Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To Delist Astragalus magdalenae var. peirsonii (Peirson's milk-vetch), 41007-41022 [E8-16041]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 73, Number 138 (Thursday, July 17, 2008)]
[Proposed Rules]
[Pages 41007-41022]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-16041]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R8-ES-2008-0081; 92220-1113-0000-C5]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To Delist Astragalus magdalenae var. peirsonii (Peirson's 
milk-vetch)

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 remove Astragalus magdalenae var. 
peirsonii (Peirson's milk-vetch) from the Federal List of Threatened 
and Endangered Plants under the Endangered Species Act. After reviewing 
the best scientific and commercial information available, we find that 
the petitioned action is not warranted. We ask the public to submit to 
us any new information that becomes available concerning the status of, 
or threats to, the species. This information will help us monitor and 
encourage the conservation of this species.

DATES: The finding announced in this document was made on July 17, 
2008.

ADDRESSES: This finding is available on the Internet at https://
www.regulations.gov, https://www.fws.gov/endangered, and https://
www.fws.gov/Carlsbad. Supporting documentation we used in preparing 
this finding is available for public inspection, by appointment, during 
normal business hours at the Carlsbad Fish and Wildlife Office, U.S. 
Fish and Wildlife Service, 6010 Hidden Valley Road, Carlsbad, CA 92011; 
telephone 760-431-9440; facsimile 760-431-5901. Please submit any new 
information, materials, comments, or questions concerning this finding 
to the above street address or via electronic mail (e-mail) at 
FW8cfwocomments@fws.gov.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, U.S. 
Fish and Wildlife Service, Carlsbad Fish and Wildlife Office (see 
ADDRESSES section). If you use a telecommunications device for the deaf 
(TDD), call the Federal Information Relay Service (FIRS) at 800-877-
8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(A) of the Endangered Species Act (Act) (16 U.S.C. 
1531 et

[[Page 41008]]

seq.) requires that we make a finding on whether a petition to list, 
delist, or reclassify a species presents substantial information to 
indicate the petitioned action may be warranted. Section 4(b)(3)(B) of 
the Act requires that within 12 months after receiving a petition to 
revise the Lists of Threatened and Endangered Wildlife and Plants 
(Lists) that contains substantial information indicating that the 
petitioned action may be warranted, the Secretary shall make one of the 
following findings: (a) The petitioned action is not warranted, (b) the 
petitioned action is warranted, or (c) the petitioned action is 
warranted but precluded by pending proposals to determining whether any 
species is an endangered or threatened species and expeditious progress 
is being made to add qualified species to, and remove species from, the 
Lists. Such 12-month findings are to be published promptly in the 
Federal Register.
    Astragalus magdalenae var. peirsonii (Peirson's milk-vetch) was 
listed as threatened on October 6, 1998 (63 FR 53596). At the time of 
listing, the primary threat to A. magdalenae var. peirsonii was the 
destruction of individuals and dune habitat from off-highway vehicle 
(OHV) use and associated recreational development. On October 25, 2001, 
we received a petition to delist A. magdalenae var. peirsonii dated 
October 24, 2001, from David P. Hubbard, Ted J. Griswold, and Philip J. 
Giacinti, Jr. of Procopio, Cory, Hargreaves & Savitch, LLP, that was 
prepared for the American Sand Association (ASA), the San Diego Off-
Road Coalition, and the Off-Road Business Association (ASA 2001). On 
September 5, 2003, we announced a 90-day finding in the Federal 
Register that the petition presented substantial information to 
indicate the petitioned action may be warranted (68 FR 52784). In 
accordance with section 4(b)(3)(A) of the Act, we completed a status 
review of the best available scientific and commercial information on 
the species, and published our 12-month finding on June 4, 2004 (69 FR 
31523). We determined that the petitioned action was not warranted at 
that time.
    On July 8, 2005, we received an updated petition to delist 
Astragalus magdalenae var. peirsonii (Peirson's milk-vetch) that was 
prepared by David P. Hubbard for the American Sand Association, the 
Off-Road Business Association, the San Diego Off-Road Coalition, the 
California Off-Road Vehicle Association, and the American Motorcycle 
Association District 37 (ASA 2005). On November 30, 2005, we announced 
our 90-day finding that the updated petition presented substantial 
scientific or commercial information indicating that the petitioned 
action may be warranted, and initiated a status review for A. 
magdalenae var. peirsonii (70 FR 71795). The updated petition claims to 
``demonstrate, through four years of additional data collection, that 
the Peirson's milk-vetch is even more abundant than was reported in 
ASA, et al.'s original petition, and that the plant's population and 
reproductive capacity are so stable and strong as to warrant 
delisting'' (ASA 2005, p. 5).
    Included again in the updated petition and its associated documents 
(ASA 2005) is the assertion made in the ASA 2001 petition that 
Astragalus magdalenae var. peirsonii was listed without the support of 
abundance data. That assertion was addressed in our June 4, 2004, 12-
month finding (69 FR 31523) on their previous petition to delist A. 
magdalenae var. peirsonii, and the updated petition did not provide any 
additional information that would alter our previous analysis. All of 
the information in our prior (June 4, 2004) 12-month finding (69 FR 
31523) applies to this action, and the status review provided in this 
document continues to validate that our original decision to list A. 
magdalenae var. peirsonii as a threatened species (63 FR 53596) was not 
made in error or without supporting data.

Species Information

Species Description

    Astragalus magdalenae var. peirsonii (Peirson's milk-vetch) is an 
erect to spreading, herbaceous, short-lived perennial in the Fabaceae 
(Pea family) (Barneby 1959, 1964). Plants may reach 8 to 27 inches (in) 
(20 to 70 centimeters (cm)) in height and develop taproots (Barneby 
1964, pp. 862-863) that penetrate to the deeper, moister sand. 
According to Phillips and Kennedy (2003), plants largely die back to a 
root crown in the summer. The stems and leaves are covered with fine, 
silky appressed hairs. The leaflets, which may fall off in response to 
drought, are small and widely spaced, giving the plants a brushy 
appearance. This taxon is unusual in that the terminal leaflet (leaflet 
at the tip) is continuous with the rachis (the central axis of a 
compound leaf along which leaflets are attached) rather than 
articulated with it (Barneby 1959, p. 879; Spellenberg 1993, p. 598). 
Each flower stalk (classified as a raceme) arises from a point where a 
leaf joins the stem (axil), and supports 10 to 17 purple flowers 
(Barneby 1959, p. 879).

Taxonomy

    The taxonomic status of Astragalus magdalenae var. peirsonii was 
discussed in the final listing rule (63 FR 53596). Although originally 
described at the species rank, Peirson's milk-vetch is currently 
recognized at the varietal level as A. magdalenae var. peirsonii 
(Spellenberg 1993, p. 598). Although two other recognized varieties 
exist for A. magdalenae, these taxa are restricted to Mexico. However, 
recent genetic analysis suggests that Barneby's (1964, pp. 862-863) 
reduction of A. peirsonii to varietal status may be inappropriate and 
that A. magdalenae var. peirsonii should be recognized as a species [as 
originally described by Munz and McBurney (Munz 1932, p. 7)] (Porter 
and Prince 2006, p. 7; 2007, pp. 10-11).
    Two other Astragalus taxa occur in the vicinity of the Algodones 
Dunes. They are A. lentiginosus var. borreganus (Spellenberg 1993, p. 
597), easily distinguished by its conspicuously broad leaflets, and A. 
insularis var. harwoodii (Spellenberg 1993, p. 594), which is easily 
distinguished by its smaller stature and shorter banner petals.

