Lichens are pervasive across Wyoming. From the driest basins to the Rocky Mountain peaks, lichens inhabit the surfaces of soils, rocks, and wood (both living and dead). They play significant roles in biogeochemical cycling (Cornelissen et al. 2007, Nash 2008a), weathering (Stretch and Viles 2002, Hoffland et al. 2004), and soil stabilization (Belnap and Lange 2001) and contribute to aboveground productive biomass and biodiversity, especially in dry and cold climates (Nash 2008b). Lichens serve as an important or occasional source of forage for several Wyoming game animals (e.g., pronghorn, moose, elk, bighorn sheep), nongame mammals and birds, and a variety of invertebrates (Sharnoff 1994;  http://www.lichen.com/animals.html). The number of lichen species in North America (>3600 north of Mexico; Brodo et al. 2001) exceeds the number of North American bird and mammal species combined (< 1500; Kays and Wilson 2002;  http://www.birdwatching.com/software/birdlists/north_amer98.html), yet lichens have been, for the most part, overlooked by most biologists and the public.

Although the lichens of Wyoming have been surveyed sporadically, at best, lichenology has a long history in the region. More than 70 lichen specimens were collected by the Hayden Expedition of 1872. These specimens were sent to Henry Willey of New Bedford, MA, for identification and were reported in the sixth annual report of the USGS in 1873. Unfortunately, location information was given for only a few species, with Wyoming localities mentioned for 9 species (Hayden 1873). A decade and a half later, Tuckerman (1888) mentioned 2 lichens found in Wyoming (almost certainly by the Hayden Expedition): Buellia epigaea (Pers.) Tuck., “upon the earth in calcareous regions,” and “[O]n the North Platte river, Wyoming, accompanying, as in Europe, Placodium fulgens” [now Fulgensia fulgens (Sw.) Elenkin]. The former has not been recorded from Wyoming since, though it has been collected in neighboring states (CO, MT, UT, and ID; CNALH 2011).

The first compilation of lichens found for Wyoming was that by Aven Nelson (1900), botanist at the University of Wyoming. Nelson's list of 60 taxa was based primarily on his own collections around the state, with identifications provided by “Prof. TA. Williams of the Division of Agrostology of the U.S. Department of Agriculture.” Many of his collections were from underrepresented parts of the state, including Albany, Carbon, and Sweetwater counties. Unfortunately, some species have changed in both name and concept in the century since Nelson's work, and application of current names to Nelson's species was not always possible. As a consequence, only 36 of his taxa could be included in the current project. Fortunately, his specimens are still available at the Rocky Mountain Herbarium (University of Wyoming, Laramie, WY), awaiting further review.

Recent work has focused largely on federally managed parks and forests, especially Yellowstone National Park (Eversman 1990, Eversman et al. 2002, Eversman and Horton 2004, NPLichen 2011), Grand Teton National Park (Eversman 1998, NPLichen 2011), the Black Hills (Wetmore 1967, NPLichen 2011 for Devil's Tower NM), and the Big Horn Mountains (Wetmore 2009). Far less attention has been given to the basins and grasslands, though it must be pointed out that the majority of mountain ranges have not been surveyed.

The importance of biological soil crusts as contributors to biodiversity and ecosystem function has been recognized in recent decades (e.g., Belnap and Lange 2001, Bowker et al. 2010), yet their significance in Wyoming has barely been addressed. Generally speaking, the relative proportion of lichen biomass within biological crusts increases with cooler temperatures (Rosentreter and Belnap 2001), suggesting that lichens may contribute a significant portion of the carbon fixation in Wyoming's arid rangelands. Cyanolichens associated with biological crusts, along with free-living cyanobacteria, may also be an important source of fixed N in some arid ecosystems (Belnap 2002), thus increasing soil fertility. Only one study (Muscha and Hild 2006) has characterized biological soil crusts in Wyoming, although 2 others have identified Wyoming soil crust lichens as part of another project (St. Clair et al. 1993, States and Christensen 2001).

METHODS

Only published reports (print or webbased) of lichens have been included in this checklist, and no attempt has been made to examine herbarium collections or to verify identifications. Names have been standardized to Esslinger (2011), and synonyms combined. In a few cases, reported taxa were not included in Esslinger, or they were included but noted as misidentifications for North America. In both cases, those taxa have not been included in the final checklist. Older names, especially those applied by Nelson (1900), were difficult to associate with current nomenclature. Those taxa have also been excluded from the list.

