feet (ft) (46 meters (m)) from wind-blown
sand deposits (Norris 1958, p. 257). Norris believed that fringe-toed
lizards are totally restricted to areas of wind-blown sand. For this
reason, Mojave fringe-toed lizards, in the absence of intervening
suitable habitat, have historically been considered to be restricted to
active dunes, and in a few cases, sandy habitat associated with dry
lakes and washes.
Genetics
Mojave fringe-toed lizard phylogenetics have been studied by Murphy
et al. (2006, pp. 226-247) and more recently by Gottscho (2010, pp. 1-
81). Phylogenetics is the study of the evolutionary relationships
between groups of organisms, such as families, subfamilies, genera, and
species, based on genetic material. Murphy et al. (2006, pp. 231-233)
analyzed the relationships between different populations of Mojave
fringe-toed lizards based on mitochondrial DNA. Mitochondrial DNA is
inherited from the female parent and not the male; thus, the genetic
information reflects the matrilineal history. In the mitochondrial DNA
study, tissue samples from 79 lizards were collected from 21 major dune
systems, including 1 dune in Arizona, known to be occupied by the
Mojave fringe-toed lizard as verified by collections in the California
Academy of Sciences and Los Angeles County Museum of Natural History.
Murphy et al. (2006, p. 232) detected 52 unique haplotypes among the 21
dune systems sampled. A haplotype is a set of closely linked genetic
markers on a single chromosome that tend to be inherited together. The
number of tissue samples collected per dune was small, with three or
fewer samples collected from the majority (57 percent) of dunes (Murphy
et al. 2006, p. 230). Based on mitochondrial DNA sequence data from two
mitochondrial genes, Murphy et al. (2006) developed a phylogenetic tree
(a diagram consisting of branches that represent genetic relationships,
similar in appearance to a family tree) for the Mojave fringe-toed
lizard.
Murphy et al. (2006, pp. 232-233) concluded that the lizards from
the 21 dune systems consisted of 6 genetically related groupings or
clades. One of the six is the Amargosa River clade, which Murphy
determined consists of Ibex and Dumont Dunes, Coyote Holes, and Red
Pass Dune (Murphy et al. 2006, p. 234). Red Pass Dune is geographically
associated with the Mojave River drainage system clade, which is the
next population to the south of the Amargosa River population. Although
Murphy et al. (2006, pp. 232-233) classified lizards from the Amargosa
River population as constituting a separate genetic clade than lizards
in the Mojave River drainage system, the population of Mojave fringe-
toed lizards occurring at Red Pass Dune is unique in that it shares a
haplotype with both the Amargosa River clade and the Mojave River
drainage system clade. For this reason, Red Pass Dune appears twice in
the phylogenetic tree developed by Murphy et al. (2006, p. 233), once
in the Amargosa River clade and once in the Mojave River drainage
system clade. However, Murphy et al.'s (2006, p. 241) overall
conclusion was that the Amargosa River population is genetically
distinct from other Mojave fringed-toed lizard populations.
Gottscho (2010, pp. 9-18) also studied the relationships between
different populations of Mojave fringe-toed lizards but based his
analysis on nuclear DNA instead of on mitochondrial DNA. Nuclear DNA is
inherited from both the female and male; thus each tissue sample had
genetic information inherited from both the mother and father as
opposed to mitochondrial DNA, which has genetic information inherited
from the mother only. Gottscho conducted his DNA analysis on tissue
samples collected from lizards at 20 major dune systems throughout the
range of the species. Fifteen unlinked DNA sequences (or loci) from
each tissue sample were analyzed to determine genetic divergence
between population locations. Unlinked DNA sequences represent random
segments of DNA that are not typically inherited together and thus
represent independent samples of genetic variation across the entire
genome. Based on the nuclear DNA sequences from the 15 loci, Gottscho
developed 15 gene trees for the Mojave fringe-toed lizard, and none of
these gene trees showed evidence of genetic divergence between the
Amargosa River population and other Mojave fringed-toed lizard
populations (Gottscho 2010, pp. 54-68). Gottscho (2010, p. 26) found
that ``No geographic structuring within U. scoparia is evident,
particularly between the Mojave and Amargosa populations, which is
expected given that they have 0% sequence divergence.'' Thus, based on
his analysis of 15 nuclear DNA loci, Gottscho found no evidence that
the Amargosa River population of Mojave fringed-toed lizard was
genetically distinct from other Mojave fringed-toed lizard populations
(see Distinct Vertebrate Population Segment (DPS) section for
additional discussion of research results of Gottscho (2010) and Murphy
et al. (2006)).