Range and Distribution

    In the United States, Astragalus magdalenae var. peirsonii is 
restricted to specific habitat areas within about 53,000 acres (ac) 
(21,500 hectares (ha)) in a narrow band running 40 miles (64 
kilometers) northwest to southeast along the western portion of the 
Algodones Dunes (= Imperial Sand Dunes) of eastern Imperial County, 
California, which is the largest sand dune field in North America. 
Astragalus magdalenae var. peirsonii has also been documented from the 
Gran Desierto of Sonora, Mexico (Felger 2000, p. 300), from an area 
south and southeast of the Sierra Pinacate lava field, but the Service 
has no additional information on the extent of area occupied, the size 
of the population, or its current condition (see 63 FR 53599). 
Astragalus magdalenae var. peirsonii was also noted from the Borrego 
Valley, California, by Barneby (1959, p. 879), but not verified, 
reproducing population exists (Porter et al. 2005, pp. 9-10). Other 
observations from Yuma, Arizona, and San Felipe, Baja California, 
Mexico, were based on misidentified specimens (see Porter et al. 2005, 
pp. 9-10, and Phillips et al. 2001, p. 7, for detailed accounts).
    The Algodones Dunes are often referred to as the Imperial Sand 
Dunes. Nearly all of the lands in the Algodones Dunes are managed by 
the Bureau of Land Management (BLM) as the Imperial Sand Dunes 
Recreation Area

[[Page 41009]]

(ISDRA). However, the State of California and private individuals own 
small inholdings in the dune area. On August 4, 2004, approximately 
21,836 ac (8,838 ha) of the 167,800-ac (67,900-ha) ISDRA were 
designated as critical habitat for Astragalus magdalenae var. peirsonii 
(69 FR 47330). In a September 25, 2006, court order, the District Court 
for the Northern District of California ordered the Service to submit a 
new final critical habitat rule to the Federal Register for publication 
no later than February 1, 2008 (Center for Biological Diversity et al. 
v. Bureau of Land Management et al., Civ. No. C 03-2509 SI). On 
February 14, 2008, the Service designated revised critical habitat for 
A. magdalenae var. peirsonii (73 FR 8748). In total, approximately 
12,105 ac (4,899 ha) in Imperial County, California, fall within the 
boundaries of the revised designation of critical habitat.

Life History

    Astragalus magdalenae var. peirsonii has variously been considered 
an annual or perennial plant (Munz 1932, p. 7; 1974, p. 432; Barneby 
1959, p. 879; 1964, p. 862; Spellenberg 1993, p. 598; Willoughby 2001, 
p. 21; Porter et al. 2005, p. 7). Willoughby (2001, p. 21) observed 
that A. magdalenae var. peirsonii is a short-lived perennial and, as 
such, its response to rainfall was predictable. Recent evidence 
confirms this observation (Phillips and Kennedy 2004, p. 5; Groom et 
al. 2007, p. 121) and that, depending upon conditions and germinating 
time, A. magdalenae var. peirsonii is capable of flowering before it is 
a year old (Barneby 1964, p. 862; Romspert and Burk 1979 p. 16; 
Phillips et al. 2001, p. 10; Phillips and Kennedy 2005, p. 22; Porter 
et al. 2005, p. 31).
    Based on current understanding of the species' life history, 
sufficient rain in conjunction with cool fall temperatures appears to 
trigger germination events. Seedlings are often present in suitable 
habitat throughout the dunes, especially during above-normal 
precipitation years. In intervening dry years, plant numbers decrease 
as individuals die and are not replaced by new seedlings. Porter et al. 
(2005, p. 35) estimated that a total or near-total failure of seedling 
recruitment occurs 20 percent of the time (once every 5 years). This 
species likely depends on the production of seeds in the wetter years 
and the persistence of the seed bank from previous years to survive 
until appropriate conditions for germination occur again. However, 
individual plants that perennate (i.e., survive from year to year with 
a period of reduced activity) likely give ``continuity'' to the 
presence of Astragalus magdalenae var. peirsonii through years of low 
recruitment (Beatley 1970, p. 331).
    If winter rains begin in early November, seeds germinating in early 
December may develop rapidly to produce flowering plants by February 
and set seed in March (Barneby 1964, p. 862; Romspert and Burk 1979, 
pp. 15-16). In wetter years, a second germination event may occur in 
late winter (Phillips et al. 2001, p. 10; Phillips and Kennedy 2005, p. 
22), but these plants often fail to reproduce and die in large numbers 
at the onset of summer drought (Phillips et al. 2001, p. 10; Phillips 
and Kennedy 2003, p. 20). If winter rains do not occur until late 
January, sufficient soil moisture or time may not exist for young 
plants to develop the root structure needed to flower and set seeds 
before the onset of desiccating summer heat. Young plants often die 
during summer drought in significant numbers probably because such 
plants lack a sufficiently developed root system to tap water at lower 
horizons, i.e. deeper soil layers. Older plants also die during this 
period. However, some plants develop an adequate root system and 
perennate to live 2 to 3 years. Some perennial individuals will flower 
and produce seeds in years with no precipitation (Phillips and Kennedy 
2006, pp. 5, 9; USFWS 2007, pp. 13, 15), thereby assuring the 
continuity of the seed bank. Years with optimal or prolonged 
precipitation may experience two or more germinations and increased 
seed production (Phillips and Kennedy 2005, p. 20).
    Plants, regardless of age, may flower from as early as mid-November 
through May (Barneby 1964, p. 862; Phillips and Kennedy 2002, p. 2; 
Porter et al. 2005, p. 11). The onset of germination and flowering are 
expected to vary from year to year depending upon the timing of winter 
rains. As a result, the life stages are coincident with cooler 
temperatures and a likely hydrated dune substrate. Barneby (1964, p. 
862), Phillips and Kennedy (2005, p. 22), and Porter et al. (2005, p. 
34) recorded plants that germinate in November can produce fruit in as 
little as 3 months. Mature fruits are found on plants from the 
beginning of February to late June (Phillips and Kennedy 2005, p. 13; 
Porter et al. 2005, pp. 22-24; Romspert and Burk 1979, p. 16), with 
peak production occurring in March and April (USFWS 2007, Figure 6).
    Not all plants, even those seemingly capable of flowering and even 
under favorable conditions, flower in a given year (Phillips and 
Kennedy 2003, p. 20; Willoughby 2005b, p. 11; USFWS 2007, p. 15). In 
2005, the BLM surveys recorded that 75 percent of all plants counted 
flowered (Willoughby 2005b, p. 11), while the Service recorded 54 
percent of plants flowered during the 2006 surveys (USFWS 2007, p. 15). 
Smaller first season specimens, if flowering, produce relatively few 
flowers and contribute little to the seed bank of Astragalus magdalenae 
var. peirsonii compared with larger, older individuals that have more 
flowers (Romspert and Burk 1979, p. 19; Phillips and Kennedy 2005, p. 
20). In low rainfall years, the reproductive output of older plants may 
range from as few as one seed pod to hundreds of pods per plant 
(Phillips and Kennedy 2005, pp. 16-17; USFWS 2007, p. 15). Phillips and 
Kennedy (2002, p. 27) estimated that plants counted in the spring 2001 
survey averaged five fruits per plant. From a small sample in winter 
2001-2002, they calculated that plants about 6 months older had an 
average of 171 fruits per plant (Phillips and Kennedy 2002, p. 27). In 
the 2006 survey, the Service calculated the median number of pods per 
plant on plants more than 1 year old at 139 (USFWS 2007, p. 15).

