[Federal Register: June 19, 2006 (Volume 71, Number 117)]
[Rules and Regulations]               
[Page 35195-35198]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]

[[Page 35195]]



Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AI79

Endangered and Threatened Wildlife and Plants; Delisting of Agave 
arizonica (Arizona agave) From the Federal List of Endangered and 
Threatened Wildlife and Plants

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.


SUMMARY: We, the U.S. Fish and Wildlife Service (Service), under the 
Endangered Species Act of 1973, as amended (Act), have determined that 
it is appropriate to remove Agave arizonica (Arizona agave) from the 
Federal List of Endangered and Threatened Wildlife and Plants. This 
determination is based on a thorough review of all available data, 
which indicate that this plant is not a discrete taxonomic entity and 
does not meet the definition of a species under the Act. Evidence 
collected subsequent to the listing indicates that plants attributed to 
Agave arizonica do not constitute a distinct species but rather are 
individuals that have resulted from recent and sporadic instances of 
hybridization between two species. Current taxonomic practice is not to 
recognize such groups of individuals as a species. Since Agave 
arizonica is not recognized as a species, it no longer qualifies for 
protection under the Act.

DATES: This rule is effective July 19, 2006.

ADDRESSES: Supporting documentation for this rulemaking is available 
for public inspection, by appointment, during normal business hours at 
the Arizona Ecological Services Field Office of the U.S. Fish and 
Wildlife Service, 2321 West Royal Palm Road, Suite 103, Phoenix, 
Arizona 85021-4951.

Service, located in the Arizona Ecological Services Tucson Sub-office, 
201 North Bonita Avenue, Suite 141, Tucson, Arizona 85745 (telephone 
520/670-6150 ext. 225; facsimile 520/670-6154).