Distinct Vertebrate Population Segment (DPS)
Section 3(16) of the Act defines ``species'' to include ``any
subspecies of fish or wildlife or plants, and any distinct population
segment of any species of vertebrate fish or wildlife which interbreeds
when mature'' (16 U.S.C. 1532 (16)). Under the joint DPS
[[Page 61326]]
policy of the Service and National Marine Fisheries Service (61 FR
4722; February 7, 1996), three elements are considered in the decision
concerning the establishment and classification of a possible DPS.
These are applied similarly for additions to or removal from the List
of Endangered and Threatened Wildlife. These elements include:
(1) The discreteness of a population in relation to the remainder
of the species to which it belongs;
(2) The significance of the population segment to the species to
which it belongs; and
(3) The population segment's conservation status in relation to the
Act's standards for listing, delisting, or reclassification (i.e., Is
the population segment, when treated as if it were a species,
endangered or threatened?).
Under the DPS Policy, we must first determine whether the
population qualifies as a DPS; this requires a finding that the
population is both: (1) Discrete in relation to the remainder of the
species to which it belongs; and (2) biologically and ecologically
significant to the species to which it belongs. If the population meets
the first two criteria under the DPS policy, we then proceed to the
third element in the process, which is to evaluate the population
segment's conservation status in relation to the Act's standards for
listing as an endangered or threatened species. The DPS evaluation in
this finding concerns the Amargosa River population as it has been
defined herein.
Discreteness
Under the DPS Policy, a population segment of a vertebrate taxon
may be considered discrete if it satisfies either one of the following
conditions:
(1) It is markedly separated from other populations of the same
taxon as a consequence of physical, physiological, ecological, or
behavioral factors. Quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation.
(2) It is delimited by international governmental boundaries within
which differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act.
Markedly Separated From Other Populations of the Taxon
Under the first test of discreteness in our DPS policy, a
population segment may be considered discrete if it is ``markedly
separated from other populations of the same taxon as a consequence of
physical, physiological, ecological, or behavioral factors.
Quantitative measures of genetic or morphological discontinuity may
provide evidence of this separation.'' Although absolute separation is
not required under our DPS Policy, the use of the term ``markedly'' in
the Policy indicates that the separation must be strikingly noticeable
or conspicuous.
As part of the status review associated with this finding, we have
examined the Amargosa River population of Mojave fringed-toed lizard
and expanded the definition of this population to include the newly
discovered occupied dunes, as described above in the ``Species Range,
Habitat, and Dispersal'' section. We have examined the Amargosa River
population of the Mojave fringe-toed lizard to determine if it is
markedly separated from other populations of the same taxon.
The important question with regard to discreteness under our DPS
policy is whether or not the Amargosa River population is markedly
separated from other populations of Mojave fringed-toed lizard. The
Amargosa River population could be found to be markedly physically
separated if the distance between any part of that population and any
other population is greater than the distance the lizard is believed to
be able to travel across areas without suitable habitat (i.e., without
windblown sand). Mojave fringe-toed lizard movement among dunes is
considered unlikely in the absence of nearby areas of wind-blown sand.
Mojave fringe-toed lizards have historically been considered to be
restricted to active dunes and, in a few cases, sandy habitat
associated with dry lakes and washes (Hollingsworth and Beaman 1999, p.
3).
