From: Subject: Recognition of Distinct Vertebrate Population Segments , Endangered Species; U.S. Fish & Wildlife Service Date: Tue, 14 Aug 2007 13:09:58 -0600 MIME-Version: 1.0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.fws.gov/endangered/policy/pol005.html X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 Recognition of Distinct Vertebrate Population = Segments , Endangered Species; U.S. Fish & Wildlife Service [From The Federal Register for Wednesday, = February=20 7, 1996 (Vol. 61), p. 4722]
=20

DEPARTMENT OF THE INTERIOR=20

Fish and Wildlife Service=20

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration=20

Policy Regarding the Recognition of Distinct Vertebrate Population = Segments=20 Under the Endangered Species Act=20

AGENCIES: Fish and Wildlife Service, Interior; National Marine = Fisheries=20 Service, Commerce.=20

ACTION: Notice of policy.=20

SUMMARY: The Fish and Wildlife Service and the National Marine = Fisheries Service (Services) have adopted a policy to clarify their=20 interpretation of the phrase "distinct population segment of any species = of=20 vertebrate fish or wildlife" for the purposes of listing, delisting, and = reclassifying species under the Endangered Species Act of 1973, as = amended (16=20 U.S.C. 1531 et seq..) (Act).=20

SUPPLEMENTARY INFORMATION:=20

Background=20

The Endangered Species Act of 1973, as amended (16 U.S.C. 1531 = et.=20 seq.). (Act) requires the Secretary of the Interior or the = Secretary of=20 Commerce (depending on jurisdiction) to determine whether species are = endangered=20 or threatened. In defining "species," the Act as originally passed = included,=20 "...any subspecies of fish or wildlife or plants and any other group of = fish or=20 wildlife of the same species or smaller taxa in common spatial = arrangement that=20 interbreed when mature." In 1978, the Act was amended so that the = definition=20 read "...any subspecies of fish or wildlife or plants, and any distinct=20 population segment of any species of vertebrate fish or wildlife which=20 interbreeds when mature." This change restricted application of this = portion of=20 the definition to vertebrates. The authority to list a "species" as = endangered=20 or threatened is thus not restricted to species as recognized in formal=20 taxonomic terms, but extends to subspecies, and for vertebrate taxa, to = distinct=20 population segments (DPS's).=20

Because the Secretary must "...determine whether any species is an = endangered=20 species or a threatened species" (section 4(a)(1)), it is important that = the=20 term "distinct population segment" be interpreted in a clear and = consistent=20 fashion. Furthermore, Congress has instructed the Secretary to exercise = this=20 authority with regard to DPS's "...sparingly and only when the = biological=20 evidence indicates that such action is warranted." (Senate Report 151, = 96th=20 Congress, 1st Session). The Services have used this authority relatively = rarely;=20 of over 300 native vertebrate species listed under the Act, only about = 30 are=20 given separate status as DPS's.=20

It is important in light of the Act's requirement to use the best = available=20 scientific information in determining the status of species that this=20 interpretation follows sound biological principles. Any interpretation = adopted=20 should also be aimed at carrying out the purposes of the Act (i.e., = "...to=20 provide a means whereby the ecosystems upon which endangered species and = threatened species depend may be conserved, to provide a program for the = conservation of such endangered species and threatened species, and to = take such=20 steps as may be appropriate to achieve the purposes of the treaties and=20 conventions set forth in subsection (a) of this section" (section 2(b)). =

Available scientific information provides little specific = enlightenment in=20 interpreting the phrase "distinct population segment." This term is not = commonly=20 used in scientific discourse, although "population" is an important term = in a=20 variety of contexts. For instance, a population may be circumscribed by = a set of=20 experimental conditions, or it may approximate an ideal natural group of = organisms with approximately equal breeding opportunities among its = members, or=20 it may refer to a loosely bounded, regionally distributed collection of=20 organisms. In all cases, the organisms in a population are members of a = single=20 species or lesser taxon.=20

