December 2012 Number 1 - Utah Native Plant Society

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Utah Native Plant Society Table 1. Scores for Ranking Factors. Ranking Factor Category or Condition Points 1. Geographic Range (only taxa native to the state are scored) 2. Number of Populations 3. Abundance Local endemic (global range less than 16,500 km 2 or about 1 degree of latitude x 2 degrees of longitude) Regional endemic (global range covering 16,501-250,000 km 2 or an area about the size of Wyoming) Disjunct (globally widespread but state population is isolated from the main contiguous range of the species by a gap of more than 800 km) Peripheral (globally widespread but state population is at the margin of its continuous range and occupies less than 5% of the state’s area near state boundary) Sparse (globally widespread, but distribution patchy and discontinuous in the state and covering less than 5% of the state’s area) Widespread (occurs widely across North America [covering more than 250,000 km 2 ] and across the state [occupying well over 5% of the area]) Unknown 0-1 Low (fewer than 25 extant populations in state) 1 Medium to High (25 or more extant populations in state) 0 Unknown 0-1 Low (depends on life history of species, but typically less than 30,000 individuals for perennials [higher numbers allowable for annuals] or occupying an area of less than 3000 acres in state) Medium to High (known from well over 30,000 individuals for perennials or occupying an area greater than 3000 acres in state) Unknown 0-1 4. Habitat Specificity High (“Specialist” restricted to one or a few specialized geologic substrates, soil types, or vegetation types) Medium to Low (“Generalist” found in numerous geologic substrates, soil types, or vegetation types) Unknown 0-1 5. Intrinsic Rarity High (unusual life history, dependence on rare or specialized pollinators, poor dispersal, low fecundity, poor seedling survival, etc.) 6. Magnitude and Imminence of Threats Medium to Low (no unusual life history or biological attributes limiting establishment or persistence Unknown 0-1 High (current or foreseeable threats significant or broad in scale or scope 1 Medium to Low (threats minimal or limited to small percentage of populations now or in the foreseeable future) Unknown 0-1 7. Population Trend Decreasing (short to long-term decline in number, size, or vigor of populations) 1 Increasing, stable, or oscillating around a mean 0 Unknown 0-1 198 2 1 1 1 1 0 1 0 1 0 1 0 0
Calochortiana December 2012 Number 1 ber of populations is not necessarily equivalent to the number of collections of a species, especially if these collections are from the same general area. 3. Abundance. Abundance refers to the number of individual plants known statewide. If census data are lacking, abundance can be approximated from the relative dominance of a species within its area of occupied habitat. 4. Habitat Specificity. This factor assesses the degree to which a species is a habitat specialist restricted to a particular soil or geologic substrate (edaphic endemics) or vegetation type, or is a generalist found in a wide variety of substrates or plant communities. 5. Intrinsic Rarity. Analogous to habitat specificity, intrinsic rarity addresses those attributes of a species’ life history that may limit its establishment or persistence. Examples include low fecundity, poor dispersal, low seedling survival, low genetic diversity, or dependence on specialized pollinators. 6. Magnitude and Imminence of Threats. This criterion assesses the scope, severity, and immediacy of current or future negative impacts on a species. Potential threats include habitat destruction, over-collection, herbivory, trampling or soil compaction from recreation, or competition from invasive plants. 7. Population Trend. Trend is the change in population size, extent, and vigor over time. Assigning scores to each criterion Following the model of Rabinowitz (1981), six of the seven preceding criteria are scored using a binary rating (high/low or increasing/decreasing). A score of 1 is assigned to those conditions that make a species highly vulnerable to extinction or extirpation, while a score of 0 is given for conditions that only moderately impact or do not adversely affect a species’ persistence in the state. The only exception is geographic range in which three scores are possible (0, 1, or 2) to allow greater weighting of locally endemic species. If there is insufficient data to rate a specific criterion, or available information is inconclusive, a value of “U” (unknown) may be assigned. Scores for individual criteria are shown in Table 1. Scoring is based on a review of pertinent literature, specimen databases, and expert knowledge and should be supported by corroborating data. Scores can be tabulated in a spreadsheet or in a simple data form (see Table 2 for an example). Determining conservation priority Once the ranking form or table is completed, the individual scores for each of the seven ranking factors are summed to derive both a minimum and potential (maximum) score (Table 2). These scores can range from 0 to 8. The minimum score includes only those factors for which information is available, with any unknowns scored as 0. The potential score includes the same values but with unknowns given a “worst case” score of 1. The minimum and potential scores are then averaged (with the sum rounded down) to derive an overall score (Table 2). The final score can be used to assign each species to one of the following six conservation priority categories: Extremely High (7 or 8 points): species at extreme risk of extirpation across its range due to all seven of the following conditions: limited geographic range, small number of populations, low number of individuals, high habitat specificity, high intrinsic rarity, high threats, and downward population trend. High (6 points): species at high risk of extirpation rangewide or in the state. High priority species are scored as vulnerable for at least six of the seven ranking criteria. Watch (5 points): species currently secure but vulnerable to downward changes in status. These taxa are scored as vulnerable for at least five of the seven ranking criteria. Medium (4 points): species secure rangewide but vulnerable to extirpation in the state. Medium priority species are scored as vulnerable for at least four of the seven ranking criteria. Low (0-3 points): species secure rangewide and in the state. These species are scored as vulnerable for three or less of the seven ranking criteria. Need Data: insufficient data available to score species for at least three of the seven ranking criteria. If information were available. these species would likely be ranked as Extremely High, High, Watch, or Medium priority rather than Low priority. An example of ranking a Utah species The following example demonstrates the application of the Wyoming protocol. Penstemon gibbensii is a narrow endemic of extreme NE Utah (Daggett County), adjacent NW Colorado, and SC Wyoming, earning it 2 points for geographic range. In Utah, it is known from a single occurrence in the Browns Park area (1 point for low number of populations) containing approximately 700 plants (1 point for low number of individuals) (Utah Division of Wildlife Resources 1998). It is restricted to barren white shales of the Browns Park Formation (1 point for high habitat specificity). Little is known about the pollination biology or life history of P. gibbensii (Heidel 2009), suggesting an “unknown” score is appropriate for intrinsic rarity. Threats from trampling, soil erosion, and over-collection by gardeners are high throughout its range (1 point for threats). Trends in Utah are unknown, although some populations in Wyoming appear to be declining (Heidel 2009). The mini- 199
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A. lentiginosus var. ursinus (publi
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December 2012 Number 1 - Utah Native Plant Society

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