As noted above in the ``Species Range, Habitat, and Dispersal''
section, surveys conducted subsequent to the submittal of the petition
show that there are more Mojave fringe-toed lizards in the Amargosa
River area than was previously thought. New locations with documented
Mojave fringe-toed lizards include Little Dumont Dunes, Valjean Dunes,
the area between Dumont and Valjean dunes, and three unnamed dunes
located between Valjean Dunes and Coyote Holes (Glenn 2008, in litt.;
Encinas 2008, in litt.) (Figure 1). The Mojave fringe-toed lizard is
also now known to occur in additional areas of Ibex Dunes, Dumont
Dunes, and Coyote Holes (Encinas 2008, in litt.). In combination, these
new areas have expanded the range of the Amargosa River population
beyond what was described in the petition. However, the expanded
Amargosa River population, including these new areas, is still
approximately 17 mi (27 km) from the next nearest location known to be
occupied by the species (Silver Lake, Figure 1).
As also noted above in the ``Species Range, Habitat, and
Dispersal'' section, there are other dunes and areas of suitable wind-
blown sand that could allow for movement of lizards between
populations. Two dry lakes, the larger Silurian Lake and a smaller,
unnamed lake, lie between the Amargosa River population at Dumont Dune
and the Mojave River drainage population at Silver Lake, all of which
are connected by a dry streambed. In the past, Norris (1958, p. 263)
personally observed this area covered in sand and occupied by Mojave
fringe-toed lizards and specifically mentioned dunes at Silurian Lake
being occupied. He noted migration between river drainages was allowed
across low divides, such as the divide between the Mojave and the
Amargosa Rivers when sand shadows (an accumulation of sand formed in
the shelter of a fixed obstruction, such as clumps of vegetation) and
blow-ups were present (Norris 1958, p. 316). Sand dunes are highly
dynamic and continually moving, in some cases, moving several meters
per year (Norris 1958, p. 262). This dune movement may have accounted
for the species' movement and occupancy of the low divide between the
Mojave and Amargosa River drainages, providing a corridor between
populations (Norris 1958, p. 263). However, based on our review of
aerial photos taken subsequent to Norris' observations, suitable dune
habitat does not appear to currently exist around Silurian Lake.
Gottscho (2010, p. 31) also noted that the low-divide area between the
Mojave and Amargosa River drainages that Norris referred to in 1958 as
being covered by sand and occupied by Mojave fringe-toed lizards does
not appear to be covered by sand or occupied by Mojave fringe-toed
lizards currently. Therefore, at the present time, the Amargosa River
population appears to be physically isolated from other populations of
Mojave fringed-toed lizards.
Thus, based on the best scientific and commercial information
currently available, we believe that the 17 mi (27 km) of unsuitable
habitat between the Amargosa River population and the next nearest area
known to be currently occupied by the species is beyond the dispersal
capability of the species, and we conclude that the Amargosa River
population is markedly physically separated from other populations.
Therefore, we have determined that the Amargosa River population of the
[[Page 61327]]
Mojave fringe-toed lizard meets the discreteness element of our DPS
policy.
International Boundaries
A population segment of a vertebrate species may be considered
discrete if it is delimited by international governmental boundaries
across which differences in control of exploitation, management of
habitat, conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act. The range of the
Mojave fringe-toed lizard occurs solely within the continental United
States and is not delimited by international governmental boundaries.
Therefore, the Amargosa River population of Mojave fringe-toed lizard
does not satisfy this condition.
Summary for Discreteness
We find that the Amargosa River population is markedly physically
separated from other populations because of the limited dispersal
capability of the Mojave fringe-toed lizard and the absence of
intervening habitat that could provide for the regular movement of
lizards between this population and other populations. Consequently,
and based upon review of the best available information, the Service
finds that the Amargosa River population meets the discreteness element
of our DPS policy.
Significance
Because we have determined that the Amargosa River population of
Mojave fringe-toed lizard is discrete under our DPS policy, we will
next consider its biological and ecological significance to the taxon
to which it belongs in light of Congressional guidance that the
authority to list DPSs be used ``sparingly'' while encouraging the
conservation of genetic diversity. To evaluate whether a discrete
vertebrate population may be significant to the taxon to which it
belongs, we consider available scientific evidence of the population
segment's importance to the taxon to which it belongs. Because precise
circumstances are likely to vary considerably from case to case, the
DPS policy does not describe all the classes of information that might
be used in determining the biological and ecological importance of a
discrete population. However, the DPS policy describes four possible
classes of information that provide evidence of a population segment's
biological and ecological importance to the taxon to which it belongs.