The National Marine Fisheries Service (NMFS) has developed a Policy = on the=20 Definition of Species under the Endangered Species Act (56 FR = 58612-58618;=20 November 20, 1991). The policy applies only to species of salmonids = native to=20 the Pacific. Under this policy, a stock of Pacific salmon is considered = a DPS if=20 it represents an evolutionarily significant unit (ESU) of a biological = species.=20 A stock must satisfy two criteria to be considered an ESU:=20

(1)It must be substantially reproductively isolated from other = conspecific=20 population units; and=20

(2) It must represent an important component in the evolutionary = legacy of=20 the species.=20

This document adopts an interpretation of the term "distinct = population=20 segment" for the purposes of listing, delisting, and reclassifying = vertebrates=20 by the U.S. Fish and Wildlife Service (FWS) and NMFS. The Services = believe that=20 the NMFS policy, as described above, on Pacific salmon is consistent = with the=20 policy outlined in this notice. The NMFS policy is a detailed extension = of this=20 joint policy. Consequently, NMFS will continue to exercise its policy = with=20 respect to Pacific salmonids.=20

The Services' draft policy on this subject was published on December = 21, 1994=20 (59 FR 65885) and public comment was invited. After review of comments = and=20 further consideration, the Services adopt the policy as issued in draft = form.=20

Summary of Comments and Recommendations=20

The Services received 31 letters from individuals and organizations=20 commenting on the draft policy. In addition, since publication of the = draft=20 policy, the National Academy of Sciences, National Research Council = (NRC), has=20 published a report titled "Science and the Endangered Species Act," = prepared by=20 a committee appointed by the Academy at the request of several members = of=20 Congress. This report in part examines the definition of "species" under = the=20 Act, and endorses the recognition of scientifically identified = evolutionary=20 units for conservation purposes. It discusses the recognition of DPS's = in terms=20 of "distinctiveness," which is consistent with the concept of = "discreteness" as=20 presented in the draft policy except that it would not recognize an=20 international political boundary to delimit a DPS. The committee noted = that:=20 "Although there can be good policy reasons for such delineations, there = are not=20 sound scientific reasons to delineate species only in accordance with = political=20 boundaries." The Services agree that the inclusion of international = boundaries=20 in determining whether a population segment is discrete is sometimes = undertaken=20 as a matter of policy rather than science. Although the committee = expressed the=20 belief that application of a distinctiveness test (analogous to the = standard of=20 discreteness in the policy) would adequately carry out the congressional = instruction that the authority to address DPS's be exercised sparingly, = the=20 Services continue to believe that a judgement regarding the significance = of any=20 unit found to be discrete is necessary to comply with congressional = intent.=20

Respondents presented a wide range of opinion regarding the = recognition of=20 DPS's. Some argued that the draft policy would be too restrictive and = make it=20 difficult or impossible to protect important elements of biodiversity; = others=20 maintained that the draft was not restrictive enough and would allow the = Services to extend protection to entities never intended to be eligible = for=20 protection under the Act. A few respondents questioned the need for any = policy=20 framework and advocated case-by-case determinations of the eligibility = of=20 entities for listing under the DPS provision. The Services continue to = believe=20 that the Act will be best administered if there is a general policy = framework=20 governing the recognition of DPS's that can be disseminated and = understood by=20 the affected public.=20

Several respondents questioned the relationship of the draft policy = to the=20 NMFS policy regarding salmonids. The Services believe that the NMFS = policy for=20 salmonids is consistent with the general policy outlined in this notice, = although the salmonid policy is formulated specifically to address the = biology=20 of this group. Several respondents also questioned the use of qualifying = words=20 such as "significant" or "markedly" in the policy. The Services intended = these=20 words to have their commonly understood senses. At the time any distinct = population is recognized or not recognized the reasons for which it is = believed=20 to satisfy or not satisfy the conditions of the policy will be fully = explained.=20

