Region 2 Sensitive Species Evaluation Form

ATTACHMENT SS2

REGION 2 SENSITIVE SPECIES EVALUATION FORM

Species: Evax prolifera / Big-head Evax

Criteria Rank Rationale Literature Citations Big-head evax is at or near the northern end of its distribution in Region 2. In • Dorn 2001 1 AD Wyoming, it is known only from the Hartville Uplift area in Platte County. A previous Distribution • Fertig 1997 within R2 report from Natrona County is based on a misidentified specimen of Psilocarphus • Great Plains Flora brevissimus. While this lies entirely with the Region 2 perimeter, the species is not Association known to occur on or near U.S. Forest Service-administered lands in Wyoming. It is • Hazlett et al. 1997 possible that it occurs on Thunder Basin National Grassland, and it was found to the • Heidel and Marriott 1996 north on Custer National Forest – Ashland District by Marriott (Heidel and Marriott • USDA Forest Service R2 1996). It also occurs in southwestern South Dakota, Colorado, and Nebraska, 2001 including the Oglala National Grassland. Additional information is needed from these states to determine its Region 2 status.

It is reported from "prairies, pastures, and stream valleys" (Great Plains Flora Association 1986). The single known Wyoming population occurs in disturbed mixed grass prairie on sandy loamy soil at 4800 feet.

Confidence in Rank Medium Big-head Evax is a Great Plains species ranging from southwestern South Dakota • Great Plains Flora 2 C and southeastern Montana to New Mexico and Texas. Distribution Association outside R2 • Heidel and Marriott 1996

Confidence in Rank High The inflorescences readily break from the flowering stalk when dry, and it may be • - 3 CD transported by wildlife or livestock (Heidel personal obs.) Dispersal Capability

Confidence in Rank Low It is known from one occurrence in Wyoming, discovered in 1996, and reported as • Hazlett et al. 1997 4 D "locally common" at the Camp Guernsey site. But it is not on or near national forest or Abundance in • NatureServe 2002 R2 national grassland. It is ranked “S1” in Wyoming, and “S5” in Nebraska. It is present but not tracked in Colorado, Kansas and South Dakota.

Confidence in Rank High

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Species: Evax prolifera / Big-head Evax

Criteria Rank Rationale Literature Citations Not known. • - 5 D Population Trend in R2 Confidence in Rank High

The habitat at the single known Wyoming occurrence was characterized as disturbed. • Hazlett et al. 1997 6 BD The first collection of this species in Montana was from a range experiment station in Habitat Trend in R2 the 1930’s, indicating that this species is resilient to disturbance if not an increaser under livestock grazing. If this were the case, then species’ habitat may be stable or increasing.

Confidence in Rank Low Probably low (see above). • - 7 CD Habitat Vulnerability or Confidence in Rank Low Modification Big-head Evax is an annual species. It has a highly-reduced flower covered by hairs • Stebbins 1974 8 D that may confer drought adaptation. Many annual species are self-pollinated and Life History and prolific seed-producers, adaptations for frequent colonization of new habitats (Stebbins Demographics 1974).

Additional information on the species’ biology is not available.

Confidence in Rank High Initial Evaluator(s): Date: 8 February 2002 Bonnie Heidel and Walter Fertig

National Forests in the Rocky Mountain Region where species is KNOWN (K) or LIKELY(L)1 to occur:

1 Likely is defined as more likely to occur than not occur on the National Forest or Grassland. This generally can be thought of as having a 50% chance or greater of appearing on NFS lands.

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Colorado NF/NG Kansas NF/NG Nebraska NF/NG South Dakota Wyoming NF/NG

NF/NG

y y

y y Known Likel Known Likel Known Likely Known Likel Known Likel Arapaho-Roosevelt NF Cimmaron NG Samuel R.McKelvie NF Black Hills NF Shoshone NF White River NF Halsey NF Buffalo Gap NG Bighorn NF Routt NF Nebraska NF Ft. Pierre NG Black Hills NF Grand Mesa, Ogalala NG X Medicine Bow NF Uncompahgre, Gunnison NF San Juan NF Thunder Basin NG ? Rio Grande NF Pike-San Isabel NF Comanche NG

Literature cited Dorn, R.D. 2001. Vascular Plants of Wyoming, third edition. Mountain West Publishing, Cheyenne, WY.

Fertig, W. 1997. Additions to the flora of Wyoming. Castilleja 16(3):5.

Great Plains Flora Association. 1986. Flora of the Great Plains. Univ. Kansas Press, Lawrence, KS.

Hazlett, D.L., C.A. Popolizo, and P.P. Douglas. 1997. Floristic survey of Camp Guernsey, Platte County, Wyoming. Unpublished report prepared the Wyoming National Guard by the Center for Ecological Management of Military Lands, Colorado State University, Ft. Collins, CO.

Heidel, B. and H. Marriott. 1996. Rare plant survey on the Custer National Forest – Ashland District. Report to the Custer National Forest. Montana Natural Heritage Program, Helena.

NatureServe. 2002. Explorer – an encyclopedia of life. Plant and animal data posted at www.natureserveexplorer.org, Arlington, VA.

Stebbins, G. L. 1974, 2nd ed. Flowering Plants, Evolution above the Species Level. The Belknap Press of Harvard University Press. Cambridge, MA.

USDA Forest Service – Region 2. 2001. “Wyoming plant species” evaluation list and criteria provided to Wyoming Natural Diversity Database. Denver, CO.

University of Wyoming – Rocky Mountain Herbarium. 1998. Atlas of the Flora of Wyoming. Posted electronically through 1998 at: http://www.esb.utexas.edu/tchumley/wyomap/ and unposted accession information at the Rocky Mountain Herbarium through 2001.

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