As specified in the DPS policy (61 FR 4722), this consideration of the
population segment's significance may include, but is not limited to
the following:
(1) Persistence of the discrete population segment in an ecological
setting unusual or unique for the taxon,
(2) Evidence that loss of the discrete population segment would
result in a significant gap in the range of a taxon,
(3) Evidence that the discrete population segment represents the
only surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historical range, or
(4) Evidence that the discrete population segment differs markedly
from other populations of the species in its genetic characteristics.
A population segment needs to satisfy only one of these criteria to
be considered significant. Furthermore, the list of criteria is not
exhaustive; other criteria may be used as appropriate. Here we evaluate
the four potential factors suggested by our DPS policy in evaluating
significance.
Persistence of the Discrete Population Segment in an Ecological Setting
Unusual or Unique for the Taxon
Available information does not indicate that differences exist in
the ecological setting between the Amargosa River population and other
populations within the species' range. The habitat occupied by the
Amargosa River population is wind-blown sand, which is typical of other
populations of Mojave fringed-toed lizard. There is no difference in
climate or other physical or biological factors between the Amargosa
River population and the Silver Lake population, which is located 17 mi
(27 km) to the south but is part of the Mojave River drainage
population. There is no available information that would suggest the
existence of any morphological, behavioral, or physiological
differences between individuals from the Amargosa River population and
individuals from other Mojave fringed-toed lizard populations. We
therefore determine that the Amargosa River population of the Mojave
fringe-toed lizard does not meet the significance element of the DPS
policy based on this factor.
Evidence that Loss of the Discrete Population Segment Would Result in a
Significant Gap in the Range of a Taxon
We estimate that the areas covered by wind-blown sand habitat at
Ibex and Dumont dunes and Coyote Holes, along with the newly discovered
areas that constitute the Amargosa River population as defined herein,
make up less than 5 percent of the total wind-blown sand habitat
occupied by the species (73 FR 1855; January 10, 2008). The Amargosa
River population is the most northerly population of the species, and
as such, the loss of the Amargosa River population would not result in
the isolation of any other populations to the south.
The Amargosa River population is a peripheral population, and
peripheral populations can be important in species conservation if they
are genetically divergent from populations in the central portion of
the species' range (Lesica and Allendorf 1995, pp. 753-760; Lomolino
and Channell 1998, pp. 481-484; Fraser 2000, pp. 49-53). Peripheral
populations that are spatially distant from central populations may be
exposed to different environmental conditions and thus different
natural selection forces, which in some populations may result in
unique adaptations that may be important for the species in adapting to
future environmental changes. However, as discussed above, habitat and
climate in the area occupied by the Amargosa River population are
similar to environmental conditions elsewhere in the species' range. If
different natural selection pressures were acting on the Amargosa River
population, differences in morphological, behavioral, or physiological
characteristics might be expected between Amargosa River Mojave
fringed-toed lizards and Mojave fringed-toed lizards in other
populations to the south, but there is no available evidence of such
differences. Evidence of genetic differences is discussed below.
We conclude that the loss of the Amargosa River population would
not result in a significant gap in the range of the species because the
population represents only a small percentage (less than 5 percent) of
the species' range, and potential loss of the population would not
result in the isolation of any other Mojave fringed-toed lizard
populations. Peripheral populations can have conservation value, but
available evidence does not indicate that individuals from the Amargosa
River population have unique morphological, behavioral, or
physiological adaptations that may be significant to the species'
conservation.
Whether the Population Represents the Only Surviving Natural Occurrence
of the Taxon
The Amargosa River population is not the only surviving natural
occurrence of the species. Mojave fringe-toed lizards are known to
occur at more than 35 sand dune complexes in California, and one in
Arizona, all of which are naturally occurring within the species'
[[Page 61328]]
historical range. Consequently, we conclude that the Amargosa River
population of the Mojave fringe-toed lizard does not meet this factor
of the significance criterion of the DPS policy.
Evidence That the Discrete Population Segment Differs Markedly From
Other Populations of the Species in Its Genetic Characteristics
Two studies have compared genetic characteristics between the
Amargosa River population and other Mojave fringed-toed lizard
populations (see ``Genetics'' section). One study, based on analysis of
mitochondrial DNA, found that individuals from the Amargosa River
population possessed unique haplotypes and differed genetically from
other Mojave fringed-toed lizard populations (Murphy et al. 2006, pp.