Several respondents maintained that a policy of this nature required = adoption=20 under rulemaking procedures of the Administrative Procedure Act. The = Services=20 disagree, and continue to regard the policy as non-regulatory in nature. = Specific recommendations advanced by respondents are paraphrased and = responded=20 to below.=20

Only full species are genetically distinct from one another, and = listing=20 should only be extended to these genetically distinct entities.=20

Restricting listings to full taxonomic species would render the Act's = definition of species, which explicitly includes subspecies and DPS's of = vertebrates, superfluous. Clearly, the Act is intended to authorize = listing of=20 some entities that are not accorded the taxonomic rank of species, and = the=20 Services are obliged to interpret this authority in a clear and = reasonable=20 manner.=20

The Services should focus on genetic distinctness in recognizing a = distinct population segment. Conversely, some respondents believed there = should=20 be no requirement that a DPS be genetically differentiated or = recognizable for=20 it to be protected under the Act.=20

There appears to be a diversity of understanding regarding the = purposes of=20 the Act, with some individuals viewing it as directed almost exclusively = toward=20 the conservation of unique genetic resources while other individuals = emphasize=20 its stated intention of conserving ecosystems. This diversity of = viewpoints is=20 reflected in comments addressing the role to be played by genetic = information in=20 the draft policy. The Services understand the Act to support = interrelated goals=20 of conserving genetic resources and maintaining natural systems and = biodiversity=20 over a representative portion of their historic occurrence. The draft = policy was=20 intended to recognize both these intentions, but without focusing on = either to=20 the exclusion of the other. Thus, evidence of genetic distinctness or of = the=20 presence of genetically determined traits may be important in = recognizing some=20 DPS's, but the draft policy was not intended to always specifically = require this=20 kind of evidence in order for a DPS to be recognized. The ESU policy of = NMFS=20 also does not require genetic data before an ESU can be identified. Thus = in=20 determining whether the test for discreteness has been met under the = policy, the=20 Services allow but do not require genetic evidence to be used. At least = one=20 respondent evidently understood the draft policy to require that genetic = distinctness be demonstrated before a DPS could be recognized, and = criticized=20 the draft on that basis. As explained above, this was never intended.=20

The elements describing reasons for considering a population = segment=20 significant should be laid out comprehensively, rather than presented as = an=20 open-ended set of examples as in the draft policy.=20

The Services appreciate the need to make a policy on this subject as = complete=20 and comprehensive as possible, but continue to believe that it is not = possible=20 to describe in advance all the potential attributes that could be = considered to=20 support a conclusion that a particular population segment is = "significant" in=20 terms of the policy. When a distinct population is accepted or rejected = for=20 review pursuant to a petition or proposed for listing or delisting, the = Services=20 intend to explain in detail why it is considered to satisfy both the=20 discreteness and significance tests of the policy.=20

In assessing the significance of a potential distinct population = segment,=20 the Services should focus on its importance to the status of the species = to=20 which it belongs. Alternatively, the Services should emphasize the = importance of=20 a potential DPS to the environment in which it occurs.=20

Despite its orientation toward conservation of ecosystems, the = Services do=20 not believe the Act provides authority to recognize a potential DPS as=20 significant on the basis of the importance of its role in the ecosystem = in which=20 it occurs. In addition, it may be assumed that most, if not all, = populations=20 play roles of some significance in the environments to which they are = native, so=20 that this importance might not afford a meaningful way to differentiate = among=20 populations. On the other hand, populations commonly differ in their = importance=20 to the overall welfare of the species they represent, and it is this = importance=20 that the policy attempts to reflect in the consideration of = significance.=20

International boundaries are not appropriate in determining that a = population is discrete in the draft policy; political boundaries other = than=20 those between nations may be appropriate in some cases to delimit = DPS's.=20