Pollination and Breeding System

    Porter et al. (2005, p. 32) identified a white-faced, medium-sized, 
solitary bee (Habropoda pallida) as the only effective pollinator of 
Astragalus magdalenae var. peirsonii. Otherwise, little is known about 
the pollination ecology of A. magdalenae var. peirsonii. Porter et 
al.'s (2005, p. 34) preliminary experiments in the field and under 
greenhouse conditions indicate that A. magdalenae var. peirsonii plants 
are not capable of self-pollination, and thus require pollinators for 
outcrossing. Moreover, Porter et al. (2005, p. 34) reported from 
microscopic examination of hand-pollinated flowers that pollen from the 
same flowers did not adhere to the stigmatic surface, while pollen from 
another plant did adhere. Unless pollen grains adhere, fertilization 
cannot occur. These results indicate that A. magdalenae var. peirsonii 
exhibits traits consistent with self-incompatibility (Porter and Prince 
2007, pp. 10-11). Self-incompatibility (SI) is a genetic mechanism in 
plants that prevents self-fertilization, or fertilization by pollen 
from plants that share the same SI allele. This means that inbreeding 
depression is avoided because only pollen from plants that do not share 
SI alleles with the maternal plant will be able to successfully 
fertilize eggs (Frankham et al. 2002, pp. 37-38; Castric and Vekemans 
2004, p. 2873). This observation is a significant

[[Page 41010]]

consideration for assessing the adequacy of population size, structure, 
and function. Large populations of standing individuals, with high SI 
allele diversity, are likely necessary to provide adequate numbers of 
individuals that can potentially fertilize the available eggs and 
ensure that seed is produced. In the Algodones Dunes, large SI allele 
diversity may be necessary spatially across the dunes, and temporally 
through periods of drought. Further research and modeling are necessary 
to better understand the dynamics of the A. magdalenae var. peirsonii 
breeding system and how the species may be responding to natural and 
man-made disturbances within its range.

Seed Biology

    Seed development. The fruits or pods of Astragalus magdalenae var. 
peirsonii are 0.8 to 1.4 in (2 to 3.5 cm) long, single-chambered, 
hollow, and inflated. Developing pods contain 11 to 16 ovules 
(structures containing immature eggs, or seeds, prior to fertilization) 
(Barneby 1964, p. 862). The seeds, among the largest seeds of any 
Astragalus in North America (Barneby 1964, pp. 862-863), average less 
than 0.1 ounce (oz) (15 milligrams (mg)) each in weight and are up to 
0.2 in (4.7 millimeters (mm)) in length (Bowers 1996, p. 69; McKinney 
et al. 2006, p. 85).
    Only a portion of a pod's ovules develop into mature seeds. Some 
desiccate, while others are lost to insects (McKinney et al. 2006, p. 
85). Seeds are either dispersed locally by falling from partly opened 
fruits (pods) retained on the parent plant or disperse over greater 
distances by their release from fruits (pods) blown across the sand 
after falling from the parent plant.
    Seed germination. Astragalus magdalenae var. peirsonii seeds 
require no pre-treatment to induce germination, but germination success 
improved dramatically when the outer seed coat was scarified (e.g., 
scratched, chipped). Porter et al. (2005, p. 29) reported about 99.1 
percent of scarified seeds germinated in laboratory trials, while only 
5.3 percent of unscarified seeds germinated. However, in artificial 
dune experiments, Porter et al. (2005, p. 29) reported the germination 
rate dropped to 27 percent. In germination trials conducted by Romspert 
and Burk (1979, pp. 45-46), 92 percent or more seeds germinated within 
29 days at temperatures of 77 [deg]F (25 [deg]C) or less, and no seeds 
germinated at temperatures of 86 [deg]F (30 [deg]C) or higher. This 
observation indicates that seeds on the dunes likely germinate in the 
cooler months of the year. Porter et al. (2005, p. 29) identified the 
primary dormancy mechanism in A. magdalenae var. peirsonii is the 
impermeability of the seed coat to water and demonstrated little loss 
of viability in seeds stored for 5 years. Impermeability of the seed 
coat to water as a dormancy mechanism is consistent with species having 
a seed bank (Given 1994, p. 67; Bowers 1996, p. 71). Dispersed seeds 
that do not germinate during the subsequent growing season become part 
of the soil seed bank (Given 1994, p. 67).
    Annual or short-lived perennial plant populations can fluctuate 
between large numbers of plants to few or even no plants. Many species, 
and Astragalus magdalenae var. peirsonii may be one of them, rely on 
periodic ``rescue'' episodes from the seed bank where large numbers of 
plants germinate when conditions are suitable (Elzinga et al. 1998, p. 
285; Pake and Venable 1996, pp. 1433-1434). Lincoln et al. (1993, p. 
223) define the soil seed bank as ``the store of dormant seed buried in 
soil,'' the store of seeds that do not germinate when otherwise 
adequate conditions are present. The number of seeds in the seed bank 
changes, depending upon the balance between processes or factors that 
remove seeds from the seed bank and those that contribute seeds to it. 
Deposition to the A. magdalenae var. peirsonii seed bank depends upon 
standing plants that successfully produce seeds. This deposition is 
diminished to the extent that plants are precluded from adding seeds to 
the seed bank (Harper 1977, pp. 457-468; Louda and Potvin 1995, pp. 
240-243). Other decreases to the seed bank can be attributed to loss of 
plants or reduced reproductive output due to herbivory (Louda 1982, pp. 
47-49; Baron and Bros 2005, pp. 49-51), direct or indirect OHV damage 
(Pavlik 1979, pp. 73-85), or environmental conditions (e.g., summer or 
winter drought, wind blown sand damage, dune shifts, or deep burial) 
(Baskin and Baskin 2001, pp. 149-160). Increases in the available seed 
bank can be attributed to rescue episodes in years favorable for 
reproduction (Pake and Venable 1996, p. 1434).
    Development of a seed bank and the associated dormancy allows plant 
species to grow, flower, and set seed in years with most favorable 
conditions (Given 1994, p. 67). When measuring seed bank dynamics, 
estimations of the rate of seed mortality and aging, the amount of seed 
lost to predators, and the variability in germination events are among 
the information considered necessary to determine the viability and 
productivity of a seed bank (Elzinga et al. 1998, p. 284).

Abundance and Population Trend

    The updated petition (ASA 2005, pp. 11-12, 38-46) asserts that 
Astragalus magdalenae var. peirsonii is abundant and thriving, and 
therefore should not be listed, and also again asserts that the 
original listing (63 FR 53596) was made without the support of 
abundance data. In fact, for a species that fluctuates widely in 
numbers from year to year, an assessment of abundance may not be the 
most meaningful measure of the likelihood of persistence. Assessing the 
population trend, resilience, and long-term viability of A. magdalenae 
var. peirsonii is more relevant but is complex due to (1) the large 
fluctuations in numbers of above-ground plants from year to year (often 
the result of variations in rainfall or other climate conditions from 
year to year), and (2) the intricacies associated with studying and 
understanding seed banks and their dynamics. Although abundance data 
will not likely completely clarify the likelihood of persistence for A. 
magdalenae var. peirsonii, we review the available data below because 
it has been the subject of much discussion over recent years. The data 
presented in this section supports our original decision to list A. 
magdalenae var. peirsonii as threatened. In addition, we discuss the 
suitability of comparing available surveys. This is relevant because 
multiple years of survey data are needed to detect population trends, 
and using data from different surveys together to detect a trend can 
only be legitimately done if the survey methodologies are comparable. 
Finally, we discuss the available data on seed production and seed bank 
dynamics, which is also relevant to our analysis of the long-term 
persistence of A. magdalenae var. peirsonii.
    Overview of survey data. A number of abundance surveys have been 
conducted for Astragalus magdalenae var. peirsonii. Early surveys 
incorporated a methodology whereby plants encountered along driving or 
walking transects covering the entire 167,000 ac (67,900 ha) ISDRA were 
qualitatively indexed to an abundance value (see WESTEC 1977, Table 2-
3) and represented in quadrants measuring 0.45 mile on each side. 
Analysis of these coarse, dune-wide surveys conducted by WESTEC in 
1977, and BLM (Willoughby) in 1998 through 2002, could only provide 
relative comparisons of mean abundance values between years. In 
comparing survey results for these years, the species was most abundant 
in 1998, the highest rainfall year, and least abundant in 2000, the 
lowest rainfall year (Willoughby 2001,

