56426 Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 

6We estimated that the total cost of the 

requirement would exceed $240 million. This 

estimate does not include the cost of installation 

and maintenance. 

availability and value of installing a 

carbon monoxide detector; and (4) the 

agency issue press releases and 

consumer advisories with information 

regarding the availability and value of 

CO detectors. The petitioner cited the 

results of the 1996 Research Note and 

stated, ‘‘many if not most of these 

deaths could be prevented by carbon 

monoxide detectors,’’ but did not offer 

any data to support this assertion. 

NHTSA denied the Denenberg petition 

because the costs would have been 

unjustifiable 6 in relation to the benefits. 

The effectiveness of CO detectors 

lessens substantially over time and most 

vehicle-related CO deaths involve older 

vehicles. 

The agency is denying this 

petitioner’s request for the same 

reasons. In addition to our previously 

stated reasons for denying the petition, 

the agency is also concerned that the 

automatic engine shut-off device 

proposed by the petitioner could prove 

to be a hazard. For example, in a tunnel 

with congested traffic, the concentration 

of CO may cause the device to shut off 

the engine, resulting in further traffic 

congestion or even possible crashes. 

In accordance with 49 CFR part 552, 

this completes the agency’s technical 

review of the petition for rulemaking 

from Mr. Albert Donnay. Based on this 

review, the agency has concluded its 

resources would be more productively 

directed to other areas. Therefore, Mr. 

Donnay’s petition is denied. 

Issued on: September 20, 2005. 

Stephen R. Kratzke, 

Associate Administrator for Rulemaking. 

[FR Doc. 05–19214 Filed 9–26–05; 8:45 am] 

BILLING CODE 4910–59–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

Endangered and Threatened Wildlife 

and Plants; 12-Month Finding on a 

Petition To List the Gentry Indigo Bush 

as Endangered 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Notice of 12-month petition 

finding. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), announce a 

12-month finding on a petition to list 

the Gentry indigo bush (Dalea 

tentaculoides) as endangered under the 

Endangered Species Act of 1973, as 

amended. After reviewing the best 

available scientific and commercial 

information, we find that listing the 

species is not warranted at this time. 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 the status of the species. 

DATES: The finding announced in this 

document was made on September 14, 

2005. Although no further listing action 

will result from this finding, we request 

that you submit new information 

concerning the status of, or threats to, 

this species whenever it becomes 

available. 

ADDRESSES: The complete file for this 

finding is available for inspection, by 

appointment, during normal business 

hours at the Arizona Ecological Services 

Office, 2321 West Royal Palm Road, 

Suite 103, Phoenix, AZ 85021–4951. 

Please submit any new information, 

materials, comments, or questions 

concerning this species or this finding 

to the above address. 

FOR FURTHER INFORMATION CONTACT: 

Mima Falk, Plant Ecologist, Arizona 

Ecological Services Tucson Sub-Office, 

201 North Bonita Ave., Suite 141, 

Tucson, AZ, 85745; 520–670–6150, ext. 

225. 

SUPPLEMENTARY INFORMATION: 

Background 

Section 4(b)(3)(B) of the Endangered 

Species Act of 1973, as amended (Act) 

(16 U.S.C. 1531 et seq.), requires that, 

for any petition to revise the List of 

Threatened and Endangered Species 

that contains substantial scientific and 

commercial information that listing may 

be warranted, we make a finding within 

12 months of the date of receipt of the 

petition on whether the petitioned 

action is (a) not warranted, (b) 

warranted, or (c) warranted but that the 

immediate proposal of a regulation 

implementing the petitioned action is 

precluded by other pending proposals to 

determine whether any species is 

threatened or endangered, and 

expeditious progress is being made to 

add or remove qualified species from 

the List of Endangered and Threatened 

Species. Section 4(b)(3)(C) of the Act 

requires that a petition for which the 

requested action is found to be 

warranted but precluded be treated as 

though resubmitted on the date of such 

finding, i.e., requiring a subsequent 

finding to be made within 12 months. 

Such 12-month findings must be 

published in the Federal Register. 

On January 7, 2002, we received a 

petition dated January 2, 2002, 

requesting that we list the Gentry indigo 

bush (Dalea tentaculoides) as an 

endangered species, and that critical 

habitat be designated concurrently with 

the listing. In a Stipulated Settlement 

Agreement, signed June 14, 2004 [Center 

for Biological Diversity v. Norton, CV 

03–473–TUC–FRZ (D. Az)], we agreed to 

submit a 90-day finding to the Federal 

Register by January 31, 2005. On 

January 25, 2005, we made our 90-day 

petition finding that the petition 

provided substantial information 

indicating that listing may be warranted. 

The finding and our initiation of a status 

review was published in the Federal 

Register on February 2, 2005 (70 FR 

5401). We are required, pursuant to the 

court approved Stipulated Settlement 

Agreement, to make our 12-month 

finding pursuant to the Act [16 U.S.C. 

1533(b)(3)(B)] by September 15, 2005. 

Biology and Distribution 

Gentry indigo bush is an erect 

perennial shrub that grows from a 

woody root crown and can be up to 1 

meter (m) (3.2 feet (ft)) tall. It is a 

member of the Fabaceae (Pea) Family. 

The leaves are compound, 3–6 

centimeters (cm) (1.2–2.4 inches (in)) 

long with 9–17 pairs of leaflets. The 

leaflets are hairless, notched at the tip, 

and dotted with punctuate glands 

(translucent pitted glands or colored 

dots) on the lower surface. The flowers 

are sessile (lacking a stalk), 6 

millimeters (mm) (0.24 in) in length, 

and are presented in oblong clusters. 

The flower petals are rose-purple. Plants 

flower in the spring, from late March to 

mid-May. They may produce a second 

set of flowers in late summer and fall in 

response to monsoon precipitation. 

Howard S. Gentry originally described 

the species in 1950. It is a distinctive 

member of the genus Dalea with no 

closely related species (Gentry 1950; 

Barneby 1977). The main distinguishing 

character that separates this species 

from other sympatric species is the 

presence of elongate, brown, tentaclelike glands on the calyx (the outer whorl 

of flowering parts), lobes, floral bracts 

(the reduced or modified leaf 

subtending a flower), and branches. 

Gentry indigo bush is known 

historically in the United States from 

only three areas in southern Arizona: 

The western and northern slopes of the 

Baboquivari Mountains (Tohono 

O’odham Nation), the Coyote Mountains 

(Mendoza Canyon), and Sycamore 

Canyon (Coronado National Forest) in 

Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 56427 

the Atascosa Mountains. Today, plants 

are only known to occur in Sycamore 

Canyon and on lands within the Tohono 

O’odham Nation (Schmalzel 2005). 

The plant has also been found at three 

locations in Mexico. The first location 

was found in 1995, northeast of 

Hua ́sabas in the State of Sonora. In 

2004, the species was documented to 

occur in Sierra El Humo, southsouthwest of Sasabe, Arizona, in 

northwestern Sonora, Mexico (L. Hahn, 

pers. comm., 2004). Surveys in 2005 

documented the persistence of those 

two populations and discovered a third 

in the Sierra de La Madera (Van 

Devender 2005). 

Surveys in Sycamore Canyon, AZ 

Gentry indigo bush grows in scattered 

patches at elevations of 1,097 to 1,219 

m (3,600 to 4,000 ft) in Sycamore 

Canyon and several side channels. 

Plants are usually found on floodplain 

terraces in sandy or gravel soils, or, less 

commonly, on talus slopes (a slope 

formed by an accumulation of rock 

debris) close to the floodplain. The 

usual tree canopy for Gentry indigo 

bush consists of Arizona sycamore 

(Platanus wrightii), Arizona ash 

(Fraxinus velutina), Arizona walnut 

(Juglans major), and several oak species. 