226-247). Another study, based on analysis of 15 nuclear DNA loci,
found no genetic divergence between the Amargosa River population and
other Mojave fringed-toed lizard populations (Gottscho 2010, pp. 21-
68).
Different patterns of genetic variation between mitochondrial and
nuclear DNA analyses are not uncommon (Moore 1995, pp. 718-726; Avise
2004, pp. 273-276, 372-380; Ballard and Whitlock 2004, pp. 729-744;
Bazin et al. 2006, pp. 570-572; Zink and Barrowclough 2008, pp. 2107-
2121). Mitochondrial and nuclear DNA differ in important aspects. Genes
in the mitochondrial genome evolve as a single linkage unit (Allendorf
and Luikart 2007, p. 159). Mitochondrial DNA analysis thus yields only
a single gene tree, and single gene trees potentially misrepresent the
taxon's evolutionary history (Ballard and Whitlock 2004, p. 734; Zink
and Barrowclough 2008, p. 2108). For most animal species, including the
Mojave fringed-toed lizard, individuals inherit mitochondrial DNA from
only the mother; nuclear DNA is inherited from both mother and father
(Allendorf and Luikart 2007, p. 159). These and other differences
between mitochondrial and nuclear DNA have led some to caution against
the sole use of mitochondrial DNA analysis when trying to understand
the phylogeography or evolutionary history of a species or population
(Moore 1995, pp. 718-726; Hare 2001, pp. 700-706; Ballard and Whitlock
2004, pp. 729-744; Bazin et al. 2006, 570-572).
One of the implications of the differences between mitochondrial
and nuclear DNA is that genetic drift will cause divergence between
isolated populations to occur more slowly at nuclear gene loci than at
mitochondrial gene loci (Hare 2001, pp. 701-702; Zink and Barrowclough
2008, p. 2109). Genetic drift is change in the frequency of a gene
variant, or allele, within a population due to random sampling. Zink
and Barrowclough (2008, pp. 2107-2121) concluded that mitochondrial DNA
is more likely than nuclear DNA to reveal more recent evolutionary
splits and that nuclear markers are more lagging indicators of changes
in population structure.
Another implication of the differences between mitochondrial and
nuclear DNA is that mitochondrial DNA is a single molecule with a
single specific history that, for various reasons, can differ from the
true evolutionary history of the species or population (Ballard and
Whitlock 2004, p. 734). For example, because mitochondrial DNA is
inherited only from the mother, mitochondrial DNA patterns might be a
biased portrayal of the overall lineage history of the species if the
species exhibits different dispersal patterns between males and females
(Avis 2004, pp. 274-277; Zink and Barrowclough 2008, p. 2108). Indeed,
sex-biased dispersal is known to occur in various lizard species
(Doughty et al. 1994, pp. 227-229; Johansson et al. 2008, p. 4426;
Urqhhart 2008, p. 2). In Mojave fringe-toed lizards, although the
dispersal of males compared to that of females has not been studied,
males do display territorial behavior causing rival males to be pushed
out of their territory (Carpenter 1963, p. 406). In addition, there is
evidence that the home ranges of male Mojave fringe-toed lizards are
larger than those of females (Penrod et al. 2008, p. 47). Because it is
likely that Mojave fringe-toed lizard males disperse farther than
females, we would expect more gene flow to occur among nuclear genes
than among mitochondrial genes because mitochondrial genes are only
inherited from the female. As a result of reduced female dispersal,
gene flow among mitochondrial genes may be reduced compared to nuclear
gene flow in species with sex-biased dispersal patterns (Avise 2004,
pp. 273-276; Gottscho 2010, p. 32). Reduced flow of mitochondrial genes
compared to nuclear genes would be expected to result in greater
genetic divergence between individuals and populations in mitochondrial
DNA-based studies compared to nuclear DNA-based studies, which is
consistent with the pattern observed in the Murphy et al. (2006, pp.
226-247) mitochondrial DNA-based study and the Gottscho (2010, pp. 1-
81) nuclear DNA-based study.