Collection locations have been designated by county, with the exceptions of specimens from Yellowstone National Park (YNP) and a few records that did not specify exact locations. For those species recorded only from YNP, an effort was made to verify if the collection was made in Wyoming. Most of the included YNP records are known to be from the Wyoming portion of the park; however, some have not been verified as from the state. In most cases, verification was possible by searching the University of Minnesota Herbarium through the Consortium of North American Lichen Herbaria (CNALH) web site ( http://symbiota.org/nalichens/), or through the references cited on NPLichen. Sharon Eversman was very helpful in providing locations for species from her publications. In a few cases, verification was not possible; those records, mostly from NPLichen, are indicated with the location code Y^*. Similarly, a number of species from the Beartooth Plateau, which spans the Wyoming-Montana border, are not verified for Park County, Wyoming, and are designated with P?. All of those species, however, are verified from other locations within the state. Several authors gave no location information other than within the state (e.g., Neitlich et al. 1999), or locations were indicated very broadly (e.g., Thomson 1987, McCune and Goward 1995), and have been coded differently. See checklist footnotes for complete code information.

Global rank, an indicator of relative abundance and conservation status, was taken directly from the NatureServe web site ( http://www.natureserve.org/explorer/index.htm). Those species for which no rank is provided are not included in the NatureServe database. A complete explanation of the ranking codes is available at  http://www.natureserve.org/explorer/ranking.htm. In brief, the lower the number, the less common the taxon is on a global scale. Number ranges (e.g., G3G5) indicate that the true rank is thought to be within the range but has not been determined, and GNR indicates that the taxon has not been ranked. State ranks have yet to be assigned for any lichen in Wyoming.

Fig. 1.

Numbers of species recorded from Wyoming counties and Yellowstone National Park. Elevation contours are at 4500, 6000, 7500, 9000, and 12,000 feet. Map source:  geology.com/state-map/Wyoming.shtml

The list was compiled from approximately 1800 records from 25 published accounts and 2 online databases. The earliest published report that has been included is Tuckerman (1888); earlier reports from the Hayden expedition (Hayden 1873) have not been included because of the very sparse location information provided.

RESULTS AND DISCUSSION

Since 1888, at least 796 lichen taxon names have been reported for Wyoming and Yellowstone National Park. Standardization of names reduced the number by about 100 taxa, and 40 taxa were removed from the list because either the currently accepted names belong to taxa not found in North America, or because the current acceptable name could not be determined. Additional taxa were removed because they were recorded only from the Montana portions of YNP or of the Beartooth Plateau. The final list includes 608 taxa.

Figure 1 shows the distribution of recorded collections by county (or region, for YNP). Not surprisingly, Yellowstone National Park has the largest share of species—two-thirds of the species on the list are found in YNP Teton County has the greatest number of records outside YNP; nearly all of the reports are from Grand Teton National Park. Similarly, Crook County has a high number of collections from Devil's Tower National Monument (NPLichen 2011) and the Black Hills National Forest (Wetmore 1967), which extends into Weston County. The large number of species known from Sublette County are the result of a single project in the Bridger Wilderness Area (St. Clair and Newberry 1993), and all of the collections in Campbell County are from a single report (Medina 1994) covering the Rochelle Hills.

Clearly, most of the area has not been surveyed, even when relatively high numbers suggest otherwise. Albany County's figure is higher than many counties only because it was the home of Aven Nelson, who traveled and collected there and in Carbon County. Uinta County's 2 records are > 100 years old (Nelson 1900), and Lincoln County has only a single record, albeit fairly recent, and a type specimen (Xanthoparmelia lipochlorochroa Hale & Elix; Hale 1989, St. Clair et al. 1993).

All of the major surveys to date have occurred in the mountainous or hilly regions of the state; basin collections have been mostly sporadic and relatively small. An exception is Muscha and Hild's (2006) survey of soil crusts in basins, which added important, though small, numbers of species to Sweetwater, Fremont, Hot Springs, Washakie, and Natrona counties. Eight counties remain essentially unexplored for lichens (Lincoln, Uinta, Sublette, Laramie, Goshen, Platte, Niobrara, and Converse), despite the fact that most of these counties include mountain ranges and large tracts of federally managed lands. The distribution of lichen species in Wyoming must remain a mystery until much more of the state has been surveyed.