Plants can be found growing under 

these trees or out in the open. Where 

Gentry indigo bush grows in the semiactive floodplain, plants are exposed to 

periodic flooding and scouring events. 

Observations made by Gori et al. (1992) 

and Falk (1993) support the idea that 

plants are adapted to periodic, lowintensity floods. Plants that had been 

covered with sediment were found to be 

growing up through the deposited 

material. The plants can reproduce 

vegetatively (asexually), and roots have 

been found to connect young plants to 

nearby larger clumps. The ability to 

reproduce asexually presents a problem 

in estimating population numbers in 

that it is impossible to determine if 

plants are connected, except by 

uprooting them. As a result, the number 

of stems counted may not equal the 

number of individuals. Thus, the data 

from field surveys described below 

should be considered only rough 

estimates of population numbers. 

There have been limited observations 

of sexual reproduction in the field. Gori 

et al. (1992) documented some 

reproduction on the monitoring plot, 

although they had difficulty 

determining if the new recruits were 

ramets (vegetative offshoots) or 

seedlings. Small plants located in May 

2005 were pulled up and were 

identified as seedlings, not vegetative 

offshoots (Baker 2005). It is not known 

if the seeds had lain dormant in the seed 

bank or were from a recent reproductive 

event. None of the adult plants had seed 

pods, and no seed pods were found on 

the ground (Falk, pers. obs. 2005). In 

fact, plants rarely have been observed to 

produce seed (Falk 1993; Gori et al. 

1992). This may be the result of timing, 

as plants may not have been producing 

fruit at the time surveys were 

conducted. Schmalzel (2005) found 

seeds within dried inflorescences (i.e., 

flowers) during his survey work in July. 

Staff from the Desert Botanical Garden 

collected approximately 15 seeds from 

plants they assumed to be Gentry indigo 

bush in 1998 and 1999, but the 

quantities are too small to conduct 

germination tests (K. Rice, pers. comm. 

2005). 

Although this species has adaptations 

to withstand periodic, low-intensity 

flooding, the population in Sycamore 

Canyon has experienced population 

fluctuations, some of those associated 

with flood events. In 1982, a status 

report documented only 100 plants from 

Sycamore Canyon (Toolin 1982). 

Following severe winter flooding in 

1993, a large portion of a monitoring 

plot that had been established on a 

floodplain terrace washed away, and the 

overall population within Sycamore 

Canyon declined to 15–30 plants (Falk 

1993). Gori et al. (1992) estimated that 

there were 1,400 ‘‘individuals’’ in 

Sycamore Canyon before the heavy rains 

of 1993. The population in Sycamore 

Canyon has been monitored 

sporadically since 1993. Bertelsen 

(1997) recorded approximately 500 

individuals. Brooks (1999) found 194 

plants, including a small group (15) in 

Pen ̃ asco Canyon. A U.S. Forest Service 

biologist reported seeing some patches 

of Gentry indigo bush while surveying 

for Sonora chub in the canyon (2000, 

2001). In three separate surveys over 

consecutive years the numbers of plants 

varied. Baker (2003) found 100 plants, 

and Reina and Van Devender found 36 

plants in 2004 (Baker 2005). In 2005, 

Baker recorded approximately 450 

plants, with many seedlings and some 

resprouts from plants thought to be dead 

(bare branches, no leaves). The latter 

survey was done in May 2005, when the 

biologists (including Service staff) knew 

the plants would be flowering, allowing 

easy identification of Gentry indigo 

bush. Additional surveys in Sycamore 

Canyon were conducted in April and 

May (Darling 2005). These surveys were 

conducted on four separate visits, and 

approximately 922 plants were found. 

Of note was the location of many plants 

on talus slopes out of the floodplain. 

Due to variation in survey 

methodologies, the current estimate for 

Sycamore Canyon is thus between 450 

and 922 plants. Schmalzel (2005) 

observed during his surveys that plants 

were associated with grussy colluvium 

(i.e., a loose accumulation of particles 

from decomposing granite) found on the 

sides of canyons, and he believed that 

locations in the floodplain may not be 

as important as those on the sides of the 

canyon. Schmalzel’s 2005 observation is 

consistent with the results of Darling’s 

2005 survey report where Gentry indigo 

bush was found on talus slopes in 

Sycamore Canyon. 

The distribution of sub-populations in 

Sycamore Canyon has changed over 

time. The overall population in 

Sycamore Canyon is best described as a 

metapopulation, that is, a population 

consisting of many ‘‘local’’ subpopulations or patches. Sub-populations 

may undergo extirpation (i.e., loss) 

while others are created, such that 

distribution within the larger 

population is dynamic in nature and the 

species persists at a larger scale— in this 

case, throughout the canyon. This 

pattern follows Levins’ dynamic 

metapopulation model (1969, 1970) 

describing habitat patches, or islands, 

with some of the patches disappearing 

but then undergoing recolonization from 

the remaining patches. For instance, a 

flood event could remove some subpopulations from the canyon, but the 

remaining sub-populations would 

persist and serve as a source of 

recolonization. 

As a result, it is very difficult to track 

individual patches in the canyon over 

time. Early monitoring efforts 

documented the location of patches, but 

successive surveyors have found that 

previously documented patches are not 

always present. This indicates that 

patch location is very dynamic in the 

canyon. Based on the Baker 2005 

survey, the densest plant patches are 

located in the central portion of the 

canyon (centered around where Pen ̃ asco 

Canyon enters into Sycamore Canyon) 

and areas directly to the north and 

south. The dynamic nature of plant 

distribution is likely influenced by 

drought and flooding, which is not 

uncommon for plants found in canyons 

subject to episodic climate events. 

Additional Survey Work in Arizona 

and Mexico 

Gori et al.(1992) status report 

included a review of historic localities 

in the United States and areas of 

suitable habitat in Arizona and Mexico, 

except areas within the Tohono 

O’odham Nation. No plants were found 

in the Coyote Mountains, and the 

authors surmised in the status report 

56428 Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 

that the population was extirpated, 

possibly due to past grazing practices. 

In Mexico, surveys were conducted in 

areas not previously known to support 

Gentry indigo bush plants, but where 

the habitat appeared to be suitable. No 

plants were found in the areas surveyed, 

which included canyons in the 

following mountain ranges in Sonora, 

Mexico: Sierra Cibuta, La Colorada, 

Sierra el Tigre, Sierra los Ajos, Sierra 

Azul, Arroyo Las Fresnos, Sierra San 

Diego, La Angostura, and Sierra San 

Luis (Gori et al. 1992). 

Extensive survey work has also been 

completed in other areas of habitat in 

Arizona that appear to be suitable, but 

that were not known to have ever 

supported Gentry indigo bush. 

Specifically, in Arizona in 1991, 1998, 

2003, and 2005, surveys were conducted 

with negative results in all efforts. Areas 

surveyed include the Atascosa/Pajaritos 

(Upper Peck Canyon, California Gulch, 

Holden Canyon, and Rock Corral 

Canyon), the Baboquivaris (Thomas and 

Sabino canyons), and the Patagonia 

Mountains (Harshaw Creek, Finley and 

Adams canyons, Flux Canyon, and 

upper Mowry Wash) (Gori et al. 1992). 

Gentry indigo bush was not found in 

Atascosa, Pen~asco, or unnamed 

canyons in the Atascosa Mountains 

(Baker 2005), or in the upper reaches of 

Sycamore Canyon (Baker 2003). 

However, in 2005, Gentry indigo bush 

was located on the Tohono O’odham 

Nation (Schmalzel 2005). The Tribe 

should be contacted for additional 

information, if needed. 