    Agave arizonica, a member of the agave family, was first discovered 
by J.H. Houzenga, M.J. Hazelett, and J.H. Weber in the New River 
Mountains of Arizona. Drs. H.S. Gentry and J.H. Weber described this 
species in the ``Cactus and Succulent Journal'' in 1970 (Gentry and 
Weber 1970). This perennial succulent has leaves growing from the base 
in a small basal rosette (i.e., an arrangement of leaves radiating from 
a crown or center), and is approximately 20-35 centimeters (cm) (8-14 
inches (in)) high and 30-40 cm (12-16 in) wide. The leaves are dark 
green with a reddish-brown to light gray border extending nearly to the 
base, approximately 13-31 cm (5-12 in) long and 2-3 cm (1 in) wide. The 
slender, branched flowering stalk is 2.5-4 meters (m) (8.2-13 feet 
(ft)) tall with urn-shaped flowers 25-32 millimeters (mm) (1 in) long 
(Hodgson 1999). Some plants, including Agave arizonica, are able to 
produce copies of themselves without sexual reproduction. These copies 
(clones) may remain physically connected to the original plant 
(vegetative offsets) or may be physically separate plants.
    Agave arizonica is found on open slopes in chaparral or juniper 
grassland in Gila, Maricopa, and Yavapai counties between 1,100-1,750 m 
(3,600-5,800 ft) in elevation. The plants are often found associated 
with native junipers (Juniperus spp.), mountain mahogany (Cercocarpus 
montanus), Opuntia spp., sotol (Nolina microcarpa), and banana yucca 
(Yucca baccata), among other species common to the chaparral/juniper-
oak transition (Hodgson and DeLamater 1988). There are estimated to be 
fewer than 100 plants in the wild, occurring mainly on the Tonto 
National Forest and a few locations on private property. Agave 
arizonica plants are associated with shallow, cobbled, and gravelly 
soils on strongly sloping to very steep slopes and rock outcrops on 
mid-elevation hills and mountains. The soils are well-drained and 
derived from a variety of rocks, including granite, gneiss, rhyolite, 
andesite, ruffs, limestone, sandstone, and basalt (Hodgson and 
DeLamater 1988). Plants typically flower from May to July.
    Field studies on Agave arizonica began in 1983. A natural 
distribution study was not finalized until August 1984 (DeLamater 
1984), after the final listing rule (49 FR 21055, May 18, 1984) was 
published. Surveys for this study were conducted in the New River 
Mountains, and by 1984, ten new clones were found in these mountains. 
These were individual clones of 2-5 rosettes. All of the clones 
occurred together with two other agaves, Agave toumeyana ssp. bella and 
A. chrysantha, neither of which is considered rare. A. chrysantha is 
found in southern and eastern Yavapai County, through much of Gila and 
Maricopa counties, northern and eastern Pinal County, and northeastern 
Pima County. Agave toumeyana ssp. bella is restricted to the eastern 
slope of the Bradshaw Mountains in eastern Yavapai to northwestern and 
central to southern Gila County, and northeastern Maricopa to northern 
Pinal County.
    A comparison of plant characters showed Agave arizonica to be 
intermediate to the other two agave species with which it is always 
found in association (DeLamater and Hodgson 1986). Pinkava and Baker 
(1985) suggested that plants recognized as Agave arizonica may be the 
result of continuing production of hybrid individuals rather than a 
distinct species, based on observations that hybrid individuals are 
found only where the ranges of the putative parents overlap; they are 
found only in random, widely scattered locations of individual plants 
and clones; their putative parents have overlapping flowering periods; 
Agave arizonica's morphological characters are intermediate between the 
putative parents; and, they appeared to be subfertile (reduced 
fertilization), producing pollen with a low percent of stainability (a 
measure of pollen viability). Agave arizonica has the same chromosome 
count ((2n) of 60) as both of its parents which allows for continued 
reproduction with its parents (backcrossing). Polyploidy (a genetic 
variation wherein an individual plant has more than the two normal sets 
of homologous chromosomes) is one factor in determining if a hybrid 
between two species can become genetically stable. This condition is 
not present in the genetic constitution of Agave arizonica.
    Survey work continued in areas that supported populations of the 
two parent species. These surveys resulted in the discovery of two 
clones in the Sierra Ancha Mountains, 100 miles disjunct from the New 
River Mountain locations. To date, plants and clones have been 
identified in three areas on the Tonto National Forest (New River 
Mountains, Sierra Ancha Mountains, and the Humboldt Mountains). The New 
River population is the most numerous, located 17.94 kilometers (km) 
(10.7 miles (mi)) west-northwest of the Sierra Ancha population. Only 
one individual was found in the Serra Anch Mountains (Tr[auml]bold 
2001). The Humboldt Mountains support a population of Arizona agave, as 
well as another agave hybrid. This different hybrid agave is produced 
from a cross between A. toumeyana ssp. toumeyana and A. chrysantha 
(Pinkava and Baker 1985). That hybrid is a triploid (3n=90), and 
therefore has a different chromosome count than Agave arizonica.

[[Page 35196]]

