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Figure 48—Numbers of federally listed candidate category C1 or C2 vertebrate species by 4th-code hydrologic unit in the
basin assessment area (see table 15 for list of species, and text footnote 11 for explanation of recent changes in the
candidate species listing).
ICBEMP
Basin boundary
4th field hydrologic
units
State boundaries
Species > 16 − 19
Species > 10 − 13
Species > 13 − 16
Species = 8 − 10
Legend
Although some potential vertebrate habitat corridors could be identified—such as linking Glacier
National Park with Yellowstone National Park,
or the Blue Mountains and the central Idaho
mountains, for many montane or alpine species
including mustelids—they did not meet the second criterion for this particular component of
being the only locations of associated vertebrate
species within the basin assessment area. They
are included, however, in the “Full Trophic Ladder Component,” 3(h), discussed below. The following integrity component relates to habitat connectivity as defined above.
Component (1d):13 Distribution of species occurring along key habitat corridors—One major
habitat corridor that met all the above criteria
was found along the eastern spine of the Cascade
Range. An assemblage of seven vertebrates14
(table 16) occurs in the basin assessment area
only along the spine or eastern flanks of the
Cascade Range in Washington and Oregon collectively delineate a mid- to high-elevation montane corridor. The database and map show presence of this corridor by 4th code HUC (fig. 49).
The corridor occurs along the eastern flanks of
the Cascade Range; additional 4th code HUCs in
eastern Washington, northern Idaho, and western
Montana also contain disjunct populations of
these species and are indicated on the map.
13
This component is numbered out of sequence here to
remain consistent with the map index codes on record for
ICBEMP.
14
An additional, eighth species fitting these criteria is
mountain beaver (Aplodontia rufa), which was not mapped
in time for this analysis. Its inclusion would not alter the
results, as its distributional range within the basin assessment area matches that of the other species listed for this
component. Other vertebrate species such as northwestern
salamander, Cope’s giant salamander, ensatina (Ensatina
eschscholtzii), Larch Mountain salamander, Columbian
black-tailed deer (Odocoileus hemionus columbianus), and
others also occur within the basin assessment area only in
the Cascade Range, but not broadly along the spine or
eastern front.
Ecological Integrity Goal 2:
Maintain Long-Term Evolutionary
Potential of Species
The overall concept of maintaining long-term
evolutionary potential of species entails, in part,
maintaining unique ranges and centers of biodiversity, rarity, and endemism.
Species components—The following integrity
component relates to distribution of species that
may be critical to maintaining long-term evolutionary potential. Other species components to
help meet this goal include maintaining unique
ecotypes of species, maintaining species at the
periphery of their global range, and maintaining
unique subspecies, varieties, or phenotypes
(Marcot and others 1996). These additional components were not available for mapping in this
analysis.
Component (2a): Distribution of disjunct vertebrate species populations—Managing for disjunct populations of plants and animals is an
important facet of maintaining genetic diversity
and longterm evolutionary potential of species
(Kruckeberg and Rabinowitz 1985, Millar and
Libby 1991).
Some 11 vertebrate species are coded in the SER
database as having disjunct ranges within the basin assessment area. Two of these species, however, Virginia opossum (Didelphis virginiana)
and bullfrog (Rana catesbeiana), are mainly recent invaders or introduced, are not of conservation concern, and are not included in this analysis.
In fact, bullfrogs, widely introduced to ponds and
lakes throughout the basin assessment area, are
predators on some of the more increasingly scarce
native amphibians such as red-legged frog. A
third species with a disjunct range, pygmy shrew
(Sorex hoyi), is largely contiguous within the basin assessment area (as mapped at the broad scale
used by the expert panels for this project) with
only a small portion of its range disjunct, so it
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Table 16—Vertebrates that occur within the basin assessment area only along a broad latitudinal
extent of the eastern flanks of the Cascade Rangea
Species
code
Scientific name
Common name
RANCAS
Rana cascadae
Cascades frog
TARGRA
Taricha granulosa
Rough skinned newt
STROCA
Strix occidentalis caurina
Northern spotted owl
SORTRO
Sorex trowbridgii
Trowbridge’s shrew
NEUGIB
Neurotrichus gibsii
Shrew mole
SPESAT
Spermophilus saturatus
Cascade golden mantled ground squirrel
ZAPTRI
Zapus trinotatus
Pacific jumping mouse
a
These include species that might benefit by latitudinal habitat corridors of montane and subalpine forests along the eastern
slope of the Cascade Range. This list does not include species that enter the basin assessment area from the west only at one
point across the spine of the Cascade Range or only up the Columbia River Gorge.
Legend
Present
Absent
4th field hydrologic
units
State boundaries
Basin boundary
ICBEMP
Figure 49—Occurrence of a habitat corridor for vertebrates of the Cascade Range by 4th-code
hydrologic unit in the basin assessment area (see text for further explanation of the extraneous
hydrologic units shown shaded here).
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