The Services recognize that the use of international boundaries as a = measure=20 of discreteness may introduce an artificial and non-biological element = to the=20 recognition of DPS's. Nevertheless, it appears to be reasonable for = national=20 legislation, which has its principal effects on a national scale, to = recognize=20 units delimited by international boundaries when these coincide with = differences=20 in the management, status, or exploitation of a species. Recognition of=20 international boundaries in this way is also consistent with practice = under the=20 Convention on International Trade in Endangered Species of Wild Fauna = and Flora,=20 which is implemented in the United States by the Act. Recognition of = other=20 political boundaries, such as State lines within the United States, = would appear=20 to lead to the recognition of entities that are primarily of = conservation=20 interest at the State and local level, and inappropriate as a focus for = a=20 national program. The Services recognize, as suggested in some comments, = that=20 infra-national political boundaries offer opportunities to provide = incentives=20 for the favorable management of species if they were used as a basis for = recognizing discrete entities for delisting or for exclusion from a = listing.=20 Particularly when applied to the delisting or reclassification of a = relatively=20 widespread species for which a recovery program is being successfully = carried=20 out in some States, recognition of State boundaries would offer = attractive=20 possibilities. Nevertheless, the Act provides no basis for applying = different=20 standards for delisting than those adopted for listing. If the Services = do not=20 consider entities for listing that are not primarily of conservation = interest at=20 a national level, they must also refrain from delisting or reclassifying = units=20 at this level.=20

Complete reproductive isolation should be required as a = prerequisite to=20 the recognition of a distinct population segment.=20

The Services do not consider it appropriate to require absolute = reproductive=20 isolation as a prerequisite to recognizing a distinct population = segment. This=20 would be an impracticably stringent standard, and one that would not be=20 satisfied even by some recognized species that are known to sustain a = low=20 frequency of interbreeding with related species.=20

The Services should emphasize Congress' instruction to use their = authority=20 to address DPS's "sparingly."=20

The Services believe that application of the policy framework = announced in=20 this document will lead to consistent and sparing exercise of the = authority to=20 address DPS's, in accord with congressional instruction.

The occurrence of a population segment in an unusual setting = should not be=20 used as evidence for its significance.=20

The Services continue to believe that occurrence in an unusual = ecological=20 setting is potentially an indication that a population segment = represents a=20 significant resource of the kind sought to be conserved by the Act. In = any=20 actual case of a DPS recognized in part on this basis, the Services will = describe in detail the nature of this significance when accepting a = petition or=20 proposing a rule.=20

The authority to address DPS's should be extended to plant and=20 invertebrate species.=20

The Services recognize the inconsistency of allowing only vertebrate = species=20 to be addressed at the level of DPS's, and the findings of the NRC = committee=20 also noted that such recognition would be appropriate for other species. = Nevertheless, the Act is perfectly clear and unambiguous in limiting = this=20 authority. This policy acknowledges the specific limitations imposed by = the Act=20 on the definition of "species."=20

The Services should stress uniqueness and irreplaceability of = ecological=20 functions in recognizing DPS's.=20

The Services consider the Act to be directed at maintenance of = species and=20 populations as elements of natural diversity. Consequently, the = principal=20 significance to be considered in a potential DPS will be the = significance to the=20 taxon to which it belongs. The respondent appears to be recommending = that the=20 Services consider the significance of a potential DPS to the community = or=20 ecosystem in which it occurs and the likelihood of another species = filling its=20 niche if it should be extirpated from a particular portion of its range. = These=20 are important considerations in general for the maintenance of healthy=20 ecosystems, and they often coincide with conservation programs supported = by the=20 Act. Nevertheless, the Act is not intended to establish a comprehensive=20 biodiversity conservation program, and it would be improper for the = Services to=20 recognize a potential DPS as significant and afford it the Act's = substantive=20 protections solely or primarily on these grounds.=20

Congress did not intend to require that DPS's be discrete. In a = similar=20 vein, Congress did not require that a potential DPS be significant to be = considered under the Act.=20