[[Page 41011]]

p. 21; 2004, p. 10). Mean abundance values for the years 1998 through 
2002 were based upon total plant counts ranging from 86 plants in 2000 
to 5,930 plants in 2001 (Willoughby 2004, p. 36). From this comparative 
analysis, Willoughby (2004, p. 26) determined that there was little 
change in A. magdalenae var. peirsonii abundance between 1977 and 2002.
    In 2001, Dr. Arthur M. Phillips began a multi-year effort to 
monitor Astragalus magdalenae var. peirsonii. Astragalus magdalenae 
var. peirsonii abundance values were tabulated for 4 years: 2001, 2003, 
2005, and 2006. In 2001, during an initial reconnaissance of the dunes, 
Phillips et al. (2001, p. 6) counted 71,926 A. magdalenae var. 
peirsonii from 127 specific locations covering an unspecified area of 
about 35,000 ac (14,165 ha) (Phillips and Kennedy 2002, p. 8, Appendix 
A), and they therefore calculated a density of about 2 plants/ac (5/
ha). From the 127 locations, Phillips and Kennedy (2002, p. 10) 
selected 25 monitoring sites to use for the multi-year effort. The 
effective area (i.e., the total area represented by data) covered by 
the 25 sites was about 138 ac (56 ha) (Phillips and Kennedy 2005, p. 
9). Phillips and Kennedy reported 30,771 plants in 2001 (Phillips and 
Kennedy 2002, Appendix A); 33,202 plants in 2003 (Phillips and Kennedy 
2003, Appendix A); 77,922 plants in 2005 (Phillips and Kennedy 2005, p. 
10); and 1,233 plants in 2006 (Phillips and Kennedy 2006, p. 6) for 
these 25 monitoring sites. Plant density ranged from 565 plants/ac 
(1,392/ha) in 2005, to 8.9 plants/ac (22/ha) in 2006. In addition, in 
2005 and 2006, Phillips and Kennedy used the data from the 25 
monitoring sites to estimate the population for 60 of their original 
sites at 173,328 and 2,035, respectively (Phillips and Kennedy 2005, p. 
11; 2006, p. 6).
    The BLM embarked on a new sampling methodology in 2004 that sampled 
a larger portion of the dunes in greater detail (Willoughby 2005a, pp. 
1-5), and increased the number of sample transects from 135 in 2004 to 
510 for the spring 2005 surveys (Willoughby 2005b, p. 2). Willoughby's 
(2005a and 2005b) analyses were based upon these sample transects, 
which were comprised of 37,169 25-by-25-meter sample cells in 2004 
(USFWS 2006a, Table 1) and 123,488 sample cells in 2005 (USFWS 2006b, 
Table 1). Willoughby (2005a, Table 1-1) estimated the total population 
size at 286,374 plants in 2004, for an estimated density of 5.5 plants/
ac (13.5/ha). Plants were most abundant in 2005 in what was an 
exceptional year with well-timed rainfall and cool temperatures from 
October 2004 through March 2005 (Willoughby 2005b, p. 6). In 2005, 
Willoughby (2005b, Table 4) estimated 1,831,076 plants were in the 
dunes, with an estimated density of 35 plants/ac (86.3/ha). A 
randomized sample of 2005-occupied cells during the very dry winter and 
spring of 2006 yielded an estimated population size of 83,451 plants, 
or 1.5 plants/ac (3.9/ha) (Willoughby 2006, p. 6). The effective area 
of these surveys covered about 53,000 ac (21,200 ha) and encompassed 
all BLM management areas containing Astragalus magdalenae var. 
peirsonii. In 2007, the BLM estimated the population size as 293,102 
plants, or 14.2 plants/ac (35/ha), for portions of the Gecko, AMA and 
Ogilby management areas, with an effective area of 20,692 ac (8,374 ha) 
(Willoughby 2007, Table 5). However, the precision of the 2006 and 2007 
population estimates was poor due to the low numbers of plants sampled 
and their spatial variability (Willoughby 2006, p. vi; 2007, p. 11).
    The disparity among these three survey methods and the data 
collected make it difficult to assess the Astragalus magdalenae var. 
peirsonii population. As presented in Table 1 below, the 2005 survey 
conducted by BLM is the most extensive and precise effort to determine 
overall population abundance and distribution. The amount of data 
gathered in 2005 was the result of an exceptionally good rainfall year 
and an extraordinary monitoring effort, and represents the best 
estimate of the potential population and extent of habitat for A. 
magdalenae var. peirsonii. The year 2006 was exceptionally dry, with no 
reported A. magdalenae var. peirsonii germination and few surviving 
plants from 2005. The 2007 rainfall pattern was not evenly distributed 
throughout the dunes and contributed to the spatial variability that 
yielded poor precision for the population estimates of that year 
(Willoughby 2007, pp. 6-7 and Table 2).

                 Table 1.--Abundance Values Submitted for A. Magdalenae var. Peirsonii in the Algodones Dunes in 14 Unpublished Reports
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        No. plants       Estimated     x8 abundance
              Year                     Surveyor           counted       population         class        No. samples             Effective area
--------------------------------------------------------------------------------------------------------------------------------------------------------
1977............................  WESTEC............             N/A             N/A             4.3           1,611  167,800 ac (67,900 ha).
1998............................  BLM \1\...........           5,064             N/A             6.3             542  167,800 ac (67,900 ha).
1999............................  BLM \1\...........             942             N/A             2.8             542  167,800 ac (67,900 ha).
2000............................  BLM \1\...........              86             N/A             1.1             542  167,800 ac (67,900 ha).
2001............................  BLM \1\...........           5,930             N/A             4.7             542  167,800 ac (67,900 ha).
2002............................  BLM \1\...........           2,297             N/A             3.3             542  167,800 ac (67,900 ha).
2001............................  Phillips \2\......      \3\ 71,926             N/A  ..............             127  35,000 ac (14,165 ha).
2001............................  Phillips \2\......          30,771             N/A  ..............              25  138 ac (56 ha).
2003............................  Phillips \2\......          33,202             N/A  ..............              25  138 ac (56 ha).
2005............................  Phillips \2\......          77,922     \4\ 173,328  ..............              25  138 ac (56 ha).
2006............................  Phillips \2\......           1,233       \4\ 2,035  ..............              25  138 ac (56 ha).
2004............................  BLM \1\...........          25,798         286,374  ..............             135  53,000 ac (21,200 ha).
2005............................  BLM \1\...........         739,805       1,831,076  ..............             510  53,000 ac (21,200 ha).
2006............................  BLM \1\...........             761          83,451  ..............             775  53,000 ac (21,200 ha).
2007............................  BLM \1\...........           1,435         293,102  ..............             735  20,692 ac (8,374 ha).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ BLM reports cited as Willoughby.
\2\ Phillips reports cited as Phillips et al. or Phillips and Kennedy.
\3\ Reconnaissance of unspecified area.
\4\ Estimated population for 60 specific sample sites.