In 2005, Dr. Tom Van Devender and 

Ana Lilia Reina conducted extensive 

surveys for Gentry indigo bush in 

Mexico. From April through June, they 

visited 22 potential sites in 7 mountain 

ranges in Sonora, Mexico. The ranges 

surveyed west-southwest of Sa ́sabe to 

southwest of Cananea were the Sierra El 

Humo, Sierra Las Avispas, Sierra 

Cı ́buta/Guacomea, Sierra Jojoba, Sierra 

de Los Pintos, Sierra de La Madera, and 

Sierra Azul. Sites surveyed were 1,045 

to 1,518 m (3,400 to 5,000 ft) in 

elevation and mostly in canyons in 

desert grassland/oak woodland 

transition or oak woodland (Van 

Devender 2005). They also revisited the 

2004 location of Gentry indigo bush in 

the Sierra El Humo, an isolated 

mountain range near the Arizona border 

in the Municipio of Altar, and a total of 

126 plants were found in 6 patches in 

an unnamed canyon. A new population 

was located in the Sierra de La Madera. 

This mountain range is located east of 

interstate MEX 15 between Imuris and 

Magdalena. Plants were found in Cajo ́n 

El Chorro, within the Sierra de La 

Madera. A total of 98 individuals were 

found in 2 patches. Van Devender 

returned to the 1995 Hua ́sabas site and 

documented 170 Gentry indigo bush 

plants. This site is atypical, as the plants 

were found under Chihuahua oaks on 

gentle north-facing slopes, not in 

canyon bottoms (Van Devender 2005). 

Overall, surveys in Mexico in 2005 

documented 394 Gentry indigo plants at 

3 locations. No other populations of 

Gentry indigo bush were located, and no 

historical records are known from any of 

the other 19 sites surveyed (Van 

Devender 2005). 

In summary, Gentry indigo bush 

remains a rare, narrow endemic (i.e., 

restricted to a particular region) in terms 

of its overall numbers, number of 

populations, and geographic 

distribution. Dedicated, extensive 

surveys conducted over the years have 

documented few new locations, and all 

known populations are small. No new 

locations have been found in Arizona 

despite fairly extensive surveys of 

apparently suitable habitat. In Sycamore 

Canyon, the overall population has 

fluctuated greatly since surveys began, 

and recovery from flooding in 1993 has 

been slow. Currently, the population 

constitutes only 32 to 67 percent of the 

pre-flood numbers. Most of the older 

plants are gone but there are many 

seedlings, which provides some 

evidence of the species’ resiliency and 

ability to persist. However, it is not 

known how many of these seedlings 

will survive and contribute to the 

reproductive potential of the 

population. The limited demographic 

monitoring data show higher mortality 

in the small age classes (Gori et al. 

1992). In some locations, larger and 

older plants were found completely out 

of the floodplain and up against the 

canyon walls, which provides some 

assurance that not all of the species’ 

habitat is susceptible to flooding. The 

species has persisted at known locations 

for some time (based on herbarium 

records), and it seems likely that other 

areas that may support the plant were 

overlooked in previous survey efforts. 

Previous Federal Actions 

Gentry indigo bush was determined to 

be a candidate species as published in 

the 1980 Plant Notice of Review (45 FR 

82480). A species with candidate status 

is one for which we have collected and 

assessed information sufficient to 

propose listing the species. On April 2, 

1998 (63 FR 16217), we removed the 

Gentry indigo bush from candidate 

status. The reasons supporting removal 

from the candidate list were (1) the 

taxon was more abundant or widespread 

than previously believed or not subject 

to any identifiable threats; and (2) the 

Service had insufficient information on 

biological vulnerability and threats to 

support issuance of a proposed rule to 

list. Following receipt of the 2002 

petition, and pursuant to a stipulated 

settlement agreement, we published a 

90-day finding on February 2, 2005 (70 

FR 5401), finding that the petitioners 

had provided sufficient information to 

indicate that listing of the Gentry indigo 

bush may be warranted. In order to use 

the best scientific and commercial 

information available to determine 

whether listing of the species was 

indeed warranted, two public comment 

periods were opened. The initial 

comment period was opened by the 

February 2, 2005, 90-day petition 

finding for a period of 60 days, through 

April 4, 2005, and the comment period 

on the 90-day finding was reopened on 

July 25, 2005 (70 FR 42520), for an 

additional 10 days. 

Summary of Factors Affecting the 

Species 

Section 4 of the Act (16 U.S.C. 1533), 

and implementing regulations at 50 CFR 

424, set forth procedures for adding 

species to the Federal List of 

Endangered and Threatened Species. In 

making this finding, information 

regarding the status and threats to this 

species in relation to the five factors 

provided in section 4(a)(1) of the Act is 

summarized below. 

In general, we have focused much of 

the five factor discussion below on the 

Sycamore Canyon population in 

Arizona because we have specific 

information about it. Where we have 

information for populations in Mexico 

and on the Tohono O’odham Nation, we 

have specifically addressed that below. 

Factor A: The Present or Threatened 

Destruction, Modification, or 

Curtailment of the Species’ Habitat or 

Range 

Modifications and alteration of Gentry 

indigo bush habitat are associated with 

watershed degradation, roads, 

recreational activities, undocumented 

immigrant traffic and associated U.S. 

Border Patrol activities to control illegal 

entry, and the spread of invasive plant 

species. All of these factors have the 

potential to alter and degrade the 

species’ habitat. 

Watershed Degradation 

In general, human-related activities 

can have an adverse impact on the arid 

watersheds of the Southwest (Bahre and 

Bradbury 1978; Bahre 1995; Hadley and 

Sheridan 1995). Such impacts may 

include erosion of stream channels and 

loss of herbaceous vegetation caused by 

overgrazing, altered fire regimes, mining 

Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 56429 

runoff, off-road vehicle use, road 

construction, and other anthropogenic 

activities, and all have contributed to 

reduced quality and quantity of riparian 

and wetland habitat (Hendrickson and 

Minckley 1984; Bahre 1995; Hadley and 

Sheridan 1995; Ohmart 1995; Whelan 

1995; Debano and Neary 1996; Belsky 

and Blumenthal 1997; Wang et al. 

1997). 

Watershed degradation may be a 

concern in Sycamore Canyon, which is 

a small canyon cutting through rugged 

hills located within the Coronado 

National Forest, Nogales Ranger District. 

Special protection for the Canyon is 

provided by inclusion within the 

Goodding Research Natural Area (RNA) 

and the Pajarita Wilderness. Lefevre 

(2000) concluded that human influence 

on Sycamore Canyon is mostly related 

to downcutting of the channel system, 

sediment movement, and sediment 

yield to the stream, and has resulted in 

erosion rates above that which would be 

expected under unroaded, unmined, 

and ungrazed conditions. Within the 

Goodding RNA, mining, roads, and 

grazing are prohibited, as discussed 

below. However, such activities occur in 

the hills outside of the Canyon and may 

influence conditions within it. 

Grazing Effects on Watershed 

The Sycamore Canyon watershed is 

6,737 hectares (ha) (16,648 acres (ac)) in 

size (Lefevre 2000). All but 874 ha 

(2,160 ac) are within grazing allotments. 

The majority of those lands are on the 

Coronado National Forest, where many 

different types of uses are authorized 

(e.g., livestock grazing, mining, roads, 

wilderness). Livestock grazing is not 

permitted within the boundaries of the 

RNA, including Sycamore Canyon. 