    The Desert Botanical Garden (DBG), in Phoenix, initiated ecological 
studies of Agave arizonica in the mid-1980s through 1994. They 
conducted numerous surveys on the Tonto National Forest, collected 
seeds in situ (in the natural or original environment), conducted 
experimental crosses in situ and ex situ (in an artificial 
environment), and started an ex situ collection. DBG's work has shown 
that Agave arizonica can produce viable seed. In 1985, three different 
crosses were performed on clone 52, in situ, using flowers 
from different panicles (flower stalks). One cross used frozen pollen 
collected from Agave arizonica at the DBG, the second cross was self-
fertilization of clone 52, and the third cross was 
uncontrolled outcrossing of clone 52 (flowers were left open 
to be pollinated by various donors). Seed was collected from all three 
crosses. Cross 1 produced 250 seeds, cross 2 produced 
20 seeds, and cross 3 produced a large quantity of seeds 
(Hodgson and DeLamater 1988). Outcrossing with Agave arizonica pollen 
(Cross 1) produced a high proportion of viable seed, as did 
uncontrolled outcrossing (Cross 3), while self-fertilization 
(Cross 2) produced a poor seed set. The majority of the seeds 
were planted. Ten months after planting, 10 of the 105 seeds produced 
from cross 1 germinated. Some of those resembled Agave 
arizonica, while others did not (W. Hodgson, Desert Botanical Garden, 
pers. comm. 2003). DBG also conducted controlled crosses of A. 
chrysantha and A. toumeyana ssp. bella. The seeds produced from this 
cross resulted in Agave arizonica plants. Individual Agave arizonica 
plants can therefore be created by crosses of the parental species. 
These results support the hypothesis that Agave arizonica is composed 
of individuals that resulted from recent and spontaneous instances of 
hybridization between two species, and is not, at this time, a species 
of hybrid origin.
    Agave arizonica is most likely a first-generation (F1) hybrid 
between two other species. It is not known if any individuals of the F1 
generation, in situ, have backcrossed with either one of the parents or 
with another Agave arizonica individual. The latter seems unlikely 
given the low numbers of individuals and the great distance separating 
them. Seeds have been produced in the wild, but it is not known if 
those seeds were produced from crosses of Agave arizonica and either 
parent species or Agave arizonica and Agave arizonica. Seeds grown out 
in greenhouse conditions produced plants with wide phenotypic (visible) 
variations; not all seedlings presented `pure' Agave arizonica traits. 
The fact that Agave arizonica can be reliably produced by crossing the 
putative parents ex situ lends support to the hypothesis that Agave 
arizonica is a recurring F1 hybrid. All evidence supports that Agave 
arizonica individuals are derived from crosses between different 
species. In other words, each individual Agave arizonica was created 
spontaneously and independently from separate crossings of the putative 
parental species (M. Baker, pers. comm. 2004).
    Agave arizonica plants are rare in the wild. The likelihood is low 
that two of these plants would breed with one another because it is 
unlikely that two such plants would be close enough to one another and 
bloom in the same year. Clones still attached or near to the parent 
plant may produce flowers at the same time, but spatially separated 
clones may not all bloom at the same time. The flowering period of 
Agave arizonica overlaps with that of its putative parents, and the 
same insects (bumblebees, mining bees of the family Halictidae, and 
solitary bees) visit all three agave species. This condition can lead 
to back-crosses with one of the putative parents. Agave arizonica is 
not likely to maintain a separate genetic identity due to low numbers, 
overlap of flowering period with the putative parents, and lack of an 
effective reproductive isolating mechanism to promote genetic 
    In 1999, Hodgson published a treatment for the Agave family for the 
``Flora of Arizona'' (Hodgson 1999). Agave arizonica was not recognized 
as a species in that treatment, which indicated that it should be 
referred to as Agave arizonica, a hybrid of recent origin involving A. 
chrysantha and A. toumeyana var. bella.
    Jolly (in Riesberg 1991) has suggested protection for a hybrid 
taxon if (1) its evolution has gone past the point where it can be 
reproduced through crossing of its putative parents, (2) it is 
taxonomically distinct from its parents, and (3) it is sufficiently 
rare or imperiled. Under these criteria, F1 hybrids such as Agave 
arizonica should receive no protection because it is still backcrossing 
with its parents and is not taxonomically distinct.
    In summary, the plant species formerly referred to as Agave 
arizonica is now recognized as an interspecific hybrid produced 
sporadically and spontaneously by the cross of Agave chrysantha and 
Agave toumeyana var. bella. Individuals have been determined to be 
hybrids for the following reasons: (1) They share the same chromosome 
number (2n=60) with the putative parents, indicating that there are no 
chromosomal barriers (i.e., reproductive isolating mechanisms) in place 
to facilitate genetic stability, (2) flowering periods of the putative 
parents overlap, (3) morphological characters of Agave arizonica are 
intermediate with those of the putative parents, (4) Agave arizonica 
only occurs where there is overlap with the putative parents, (5) it 
appears to be subfertile, producing pollen with low percent 
stainability, (6) Agave arizonica can be created, ex situ, by crossing 
the putative parents, indicating that there may be no unique genetic 
characters associated with these plants, and (7) it has not, to our 
knowledge, reproduced sexually in the field.