Gottscho (2010, pp. 21-68) found zero percent genetic divergence
between the Amargosa population and other Mojave fringed-toed lizard
populations at 15 independent nuclear loci. He concluded that lack of
genetic divergence is best explained by past gene flow between Mojave
fringed-toed lizard populations (Gottscho 2010, pp. 26-34). He noted
that the lack of a single fixed difference between the Amargosa River
population and Mojave River population was not unexpected given that
the Mojave River overflows into the Amargosa River when its current
terminus at Silver Lake reaches capacity, and no mountains exist that
might have impeded the movement of sand dunes and lizards between these
drainages in historical times (Gottscho 2010, p. 26). Gottscho (2010,
pp. 32-33) noted that although sand dune complexes may seem isolated
today, in geologic time (evolutionary time) they have moved across the
landscape regularly with changing climate.
We conclude that the results of Murphy et al. (2006) do not reflect
deep genetic divergence between the Amargosa River population and other
Mojave fringed-toed lizard populations, as evidenced by the shared
haplotypes from the Amargosa River clade and Mojave River drainage
clades at the Red Pass Dune location, which is located outside of the
Amargosa River drainage (see Genetics section). We conclude that the
results of Murphy et al. (2006) and Gottscho (2010) are best explained
by relatively recent evolutionary population divergence between the
Amargosa River population and Mojave River drainage populations: the
relatively recent divergence has been enough for subtle differences in
the mitochondrial DNA to develop, as indicated by the Murphy et al.
(2006) study, but not enough for differences in the nuclear DNA genetic
markers to develop, as indicated by the Gottscho (2010) study (Gottscho
2011, pers. comm.). We find that the best available information is not
indicative of marked differences in genetic characteristics between the
Amargosa River population and other Mojave fringed-toed lizard
populations because: (1) The Gottshco (2010) study, which showed no
genetic differentiation between the Amargosa River population and other
Mojave fringed-toed lizard populations, was based on analysis of
multiple, independent nuclear gene loci, whereas the Murphy et al.
(2006) study was based on analysis of a single mitochondrial gene locus
and thus may not present a full and accurate representation of the
population's evolutionary history (see discussion above of potential
limitations of mitochondrial DNA studies); (2) the
[[Page 61329]]
results of Murphy et al. (2006) are not indicative of deeply divergent
genetic differentiation, as evidenced by the shared haplotypes from the
Amargosa River clade and Mojave River drainage clades at the Red Pass
Dune location.
Summary for Significance
Based on the best information available, we do not find that the
Amargosa River population occurs in a unique ecological setting because
the population occurs in an ecological setting similar to other nearby
populations. Climate and habitat within the Amargosa River population
area are similar to climate and habitat in nearby population areas
within the Mojave River drainage. We also do not find that the loss of
the Amargosa River population would result in a significant gap in the
range of the species because the loss of the population would not
result in the isolation of other Mojave fringed-toed lizard
populations, and the Amargosa River population makes up only a small
percentage (less than 5 percent) of the entire range of the species.
The Amargosa River population is not the only surviving natural
occurrence of the taxon, as all known areas currently occupied by the
species (see Figure 1) are naturally occurring populations within the
historical range of the species. We also find that the Amargosa River
population does not differ markedly from other Mojave fringed-toed
lizard populations in its genetic characteristics. One study found
evidence of certain genetic differences between the Amargosa River
population and other Mojave fringed-toed lizard populations (Murphy et
al. (2006)), and another study found evidence of no genetic
differentiation between populations (Gottscho (2010)). We conclude that
in total, the best available data from these studies does not rise to
the level of meeting the standard of marked differences in genetic
characteristics between the Amargosa River population and other Mojave
fringed-toed lizard populations. We also note that there is no evidence
of morphological, physiological, or behavioral differences between
individuals from the Amargosa River population and individuals from
other Mojave fringed-toed lizard populations; such differences may be
expected if Mojave fringed-toed lizards from the Amargosa River
population possessed unique evolutionary adaptations. Moreover, the
best available scientific evidence does not indicate any other classes
of information that may provide evidence of the Amargosa River
population's biological and ecological importance to the Mojave fringe-
toed lizard species.
