Wyoming Basins Ecoregion Target Plant Species and Potential Plant Conservation Sites Prepared for the Wyoming Nature Conservancy By Walter Fertig Wyoming Natural Diversity Database · University of Wyoming PO Box 3381 Laramie, WY 82071 22 November 1999 I"- ACKNOWLEDGEMENTS I wish to thank the following individuals for their assistance with this analysis: David Anderson, Colorado Natural Heritage Program, Ft. Collins, CO Frank Blomquist, BLM Rawlins Field Office, Rawlins, WY Charmaine Delmatier, botanical consultant, Green River, WY Robert Dorn, Mountain West Environmental Services, Cheyenne, WY Ben Franklin, Utah Natural Heritage Program, Salt Lake City, UT Jerry Freilich, Wyoming Nature Conservancy, Lander, WY Sherel Goodrich, Ashley National Forest, Vernal, UT Ron Hartman, Rocky Mountain Herbarium, University of Wyoming, Laramie, WY Bonnie Heidel, MontanaNatural Heritage Program, Helena, MT George Jones, Wyoming Natural Diversity Database, Laramie, WY Tom Kohley, Beartooth Mapping, Red Lodge, MT Steve Laster, BLM Pinedale Field Office, Pinedale, WY Peter Lesica, botanical consultant, Missoula, MT Michael Mancuso, Idaho Conservation Data Center, Boise, ID Stuart Markow, Wyoming Natural Diversity Database, Laramie, WY Bob Moseley, Idaho Conservation Data Center, Boise, ID B. Ernie Nelson, Rocky Mountain Herbarium, University of Wyoming, Laramie, WY Jean Nitscheke-Sinclear, BLM Vernal Field Office, Vernal, UT William Reiners, Wyoming Natural Diversity Database, Laramie, WY Amy Roderick, University of Wyoming, Laramie, WY Richard Scott, Central Wyoming College, Riverton, WY Susan Spackman, Colorado Natural Heritage Program, Ft. Collins, CO Alan Ward, Utah Natural Heritage Program, Salt Lake City, UT Beth Ward, botanical consultant, Spearfish, SD Laura Welp, Wyoming Natural Diversity Database, Laramie, WY 2 CONTENTS Page Acknowledgements . 2 Introduction .................................................... 4 Methods .................................................... 4 Results ....................................................... 5 Discussion . 47 Literature Cited . 48 FIGURES 1. Wyoming Basins Ecoregion . map folder TABLES 1. Vascular Plant Species of Concern in the Wyoming Basins Ecoregion . 6 APPENDICES Appendix A. Potential Plant Conservation Sites in the Wyoming Basins Ecoregion . 52 Appendix B. Rejected Taxa . 68 3 INTRODUCTION The Wyoming Basins Ecoregion (WBE) comprises the eastern portion of the Intermountain Semi desert Province (Bailey 1995) and consists of a series of mid­ continental desert shrub and grassland basins and low mountain ranges bounded by the Utah/Wyoming and Colorado Rocky Mountains and Northern Great Plains ecoregions (The Nature Conservancy 1997). The WBE extends from the Montana border through central and southwestern Wyoming to extreme southeastern Idaho, northeastern Utah, and northwestern Colorado. The region includes the Bear River, Bighorn, Bridger, Great Divide, Green River, Hanna, Laramie, Shirley, Uinta, Washakie, Wind River, and Yampa River basins, as well as granite and sedimentary-cored uplifts in central Wyoming (Bridger, Ferris, Granite, Green, Owl Creek, Pedro, Rattlesnake, Seminoe, and Shirley mountains) (Figure 1). The Nature Conservancy (TNC) has identified the WBE as an important conservation area and TNC's Wyoming Field Office is currently working with neighboring states to develop a comprehensive, region-wide conservation blueprint. TNC has contracted with the Wyoming Natural Diversity Database and other regional heritage programs to determine which plant and animal species and native plant associations should be targets for ecoregional planning efforts, what the conservation goals for each target should be, and where potential conservation sites are located. This report summarizes the goals for selected vascular plant species and describes potential plant conservation sites in the WBE. METHODS Target vascular plant species were chosen because of their global rarity, limited geographic distribution, and evidence of decline based on data from state heritage programs and regional floras (Colorado Natural Heritage Program 1997, Cronquist et al. 1972, Dorn 1992; Fertig and Beauvais 1999, Goodrich and Neese 1986, Heidel1999, Idaho Conservation Data Center 1999, Stone 1998, Weber 1987, Welsh et al. 1993). Highest priority was assigned to WBE endemics or species known from 20 or fewer extant populations rangewide. Species at the periphery of their range were not included in this analysis, even though they may be considered "species of special concern" in their respective states. The final list of target species is included in Table 1 and excluded species are listed in Appendix B. For each target species, information was assembled on WBE distribution, abundance, and