Previous Federal Action

    Federal Government action concerning Agave arizonica began with 
section 12 of the Act, which directed the Secretary of the Smithsonian 
Institution to prepare a report on those plants considered to be 
endangered, threatened, or extinct. This report (House Document No. 94-
51), which included Agave arizonica, was presented to Congress on 
January 9, 1975, and accepted by the Service under section 4(c)(2), now 
section 4(b)(3)(A), of the Act as a petition to list these species. The 
report, along with a statement of our intention to review the status of 
the plant taxa, was published in the Federal Register on July 1, 1975 
(40 FR 27823). On June 16, 1976, we published a proposed rule in the 
Federal Register (41 FR 24523) to determine approximately 1,700 
vascular plants to be endangered pursuant to section 4 of the Act. 
Agave arizonica was included in this proposal. On December 10, 1979, we 
withdrew all outstanding proposals not finalized within two years of 
their first publication, as required by the 1978 amendments to the Act. 
On August 26, 1980, the Service received a status report prepared by 
four researchers employed by the Museum of Northern Arizona. This 
report documented the status of, and threats to, the species. On 
December 5, 1980, we published a revised notice for plants (45 FR 
82479) and included Agave arizonica in category 1. Category 1 was 
comprised of taxa for which we had sufficient biological information to 
support their being listed as endangered or threatened species. We 
published a proposed rule to list Agave arizonica as an endangered 
species on May 20, 1983 (48 FR 22757). No critical habitat was 
proposed. The final rule listing Agave arizonica as endangered was 
published on May 18,

[[Page 35197]]

1984 (49 FR 21055), and no critical habitat was designated.
    In 1985, a year after Agave arizonica was listed, the U.S. 
Department of Agriculture Forest Service petitioned us to delist Agave 
arizonica because of its hybrid status. We sent out the work on Agave 
arizonica that had been published for peer review and solicited 
comments. Many of the comments supported delisting based on the 
available evidence; however, the Service disagreed that the available 
data conclusively proved that Agave arizonica was a hybrid. The Service 
believed that the results of the controlled crosses were important for 
the analysis, and those had not been completed at the time of the 
review. Therefore, on January 21, 1987 (52 FR 2239), we announced that 
delisting was not warranted.
    We published a proposed rule to remove Agave arizonica from the 
Federal List of Endangered and Threatened Plants on January 11, 2005 
(70 FR 1858), based on additional information indicating that Agave 
arizonica is a hybrid and does not meet the definition of a species as 
defined by the Act.

Summary of Comments and Recommendations

    In the January 11, 2005, proposed rule (70 FR 1858) and associated 
notifications, we invited all interested parties to submit comments or 
information that might contribute to the final delisting determination 
for this species. The public comment period ended March 14, 2005. We 
contacted and sent announcements of the proposed rule to appropriate 
Federal and State agencies, county governments, scientific 
organizations, and other interested parties. In addition, we solicited 
formal scientific peer review of the proposal in accordance with our 
July 1, 1994, Interagency Cooperative Policy for Peer Review in 
Endangered Species Act Activities (59 FR 34270). We requested five 
individuals with expertise in one or several fields, including 
familiarity with the species, familiarity with the geographic region in 
which the species occurs, and familiarity with the principles of 
taxonomy, to review the proposed rule by the close of the comment 
period. We received comments from six parties, including three 
designated peer reviewers. All three of the responding peer reviewers, 
the U.S. Department of Agriculture Forest Service, and one public 
commenter agreed with our assessment that the scientific evidence 
presented in our proposed rule supports the hybrid status of Agave 
arizonica and, therefore, the plant does not merit protection under the 
Act. The comments are addressed in the following summary. We did not 
receive any requests for a public hearing.
    Issue: We are too hasty in our proposal to delist Agave arizonica 
because hybrids can often succeed in combining genes in new ways to 
become successful breeding populations, leading to new species 
    Our Response: Many vascular plants are of hybrid origin, and we 
acknowledge that hybrids play an important role in speciation. Current 
evidence does not support the view that Agave arizonica is a successful 
breeding population. We based our delisting decision upon the best 
available scientific and commercial information. After a review of all 
available data, we have made the determination that Agave arizonica 
does not meet the definition of a species under the Act. If new 
information becomes available that shows Agave arizonica is exhibiting 
characteristics of a species (i.e., reproductive isolation from the 
parent species and ability to reproduce sexually and maintain a degree 
of genetic stability), we will reexamine the threats to determine if it 
should be listed again.