    As illustrated in Table 1, two substantial issues are associated 
with the body of survey work for Astragalus magdalenae var. peirsonii. 
These two issues are (1) comparison of BLM data with WESTEC data and 
(2)

[[Page 41012]]

interpretation of abundance values. Each issue is discussed below.
    Comparison of BLM data with WESTEC data. The first issue concerns 
the early surveys conducted between 1977 and 2002. Although mean 
abundance class values were calculated from sample transects across the 
entire dunes, class values were only comparable between years. It is 
not appropriate to compare these class values with more recent or finer 
scale data that is based on counts of plants (rather than abundance 
classes). Willoughby (2000, p. 7) recognized that the 1998 BLM data, 
and the data BLM collected through 2002, might not be directly 
comparable to the 1977 (WESTEC 1977) data (Willoughby 2000, p. 7). 
Therefore, he (Willoughby 2000, p. 34, and reiterated 2001, p. 28) 
addressed the limitations of the monitoring data to that point in time 
by recognizing that statistically significant sample values between 
1977 and 1998 were not ``proof'' that Astragalus magdalenae var. 
peirsonii had increased significantly. Our assessment of the data 
indicates that the density classes of WESTEC (1977) and BLM (Willoughby 
1998-2002) are qualitative and are not based on particular numbers of 
individual plants but rather on the apparent visual density of plants 
as a feature of the landscape. These reports (WESTEC 1977 and BLM 1998-
2002) do not include quantitative measures of density, based upon 
counts of numbers of plants per unit area. We are not aware of any 
quantitative measures of density for A. magdalenae var. peirsonii for 
the years included in these reports.
    Although Willoughby (2000, p. 7) noted the limitations of the 
WESTEC (1977) data, he converted the qualitative measures into 
quantitative measures for comparison with the BLM survey data in an 
attempt to assess abundance among years. The magnitude of non-sampling 
error (subjective errors arising from activities other than sampling or 
measuring) in the WESTEC (1977) study, however, makes comparison with 
the BLM data problematic (L. Ball USFWS in litt. 2003, p. 2, comment 
for ASA (2001) petition). In addition, peer reviewers also commented on 
the inappropriateness of comparisons between the BLM study results and 
those of WESTEC (1977). In his peer review comments for the ASA (2001) 
petition, Pavlik (in litt. 2003, p. 3, comment for ASA (2001) petition) 
stated that ``[a]ny attempt to establish population trends by 
comparison to the 1977 WESTEC study should be rejected because there is 
no objective way to replicate with certainty WESTEC's vague and highly 
subjective relative abundance codes'' (see WESTEC 1977, Table 2-3).
    Climatic variability should also be considered when comparing the 
1977 WESTEC study with more recent surveys. Pavlik (in litt. 2003, p. 
4, comment for ASA (2001) petition) stated that rainfall during the 
October through March period, most critical for germination, was less 
in 1977 than in 1998, and, therefore, if more plants were present in 
1998, it could have been due to increased rainfall rather than lack of 
OHV impacts. He noted that this was stated explicitly in Willoughby 
(2000, p. 34), but not in ASA (2001). In her peer review, Bowers (in 
litt. 2006) noted that the updated petition (ASA 2005, p. 36) stated 
that despite increasing OHV traffic, Astragalus magdalenae var. 
peirsonii rebounded after the 1977 survey made by WESTEC. Bowers (in 
litt. 2006, pp. 6-7) stated that:

at the time of the 1977 surveys, when PMV [A. magdalenae var. 
peirsonii] was apparently at a low ebb, the southwestern United 
States had only recently emerged from a long and serious drought 
[see Swetnam and Betancourt 1998, p. 3131]. This suggests that under 
relatively light OHV use, PMV is sensitive to severe drought. The 
post-1977 increase in PMV occurred during the wettest two decades in 
the twentieth century. In fact, the period from 1976 to 1998 was 
among the wettest during the past one thousand years [see Swetnam 
and Betancourt 1998, pp. 3140-3141; Willoughby 2006, Figure 3]. This 
suggests that PMV thrived under increasing OHV pressure only because 
climate favored regeneration. I cannot emphasize too strongly that 
our belief in the resilience of this species is biased by unusually 
favorable conditions for reproduction in recent years.

Kalisz and McPeet (1993, p. 319) note that multiple years of poor 
conditions magnify this impact on population growth rates and the 
dormant seed bank.
    Therefore, the information available to us indicates that using the 
WESTEC data, in comparison with other data, to assess abundance trends 
in Astragalus magdalenae var. peirsonii is inappropriate. This suggests 
that claims of trends of population increases based on comparisons of 
BLM surveys (Willoughby 2000, 2001, and 2004) and the WESTEC survey 
(1977) are not supportable, both because the surveys are not comparable 
due to differences in methodology and because of climatic variability 
between the years surveyed (i.e., any increases observed could be due 
to increases in rainfall in later years rather than to actual increases 
in numbers of plants). At the time of listing in 1998, the available 
data (WESTEC 1977) indicated that A. magdalenae var. peirsonii was not 
abundant within the Algodones Dunes, and an analysis of threats to the 
species, in light of the species' life history traits, indicated that 
listing the species as threatened was warranted.
    Interpretation of abundance values. The second issue associated 
with the survey work for Astragalus magdalenae var. peirsonii concerns 
the abundance values reported from 2001 through 2006 by Phillips et al. 
(2001), Phillips and Kennedy (2003, 2005, and 2006), and Willoughby 
(2005a, 2005b, 2006, and 2007). The Phillips reports (Phillips et al. 
(2001), Phillips and Kennedy (2003, 2005, and 2006)) and the BLM 
reports (Willoughby (2005a, 2005b, 2006, and 2007)) used different 
sampling protocols and estimation procedures. Because the methodologies 
for these surveys differed from one another, caution should be used in 
comparing them. Phillips et al.'s (2001) reconnaissance covered an 
unspecified large area, but observations were reported from only 127 
locations (Phillips et al. (2001, Appendix A). The 25 monitoring sites 
established by Phillips and Kennedy (2001, 2002) were subjectively 
selected for A. magdalenae var. peirsonii presence and not designed to 
estimate abundance beyond the extent of the 138-ac (56-ha) sampling 
area (Phillips and Kennedy 2002, p. 10). In contrast, the BLM surveys 
were designed to estimate the standing A. magdalenae var. peirsonii 
population (Willoughby 2005a, 2005b, 2006) throughout its entire range 
in the dunes. Data were compiled in 25-by-25-meter cells derived from 
transects totaling 577 mi (930 km) in 2004 (Willoughby 2005a, Table 1) 
and 1,922 mi (3,095 km) in 2005 (Willoughby 2005b, Table 1), covering 
the full length of the dunes and sampling all micro-habitats along each 
transect (Willoughby 2005b, pp. 1-3).
    According to the updated petition, the survey method used by 
Phillips et al. (2001) ``eliminated the need for a sampling methodology 
and statistical extrapolations'' because they counted every plant 
encountered (ASA 2005, p. 41; Phillips et al. 2001, p. 3). At each 
sample site, ``relatively dense'' clusters that best fit the 
requirements of the sampling design were systematically sampled 
(Phillips and Kennedy 2002, p. 10). In assessing the Phillips survey 
efforts conducted to date, we focused on Phillips et al. (2001) because 
this study was the basis for all subsequent field studies conducted by 
Phillips and Kennedy. Monitoring sites which would be sampled 
repeatedly over several years (Phillips and Kennedy 2002 through 2006) 
were randomly chosen from 60 areas designated as sites in Phillips et 
al. (2001). Twenty-five sites (40 percent of designated sites) were 
selected.

