Browse: Departments   Dates   Agencies  

CFR Citation: 50 CFR Part 17

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

NOTICE: PROPOSED RULES

ACTION: Endangered and Threatened Wildlife and Plants:

DOCUMENT ACTION: Notice of 12-month petition finding.

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

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

DOCUMENT SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 12month finding on a petition to remove Astragalus magdalenae var. peirsonii (Peirson's milkvetch) 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.

SUMMARY: 12-Month Finding on Petition to Delist Astragalus magdalenae var. peirsonii (Peirson's milk-vetch),

SUPPLEMENTAL INFORMATION

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 12month findings are to be published promptly in the Federal Register.

Astragalus magdalenae var. peirsonii (Peirson's milkvetch) 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 offhighway 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 OffRoad Business Association (ASA 2001). On September 5, 2003, we announced a 90day 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 12month 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 milkvetch) that was prepared by David P. Hubbard for the American Sand Association, the OffRoad Business Association, the San Diego OffRoad Coalition, the California OffRoad Vehicle Association, and the American Motorcycle Association District 37 (ASA 2005). On November 30, 2005, we announced our 90day 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 milkvetch 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) 12month 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 milkvetch) is an erect to spreading, herbaceous, shortlived 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. 862863) 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 milkvetch 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. 862863) 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. 1011).

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. 910). Other observations from Yuma, Arizona, and San Felipe, Baja California, Mexico, were based on misidentified specimens (see Porter et al. 2005, pp. 910, 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 167,800ac (67,900ha) 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 032509 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 shortlived 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 abovenormal 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 neartotal 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. 1516). 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 midNovember 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. 2224; 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. 1617; 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 20012002, 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 whitefaced, mediumsized, 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 selfpollination, and thus require pollinators for outcrossing. Moreover, Porter et al. (2005, p. 34) reported from microscopic examination of handpollinated 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 selfincompatibility (Porter and Prince 2007, pp. 1011). Selfincompatibility (SI) is a genetic mechanism in plants that prevents selffertilization, 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. 3738; 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 manmade 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, singlechambered, 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. 862863), 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 pretreatment 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. 4546), 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 shortlived 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. 14331434). 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. 457468; Louda and Potvin 1995, pp. 240243). Other decreases to the seed bank can be attributed to loss of plants or reduced reproductive output due to herbivory (Louda 1982, pp. 4749; Baron and Bros 2005, pp. 4951), direct or indirect OHV damage (Pavlik 1979, pp. 7385), or environmental conditions (e.g., summer or winter drought, wind blown sand damage, dune shifts, or deep burial) (Baskin and Baskin 2001, pp. 149160). 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. 1112, 3846) 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 longterm viability of A. magdalenae var. peirsonii is more relevant but is complex due to (1) the large fluctuations in numbers of aboveground 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 longterm 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, dunewide 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 multiyear 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 multiyear 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. 15), 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 25by25meter sample cells in 2004 (USFWS 2006a, Table 1) and 123,488 sample cells in 2005 (USFWS 2006b, Table 1). Willoughby (2005a, Table 11) 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 welltimed 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 2005occupied 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. 67 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 19982002) 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 nonsampling 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 23).

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. 67) 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 post1977 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. 31403141; 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 138ac (56ha) 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 25by25meter 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 microhabitats along each transect (Willoughby 2005b, pp. 13).

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). Twentyfive 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. 6263; Ott and Longnecker 2001, p. 21), or protocols for assessing demographics and censusing rare plants (e.g., Falk and Holsinger 1991, pp. 225238; Pavlik and Barbour 1988, pp. 218224; 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. 24), and Porter (in litt. 2003, pp. 15, 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 preselected 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 I8. 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 Chisquare 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. 34). 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 21). 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 shortlived perennial plants have a substantial soil seed bank. This lifehistory 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 longterm viability of a species. However, seed banks are complex and difficult to quantify (Doak et al. 2002, pp. 312, 317; Given 1994, pp. 6667).

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. 46). 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. 1617). 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. 141143) 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 (20022006) 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 firstyear 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. 111147; Fenner 1985, pp. 5771). 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. 149160). 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 seedperplant 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. 78). Phillips and Kennedy (2002, p. 27 and Table 7; 2003, pp. 2021; 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. 2021; 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 longterm 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 longterm 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 singleyear 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 onethird less than reported by Phillips and Kennedy, that seed production is as much as twothirds 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 onequarter 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 longterm 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 determined we then evaluate whether that species may be endangered or threatened because of one or more of the five factors described in section 4(a)(1) of the Act. We must consider these same five factors in delisting a species. We may delist a species according to 50 CFR 424.11(d) if the best available scientific and commercial data indicate that the species is neither endangered nor threatened for one or more of the following reasons: (1) The species is extinct; (2) the species has recovered and is no longer endangered or threatened; or (3) the original scientific data used at the time the species was classified were in error.

A recovered species is one that no longer meets the Act's definition of threatened or endangered. Determining whether a species is recovered requires consideration of the same five categories of threats specified in section 4(a)(1) of the Act. For species that are already listed as threatened or endangered, this analysis of threats is an evaluation of both the threats currently facing the species and the threats that are reasonably likely to affect the species in the foreseeable future following the delisting or downlisting and the removal or reduction of the Act's protections.

A species is ``endangered'' for purposes of the Act if it is in danger of extinction throughout all or a ``significant portion of its range'' and is ``threatened'' if it is likely to become endangered within the foreseeable future throughout all or a ``significant portion of its range.'' The word ``range'' in the significant portion of its range phrase refers to the range in which the species currently exists. For the purposes of this analysis, we will evaluate whether the currently listed species, Astragalus magdalenae var. peirsonii, should be considered threatened or endangered. Then we will consider whether there are any portions of A. magdalenae var. peirsonii's range in which the status of the species differs from that determined for the species rangewide.

MerriamWebster's Collegiate Dictionary defines ``foreseeable'' as ``being such as may be reasonably anticipated'' and ``lying within the range for which forecasts are possible'' (MerriamWebster 2001, p. 456). For the purposes of this finding, the ``foreseeable future'' is the period of time over which events or effects reasonably can or should be anticipated, or trends reasonably extrapolated. Habitat for Astragalus magdalenae var. peirsonii in the United States is almost entirely in public ownership and management at the BLM Imperial Sand Dunes Recreation Area (ISDRA). Due to recent litigation, the specifics of how the BLM will manage the ISDRA in the short term are unclear. As described under ``A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range,'' the current Recreation Area Management Plan (RAMP) (BLM 2003a) is not being implemented due to a court order, but is the most recent plan available for analysis. At some point, BLM will implement a RAMP for the area, but when that will occur is also unclear. However, based on past management by BLM and the management direction for the ISDRA described in the current RAMP, we can reasonably anticipate that BLM will continue to manage habitat within the ISDRA in the longterm for multiple use, including OHV recreation. In

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 800877 8339.