Delisting Analysis

    After a review of all information available, we are removing Agave 
arizonica from the List of Endangered and Threatened Plants, 50 CFR 
17.12. Section 4(a)(1) of the Act and regulations (50 CFR part 424) 
issued to implement the listing provisions of the Act set forth the 
procedures for adding species to or removing them from Federal lists. 
The regulations at 50 CFR 424.11(d) state that a species may be 
delisted if (1) it becomes extinct, (2) it recovers, or (3) the 
original classification data were in error. Since the time of listing, 
additional study has shown that Agave arizonica is not a distinct 
species, but consists of individuals that are the result of 
spontaneous, occasional, and continuing hybridization between two other 
distinct species. Individual hybrid plants are produced within 
populations of the parental species, but their production is random. In 
modern taxonomic practice, such groups of individuals are not 
recognized as species. We have concluded that the original taxonomic 
interpretation upon which the listing decision was based has not been 
substantiated by subsequent studies, and Agave arizonica does not 
qualify for protection because it does not fit the definition of a 
species under the Act.
    The term ``species,'' as defined in the Act, includes any 
subspecies of fish or wildlife or plants, and any distinct population 
segment of any species or vertebrate fish or wildlife which interbreeds 
when mature. Agave arizonica does not meet this definition because it 
is not known to interbreed in situ or otherwise reproduce itself. 
Hybrid origin of species is considered common within the flowering 
plants (Grant 1963), and some species of hybrid origin are capable of 
reproducing themselves and maintaining a degree of genetic stability. 
However, scientific evidence at this point supports the determination 
that Agave arizonica does not have these characteristics of a species. 
The plants are not known to have sexually reproduced in situ. Agave 
arizonica plants have sporadically developed in situ from the putative 
parents, but have not been reproductively self-sustaining. Agave 
arizonica has never been found in well-developed populations or outside 
patches of its putative parents.
    We have carefully assessed the best scientific and commercial 
information available regarding the conclusion that Agave arizonica is 
not a species, and therefore does not qualify for protection under the 
Act. We, therefore, conclude that Agave arizonica no longer warrants 
listing under the Act.

Effects of the Rule

    This action removes Agave arizonica from the List of Endangered and 
Threatened Plants. The prohibitions and conservation measures provided 
by the Act no longer apply to this species. Therefore, interstate 
commerce, import, and export of Agave arizonica are no longer 
prohibited under the Act. In addition, Federal agencies no longer are 
required to consult with us to insure that any action they authorize, 
fund, or carry out is not likely to jeopardize the continued existence 
of Agave arizonica. The plant is still protected by Arizona's Native 
Plant Law, A.R.S., Chapter 7, Section 3-901, which specifically 
prohibits collection except for scientific or educational purposes 
under permit. There is no designated critical habitat for this species.

Future Conservation Measures

    The 1988 amendments to the Act require that all species delisted 
due to recovery be monitored for at least five years following 
delisting. Agave arizonica is being removed from the List of Endangered 
and Threatened Plants because the taxonomic interpretation that it is a 
species is no longer believed

[[Page 35198]]

to be correct; Agave arizonica is a sporadically occurring hybrid, 
rather than a distinct taxon. Therefore, no monitoring period following 
delisting is required.

National Environmental Policy Act

    We have determined that an Environmental Assessment or an 
Environmental Impact Statement, as defined under the authority of the 
National Environmental Policy Act of 1969, need not be prepared in 
connection with regulations adopted pursuant to section 4(a) of the 
Act. We published a notice outlining our reasons for this determination 
in the Federal Register on October 25, 1983 (48 FR 49244).