The Bear Valley grazing allotment, 

which is located in the hills 

surrounding Sycamore Canyon, is 

9,197.5 ha (22,710 ac) in size. Sitespecific soil surveys (U.S. Fish and 

Wildlife Service 2002) indicate that 75 

percent of the allotment is in 

satisfactory condition, 16 percent is 

considered impaired, 8 percent is 

unsatisfactory, and 2 percent is in 

unsuitable condition. Where soils were 

found to be impaired, it was attributed 

to lack of vegetative ground cover. In 

addition, the soils had altered structure, 

which inhibits water infiltration 

(Lefevre 2000). Lack of ground cover 

and compaction of the soil can lead to 

increased quantities of sediment and 

water flowing into the canyon. Between 

1983 and 1997, the percent of ground 

cover has increased from 29 percent to 

33 percent on this allotment, indicating 

that conditions are improving (Lefevre 

1999). The majority of this allotment is 

in satisfactory condition and on an 

upward trend. The number of permitted 

livestock on this allotment has 

decreased dramatically since 1908, 

when 1,000 cows were allowed. The 

numbers were reduced to 650 in 1917, 

520 in 1930, and stocking was reduced 

to almost zero in 1961 due to range 

deterioration. Due to improvements in 

range condition the allotment is now 

permitted for 350 cattle. The overall 

reduction in livestock numbers from 

1,000 to 350 cows indicates that the 

current management of this allotment is 

contributing to the overall improvement 

of watershed conditions, and with 

improved watershed conditions, the 

amount of sediment entering into 

Sycamore Canyon would be reduced, 

resulting in improved habitat conditions 

for Gentry indigo bush. There will be 

continued sediment and precipitation 

run-off associated with the impaired 

soils due to livestock grazing, but the 

amounts are difficult to quantify and 

may not be significant. 

According to Van Devender (2005), 

none of the three Mexican populations 

are accessible to cattle, so grazing does 

not constitute a threat there. On the 

Tohono O’odham Nation, the influence 

of grazing is unknown, but the species 

is still present (Schmalzel 2005). 

In summary, the watershed condition 

of the Bear Valley livestock grazing 

allotment has been improving since the 

early 1900s. There has been an overall 

decrease in the permitted numbers of 

cattle on the Bear Valley allotment and 

ground cover has improved to the point 

where 75 percent of the allotment is in 

satisfactory watershed condition. The 

continuation of these sound livestockmanagement practices will likely result 

in improved habitat conditions for 

Gentry indigo bush. Sediment will 

continue to move off the allotment, due 

to the 16 percent of impaired soils, but 

the amounts are difficult to quantify and 

may or may not result in significant 

effects to the ecosystem. The Mexican 

populations are not subjected to grazing, 

but watershed conditions there are 

unknown. Similarly, there is little 

information available from the Tohono 

O’odham Nation. 

Roads 

Many roads are present in the 

Sycamore Canyon watershed, and they 

have contributed to overall watershed 

degradation. However, it is not known 

how these roads affect ongoing erosion 

and, more importantly, how much of the 

eroded material ends up in the 

Sycamore Canyon drainage. The amount 

of sediment and surface runoff within 

the Sycamore Canyon watershed may 

affect Gentry indigo bush and its 

habitat. The plants have adaptations for 

persisting in spite of flood events that 

have caused sediment to enter Sycamore 

Canyon, but it is unknown whether a 

threshold exists which, if crossed, may 

eliminate the metapopulation from the 

canyon. However, as noted above, the 

species does have the ability to 

recolonize after flood events, and plants 

located out of the floodplain and on 

associated talus slopes may provide the 

source for recolonization of the plants 

within the floodplain. The U.S. Forest 

Service maintains a road density of 0.58 

km/km2 (0.93 mile/mi2) within the 

watershed, and considers these roads to 

be ‘‘a primary source of erosion and 

sediment’’ (Lefevre 2000). This 

translates to 38.8 km (24.1 mi) of roads 

within the watershed, occupying 22.2 

ha (55 ac) (Lefevre 2000). 

The U.S. Forest Service has no 

immediate plans to address the effects 

of roads in the Sycamore Canyon 

watershed; thus sediment deposition 

and scouring in and along the stream 

channel could still occur. Again, we do 

not know if the sediment production 

associated with the roads is resulting in 

significant effects to the ecosystem and 

the habitat of Gentry indigo bush. 

However, we do know that the 

metapopulation has persisted in the 

canyon under the current road 

conditions. We also note that the U.S. 

Forest Service closed unauthorized 

roads that crossed the stream at several 

locations near the mouth of Sycamore 

Canyon and built a bridge where Forest 

Road 39 crosses Sycamore Creek, thus 

eliminating some erosion threats 

associated with roads. It is not known 

whether roads are a threat to either the 

Mexican or Tohono O’odham 

populations, but we have no evidence 

that roads have adversely affected the 

species there. 

Recreation 

Sycamore Canyon is close enough to 

Tucson and Nogales, Arizona, to make 

it a popular destination for hiking and 

birding. The flora of the canyon 

supports 624 species of vascular plants, 

and birders come from all over the 

world to see various species considered 

rare in the United States. Because there 

are no designated trails within the RNA, 

trampling and compaction of soils from 

the resulting foot traffic can negatively 

affect the Gentry indigo bush in 

Sycamore Canyon. Gentry indigo bush 

plants grow on the floodplain terraces 

where hikers often create trails to avoid 

walking in the stream. Due to its narrow 

width, there are limited terraces in the 

canyon intensifying the use of Gentry 

indigo bush habitat as places to create 

trails. Many of the remaining plant 

56430 Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 

locations are near recreational trails, 

and plants were found that had been 

trampled (Falk, pers. obs. 2005). Even 

when the plants are flowering, they are 

not particularly showy and are quite 

fragile. When they are not flowering, 

they do not stand out, and it is fairly 

easy to step on them without noticing. 

Although no overnight camping is 

allowed in the RNA, there is 

unauthorized camping occurring, as 

evidenced by fire rings and obviously 

trampled areas where human activities 

had taken place. These activities 

degrade habitat and may reduce the 

areas potentially occupiable by Gentry 

indigo bush. They may also alter and 

reduce the amount of habitat available 

for plant germination. This in turn 

affects the ability of the plant to 

reoccupy sites after disturbance events. 

We know of no plan to address the 

effects of recreation in this area or the 

larger watershed. The degree to which 

recreational activities may affect the 

population in Sycamore Canyon is not 

known. However, recreation has been 

ongoing in the canyon in the past, and 

the Gentry indigo bush continues to 

persist and increase in number; 

therefore, we do not believe recreation 

is affecting the overall population in 

Sycamore Canyon. We have no evidence 

that recreation is adversely affecting the 

Mexican or Tohono O’odham 

populations. 

Undocumented Immigrant Traffic/U.S. 

Border Patrol Actions 

The cutting and/or disrepair of the 

border fence along the U.S.-Mexican 

border by undocumented immigrants is 

an ongoing concern due to the potential 

for cattle trespassing and trampling of 

habitat. It is very difficult to monitor the 

status of this fence because it is a long 

hike or horse ride of over six miles 

down the canyon. The U.S. Forest 

Service does not monitor this fence as 

part of its allotment monitoring. It is 

possible that the fence could be cut or 

knocked down and livestock could enter 

the canyon without detection; however, 

the fence has apparently excluded 

trespass cattle since 1998. Given the 

seemingly slow recolonization of the 

Gentry indigo bush population in 

Sycamore Canyon since the 1993 flood, 

a single incursion of cattle could have 

a significant effect on individual 

clusters of plants in the canyon bottom. 

Currently, the majority of the subpopulations are in areas that would be 

accessible by cattle from the southern 

end of the canyon, absent a functional 

fence. On the other hand, the 

metapopulation has persisted even 

through times when the fence was 

down. We do not know what the longterm effects to the metapopulation 

would be from livestock grazing, but it 

seems unlikely that the entire 

metapopulation in Sycamore Canyon 

would be severely affected by 

occasional use by trespass livestock. 

