December 2012 Number 1 - Utah Native Plant Society

Calochortiana December 2012 Number 1
example, the US Fish and Wildlife Service (1983) system
for listing species under the US Endangered Species
Act is heavily weighted towards threats and taxonomic
distinctiveness at the expense of other aspects of rarity
(Master et al. 2000). The IUCN (2001) protocol focuses
chiefly on population size, trends, and likelihood of extinction
but is dependent on quantitative viability data
that are not always available for vascular plants. One
advantage of the IUCN protocol, however, is its recognition
of “data deficient” species (Akçakaya et al. 2000).
Rabinowitz (1981) introduced a simple, but elegant,
binary ranking system using just three components of
rarity: geographic range, abundance, and habitat specificity.
But several additional biological and anthropogenic
criteria (such as threat) were not incorporated,
which limits the suitability of the Rabinowitz system for
prioritizing among different kinds of rare species.
The most widely used ranking protocol today is the
natural heritage system, first developed by The Nature
Conservancy in the 1970s (Master 1991) and now administered
by NatureServe. In this system, full species
or varieties are assigned a conservation rank on a scale
of 1 (critically imperiled) to 5 (demonstrably secure)
across their entire global range (G rank) and at a subregional
scale (state/province, or S rank). Traditionally, G
and S ranks were based on the number of occurrences
(discrete biological populations), abundance, or risk of
extinction as determined by expert opinion (Master et al.
2000). In the past decade, NatureServe protocols have
become more quantitative and consider additional ranking
criteria, including long and short-term trends, area
of occupancy, condition of occurrences, intrinsic rarity,
and threat (Faber-Langendoen et al. 2009; Regan et al.
2004). Unfortunately, the revised NatureServe ranking
protocol has become more complex and less transparent.
Individual ratings are weighted differently, some criteria
are used only conditionally, and scores are tallied by a
“black box” computer algorithim (Faber-Langendoen et
al. 2009).
As part of my doctoral dissertation on plant conservation
in Wyoming (Fertig 2011), I developed a hybrid
ranking protocol by borrowing components of each of
the preceding systems. As a starting point, I adopted
most of the rarity factors from NatureServe (Regan et al.
2004), added the uncertainty components of IUCN
(2001), and included an emphasis on threats from the
US Fish and Wildlife Service (1983). The ranking system
itself is a modification of the qualitative, binary
scoring employed by Rabinowitz (1981), expanded to
include additional criteria. I added a simple scoring
component to classify plant species into six different
rarity classes reflecting each taxon’s overall conservation
priority (Fertig 2009, 2011).
In 2007, I beta-tested the “Wyoming protocol” at the
annual Utah rare plant meeting sponsored by the Utah
Native Plant Society (UNPS) and Red Butte Garden.
Following the meeting, the UNPS state board voted to
reestablish a rare plant committee and charged it with
applying this ranking system to the entire Utah vascular
plant flora in order to create a new, prioritized list of
rare plant species for the state. A draft version of the
list was presented at a special session of the Fifth Southwestern
Rare and Endangered Plant Conference, held at
the University of Utah in March 2009. Based on feedback
from meeting participants and other experts, the
list was revised and published in November 2009
(Fertig 2009). The list has since been updated twice
(Fertig 2010a, 2012) based on additional input from the
UNPS Rare Plant Committee, attendees of the Society’s
annual rare plant meeting, and review of new literature.
The purpose of this paper is to briefly describe the
Wyoming ranking protocol and its application to the
flora of Utah. Appendices 1-4 include the current lists
of Utah plants on the Extremely High Priority, High
Priority, Watch, and Need Data lists. The paper concludes
with a comparison of the current list to previous
rare plant lists for Utah and a discussion of additional
applications and future directions.
METHODS
Ranking Criteria
The Wyoming protocol is based on seven biological
and anthropogenic factors that influence the conservation
priority of a vascular plant species. These criteria
are:
1. Geographic range. Geographic range takes into
account the state’s contribution to the total global distribution
of a species. Six geographic range categories are
recognized (Table 1). Local and regional endemics
have highly restricted global distributions, ranging from
single populations covering a few acres to less than
250,000 km 2 (an area about the size of the state of Wyoming).
Widespread species, defined as occupying a
global range in excess of 250,000 km 2 , can still be considered
rare if state populations are widely isolated from
the core of the species’ range (disjunct) or are at its very
edge (peripheral). A small number of plant species may
occur widely but are limited to small, often scattered or
discontinuous habitats and occupy less than 5% of the
state (sparse). Species that are introduced to the state are
not included in the rankings.
2. Number of Populations. This criterion is based on
the number of extant populations of a species within
Utah (occurrences outside the state are not considered).
Populations are defined as aggregations of individual
plants within a specific geographic area that are separated
from other populations by a physical barrier, extensive
area of unsuitable habitat, or sufficient distance
to prevent gene flow (usually about 1-2 km). The num-
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