Taxa Inclusion for Animal Modeling in Southwest Regional Gap

Decision Rules for Taxa Inclusion, Exclusion, and Modeling Allocation
Animal Habitat Modeling in the Southwest Regional Gap Analysis Project
prepared by New Mexico Regional Animal Habitat Modeling Lab
(30 June 2002)
Preface: This document is prepared as a general guide to promote understanding and
communication among the multiple state project partners engaged in predictive modeling of
animal habitat distribution in Arizona, Colorado, Nevada, New Mexico, and Utah. The premise
of our endeavor is that we are modeling to identify areas of the landscape that contain physical
and biotic features that likely will or do support occurrence of specific animal taxa. That
modeling is based on a set of associations (wildlife habitat relationships) developed for each
taxa relative to a set of landscape features that are compiled regionally. That is to say, we are
modeling potentiality for occurrence of suitable habitat features for each animal taxa; we are not
preparing predictions of absolute occurrence of any individual taxa on any given day. Because
of the magnitude of taxa involved, we will primarily use a Boolean (binomial choice) modeling
approach, although a variety of multivariate or other modeling processes may be applied to
specific taxa. Such an approach inherently “overpredicts” habitat of a taxon as compared to
human perception of current distribution or occurrence of individual taxa. Our obligation is to
prepare models that are credible and defensible in depicting realistic species distribution
(including occupiable or reoccupiable habitat) while not being so extensive as to risk categorical
rejection by decision-makers. Predicted distributions will be used for analysis of biodiversity
patterns relative to land stewardship and prospects to provide long-term conservation of
biological diversity.
Objective: To provide specific, consistent criteria to select candidate taxa for preparing
seamless habitat distribution prediction models across the 5-state region to meet objectives of
gap analysis and other data development purposes consistent with the agreed time schedule for
The regional taxa list is compiled by the Regional Animal Habitat Modeling Lab (New Mexico)
with input from the individual state projects. Each project should begin from a recognized
master list in their project area that identifies full vertebrate species (excluding fish) that are
accepted by authoritative sources applicable to each project area (e.g., state wildlife agency,
Heritage Program, database clearinghouse, or published literature source) as having occurred
in the region. This list should include all species taxa, even if they have no breeding records in
the project area but have regular, substantive migration or wintering habitat use in the project
area, even if different from breeding range (e.g., migrant birds, bats, large ungulates). Also
include exotic (non-native) species that are naturalized and have regular and enduring
occurrence in the project area.
Exclusion Rules:
The following steps are applied by projects in consultation with the Regional Lab. When taxa
recommendations are submitted by projects to the Regional Lab, if any taxa appear to be
contrary to the inclusion rules, the regional lab will reach final resolution in consultation with
project PIs and animal habitat modeling representatives.
At species level, exclude those taxa representing the following:
Taxa with only incidental, accidental, or vagrant occurrence (see NOTE#1 below)
Taxa for which authoritative taxonomic sources have eliminated species standing (see
NOTE#2 below)
Taxa that are extirpated from the area to be modeled for 20 years or >5 demographic
generations (whichever is a greater time span) applicable to the taxa (retain
ecologically or demographically recent extirpations). Note that taxa that are
extirpated within 1 or several state project areas but have occurred anywhere in the
region within this time limit will be modeled across the region. Also, wide-ranging
taxa that have been extirpated but are considered for re-establishment may not be
excluded if projects and regional lab agree to retain for modeling.
Taxa representing unsuccessful introduction or re-establishment in the area subject to
habitat distribution modeling
Exotic (non-native), primarily urban-dwelling taxa,
Exotic taxa with restricted occurrence associated with specialized or ephemeral
landscapes or only under human manipulation such that the taxon cannot be
modeled effectively using GIS layers available for SWReGAP.
NOTE#1: Exclude incidental species with no expected routine presence or occurrence in the project area
during any 1 season. This exclusion also involves species for which occurrence is so fleeting and
unpredictable as to indicate that habitat in the region or project area is not important enough to maintain
substantive numbers of the species for breeding, migration, and/or wintering. In general, exclude any
migrant and/or winter visitor/resident taxon unless at least 10 (for large taxa) and 25 (for small species,
such as passerine birds) individuals occur in the area on a regular annual or predictable time interval
basis. Exclusion decisions should be based on information found in generally accepted technical
literature and books that describe recent distribution of species in the region. These sources may be up
to 30-40+ years old if used in conjunction with other recent sources for specific taxa. Examples are:
Arizona – Lowe (1964), Phillips et al. (1964), Monson and Phillips (1981), Hoffmeister (1986),
Lowe et al. (1986)
Colorado – Andrews and Righter (1992), Fitzgerald et al. (1994), Kingery (1998), Hammerson
Nevada – Hall (1981), Stebbins (1985), Alcorn (1988)
New Mexico - Ligon (1961), Findley et al. (1975), Degenhardt et al. (1996), New Mexico
Ornithological Society (2000)
Utah – Dalton et al. (1990), Durrant (1952), Schwin and Minden (1979), Walters and Sorenson
NOTE#2 - In cases where taxonomic changes are new or under debate, base a decision to model on
available information and consistency with taxonomic designations recognized by the authority for that
taxonomic group [e.g., AOU (1998) for birds, SSAR (2000) for herpetofauna, Hall (1981) and Wilson and
Reeder (1993) for mammals, subsequent editions of foregoing references, or more recent accepted
treatments]. In some cases, it may be appropriate to retain the old status because reliable speciesspecific distribution information is rarely available immediately following a change in species designation
or can be confused among forms. Insofar as possible, the taxonomic entities chosen, and the modeling
process and presentation, will retain information about potentially distinct taxa. Examples of recent
taxonomic viewpoints are:
Kit fox (Vulpes macrotis) and swift fox (V. velox). Possible conspecifics (Dragoo et al. 1990)
but viewed as genetically distinct (Mercure et al. 1993). They are treated as 2 separate species.