Undocumented immigrants crossing 

the border into the United States from 

Mexico cross through Sycamore 

Canyon. Although we did not detect 

high levels of use during our 2005 

survey, we did observe trash and many 

foot trails in canyons and uplands 

associated with Sycamore Canyon (i.e., 

Pen ̃ asco, Atascosa, Hank, and Yank 

Canyons). Human traffic associated with 

this activity in the canyon bottom may 

directly trample plants and is likely 

contributing to Gentry indigo bush 

habitat degradation. It follows that areas 

receiving heavy use will be under 

surveillance by the U.S. Border Patrol. 

The U.S. Border Patrol’s activities could 

also create additional disturbance by 

using the same foot trails, as well as 

increasing use of existing roads. We do 

not know if these types of activities are 

likely to increase in the future and cause 

detrimental effects to Gentry indigo 

bush and its habitat. Undocumented 

immigrants may also set fires. Although 

these fires are usually accidental (e.g., 

an escaped campfire), they may be the 

ignition source for a future grassland 

fire in the watershed. 

The border fence in Sycamore Canyon 

has remained intact since 1998. Border 

activity ebbs and flows, and it is 

difficult to predict where increased 

activity will take place. Currently, the 

level of border activity is not 

threatening the continued existence of 

the plant in Sycamore Canyon. 

Invasive Plants 

The invasive buffelgrass (Pennisetum 

ciliare) is used throughout Sonora, 

Mexico, as a pasture grass, and large 

natural grassland areas have been 

converted to buffelgrass. Buffelgrass 

lines the major highway in Sonora to the 

U.S. border. Noxious weed seeds can be 

spread by the wind, on the soles of 

shoes, and in the tire treads of vehicles. 

Riparian areas can also function as 

dispersal corridors for the movement of 

invasive plant species (Stohlgren et al. 

1998; Parendes and Jones 2000). With 

the increase in border activity, it is 

probably only a matter of time before 

this highly invasive grass species is 

found in Sycamore Canyon. The U.S. 

Department of Agriculture’s 

Agricultural Research Service has 

developed and released a cold-tolerant 

variety of buffelgrass, ‘‘Frio’’, which is 

intended to be used at higher elevations 

and in regions where current buffelgrass 

cultivars experience winter damage 

(Hussey et al. 2005). These cultivars will 

increase the potential area of invasion. 

Buffelgrass grows very quickly and 

out-competes native grass for water and 

nutrients. Once stabilized, it rapidly 

becomes the dominant plant cover. 

Should it become the dominant plant 

species on floodplain terraces, it could 

replace Gentry indigo bush along with 

other native riparian species in 

Sycamore Canyon, but it is not known 

to occur there at this time. We do not 

know if buffelgrass is found near the 

populations of Gentry indigo bush in 

Mexico, but it may be a potential threat 

to these populations in the future since 

so much planting of the grass has taken 

place in Sonora, Mexico. As of 1997, 

over one million ha (2,471,000 ac) of 

desert and thorn scrub in central Sonora 

had been cleared to plant bufflegrass 

(Van Devender and Felger 1997), but we 

do not know how close it is to invading 

canyons occupied by Gentry indigo 

bush. 

Baker (2005) found at least one, and 

possibly two, species of Pyracantha in 

Atascosa and Sycamore canyons. This 

nonnative, aggressive species, should it 

become established and spread in 

Sycamore Canyon, could potentially 

reduce suitable habitat for Gentry indigo 

bush. 

Many areas of Sonoran desert 

grasslands in southeast Arizona have 

been colonized by Lehman lovegrass 

(Eragrostis lehmanniana), an invasive 

species from South Africa. This grass 

has become so firmly established in 

southern Arizona that there may be no 

feasible control for it. Lehman lovegrass 

produces more fine fuel than native 

grass species (Cable 1971; Cox et al. 

1984), leading to increased fire spread. 

Lehman lovegrass also increases after 

fire (Ruyle et al. 1988; Sumrall et al. 

1991). Currently, the Bear Valley 

allotment does not seem to have 

continuous patches of Lehman 

lovegrass, so the effects from an altered 

fire regime due to its presence may not 

pose a threat to Gentry indigo bush. If 

the density and distribution of Lehman 

lovegrass were to increase on the 

allotment, then more frequent and 

higher intensity fires would be 

expected. This could potentially result 

in increased erosion and precipitation 

run-off, possibly leading to more 

frequent flood events in Sycamore 

Canyon. More frequent and greater 

intensity flooding may not allow for the 

recolonization of habitat and 

reestablishment of sub-populations in 

Sycamore Canyon during flood-free 

intervals, resulting in overall habitat 

and population reduction. 

Establishment of these nonnative 

grasses in Sycamore Canyon or other 

Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 56431 

occupied habitat could compromise 

habitat quality and possibly endanger 

the long-term survival of 

metapopulations because the change in 

fire frequency and intensity could 

increase the frequency and intensity of 

flood events, placing sub-populations at 

increased risk. However, the threats 

from invasive species are considered to 

be only potential at this time, as there 

are no populations of the grass species 

present in Sycamore Canyon. We do not 

know if the populations in Mexico or on 

the Tohono O’odham Nation are 

threatened by invasive species. 

In summary, there are ongoing and 

potential threats to the habitat of Gentry 

indigo bush in Sycamore Canyon. Many 

of the threats identified have been 

minimized (e.g., protection from 

livestock grazing, reduction in livestock 

numbers, overall improvement in 

watershed health) and while other 

threats are possible in the future, there 

is no evidence that they are currently 

affecting the population, and certainly 

not at a level that threatens the species 

(e.g., invasive species, recreation 

impacts, undocumented immigrant 

traffic, U.S. Border Patrol activities, and 

wildfire). Because they occupy similar 

habitat (i.e., canyon bottom), the 

populations in Mexico may be affected 

by the threats discussed in this section; 

however, due to a lack of detailed 

information regarding these sites, there 

is no direct evidence of threats to 

Mexican populations. The status of the 

populations in Mexico and on the 

Tohono O’odham Nation are not known, 

but some of the populations have 

persisted over time. 

Factor B: Overutilization for 

Commercial, Recreational, Scientific, or 

Educational Purposes 

There are no known threats to Gentry 

indigo bush from over-utilization for 

commercial, recreational, scientific, or 

educational purposes. 

Factor C: Disease or Predation 

Grazing Effects on Plants 

This section discusses the threat from 

cows directly eating the plant. Gentry 

indigo bush plants are palatable, as are 

most Dalea species. Gori et al. (1992) 

concluded, ‘‘Our surveys of Sycamore 

and Mendoza Canyons lead us to 

believe that grazing constitutes a threat 

to D. tentaculoides. We observed direct 

evidence of livestock browsing on, and 

even uprooting, the species in lower 

Sycamore Canyon where trespass cows 

from Mexico enter the canyon up to an 

impassable narrows.’’

As discussed above, Sycamore 

Canyon is found within the Goodding 

RNA and the Pajarita Wilderness within 

the boundaries of the Coronodo 

National Forest, Nogales Ranger District. 

Livestock grazing is not permitted 

within the boundaries of the RNA, but 

trespass cattle use has been a sporadic 

problem (U.S. Department of 

Agriculture 1998). Trespass cattle can 

enter the canyon from the mouth of the 

canyon at the northern end, and also 

from the southern end on U.S.-Mexico 

border. The sides of the canyon are 

generally too steep for livestock. Cattle 

have been observed in the northern 

reaches of the canyon (Brooks 1999), 

and Brooks noted heavy cattle use in the 

southern end of the canyon (i.e., below 

‘‘the narrows’’) most likely attributable 

to trespass livestock from Mexico. In 

1997, the U.S. Forest Service proposed 

a set of actions in Sycamore Canyon to 

protect the federally threatened Sonora 

chub (Gila ditaenia). One of those 

actions included building a fence at the 

northern portion of the canyon to 

restrict livestock access to the riparian 

areas. As long as this fence is 

maintained and remains effective, no 

direct threat of cattle in the upper 

reaches of Sycamore Canyon exists. 

