December 2012 Number 1 - Utah Native Plant Society

Great Basin, Colorado Plateau, and Rocky Mountains.
The next three counties with the greatest number of
species of conservation concern (Kane, Garfield, and
San Juan) are all, like Washington County, located on or
near the southern boundary of the state. Additional
counties with a high number of species of concern include
Uintah, Duchesne, Grand, and Emery counties
near the eastern border of Utah. By contrast, the number
of rare species is relatively low in the northern and
western tier of counties. Surprisingly few plant species
of conservation concern occur in the greater Salt Lake
City area, though this may be an artifact of undersampling
or reflect significant habitat losses over the
last 150 years of settlement (Fertig 2009).
Ecoregions are defined as geographic areas with a
similar climate, topography, and vegetation. The Nature
Conservancy has developed a national ecoregional classification
(Stein et al. 2000) that recognizes seven ecoregions
in Utah (Figure 2*). Of these, the Colorado Plateau
ecoregion has the highest number of plant species
of conservation concern with 323 taxa, or 37.6% of the
state total (Table 3). This region, which includes the
canyon country and La Sal and Abajo mountains of
southeast Utah, also has the highest number of endemic
species in the state (Welsh and Atwood 2009). Although
comparable in area to the Colorado Plateau, the
Great Basin ecoregion has less than half as many species
of concern (152 taxa). The Mohave Desert ecoregion
of extreme southwestern Utah is the second smallest
in area in the state (after the Columbia River Basin
in the Grouse Creek and Raft River mountains of northwest
Utah) but has the highest concentration of species
of concern per unit area (138 taxa in all). The Utah
High Plateaus, which extends from the Tavaputs Plateau
and Book Cliffs of eastern Utah to the Wasatch Plateau,
and Markagunt and Paunsaugunt plateaus of southcentral
Utah, has the second highest concentration of
endemics and taxa of conservation concern (205 species,
or 23.9% of the state total) (Table 3).
DISCUSSION
The UNPS rare plant list is just the latest in a long
series of comparable publications dating back to the
passage of the Endangered Species Act (ESA) of 1973.
No plants were included in the very first official list of
species protected under the ESA, but Congress directed
the Smithsonian Institution to develop the first national
list of vascular plants that might qualify for listing as
*Welsh and Atwood (2009) have developed a similar system
of “geoendemic areas” to identify floristic regions of Utah.
Their map depicts 12 subregions and differs from the TNC
system in lumping the Columbia River Basin with the Great
Basin and in more finely subdividing the Utah-Wyoming
Rocky Mountains, Utah High Plateaus, Colorado Plateau, and
Mohave Desert ecoregions.
Utah Native Plant Society
204
Threatened or Endangered. That list appeared in 1975
and was based on the best available information at the
time (Ayensu and DeFilipps 1978, Greenwalt 1975).
The Smithsonian Institution cited 761 plant taxa as potentially
Endangered, 1238 as Threatened, and 100 as
extinct in the continental United States (another 1088
endangered, threatened, and extinct species were reported
for Hawaii). Of these, 156 species were from
Utah, including 56 listed as endangered, 91 threatened,
and 9 extinct (Greenwalt 1975).
Welsh and others (1975) reviewed the Smithsonian
publication and developed the first Utah-specific compilation
of endangered, threatened, extinct, endemic, and
rare plant species in 1975. Welsh and his co-authors
recognized 66 Utah plant taxa as possibly endangered,
198 as threatened, 7 as extinct, and 20 as extirpated
(extinct in Utah, but extant elsewhere). Most of the recommendations
by Welsh and others (1975) were incorporated
into a revised Smithsonian list (Ayensu and De-
Filipps 1978) that became part of a proposal to list
nearly 1700 plant species as Threatened or Endangered
in 1976 (the proposal was ultimately dismissed).
These initial rare species lists were plagued by incomplete
data and taxonomic problems. Of the 156
Utah species considered endangered, threatened, or extinct
by the Smithsonian Institution in 1975, only 39
(25%) are still considered taxa of Extremely High or
High conservation priority today. At least 13 of these
species (8.3%) are no longer recognized as legitimate
taxa. Another 28 species (18%) are now known to be
much more common or less threatened and are classified
as Low priority by UNPS. Eight of the nine species
considered extinct in 1975 have been rediscovered (only
Cuscuta warneri is still thought to be extirpated in
Utah). Among the additional 225 state endemics and
other potentially rare species evaluated by Welsh and
others (1975), one half (112 taxa) are now scored as
Low priority and 26 (11.5%) are no longer recognized
taxonomically.
Over the next two decades new Utah rare plant lists
were developed by the US Fish and Wildlife Service,
Bureau of Land Management, US Forest Service, and
non-governmental organizations (such as The Nature
Conservancy and Utah Native Plant Society). The composition
of these lists continued to evolve to reflect
ever-improving knowledge of the distribution, abundance,
and status of the state’s flora (Atwood et al.
1991; Utah Division of Wildlife Resources 1998; Utah
Native Plant Society 1980, 1982; Welsh 1978; Welsh
and Chatterley 1985; Welsh and Thorne 1979). Threat
of potential listings under the ESA prompted a large
scale effort to survey rare species and remote corners of
the nation for new taxa. During the period from 1975 to
1994 nearly 1200 new vascular plant taxa were described
across North America, or approximately 60 new