Separation of solitary vireo into 3 species. The bird formerly know as solitary vireo (Vireo
solitarius) is now 3 species [plumbeous vireo (V. plumbeus), Cassin’s vireo (V. cassinii), and
blue-headed vireo (V. solitarius), of which the first 2 species reliably occur in the SWReGAP area
(AOU 1998).
Perspectives on accepted naming of North American herpetofauna. See listing and
discussion of naming in SSAR (2000).
The Regional Animal Habitat Modeling Lab will be responsible to maintain a cross-reference data base
for name changes. Any inclusions, deletions, or name changes following development of the master list
will be decided and documented with assistance from state project staff, consistent with lead assignments
for specific taxa.
Include those taxa that are recognized as full species based on recent (past 10 years)
acceptance by a recognized nomenclature authority. Regarding subspecies, the general view is
to include identifiable forms that will facilitate application of gap analysis to the array of taxa that
should broadly influence biodiversity conservation decisions in the future, not just subspecific
taxa that are of current special interest now (color variant, rare, specially classified,
management concern). Subspecific taxa for which there is wide acceptance of substantive
distinction in habitat associations (e.g., mountain and desert bighorn sheep) may be included as
requested among the projects. For subspecies, begin with a limited list of subspecies based on
the following criteria:
Current or projected importance to land managers
Subspecies taxa that are distinctive and relatively well known, so that there is a
demonstrated, legitimate information base for developing models or at least
depicting general habitat limits
Subspecies taxa that have specific and relatively well-known habitat associations that
can be represented in reasonably well-informed models
Exclusion Rules:
Species-Level Taxa (i.e., new species)
Generally, follow the decision rule applicable to species on pages 1-3.
Subspecies-level Taxa
Exclude subspecies taxa that do not have current recognition from an accepted authority
on taxonomic nomenclature for the taxonomic group involved. [e.g., Hall (1981)
alone is not a sufficient reference to establish standing for mammal subspecies
because it too liberally includes subspecies taxa without supporting taxonomic
Exclude taxa that lack sufficient distinguishing marks in the field to permit a literature that
will support development of wildlife-habitat associations
Exclude taxa for which their general range cannot be satisfactorily delineated
Exclude taxa for which a substantive literature on habitat association does not exist
Exclude taxa for which there is no observable physical distinction (e.g., color morphs)
that allows recognition based on recent acceptance by recognized nomenclature
authorities. Evidence suggesting lack of genetic distinction will exclude taxa
regardless of physical distinctiveness.
Alternative to Modeling Subspecies Taxa
Compile geographic limits of all subspecies taxa included from the process above. Use those
limits as a spatial template to overlay on respective species distribution coverages to identify
limits of predicted subspecies habitat distribution in context with the full species across the
region. This approach does not involve taxa modeling; rather it allows subspecies analyses
after species-level models are prepared. This approach is allowed on a taxon-specific basis, as
coordinated with the Regional Habitat Lab, per group agreement at the SWReGAP Habitat
Modeling Workshop in Las Cruces, New Mexico on 10-11 April 2002.
This approach is an attempt to distribute initial taxa modeling responsibilities among all projects
in a manner that capitalizes on previous modeling experience, is localized to the distribution of
taxa experts, and is sensitive to the greatest awareness about local conditions applicable to
more restricted taxa. All projects will have opportunity for input on modeling approach and
results among taxa, regardless of the lead assignment.
Taxa Allocation Decision Rule
Previously modeled in 1 state only = assign to that state project
Previously modeled in 2 states = assign to state project with primary distribution (see
NOTE#3 and #4)
Previously modeled in 3 or 4 states = assign to the state project representing the primary
distribution of the taxa OR to Regional Habitat Modeling Lab if widely distributed
across all of the states (see NOTE#4)
Previously modeled in all 5 states = assign to Regional Habitat Modeling Lab
Previously not modeled by any state in the region = assign per rules above consistent
with primary distribution of the taxon
NOTE#3: PRIMARY DISTRIBUTION = Combination of general range and occurrence of primary
habitat(s) occupied by the taxa.
NOTE#4: Where 2-4 state projects appear to equally share range of a taxon not assigned to the Regional
Lab, responsibility can be shifted among projects. A shift in responsibility assignment can be based on
different expectations about locations and habitats of expected taxa occurrence, availability of taxa
experts, or other factors. Normally these reallocations will be done by mutual agreement among the
affected state projects; the Regional Coordinator and Regional Lab need only be involved if disagreement
arises. Shifts or exchanges of modeling responsibility must be documented to the Regional Lab.
After 30 June 2002, any taxa suggested for inclusion must be specifically coordinated with the
Regional Habitat Modeling Lab. The Regional Animal Habitat Modeling Lab, conferring with
regional experts and possibly ITIS (Integrated Taxonomic Information System) staff, will be the
final authority on subspecies taxa considered valid for inclusion. The contact for ITIS is:
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