In the lower reaches of Sycamore 

Canyon, trespass cattle from Mexico 

may present another problem. Although 

the U.S.-Mexican border fence had been 

in a state of disrepair,in the fall of 1998, 

2.4 km (1.5 mi) of fence was repaired 

and information provided to us during 

our status review of the species 

indicates that the fence is currently 

functional in preventing livestock 

trespass and has not been recently cut 

(Parker 2005). Thus, while sporadic 

grazing was historically considered a 

potential threat to Gentry indigo bush, 

we do not believe that trespass cattle 

from Mexico pose a threat at this time 

in Sycamore Canyon. This 

determination is based on the protective 

status of the area as an RNA and the 

measures taken by the U.S. Forest 

Service to construct and maintain a 

fence preventing cattle from entering the 

canyon from Mexico. 

We know that livestock grazing occurs 

on Tohono O’odham Nation in the 

general area where the plants were 

known to be in the southern 

Baboquivari Mountains, but have no 

recent information on plant numbers. 

We are currently working with the 

Nation to gather information on this 

population. We anticipate that, if 

livestock grazing is determined to be a 

concern, we can work cooperatively 

with the Nation to resolve those issues. 

We do not know if the populations in 

Mexico are affected by livestock grazing; 

nothing was reported on the grazing 

regime in the areas surveyed. Van 

Devender (2005) noted that the 

populations he found were in areas not 

accessible to livestock. 

Gentry indigo bush is palatable to 

other species beside livestock. Brooks 

(1999) provided one observation of a 

plant being almost totally eaten by a 

rabbit. Schmalzel (2005) also noted one 

Gentry indigo bush that had evidently 

been clipped at the base by a valley 

pocket gopher (Thomomys bottae), but 

we do not consider this to be a major 

threat. We acknowledge that rabbits, 

gophers, and other herbivores may eat 

plants, but we do not think this 

constitutes a major threat to the species 

because of the size of mature plants and 

the abundance of other herbaceous 

plants in the canyon available for food. 

We know of no diseases threatening 

this species. 

Factor D: The Inadequacy of Existing 

Regulatory Mechanisms 

The population in Sycamore Canyon 

is on the Coronado National Forest and 

subject to the general Federal 

regulations of the National Forest 

System. Gentry indigo bush is on the 

Coronado National Forest’s Sensitive 

Species List. Populations that may be 

present on the Tohono O’odham Nation 

are not protected by any regulation of 

which we are aware. Mexican 

populations have no protection because 

they are on private land and are 

afforded no protection under Mexican 

laws. The Arizona Native Plant Law 

(State of Arizona) does consider this 

species as highly safeguarded, and thus 

a permit is required from the Arizona 

Department of Agriculture to salvage the 

plant; however, no other protection is 

afforded to the species or its habitat. 

U.S. Forest Service (Sycamore Canyon, 

AZ) 

The metapopulation of Gentry indigo 

bush in Sycamore Canyon is within the 

Goodding RNA and the Pajarita 

Wilderness. There are no other locations 

on U.S. Forest Service land. The U.S. 

Forest Service has stated that Gentry 

indigo bush is afforded a high level of 

protection because it shares its habitat 

with critical habitat of the federally 

listed Sonora chub. The U.S. Forest 

Service has done much work to improve 

the habitat of Sonora chub, including 

removal of a road at the mouth of 

Sycamore Canyon, protection of riparian 

areas at the northern end of Sycamore 

Canyon, and the expansion of the 

Goodding RNA. These actions have 

contributed to improvement of Sonora 

chub habitat and are likely to improve 

Gentry indigo bush habitat, as discussed 

above. Many activities are prohibited 

within the RNA; livestock grazing, 

56432 Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 

timber harvest, and overnight camping 

are examples. A mining withdrawal has 

also been completed for lands within 

the RNA, for a period of 25 years. In 

addition to the Sonora chub, the canyon 

also supports populations of the 

federally listed Chiricahua leopard frog 

(Rana chiricahuensis) and Mexican 

spotted owl (Strix occidentalis lucida). 

The surrounding watersheds are also 

under U.S. Forest Service management. 

A multiple-use policy allows for 

grazing, recreation, and other activities 

that may be affecting the habitat of 

Gentry indigo bush. These issues were 

discussed under Factors A and C above. 

In summary, the U.S. Forest Service 

has completed a number of conservation 

actions in Sycamore Canyon that have 

improved habitat for Gentry indigo 

bush. Road closures and the protection 

of riparian areas at the canyon mouth 

have undoubtedly increased the overall 

health of the riparian ecosystem in the 

canyon. We believe that U.S. Forest 

Service actions and the amount of 

protection the canyon receives by virtue 

of its wilderness and RNA designation 

will promote the long-term conservation 

of Gentry indigo bush in Sycamore 

Canyon. 

The Tohono O’odham Nation 

The Tohono O’odham Nation has not 

drafted specific regulations to address 

sensitive species on their sovereign 

lands. We have a Statement of 

Relationship with the Nation, and 

provide technical assistance with 

wildlife and plant issues at their 

request. The Nation is currently working 

with us on allowing us access to the 

Baboquivari Mountains so that we may 

assist them in survey and assessment of 

their Gentry indigo bush populations. 

Mexico 

Three locations of Gentry indigo bush 

have been documented in Mexico. We 

have basic information (e.g., plant 

community, associated plant species, 

elevation, and substrate) and population 

estimates for these sites. We are not 

aware of any protection for these areas, 

but Van Devender observed during his 

2005 survey work that the sites do not 

have obvious direct threats. 

Furthermore, all of the sites are in 

remote locations and in canyons with 

no livestock access (Van Devender 

2005). 

Factor E: Other Natural or Manmade 

Factors Affecting the Continued 

Existence of the Species 

The known extant Gentry indigo bush 

populations are small, isolated, and 

threatened by unpredictable variation in 

demographic and environmental 

characters (i.e. flooding). Genetic 

factors, such as reduced genetic 

variation due to small population size, 

may also contribute to this species’

overall status. Inbreeding depression 

and loss of genetic diversity may occur 

in small populations of less than a few 

hundred individuals; such loss may 

reduce the fitness of individuals and the 

ability of the population to adapt to 

change (Frankel and Soule 1981). Both 

of these genetic considerations result in 

an increased likelihood of extirpation 

(Lande and Barrowclough 1987). 

Climate change may influence 

precipitation patterns in ways that 

could affect the long-term persistence of 

the metapopulations. 

Flooding 

The past movement of water and 

sediment in Sycamore Canyon has 

affected the plants and their habitat. 

After the 1993 El Nin ̃ o winter rains, 

most of the monitoring plot was washed 

away, and the then-known overall plant 

population declined dramatically, with 

more than 90 percent of the known 

individuals washed away or covered 

with sediment. Recolonization has 

slowly occurred; at last count there were 

450 to 922 plants recorded in Sycamore 

Canyon (Darling 2005), fewer than the 

estimated 1,400 that were documented 

in 1992. 

Lefevre, a U.S. Forest Service 

hydrologist (1999), notes that the 

changes observed in Sycamore Canyon 

after the 1993 flood were, in his 

professional opinion, geologic in nature. 

Large flood events (e.g., greater than the 

25-year event) and their effects on 

channel morphology will likely 

overshadow any management activity of 

the U.S. Forest Service. 