Paperwork Reduction Act

    Office of Management and Budget (OMB) regulations at 5 CFR part 
1320 implement provisions of the Paperwork Reduction Act (44 U.S.C. 
3501 et seq.). The OMB regulations at 5 CFR 1320.3(c) define a 
collection of information as the obtaining of information by or for an 
agency by means of identical questions posed to, or identical 
reporting, recordkeeping, or disclosure requirements imposed on, 10 or 
more persons. Furthermore, 5 CFR 1320.3(c)(4) specifies that ``ten or 
more persons'' refers to the persons to whom a collection of 
information is addressed by the agency within any 12-month period. For 
purposes of this definition, employees of the Federal Government are 
not included. The Service may not conduct or sponsor, and you are not 
required to respond to, a collection of information unless it displays 
a currently valid OMB control number.
    This rule does not include any collections of information that 
require approval by OMB under the Paperwork Reduction Act. The Agave 
arizonica is being delisted because the taxonomic interpretation that 
it is a species is no longer believed to be correct; Agave arizonica is 
a sporadically occurring hybrid, rather than a distinct taxon. 
Therefore, no monitoring period following delisting would be required, 
and we do not anticipate a need to request data or other information 
from 10 or more persons during any 12-month period in order to satisfy 
monitoring information needs. If it becomes necessary to collect 
information from 10 or more non-Federal individuals, groups, or 
organizations per year, we will first obtain information collection 
approval from OMB.

Executive Order 13211

    On May 18, 2001, the President issued Executive Order 13211 on 
regulations that significantly affect energy supply, distribution, and 
use. Executive Order 13211 requires agencies to prepare Statements of 
Energy Effects when undertaking certain actions. As this final rule is 
not expected to significantly affect energy supplies, distribution, or 
use, this action is not a significant energy action and no Statement of 
Energy Effects is required.

References Cited

DeLamater, R. 1984. Natural distribution and status of Agave 
arizonica Gentry and Weber in Arizona with accompanying maps. 
Prepared for USDA Forest Service Range Management, Albuquerque, NM. 
11 pp.
DeLamater, R. and W. Hodgson. 1986. Agave arizonica: An endangered 
species, a hybrid, or does it matter? Proceedings of a California 
Native Plant Society Conference. Sacramento, CA.
Gentry, H.S. and J.H. Weber. 1970. Two New Agaves in Arizona. Cactus 
and Succulent Journal. 42(5): 223-228.
Grant, V. 1963. The Origin of Adaptations. Columbia University 
Press, New York. 606 pp.
Hodgson, W. and R. DeLamater. 1988. Agave arizonica Gentry and 
Weber; Summary of status and report on recent studies. Desert 
Botanical Gardens, Phoenix, AZ. U.S.D.I., U.S. Fish and Wildlife 
Service, Albuquerque, NM. 11 pp.
Hodgson, W. 1999. Vascular plants of Arizona: Agavaceae. Journal of 
Arizona-Nevada Academy of Science 32(1): 1-21.
Pinkava, D.J. and M.A. Baker. 1985. Chromosome and hybridization 
studies of agaves. Desert Plants. 7(2): 93-100.
Riesberg, L.H. 1991. Hybridization in rare plants: insights from 
case studies in Cercocarpus and Helianthus. In Genetics and 
conservation of rare plants. Donald A. Falk and K.E. Holsinger 
(Eds). Oxford University Press, New York. 283 pp.
Tr[auml]bold, P.A. 2001. Re-establishment--Agave arizonica. M.S. 
thesis. California State University, Fullerton, CA. 65 pp.


    The primary authors of this document are staff located at the 
Arizona Ecological Services Tucson Sub-office (see FOR FURTHER 

List of Subjects in 50 CFR Part 17

    Endangered and threatened species, Exports, Imports, Reporting and 
recordkeeping requirements, Transportation.

Regulation Promulgation

Accordingly, we hereby amend part 17, subchapter B of chapter I, title 
50 of the Code of Federal Regulations, as set forth below:


1. The authority citation for part 17 continues to read as follows:

    Authority: 16 U.S.C. 1361-1407; 16 U.S.C. 1531-1544; 16 U.S.C. 
4201-4245; Public Law 99-625, 100 Stat. 3500; unless otherwise 

Sec.  17.12  [Amended]

2. Amend Sec.  17.12(h) by removing the entry ``Agave arizonica'' under 
``FLOWERING PLANTS'' from the List of Endangered and Threatened Plants.

    Dated: May 19, 2006.
Kenneth Stansell,
Acting Director, Fish and Wildlife Service.
 [FR Doc. E6-8643 Filed 6-16-06; 8:45 am]