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, 61321-61330 [2011-25561]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[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 https://www.regulations.gov at Docket Number FWS-R8-ES-2007-0023 and at https://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

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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

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    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

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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

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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 https://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