[[Page 41013]]

    As routinely cautioned against in standard sampling or monitoring 
protocols (e.g., Elzinga et al. 1998, p. 64; Thompson et al. 1998, p. 
12; Morrison et al. 2002, pp. 62-63; Ott and Longnecker 2001, p. 21), 
or protocols for assessing demographics and censusing rare plants 
(e.g., Falk and Holsinger 1991, pp. 225-238; Pavlik and Barbour 1988, 
pp. 218-224; others as noted in Porter in litt. 2003, p. 1, comment for 
ASA (2001) petition), this sampling methodology is subject to 
introduced selection error. Kalisz (in litt. 2006, p. 6), Converse (in 
litt. 2006, pp. 2-4), and Porter (in litt. 2003, pp. 1-5, comment for 
ASA (2001) petition) commented in their peer reviews on the 
inappropriate methodology used by Phillips and Kennedy. Specifically, 
Converse (in litt. 2006, p. 4) noted that Phillips and Kennedy (2005) 
calculated plant density ``not for a pre-selected area, but for areas 
that were found to have concentrated numbers of plants, thus leading to 
seriously inflated estimates.'' In fact, density values reported by 
Phillips and Kennedy (2005) and Willoughby (2005b) are consistent with 
the concern that Phillips and Kennedy's estimates may be inflated. 
Phillips and Kennedy (2005, p. 11) estimated plant densities of 0.18 to 
0.78 plants per square meter (1,800 to 7,800 plants per hectare or 728 
to 3,156 plants per acre) as compared to Willoughby's (2005b, p. v.) 
2005 estimates of 9 to 53 plants per acre (22 to 132 plants/ha). Only 
0.1 percent of the 37,169 cells sampled by BLM in 2004 had a density 
equal to or greater than 1,800 plants/ha (USFWS 2006a), and 1 percent 
of the 123,488 cells sampled by BLM in 2005 contained a density equal 
to or greater than 1,800 plants/ha (USFWS 2006b).
    The updated petition asserted that plant counts conducted from 1998 
to 2005 by Phillips and Kennedy and BLM confirm that the Imperial Sand 
Dunes support more than 100,000 individual Astragalus magdalenae var. 
peirsonii and confirm that A. magdalenae var. peirsonii is abundant and 
thriving throughout the dunes (ASA 2005, p. 46). As noted above, there 
are weaknesses in the sampling methodology used in Phillips and Kennedy 
(2002, 2003, 2004, 2005, and 2006). These weaknesses affect the 
reliability of the estimates presented in the Phillips and Kennedy 
reports (2002, 2003, 2004, 2005, and 2006). However, we do not disagree 
with the updated petition that the Imperial Sand Dunes can support 
100,000 or more individual A. magdalenae var. peirsonii plants. The BLM 
surveys of 2005 confirm this point (USFWS 2006b, Table 2; Willoughby 
2005, p. 25).
    Distribution of Astragalus magdalenae var. peirsonii in the 
Algodones Dunes. The updated petition (ASA 2005, p. 23) cites Phillips 
et al. (2001, p. 13) in qualitatively assessing the presence and 
abundance of Astragalus magdalenae var. peirsonii in open versus closed 
areas. Phillips et al. (2001, p. 4) stated that a ``general 
reconnaissance of virtually all portions of the dunes outside of the 
administrative closures and wilderness area was performed'' and that 
``specific survey areas were selected and intensively searched for 
occurrences.'' Phillips et al. (2001, p. 13), in this reconnaissance, 
state that they observed A. magdalenae var. peirsonii colonies that 
``appeared to be similar in number and abundance'' in both the open and 
closed areas of the dunes. However, this statement is inconsistent with 
other portions of the report. For example, the report also states that 
the ``area with dense occurrences in the large central closure was 
perhaps twice the size of the area with sites south of the closure and 
north of I-8. Although no counts were possible from the helicopter, 
many sites with large numbers of plants were observed within the 
closure.'' Phillips and Kennedy (2005, p. 7) also stated that the 
purpose of the 2001 surveys ``was to locate as many occurrences of the 
subject plants as possible, and to completely census and document 
reproductive and habitat data from every area in the dune system in 
which they were found,'' but noted that ``mappable concentrations of 
plants were noted * * * in less than 25% of the dunes proper'' 
(Phillips and Kennedy 2002, p. 17). Converse (in litt. 2006, p. 3) 
noted that some areas were not searched as intensively as others. In 
sum, it appears that all extant plants were probably not found within 
the large expanse of the dunes, that A. magdalenae var. peirsonii was 
unevenly distributed in the dunes, and that large concentrations of A. 
magdalenae var. peirsonii were noticeable within the areas closed to 
OHV use.
    Survey efforts to date have clarified the uneven distribution of A. 
magdalenae var. peirsonii throughout the dunes. Even in the best of 
years, BLM observed A. magdalenae var. peirsonii in just 21 percent of 
the sample cells (USFWS 2006b, Table 1). In that year, 2005, half the 
observed A. magdalenae var. peirsonii, approximately 370,000 plants, 
occurred in 0.7 percent of the survey area (USFWS 2006b, Table 2) or 
about 145 acres (58 ha). Just over 11 percent of the survey area, or 54 
percent of the occupied area, contained a trace density of plants (less 
than 39 plants/ac (100/ha)) (USFWS 2006b, p. 3). Further, the Service 
conducted a Chi-square analysis of BLM's 2005 data which revealed that 
the odds of finding A. magdalenae var. peirsonii in areas closed to OHV 
activity was 2.63 times greater than finding it in areas open to OHVs 
(USFWS 2006b, pp. 3-4). Phillips and Kennedy's 2005 (2005, Appendix A) 
and 2006 (2006, p. 8) reports further illustrate the fact that dense 
concentrations of plants produce large quantities of seed pods, which 
can, in turn, lead to high seed production estimates and high plant 
persistence in localized areas.
    Astragalus magdalenae var. peirsonii exhibits high variability in 
density throughout the dunes, but density is highest in the southern 
half of the dunes (Willoughby 2005, Table 4; USFWS 2006b, Tables 1 and 
2, Map 1). Phillips et al. (2001) established 19 of their 25 monitoring 
sites in close proximity to areas with high plant density (USFWS 2006b, 
Map 2). The difference between the current BLM studies and those of 
Phillips and Kennedy is one of detection rate. BLM systematically 
sampled the entire dunes and reported a detection rate of 0.21 (A. 
magdalenae var. peirsonii detected in 21 percent of the sample cells) 
in the best of years (USFWS 2006b, Table 1). Phillips and Kennedy 
systematically sampled areas selected for plant density yet can neither 
calculate nor report a rate of detection.
    Phillips and Kennedy (2002, p. 10) observed that 70 to 75 percent 
of the dunes is not suitable habitat for A. magdalenae var. peirsonii. 
This observation closely corresponds to the 79 percent of unoccupied 
cells sampled by BLM and calculated by the Service (USFWS 2006b, Table 
1) for 2005. As noted above, 11 percent of the area surveyed by BLM in 
2005 contained a trace density of A. magdalenae var. peirsonii, 
suggesting that these areas are marginal habitat that supported plants 
due to the favorable conditions of 2005. Therefore, optimal habitat for 
A. magdalenae var. peirsonii may be substantially less than the 21 
percent reported (USFWS 2006b). Considering that A. magdalenae var. 
peirsonii only occurs in the United States within the Algodones Dunes, 
and only within a small percentage of the dunes, it is a rare plant.
    Astragalus magdalenae var. peirsonii is a relatively rare plant as 
further illustrated by comparison of its abundance and density to other 
psammophytic (dune loving) plants. The State endangered Helianthus 
niveus ssp. tephrodes (Algodones Dunes