With regard to the discreteness standard, the Services believe that = logic=20 demands a distinct population recognized under the Act be circumscribed = in some=20 way that distinguishes it from other representatives of its species. The = standard established for discreteness is simply an attempt to allow an = entity=20 given DPS status under the Act to be adequately defined and described. = If some=20 level of discreteness were not required, it is difficult to imagine how = the Act=20 could be effectively administered or enforced. At the same time, the = standard=20 adopted does not require absolute separation of a DPS from other members = of its=20 species, because this can rarely be demonstrated in nature for any = population of=20 organisms. The standard adopted is believed to allow entities recognized = under=20 the Act to be identified without requiring an unreasonably rigid test = for=20 distinctness. The requirement that a DPS be significant is intended to = carry out=20 the expressed congressional intent that this authority be exercised = sparingly as=20 well as to concentrate conservation efforts undertaken under the Act on = avoiding=20 important losses of genetic diversity.=20

A population should only be required to be discrete or = significant, but=20 not both, to be recognized as a distinct population segment.=20

The measures of discreteness and significance serve decidedly = different=20 purposes in the policy, as explained above. The Services believe that = both are=20 necessary for a policy that is workable and that carries out = congressional=20 intent. The interests of conserving genetic diversity would not be well = served=20 by efforts directed at either well-defined but insignificant units or = entities=20 believed to be significant but around which boundaries cannot be = recognized.=20

Requiring that a DPS be discrete effectively prevents the loss of = such a=20 segment from resulting in a gap in the distribution of a species. = Essentially,=20 if distinct populations are entirely separate, the loss of one has = little=20 significance to the others.=20

If the standard for discreteness were very rigid or absolute, this = could very=20 well be true. However, the standard adopted allows for some limited = interchange=20 among population segments considered to be discrete, so that loss of an=20 interstitial population could well have consequences for gene flow and=20 demographic stability of a species as a whole. On the other hand, not = only=20 population segments whose loss would produce a gap in the range of a = species can=20 be recognized as significant, so that a nearly or completely isolated = population=20 segment could well be judged significant on other grounds and recognized = as a=20 distinct population segment.=20

The Services lack authority to address DPS's of subspecies.=20

The Services maintain that the authority to address DPS's extends to = species=20 in which subspecies are recognized, since anything included in the taxon = of=20 lower rank is also included in the higher ranking taxon.=20

The following principles will guide the Services' listing, delisting = and=20 reclassification of DPS's of vertebrate species. Any proposed or final = rule=20 affecting status determination for a DPS would clearly analyze the = action in=20 light of these guiding principles.=20

POLICY=20

Three elements are considered in a decision regarding the status of a = possible DPS as endangered or threatened under the Act. These are = applied=20 similarly for addition to the lists of endangered and threatened = wildlife and=20 plants, reclassification, and removal from the lists:=20

1. Discreteness of the population segment in relation to the = remainder of the=20 species to which it belongs;=20

2.The significance of the population segment to the species to which = it=20 belongs; and=20

3.The population segment's conservation status in relation to the = Act's=20 standards for listing (i.e., is the population segment, when treated as = if it=20 were a species, endangered or threatened?).=20

Discreteness: A population segment of a vertebrate species may = be=20 considered discrete if it satisfies either one of the following = conditions:=20

1.It is markedly separated from other populations of the same taxon = as a=20 consequence of physical, physiological, ecological, or behavioral = factors.=20 Quantitative measures of genetic or morphological discontinuity may = provide=20 evidence of this separation.=20

2.It is delimited by international governmental boundaries within = which=20 differences in control of exploitation, management of habitat, = conservation=20 status, or regulatory mechanisms exist that are significant in light of = section=20 4(a)(1)(D) of the Act.=20