protection status from heritage databases, consultation with regional experts, recent floristic surveys, natural areas inventories, and relevant literature (Atwood et al. 1991, Cramer 1997, Delmatier 1998, Fertig 1992, 1995 a, 1998 a, Fertig and Jones 1997 a, 1997 b, Fertig et al. 1994, 1998, Haines 1988, Jones 1989, Jones and Fertig 1996, Lesica 1998, Lesica and Achuff 1992; Lichvar et al.1985, Marriott and Jones 1989, Roderick 1999, Spackman et al. 1997, Ward 1998, Weber 1987, Welp 1997, Welsh et al. 1993). These data were used to develop conservation goals for each target element that address the minimum number and distribution of populations needed to ensure long-term 4 survival. Point location data were also used to identify important biological areas that should be considered part of a "portfolio" of potential conservation sites (The Nature Conservancy 1997) (Appendix A). RESULTS 258 vascular plant taxa were initially evaluated as potential species of conservation concern in the WBE. Ofthese, 121 were selected as final targets based on their global rarity or high vulnerability to extirpation (Table 1). This number represents less than 1/3 of all plants endemic to the WBE area and surrounding foothills and basins (Fertig et al. 1998). Overall, the WBE has one of the highest rates of regional endemism for vascular plants in the north-central United States. The development of finite conservation goals for individual plant taxa is hampered by the lack of detailed knowledge about the life history, demographic structure, genetic composition, and metapopulation dynamics of most species (Given 1994, Primack 1993). In addition, the ability of many plants to produce long-lived seed banks and reproduce asexually confounds our abilities to determine the minimum population size needed for long-term survival (Menges 1991). While a universal "magic number" for the minimum viable population size of plants is probably unattainable (Givens 1994), theoreticians have suggested that minimum population sizes of 500 individuals may be sufficient for large-bodied, long-lived perennial plants of stable environments, while a minimum of 10,000 individuals might be needed for the survival of annual plants in unstable environments (Primack 1996). The number of individuals in a single population may be less important than the total number and spatial extent of all populations for ensuring the long term survival of a plant species (Given 1994). A conservation strategy that protects a suite of populations scattered across the full range of a species is likely to capture greater genetic variability than single populations and reduce the risk of a species being extirpated due to localized, stochastic environmental disturbances. How many sites are needed to ensure adequate representation will vary depending on a species' life history, growth form, population size, pollination biology, and genetic variability (Given 1994, Primack 1993). In the absence of concrete demographic and genetic data for most target species in the WBE, the following general strategy for plant species is proposed: * All populations of G 1 species should be candidates for protection or other special management attention, although priority should be given to the largest or most abundant colonies or those that occur at a distance from the core of the species' range. [continued on page 10] 5 Table 1 Wyoming Basins Ecoregion Target Vascular Plant Elements S-Rank Species G-Rank Range co ID MT UT WY Antennaria arcuata G2 Reg End Sl S2 Arabis crandallii G4 * Reg End S2 Sl Arabis lasiocarpa G3 NarEnd S3 Arab is pendulina var. G5T3 Reg End SR SR S3 russeola Arab is pulchra var. G5Tl NarEnd Sl duchesnensis Arabis pus ilia Gl NarEnd Sl Arabis selbyi G4?Q Reg End SR SR Sl Artemisia biennis var. G5TIQ NarEnd SR? Sl diflusa Artemisia porteri G2 NarEnd S2 Asclepias uncia/is G3? Disjunct SlS2 SH Astragalus chloodes G3 Nar End S3 Astragalus coltonii var. G4T3? Reg End SR SR Sl moabensis Astragalus detritalis G3 Reg End S2 S3 Astragalus diversifolius G3 Reg End Sl Sl SH var. diversifolius Astragalus drabelliformis G2G3 NarEnd S2S3 Astragalus duchesnensis G3 Reg End SlS2 SR Astragalus equisolensis Gl NarEnd SR Sl Astragalus gilviflorus var. G5T2 NarEnd S2 purpureus Astragalus grayi G4?* Reg End Sl S3 Astragalus hamiltonii Gl Nar End Sl or Sl SRF (?) Astragalus jejunus var. G3Tl NarEnd Sl articulatus Astragalus jejunus var. G3T3 Reg End Sl Sl Sl S3 jejunus Astragalus nelsonianus G2* Reg End Sl Sl S2 Astragalus oreganus G4?* Reg End Sl S3 Astragalus proimanthus Gl Nar End SP Sl Astragalus racemosus var. G5T3 Reg End S2 Sl treleasei Astragalus saurinus G3 NarEnd S3 Astragalus simplicifolius G3 Reg End S3 Astragalus wetherillii G3 NarEnd S3 SH Atriplex woljii G3G4 Reg End SR S2 Sl Chrysothamnus