[[Page 41014]]

sunflower), a psammophytic plant with closely parallel distribution to 
A. magdalenae var. peirsonii, was more abundant than A. magdalenae var. 
peirsonii in nearly all years surveyed (Willoughby 2004, p. 36; 
Willoughby 2005a, Table 2-1). Pavlik (in litt. 2006) commented on plant 
densities for common desert Astragalus and herbs. As noted by Rundel 
and Gibson (1996, Table 5.11), density for three Astragalus taxa in the 
Mojave Desert ranged from 400 to 1,200 plants per acre (1,000 to 3,000 
plants/ha). Pavlik (in litt. 2006, p. 2) stated that ``if any of the 
densities of established plants of common species * * * were multiplied 
by the size of their geographic ranges, the total populations would be 
on the order of 10\8\ to 10\10\.'' Bowers (1996) also found similar 
plant densities for psammophytic dune plants in the Sierra del Rosario 
Dunes of northern Sonora, Mexico, only 60 miles (100 km) away from the 
Algodones Dunes and with a similar climate. Density of four annual 
plant taxa ranged from 1,170 to 11,600 plants/ac (2,900 to 28,700 
plants/ha) and for three perennial plants ranged from 5,000 to 6,200 
plants/ac (12,500 to 15,400 plants/ha) (Bowers 1996, Table 2). 
Astragalus magdalenae var. peirsonii, with a density of 9 to 53 plants/
ac (22 to 132 plants/ha), is 2 to 4 orders of magnitude lower than 
other common desert and dunes plants of the California desert. By even 
a qualitative comparison with data collected by other researchers, A. 
magdalenae var. peirsonii is quite rare relative to other species and 
in its spatial distribution in the dune landscape.
    In summary, Astragalus magdalenae var. peirsonii is restricted to 
one area within the United States with a comparatively lower density 
than other dune species, with high variability in population size and 
density, climate, spatial distribution, and area occupied. The 
different population estimates presented in Table 1 above are valid in 
and of themselves but cannot be compared to one another due to 
differences in scale and methodology. Because of the differences 
between the total number of samples and the total area sampled, we 
recognize the recent BLM surveys as the most informative population 
estimates for Astragalus magdalenae var. peirsonii. The work of 
Phillips and Kennedy has been valuable in providing information on 
various parameters of A. magdalenae var. peirsonii life history, but 
cannot be used to support the assertions of the updated petition. 
Phillips and Kennedy's population estimates are appropriate only in the 
areas of their limited surveys, making it difficult to use their 
estimates to predict overall population health, trend, or stability. As 
the evidence suggests in Table 1, the size of the reproductive 
population of A. magdalenae var. peirsonii varies widely among all 
years surveyed and varies in density across the dunes (Willoughby 2005, 
Appendix 1; USFWS 2006b, Map 1). We expect these natural annual and 
spatial variations will continue and, therefore, detecting overall 
trends will be difficult for this species.

Seed Production and Seed Bank Dynamics

    As described above in the Background section, many annual and 
short-lived perennial plants have a substantial soil seed bank. This 
life-history trait complicates assessment of viability for these 
species. When seed banks are important features of the demography of a 
species, census and demographic information for adult populations may 
mislead us about population viability. Understanding the seed bank 
would help us better assess the long-term viability of a species. 
However, seed banks are complex and difficult to quantify (Doak et al. 
2002, pp. 312, 317; Given 1994, pp. 66-67).
    Phillips and Kennedy (i.e., Phillips and Kennedy 2006, p. 10) and 
the updated petition (i.e., ASA 2005, p. 44) emphasize the importance 
of understanding the seed bank to understanding the status of 
Astragalus magdalenae var. peirsonii. However, the updated petition 
seems to confuse the number of seeds produced (i.e., fecundity) with 
the number of seeds in the seed bank. In fact, the updated petition 
appears to equate seed production with recovery (ASA 2005, pp. 4-6). 
For example, Phillips and Kennedy (2002, p. 28) estimated seed 
production on their 25 survey sites at approximately 2.5 million seeds. 
However, they erroneously refer to estimated seed production as the 
seed bank (Phillips and Kennedy 2002, p. 30; 2003, pp. 13, 21; 2004, p. 
16; 2005, pp. 16-17). Lincoln et al. (1993, p. 223) define a soil seed 
bank as ``the store of dormant seed buried in soil'' whereas fecundity 
is defined as ``the potential reproductive capacity of an organism or 
population, measured by the number of gametes or asexual propagules'' 
(Lincoln et al. 1993, p. 93).
    Phillips and Kennedy (2005, Table 6) emphasize that a high seed 
estimate is, in and of itself, enough to ensure stability. Pavlik (in 
litt. 2006, p. 3), in his peer review, commented that this is incorrect 
``knowing what we know about the high rates of seed mortality observed 
in other rare plants.'' In her peer review, Bowers (in litt. 2006, p. 
8) stated that ``multiplying average fecundity per plant by number of 
plants in a sample or population yields an estimate for sample or 
population fecundity. It is incorrect to substitute fecundity for seed-
bank size.'' Phillips and Kennedy do not estimate the size of the 
persistent seed bank (Baskin and Baskin 2001, pp. 141-143) but rather 
attempt to assess the potential seed bank, and therefore population 
size, based on an estimated reproductive rate where seed pod production 
roughly equals reproductive stability.
    In addition, Phillips and Kennedy (2002-2006) compound their 
sampling bias discussed above into hypothetical seed production values. 
Annual seed production was calculated from a few sample sites and 
extrapolated to 60 sites from the Phillips et al. (2001) reconnaissance 
(Phillips and Kennedy 2006, p. 5). The average number of 171 seed pods 
per plant, median of 113 per plant (Phillips and Kennedy 2002, p. 27), 
was determined from only 10 plants (Phillips and Kennedy 2003, p. 12; 
2004, p. 16). Phillips and Kennedy (2006, p. 9) calculated seed pod 
production based on the assumption that 100 percent of perennial plants 
are reproductive. They estimated an average 14 seeds per pod using 
Barneby's (1964, p. 862) observation of 11 to 16 ovules per pod 
(Phillips and Kennedy 2002, p. 27). Phillips and Kennedy's population 
and seed production estimates are based on sample sites selected for 
Astragalus magdalenae var. peirsonii abundance (Phillips and Kennedy 
2001, p. 10), thereby introducing a sample bias to the stated estimate 
of 2.5 to 5.7 million seeds.
    In addition to this sample bias, the estimate is biased by the 
assumption that most plants were reproductive. Kalisz (in litt. 2006, 
p. 3) noted this problem in her peer review, stating that it was 
incorrect to multiply the number of pods by the total number of plants 
since many were seedlings. In fact, not all plants reproduce in a given 
year, even when the climate is favorable for reproduction. Phillips and 
Kennedy reported 45 percent of plants were reproductive in 2001 
(Phillips and Kennedy 2003, Appendix A) and 63 percent were 
reproductive in 2005 (Phillips and Kennedy 2005, Appendix A). The BLM 
estimated that 75 percent of plants were reproductive in the 2005 
surveys (Willoughby 2005, Table 4). In field surveys conducted in 2006, 
a year with no germination where the only Astragalus magdalenae var. 
peirsonii individuals alive in the Algodones Dunes were perennating 
plants, the BLM reported that 68 percent of plants