In summary, above-average flood 

events (greater than the 25-year event) 

will likely affect the dynamics of the 

metapopulation in Sycamore Canyon, 

but U.S. Forest Service actions are not 

likely to influence or minimize the 

effects from such events. The species 

does have the ability to recolonize after 

flood events, and plants located out of 

the floodplain and on associated talus 

slopes (i.e., the sides of the canyon) may 

provide the source for the 

recolonization of the plants in stream 

habitat. 

Population Size and Stochastic Events 

Estimated numbers of the 

metapopulation in Sycamore Canyon 

have fluctuated dramatically since the 

early 1990s. The sub-populations had 

seemingly been reduced to very low 

numbers in 1993, after the canyon was 

subjected to a large flood event. Since 

that time, overall numbers and patches 

have been increasing. In 2005, we 

observed many seedlings and resprouts, 

alleviating some of our concern 

regarding the plant’s seemingly low 

reproductive output. We still do not 

know the environmental factors that 

allow for successful seed germination, 

and do not know how many seedlings 

will survive. We observed no seedlings 

away from patches, although some 

patches contained only a few larger 

plants and were dominated by 

seedlings. 

This species could potentially be 

negatively affected by environmental 

stochasticity (variations over time in the 

population’s operational environment) 

and natural catastrophes (Menges 1991). 

The minimum viable metapopulation 

(MVM) size is an important estimate of 

the minimum number of interacting 

local sub-populations necessary for the 

long-term persistence of a 

metapopulation (Hanski 1999). In 

general, 15 ‘‘ 20 well-connected patches 

are required for MVM (Maschinski, in 

press). Baker (2005) found 12 patches in 

Sycamore Canyon, but that is only an 

estimate from one of the five known 

populations. There were likely more 

patches than he detected. More 

consistent monitoring could help us 

determine the patch dynamics of Gentry 

indigo bush more accurately. A decrease 

in the overall number and size of 

patches, and a lack of recolonization of 

extirpated patches, could indicate that 

the metapopulation is not at 

equilibrium. 

The most likely adverse scenario in 

Sycamore Canyon is that of catastrophic 

flooding. Increased rainfall combined 

with an altered hydrograph in Sycamore 

Canyon may result in many patches 

being washed out. Long-term drought, 

such as the one the region is 

experiencing currently, may affect the 

species’ ability to recolonize vacant 

patches. In Sycamore Canyon, the 

combination of small patch size, 

uncertain persistence of the patches, 

highly variable overall number of 

patches, and a highly dynamic and 

uncertain environment due to flooding 

and drought could make this population 

vulnerable to extirpation, although it 

has continued to persist despite such 

climatic events. 

The species is located in at least five 

locations, reducing the risk of stochastic 

events affecting all of the known 

populations simultaneously. The 

population in Sycamore Canyon, 

despite a severe reduction in overall 

numbers, still persists and is 

recolonizing the canyon. Recent 

observations of seedling recruitment 

and resprouting indicate that the 

metapopulation can recover from 

Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 56433 

environmental stochastic events. Given 

the population’s persistence in 

Sycamore Canyon, we do not believe 

that its continued existence is 

threatened now or in the foreseeable 

future. 

Genetic Factors 

Harmful genetic effects, such as 

genetic bottlenecks and founder effects, 

are often associated with small plant 

populations (Hedrick and Miller 1992). 

A genetic bottleneck is a significant 

reduction in the genetic diversity of a 

population resulting from a significant 

reduction of the number of individuals 

of a species in a specific place or time. 

It is often associated with a stochastic 

event and can result in a loss of genetic 

diversity. The founder effect (Mayr 

1963) refers to the establishment of a 

new population from only a few 

colonizing individuals, which may 

represent only a small portion of the 

overall genetic variation of the original 

population. Reductions in genetic 

diversity from these and other causes 

can have profound effects on both shortand long-term population survival, as 

genetic variation is related to a 

population’s ability to survive stochastic 

events (Huenneke 1991; Rogers and 

Montalvo 2004; Falk et al. in press). In 

Sycamore Canyon, the small number of 

individuals, small size of the 

metapopulation, and the type and 

severity of environmental factors to 

which the metapopulation is exposed 

could influence the genetic diversity of 

the metapopulation. 

The ability of a species to persist over 

time is related, in part, to genetic 

variation in a population, which 

provides the basis of adaptation to 

changing environments. The greater the 

heterozygosity (number of different 

types of alleles) present, the higher the 

probability that at least some plants in 

a population will be able to adapt to 

changing circumstances (Huenneke 

1991; Reed and Frankham 2003). As 

populations become depauperate (less 

variation) in their genetic make-up, the 

ability of the populations to adapt to 

changing environmental factors, like 

climate change or changes in the local 

environment, may decrease. 

The long-term persistence of a 

population is also related to the fitness 

of the individuals within the 

population, where fitness is typically 

measured in terms of survival and 

reproduction. Inbreeding depression is a 

relative decrease in fitness of offspring 

resulting from either selfing (pollination 

within the same plant as opposed to 

between two different plants) or mating 

between closely-related individuals 

compared with outcrossed individuals 

(Barrett and Kohn 1991). The reduction 

in fitness is associated with a higher rate 

of expression of recessive and often 

lethal alleles (parts of genes that control 

certain characters, i.e., flower color) in 

a population. This condition leads to an 

overall reduction of fitness in a 

population until the population cannot 

produce viable offspring. We do not 

know if this is a factor for Gentry indigo 

bush because we have not identified the 

type of breeding system (e.g., obligate 

outcrosser, selfing, or combination). 

Thus, we have no information to 

indicate that genetic factors and small 

population size are a threat to Gentry 

indigo bush now or in the foreseeable 

future. Further, we have no 

documentation that this species 

historically persisted in significantly 

higher numbers than it does today, so its 

rarity is not necessarily an indication of 

excessive vulnerability to extinction. 

Climate Change 

Mean annual temperatures rose 1.1–

1.7 degrees Celsius (C) (2.0–3.1 degrees 

Fahrenheit (F)) in the American 

Southwest in the 20th century, and are 

predicted to rise 4.5–6.1 degrees C (8.1–

11.0 degrees F) in the 21st century. 

Predictions of changes in precipitation 

are less certain; however, some models 

predict as much as a doubling of annual 

precipitation, with the largest increases 

in winter precipitation (Southwest 

Regional Assessment Group 2000). But 

these predictions contrast with current 

trends of a warming North Atlantic and 

cooling tropical Pacific, with associated 

changes from a relatively wet period to 

drought, insect outbreaks in 

Southwestern forests, and increasing 

wildfires (Patterson 1997; Betancourt 

2004). Some models predict dramatic 

changes in Southwestern vegetation 

communities as a result of climate 

change (Thompson et al. 1997). Climate 

change can occur abruptly, with 

associated major changes in the 

environment (National Academy of 

Sciences, Committee on Abrupt Climate 

Change 2002). Climate change could 

affect metapopulations of Gentry indigo 

bush in unpredictable ways. For 

example, changes in precipitation may 

increase the frequency and magnitude of 

flood events, possibly affecting the 

distribution and persistence of patches 

in occupied habitat. Rainfall patterns 

may shift towards more summer 

precipitation and less winter 

precipitation. The germination of seeds 

may be linked to seasonal rainfall 

events, and changes in rainfall patterns 

may affect the population dynamics of 

this species. We have no information to 

indicate that climate change constitutes 

a threat to Gentry indigo bush now or 

in the foreseeable future. 

In summary, Gentry indigo bush 

remains a rare, narrowly distributed 

endemic plant species throughout its 

range in southern Arizona and in 

Mexico. Extensive survey work in the 

United States and Mexico has increased 

the documentation of populations by 

one and reconfirmed the existence of 

two populations in Mexico. In total, 

there are approximately 1,400 

individuals, distributed among 5 sites. 