Significance: If a population segment is considered discrete = under one=20 or more of the above conditions, its biological and ecological = significance will=20 then be considered in light of Congressional guidance (see Senate Report = 151,=20 96th Congress, 1st Session) that the authority to list DPS's be used=20 "...sparingly" while encouraging the conservation of genetic diversity. = In=20 carrying out this examination, the Services will consider available = scientific=20 evidence of the discrete population segment's importance to the taxon to = which=20 it belongs. This consideration may include, but is not limited to, the=20 following:=20

1.Persistence of the discrete population segment in an ecological = setting=20 unusual or unique for the taxon,=20

2.Evidence that loss of the discrete population segment would result = in a=20 significant gap in the range of a taxon,=20

3.Evidence that the discrete population segment represents the only = surviving=20 natural occurrence of a taxon that may be more abundant elsewhere as an=20 introduced population outside its historic range, or=20

4.Evidence that the discrete population segment differs markedly from = other=20 populations of the species in its genetic characteristics.=20

Because precise circumstances are likely to vary considerably from = case to=20 case, it is not possible to describe prospectively all the classes of=20 information that might bear on the biological and ecological importance = of a=20 discrete population segment.=20

Status: If a population segment is discrete and significant = (i.e., it=20 is a distinct population segment) its evaluation for endangered or = threatened=20 status will be based on the Act's definitions of those terms and a = review of the=20 factors enumerated in section 4(a). It may be appropriate to assign = different=20 classifications to different DPS's of the same vertebrate taxon.=20

Relationship to Other Activities=20

The Fish and Wildlife Service's Listing and Recovery Priority = Guidelines (48=20 FR 43098; September 21, 1983) generally afford DPS's the same = consideration as=20 subspecies, but when a subspecies and a DPS have the same numerical = priority,=20 the subspecies receives higher priority for listing. The Services will = continue=20 to generally accord subspecies higher priority than DPS's.=20

Any DPS of a vertebrate taxon that was listed prior to implementation = of this=20 policy will be reevaluated on a case-by-case basis as recommendations = are made=20 to change the listing status for that distinct population segment. The=20 appropriate application of the policy will also be considered in the = 5-year=20 reviews of the status of listed species required by section 4(c)(2) of = the Act.=20

Effects of policy=20

This guides the evaluation of distinct vertebrate population segments = for the=20 purposes of listing, delisting, and reclassifying under the Act. The = only direct=20 effect of the policy is to accept or reject population segments for = these=20 purposes. More uniform treatment of DPS's will allow the Services, = various other=20 government agencies, private individuals and organizations, and other = interested=20 or concerned parties to better judge and concentrate their efforts = toward the=20 conservation of biological resources at risk of extinction.=20

Listing, delisting, or reclassifying distinct vertebrate population = segments=20 may allow the Services to protect and conserve species and the = ecosystems upon=20 which they depend before large-scale decline occurs that would = necessitate=20 listing a species or subspecies throughout its entire range. This may = allow=20 protection and recovery of declining organisms in a more timely and less = costly=20 manner, and on a smaller scale than the more costly and extensive = efforts that=20 might be needed to recover an entire species or subspecies. The = Services'=20 ability to address local issues (without the need to list, recover, and = consult=20 rangewide) will result in a more effective program.=20

Author/Editor=20

The editors of this policy are Dr. John J. Fay of the Fish and = Wildlife=20 Service's Division of Endangered Species, 452 ARLSQ, Washington, D.C. = 20240 and=20 Marta Nammack of the National Marine Fisheries Service's Endangered = Species=20 Division, 1335 East-West Highway, Silver Spring, Maryland 20910.=20

Authority=20

The authority for this action is the Endangered Species Act of 1973, = as=20 amended (16 U.S.C. 1531 et seq.).=20

Dated: February 1,1996=20

John G. Rogers,=20

Acting Director, Fish and Wildlife Service=20

Dated: February 1,1996=20

Nancy Foster=20

Deputy Assistant Administrator for Fisheries, National Marine = Fisheries=20 Service.=20

[FR Doc. 96-2639 Filed 2-6-96; 8:45 am]=20

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