[[Page 41015]]

were flowering adults (Willoughby 2006, p. vi). The Service reported 54 
percent of plants as being reproductive in their study areas during 
2006 (USFWS 2007, p. 13).
    Furthermore, accurate estimates of seed production depend on 
accurate estimates of the number of seed pods produced and the number 
of seeds produced per pod. Median seed pod production, and therefore 
mean seed production, likely varies annually. Using a mean production 
value from only 10 plants at a single site will not yield an accurate 
estimate for a population. Phillips and Kennedy reported that first-
year plants produce about five seed pods per plant and plants 1 year or 
more in age produce large quantities of seed pods (Phillips and Kennedy 
2002, p. 27). Phillips and Kennedy (2005, p. 17) stressed that plants 
in their second year of growth and older produce many times more seed 
pods than first-year plants. Whether median seed pod production on 
older plants is 113 (Phillips and Kennedy 2002, p. 27) or 139 (USFWS 
2007, p. 14), one of the limiting variables in Astragalus magdalenae 
var. peirsonii stability is the ability or capability of the plant to 
survive long enough to replenish the seed bank with enough seeds to 
ensure continuing cohorts of plants.
    To estimate seed production per pod, in 2005 field surveys, the 
Service collected seed pods at random from plants throughout their 
survey area in April 2005. In this study, 416 seed pods from 78 plants 
were dissected and the undeveloped ovules were counted and separated 
from mature seeds. We observed an average of 5.2 mature seeds per pod. 
The total of mature seeds and undeveloped ovules (which are undeveloped 
seeds) averaged 11.4 per pod (McKinney et al. 2006, p. 85). One pod 
contained 15 mature seeds, while another pod contained 17 undeveloped 
ovules and mature seeds, closely matching the account of Barneby (1964, 
p. 862). The average of 5.2 mature seeds per pod is considerably less 
than the 14 seed per pod value used by Phillips and Kennedy in their 
seed production estimates (Phillips and Kennedy 2002, p. 27).
    The BLM conducted a pilot seed bank study during spring 2007. This 
pilot study randomly sampled 735 of the total cells sampled during the 
spring 2005 surveys in the Gecko, Adaptive and Ogilby management areas. 
All Astragalus magdalenae var. peirsonii seeds on the sand surface 
within each cell were counted and then the cell was systematically 
sampled with 49 cores to a depth of 4 inches (10.16 cm), counting 
subsurface seed. BLM estimates a total of 53,200,000 seeds in the 
Gecko, AMA, and Ogilby management areas in 2007, corresponding to a 
density of 2,572 seeds/ac (6,356 seeds/ha) (Willoughby 2007, p. v, 
Table 5).
    Finally, it is important to note that only a small fraction of seed 
produced in a given year survive to emerge as seedlings (Harper 1981, 
pp. 111-147; Fenner 1985, pp. 57-71). Dormant seeds that persist in the 
seed bank are subjected to many factors that may limit or preclude 
their ability to germinate. These factors include predation from 
animals or invertebrates, attack by microorganisms or fungi, habitat 
altered by wind, flood or mechanical events, or senescence (Baskin and 
Baskin 2001, pp. 149-160). After 5 years of greenhouse experiments, 
Porter et al. (2005, p. 29) reported high germination rates and little 
loss in seed viability. However, in artificial dune experiments the 
germination rate dropped to 27 percent and only another 2 percent of 
seeds germinated in the second season.
    As noted above, Phillips and Kennedy (2005, p. 22) substantiated 
that plants in their first season could produce seed, although on a few 
seed-per-plant basis. The updated petition asserts that these first-
year plants contribute significantly to the seed bank and that the seed 
bank is replenished within two or three growing seasons (ASA 2005, pp. 
7-8). Phillips and Kennedy (2002, p. 27 and Table 7; 2003, pp. 20-21; 
2004, p. 17) continually calculate the number of seeds produced per 
pod, per plant, and per site and equate that production with 
replacement of the seed bank. However, we know of no research or 
studies that provide information specifically on the replacement rate 
of A. magdalenae var. peirsonii to its seed bank or the seed bank 
baseline size. Phillips and Kennedy's field observations were all 
conducted in years with highly variable precipitation as compared to 
the previous two decades (see Willoughby 2006, Figure 3), and their 
studies cover a period with large variation in demographic rates. 
However, seed banks are governed by demographic rates that can be 
difficult to quantify over short study periods (Doak et al. 2002, p. 
312). Willoughby (2007, p. 11) could not determine the seed bank age or 
associate it with the very productive year of 2005, so it is difficult 
to assign his estimate of 53,200,000 seeds as the seed bank baseline 
for the 2007 study areas. Also, no analysis of seed viability was 
conducted from the seeds sampled in spring 2007, further limiting the 
assessment of the seed bank size. Willoughby (2007, p. 11) suggests 
that seed bank sampling in a good rainfall year, after germination and 
before seed set, would address the question of seed bank depletion and 
seed bank age.
    Kalisz and McPeek (1993, p. 319) emphasize that longer runs of bad 
precipitation years can magnify the negative effects on populations. 
Negative effects can include reduced germination, lower recruitment and 
reproduction, and runs of bad years exceeding the seed viability time 
in the seed bank. Because Phillips and Kennedy's (2002, p. 27 and Table 
7; 2003, pp. 20-21; 2004, p. 17) estimates equate one seed produced 
with one plant germinated and we have no information on the seed bank 
baseline, their assertion that the seed bank is replaced within 2 or 3 
growing seasons is speculative.
    We agree with the updated petition (ASA 2005) that understanding 
the soil seed bank is important to understanding the long-term 
viability of Astragalus magdalenae var. peirsonii. However, for the 
reasons stated above, we do not agree that the work of Phillips and 
Kennedy (2002, 2003, 2004, and 2006) effectively elucidates the nature, 
extent, and dynamics of the seed bank for A. magdalenae var. peirsonii 
to the point that we fully understand the seed bank's contribution to 
the long-term persistence of A. magdalenae var. peirsonii. We also do 
not agree that these data provide evidence that A. magdalenae var. 
peirsonii will continue to persist because of the extent and nature of 
its seed bank. In fact, the information suggests that estimates of 
plant persistence and reproduction based on the anecdotal observations 
in the literature or single-year observations may not be accurate 
predictors of the nature or dynamics of the seed bank. Evidence 
suggests that not all plants (i.e., not 100 percent) reproduce in any 
given year, that seed pod production may be as much as one-third less 
than reported by Phillips and Kennedy, that seed production is as much 
as two-thirds less than that reported by Phillips and Kennedy, that 
only a small fraction of seeds may germinate from the persistent seed 
bank, and that under managed conditions about one-quarter of seeds in 
the wild may germinate. Phillips and Kennedy (2006, Table 3) did not 
consider any of these variables in their seed bank estimates. These 
variables and others (e.g., rate of seed mortality and aging, amount of 
seed lost to predators (Elzinga et al. 1998, p. 284)) must be 
considered for inclusion in models to estimate long-term persistence of 
A. magdalenae var. peirsonii. Pavlik (in litt. 2003, p. 4, comment for 
ASA (2001) petition) and Bowers (in litt. 2006, p. 9) noted that

[[Page 41016]]

Phillips and Kennedy have, however, begun to collect data valuable as 
initial parameters for these models.

Summary of Factors Affecting the Species

    Section 4 of the Act and its implementing regulations (50 CFR part 
424) set forth the procedures for listing species, reclassifying 
species, or removing species from listed status. ``Species'' is defined 
by the Act as including any species or subspecies of fish or wildlife 
or plants, and any distinct vertebrate population segment of fish or 
wildlife that interbreeds when mature (16 U.S.C. 1532(16)). Once the 
``species'' is det