There are 2 confirmed populations in 

the United States, containing over 66 

percent of the known individuals. At 

this time, the majority of Gentry indigo 

bush in the United States is located 

within Sycamore Canyon; we do not 

have an accurate assessment of the 

numbers of Gentry indigo bush on the 

Tohono O’odham Nation. We have no 

information indicating that populations 

in Mexico or on the Tohono O’odham 

Nation are experiencing any direct 

threats. The populations, based on 

observations of the Sycamore Canyon 

metapopulation, have the ability to 

recover from floods and drought. We 

have seen seedlings and plants resprout, 

alleviating our concern regarding the 

plant’s ability to reproduce and recover 

from flood events and sediment 

deposition. Threats to the Sycamore 

Canyon population have been 

minimized by U.S. Forest Service 

actions, and ongoing activities are not 

immediately threatening the population. 

Finding 

We have carefully assessed the best 

scientific and commercial information 

available regarding past, present, and 

future threats faced by the species. We 

reviewed the petition, available 

published and unpublished scientific 

and commercial information, and 

information submitted to us during the 

public comment periods on our 90-day 

finding. This finding reflects and 

incorporates information we received 

during the public comment periods. We 

also consulted with recognized plant 

experts, including those most familiar 

with this species, and other Federal 

resource agencies. On the basis of our 

review, we find that the petitioned 

action of listing the Gentry indigo bush 

is not warranted. 

In making this finding, we recognize 

that one historical population in the 

United States has been extirpated and is 

presumed lost. We also recognize that 

populations are still present on the 

Tohono O’odham Nation, but that those 

populations are under the management 

of a sovereign nation and subject to their 

laws. The same is true for populations 

in Sonora, Mexico. There are ongoing 

56434 Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / Proposed Rules 

activities and natural events that may be 

affecting the habitat and reestablishment 

of the species. Other threats, like 

undocumented immigrant traffic, are 

larger than one agency’s jurisdiction. 

However, we believe that existing 

regulatory mechanisms are sufficient to 

protect the species. The overall existing 

management of the U.S. Forest Service 

is protecting much of the habitat in 

Sycamore Canyon. We also 

acknowledge that, due to small 

population size, demographic or genetic 

factors may apply to each of the 

locations in Arizona and Sonora, 

Mexico, but we have no genetic 

information to determine whether this is 

indeed the case. 

We conclude that the Gentry indigo 

bush does not warrant listing at this 

time. In order to make a warranted 

finding, the species must, at a 

minimum, meet the definition of a 

threatened species. In accordance with 

section 3(19) of the Act, a threatened 

species is one which is likely to become 

endangered within the foreseeable 

future throughout all or a significant 

portion of its range. Based on all the 

information we have gathered and 

reviewed, we do not conclude this to be 

the case for the following reasons. 

Populations have persisted in all but 

one of the known locations over time. A 

new population was located in Mexico 

and offers hope that there may be more 

populations located with additional 

surveys. Areas that were previously 

overlooked as suitable habitat outside of 

the floodplain appear to support Gentry 

indigo bush. Thus, populations may not 

be as vulnerable to extirpation from 

flood events as previously thought since 

the species does have the ability to 

recolonize after flood events, and plants 

located out of the floodplain and on the 

sides of the canyon could provide a 

source for the recolonization of plants in 

stream habitat. The largest known 

population occurs in Sycamore Canyon 

within the Goodding RNA, where 

mining, roads, and grazing are 

prohibited and where the U.S. Forest 

Service has completed a number of 

conservation actions that have improved 

the habitat for Gentry indigo bush. 

Additionally, as noted above, the 

actions of the U.S. Forest Service and 

the protection that the canyon receives 

by virtue of its wilderness and RNA 

designations will continue to provide 

for the long-term conservation of Gentry 

indigo bush in Sycamore Canyon. The 

metapopulation in Sycamore Canyon 

has persisted through some dramatic 

environmental events, and its numbers 

have increased; thus, we believe it will 

continue to persist into the future. Other 

factors (e.g., watershed degradation, 

invasive species, undocumented 

immigrant and U.S. Border Patrol 

activities, recreation, fire, climate 

change, and genetic factors associated 

with small population size) discussed 

above have not been documented as 

more than low magnitude or potential 

threats, and therefore it is not 

reasonably foreseeable that these factors 

pose threats over a significant portion of 

the species’ range. We anticipate that we 

will have the opportunity to work 

cooperatively with the Tohono O’odham 

Nation, as we have in the past, to census 

their populations and address potential 

concerns, if necessary. We also plan to 

emphasize the need for and 

participation in future monitoring 

efforts, surveys, and genetic studies. 

The Service does not believe the 

Gentry indigo bush is likely to become 

a threatened species throughout either 

all or a significant portion of its range 

in the foreseeable future. The only 

population for which we have a 

thorough threats assessment is the one 

on U.S. Forest Service land in Sycamore 

Canyon. While the Sycamore Canyon 

population is not entirely devoid of 

potential threats, we believe that U.S. 

Forest Service management (e.g., RNA 

and Wilderness designations, exclusion 

of both domestic and Mexican cattle 

from the habitat) sufficiently 

ameliorates human-influenced threats, 

while its persistence over time through 

droughts and floods, and its discovery 

outside the floodplain, render it 

unlikely to be extirpated from the 

canyon as a result of natural factors. 

Threats facing the other populations 

are less well known. Three populations 

are known from Mexico. One 

population in Mexico has been present 

since its original discovery in 1995, 

another one was relocated in 2005 after 

it was initially detected in 2004, and the 

remaining population was only detected 

in 2005. Based on this information, two 

of the populations are known to have 

persisted. In addition, according to 

information received during the public 

comment period, the Mexico 

populations are in areas not accessible 

to cattle. We can verify that plants still 

exist on the Tohono O’odham Nation. 

The fact that the Mexican and Tohono 

O’odham Nation populations have 

persisted under current management 

and through various climatic conditions 

provides evidence that whatever threats 

may exist, if any, are not significant. In 

summary, we have no evidence to 

indicate that any portion, let alone a 

significant portion, of the species’ range 

is threatened to the extent that listing 

under the Act is warranted. 

We will continue to monitor the 

status of this species and will accept 

additional information and comments at 

any time from all concerned 

governmental agencies, the scientific 

community, industry, and any other 

interested party concerning this finding. 

This information will help us monitor 

and encourage beneficial measures for 

this species. 

References Cited 

A complete list of all references cited 

herein is available upon request from 

the Field Supervisor at the Arizona 

Ecological Services Office (see 

ADDRESSES section). 

Author 

The primary author of this document 

is the Arizona Ecological Services Office 

(see ADDRESSES section). 

Authority: The authority for this action is 

the Endangered Species Act of 1973, as 

amended (16 U.S.C. 1531 et seq.). 

Dated: September 14, 2005. 

Marshall Jones, 

Acting Director, U.S. Fish and Wildlife 

Service. 

[FR Doc. 05–18881 Filed 9–26–05; 8:45 am] 

BILLING CODE 4310–55–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

RIN 1018–AT74 

Endangered and Threatened Wildlife 

and Plants; Proposed Designation of 

Critical Habitat for Astragalus 

lentiginosus var. coachellae (Coachella 

Valley milk-vetch) 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Proposed rule; reopening of 

public comment period and notice of 

availability of draft economic analysis. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), announce the 

reopening of the public comment period 

on the proposed designation of critical 

habitat for Astragalus lentiginosus var. 

coachellae (Coachella Valley milkvetch), and the availability of a draft 

economic analysis of the proposed 

designation of critical habitat. We are 

reopening the comment period to allow 

all interested parties an opportunity to 

comment simultaneously on the 

proposed rule and the associated draft 

economic analysis. Comments 

previously submitted on this proposed 

rule need not be resubmitted as they 

have already been incorporated into the