Approximately one-third (29%) of the species recorded from Wyoming have no global rank, either because they are not in the NatureServe database (7 taxa), or they are there but have not been ranked (code = GNR, GU or GUQ; 169 taxa). Of those that have been ranked, 3 of the rarest species are Xanthoparmelia spp.: X. neowyomingica Hale, X. norchlorochloa Hale, and X. lipochlorochroa Hale & Elix (global ranks G1, G1G2, G2?, respectively). Recent analysis of DNA sequences from western North American Xanthoparmelia indicates that these taxa should not be considered as distinct species (Leavitt et al. 2011). Xanthoparmelia lipochlorochroa and X. norchlorochroa are both found with the very common X. chlorochroa (Tuck.) Hale, and are similar in appearance and vagrancy. They have been distinguished on the basis of chemistry, with minor morphological differences (Hale 1990). Likewise, X. neowyomingica has been segregated from X. wyomingica (Gyelnik) Hale by its production of stictic rather than salazinic acid, and both species are distinguished from X. chlorochroa because of their attached habit and presence of apothecia (Hale 1987, 1989, 1990). Leavitt et al. (2011) provided strong evidence based on fragments of 2 protein-coding nuclear loci and 4 nuclear ribosomal markers that these 5 taxa, along with X. cumberlandia (Gyelnik) Hale, X. coloradoënsis (Gyelnik) Hale, X. neochlorochroa Hale, and 2 additional species not reported for Wyoming, constitute a single, commonly-occurring polymorphic taxon. These 8 species of Xanthoparmelia remain on the list pending acceptance or rejection of the new molecular information.

Potentially rare species (global rank G2G3 to G2G5), other than Xanthoparmelia, found in Wyoming are Bacidia vermifera (Nyl.) Th. Fr., Cladonia imbricarica Kristinsson, Micarea denigrata (Fr.) Hedl., Parmelia omphalodes (L.) Ach., Psora luridella (Tuck.) Fink, Rhizoplaca haydenii (Tuck.) W.A. Weber, Thelocarpon epibolum Nyl., Umbilicaria hirsuta (Sw. ex Westr.) Hoffm., and Usnea baileyi (Stirton) Zahlbr. Seven of these 9 species were recorded only once or twice from the state; however, 2 species, Micarea denigrata and Rhizoplaca haydenii, were recorded 4 and 5 times, respectively, from as many counties. Rhizoplaca haydenii is a vagrant, growing on soils and calcareous gravels “at fairly high altitudes on barren, windswept terraces” (Brodo et al. 2001). Its distribution is limited to Wyoming and parts of adjacent states (Brodo et al. 2001), hence its G2G3 rank. In Wyoming, it has been recorded from the Big Horn Mountains, from Albany, Carbon, Natrona and Sweetwater counties, and from the Beartooth Plateau. Micarea denigrata, on the other hand, has a much broader distribution, including North America and northern Europe (CNALH 2011).

Several of the potentially rare species may not be globally rare, but are regionally rare. For example, Usnea baileyi is not known from western North America (Brodo et al. 2001, CNALH 2011), Bacidia vermifera is sparsely distributed only in Arizona and Colorado (CNALH 2011), and Psora luridella, while common in the central and southern Rocky Mountains, is not common to the north (McCune and Goward 1995). Of the 608 taxa recorded from Wyoming, 181 (30%) have been reported only once, but whether these taxa are truly rare in the state cannot be determined because of the limited collecting in most of Wyoming.

Approximately 9% of the lichens on the list are cyanolichens, a number just slightly lower than the worldwide proportion of 10% (Nash 2008a). Several species appear to be widely distributed across the state, including Collema tenax (Swartz) Ach. and a number of Peltigera species. Collema tenax contributes significant amounts of nitrogen to desert soils of Utah (Belnap 2002) and is the most widespread of the cyanolichens in Wyoming. It is included in several general reports and in reports from 6 soil crust sites (States and Christensen 2001, Muscha and Hild 2006).

Significant contributions to the current list can be made without fieldwork, though the value of field surveys cannot be understated. The Consortium of North American Lichen Herbaria web site includes more than 5600 specimens in 15 herbaria that were collected in Wyoming, of which only a relative few have been published and therefore are not included in the current checklist. The Rocky Mountain Herbarium, which is not a member of CNALH, has hundreds of lichen specimens dating from the time of Nelson to the present, though only a portion are from Wyoming. Regional herbaria may also contain additional taxa from Wyoming; the University of Colorado Museum contains 100,000 lichen specimens, with an unknown number from Wyoming (WA. Weber, personal communication). As understanding and appreciation of the functional diversity and ecosystem services provided by lichens increases among ecologists and land managers, the study of lichens and lichen communities will hopefully play a more important role in ecological studies. Basic knowledge of the species involved is fundamental to an understanding of the ecological roles of lichens.