Overall, based on our review of the factors for significance as
summarized herein, we find that the Amargosa River population of the
Mojave fringe-toed lizard does not satisfy the considerations of the
DPS policy for being significant in relation to the remainder of the
taxon.
Determination of Distinct Population Segment
Based on the best scientific and commercial data available, we find
that the Amargosa River population of Mojave fringed-toed lizard meets
the discreteness element of our 1996 DPS policy, but not the
significance element. To qualify as a DPS under the Services' 1996 DPS
policy, a population must meet both the discreteness and significance
elements of the policy. Therefore, the Amargosa River population does
not qualify as a DPS under our DPS policy and is not a listable entity
under the Act. Because the population does not qualify as a DPS, we
will not proceed with an evaluation of the status of the population
under the Act.
Finding
We have carefully assessed the best scientific and commercial
information available for the Amargosa River population of the Mojave
fringe-toed lizard, including information in the petition, and
available published and unpublished scientific and commercial
information. This 12-month finding reflects and incorporates
information that we received from the public and interested parties or
that we obtained through consultation, literature research, and field
visits.
On the basis of this review, we have determined that the Amargosa
River population of Mojave fringe-toed lizard, although discrete
according to our DPS policy, does not meet the significance element of
our 1996 DPS policy. The best available scientific and commercial
information does not indicate that the Amargosa River population occurs
in an ecological setting unusual or unique for the taxon; climate and
habitat in the Amargosa River population area are similar to climate
and habitat of nearby populations, and we are not aware of differences
in behavior, physiology, or morphology between lizards in the Amargosa
River population and nearby populations. The best available information
also does not indicate that loss of the Amargosa River population would
result in a significant gap in the range of the species; loss of the
population would not result in the isolation of other Mojave fringed-
toed lizard populations; and the population area makes up only a small
portion of the entire species' range. The Amargosa River population
does not represent the only surviving natural occurrence of a taxon
that may be more abundant elsewhere as an introduced population outside
its historical range. Although an analysis of mitochondrial DNA showed
genetic differences between individuals in the Amargosa River
population and individuals in other Mojave fringed-toed lizard
populations (Murphy et al. 2006, pp. 226-247), this study found that
individuals from a population area in the Mojave River drainage (Red
Pass Dune) had shared haplotypes from the Amargosa River clade and
Mojave River drainage clades. A recent study that analyzed nuclear DNA
found zero genetic divergence between lizards in the Amargosa River
population and lizards in other Mojave fringed-toed lizard populations
at all 15 independent nuclear loci analyzed (Gottscho 2010, pp. 26-30).
The best available information does not indicate that individuals from
the Amargosa River population possess unique evolutionary adaptations
as there are no known morphological, physiological, or behavioral
differences between individuals from the Amargosa River population and
other Mojave fringed-toed lizard populations. We conclude that the best
scientific and commercial data available do not indicate that the
Amargosa River population differs markedly from other populations of
the species in its genetic characteristics.
We have determined that the Amargosa River population, while
markedly separated from other existing populations of Mojave fringe-
toed lizard and thus discrete, does not meet the significance element
of our 1996 DPS policy and, therefore, does not qualify as a DPS and is
not a listable entity under the Act. Therefore, we find that the
petitioned action to list the Amargosa River population of Mojave
fringe-toed lizard as an endangered or threatened species under the Act
is not warranted.
We request that you submit any new information concerning the
status of, or threats to, this species to our Ventura Fish and Wildlife
Office (see ADDRESSES section) whenever it becomes available. New
information will help us monitor this species and promote its
conservation. If an emergency situation develops for this or any other
species, we will act to provide immediate protection.
[[Page 61330]]
References Cited
A complete list of all references cited in this document is
available on the Internet at http://www.regulations.gov, or upon
request from the Field Supervisor, Ventura Fish and Wildlife Office
(see ADDRESSES section).
Authors
The primary authors of this notice are the staff members of the
Ventura Fish and Wildlife Office (see ADDRESSES section).
Authority
The authority for this action is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: September 23, 2011.
Rowan Gould,
Acting Director, Fish and Wildlife Service,
[FR Doc. 2011-25561 Filed 10-3-11; 8:45 am]
BILLING CODE 4310-55-P