The "Martian" flora: new collections of vascular plants, lichens, fungi, algae, and cyanobacteria from the Mars Desert Research Station, Utah

Abstract The Mars Desert Research Station is a Mars analog research site located in the desert outside of Hanksville, Utah, U.S.A. Here we present a preliminary checklist of the vascular plant and lichen flora for the station, based on collections made primarily during a two-week simulated Mars mission in November, 2014. Additionally, we present notes on the endolithic chlorophytes and cyanobacteria, and the identification of a fungal genus also based on these collections. Altogether, we recorded 38 vascular plant species from 14 families, 13 lichen species from seven families, six algae taxa including both chlorophytes and cyanobacteria, and one fungal genus from the station and surrounding area. We discuss this floristic diversity in the context of the ecology of the nearby San Rafael Swell and the desert areas of Wayne and Emery counties in southeastern Utah.


Introduction "Hell yeah I'm a botanist! Fear my botany powers!" -Mark Watney (The Martian, by Andy Weir).
The Mars Desert Research Station (MDRS) (http://mdrs.marssociety.org/) is a Mars analog research site located in the desert approximately 9 km outside of Hanksville, in Wayne County, Utah, U.S.A. at 38°24'23.12"N, 110°47'30.94"W (Figs 1, 2). The station is located 5 km north of Utah State Route 24 along Cow Dung Road, which continues north for another 5 km to the Burpee Dinosaur Quarry, a recently described bone bed from the Jurassic Morrison Formation (Mathews et al. 2009).
Constructed by the Mars Society (http://www.marssociety.org/) in 2002 and operated continuously ever since, MDRS, and its Arctic counterpart, the Flashline Mars Arctic Research Station (FMARS) (http://fmars.marssociety.org/), on Devon Island, Nunavut, Canada, are designed as testbeds for future manned missions to Mars (Bamsey et al. 2009). Visiting crews from multiple scientific and engineering disciplines conduct research at the stations on how to live and work on Mars without having to leave Earth.
Astrobiology, the study of the evolution and distribution of life throughout the universe (including Earth), is a field increasingly represented at MDRS. Professionals in the field seek to refine techniques to detect life on other worlds, and to answer outstanding questions about the origins of life here on Earth (Thiel et al. 2011). At MDRS, astrobiologists have conducted studies ranging from the detection of biomarkers (Martins et The Mars Desert Research Station near Hanksville, Utah. The large white building on the left is the primary living and working structure (commonly known as the "hab"). To the right of the hab is the station's greenhouse (the "GreenHab"). This photo shows the original GreenHab, burned down on December 29th, 2014, and has since been replaced. The white building to the right is the Musk Observatory. Photo by P.C. Sokoloff. Photo taken on November 16th, 2014. al. 2011) and extremophiles (Direito et al. 2011) in the local soils, to the automated detection of life using computer algorithms (Gross et al. 2009), and more. This search for life in extreme environments on Earth is an excellent analog to the search for life on Mars. During their studies, astrobiologists, soil specialists, geologists and other scientists working at MDRS frequently come across, or seek out, vascular plants, lichens, algae, cyanobacteria, and fungi while conducting field research.
Utah is a floristically diverse state, with some 2995 vascular plant species and infrataxa distributed in diverse ecosystems (Welsh et al. 1993). The cool deserts of southeastern Utah, where MDRS is located, possess diverse vascular plant (Andersen 1996) and biological soil crust communities (Belnap 2002). The distribution of these communities is determined primarily by the underlying geology, elevation, and moisture, all of which vary across the deserts of the region (Coles et al. 2009).
There is a long history of floristic work in southeastern Utah. Complete vascular plant inventories exist for two ecologically similar areas close to MDRS: Capitol Reef National Park (Heil et al. 1993, Fertig 2009) and Glen Canyon National Recreation Area (Hill and Ayers 2009). The latter location contains the Orange Cliffs, which have a well-studied vascular plant flora (Shultz et al. 1987). Fertig (2009) presents a comprehensive overview of previous vascular plant collection efforts throughout the region. The closest and best studied flora near MDRS is that of the San Rafael Swell, approximately 23 km northwest of the station. Harris (1983) compiled a vascular plant inventory, including 478 species, for this large geological feature that dominates southeastern Utah. The inventories of vascular plants from the San Rafael Swell and Capitol Reef National Park provide a useful comparison to our own study region at MDRS. All three sites share common geological characteristics, notably the Mancos Shale and Morrison Formation (Coles et al. 2009, Direito et al. 2011, Gilluly 1929. These locations also share many common vascular plant communities based on this underlying geology. For example, the vascular plant communities of the desert flats immediately surrounding MDRS correspond well to the description of the "Salt Desert Shrub Zone" in Harris (1983), which is characteristic of the Mancos Shale (Coles et al. 2009). The vegetation found on nearby sandstone outcrops and plateaus relate to the "Mixed Desert Shrub Zone" (Harris 1983). The alkaline clay soils of the station area are dominated by Achnatherum hymenoides, Atriplex sp., Eriogonum inflatum, and Kali tragus, while the sandstone outcrops support communities of Artemisia sp., Ephedra viridis, and Dasyochloa pulchella.
Where these two ecological zones meet north of MDRS near Kent's Reservoir (a small pond immediately west of Cow Dung Road at 38°25'27.70"N, 110°47'17.01"W), there is an ecological gradient, including water-intensive stands of Tamarix ramosissima on wet alkaline soils of the Salt Desert Zone, mixed with Artemesia and Ericameria nauseosa, both characteristic of the Mixed Desert zone (Harris 1983). Further north along Cow Dung Road, the floodplains of a seasonally wet creek support healthy stands of Sarcobatus vermiculatus and other species that are known from the floodplains of the Salt Desert Zone (Harris 1983). This wide variety of habitat types, all differentiated by water availability and geological substrate, support a diverse vascular plant flora around MDRS.
The lichen flora of eastern Wayne County, in which MDRS is located, and adjacent eastern Emery County includes approximately 61 species. This is an estimate based on a catalogue of the lichens of Utah (St. Clair et al. 1991), notes on the state's lichen flora (Newberry and St. Clair 1991, St. Clair et al. 1995, and a flora of the terricolous lichens of the San Rafael Swell (Rajvanshi et al. 1998). A large part of this regional flora was found on soil (28) or rock (26). Of the total, seven species from Capitol Reef National Park in Wayne Co. were collected on either Juniperus, which was not observed in the study area, or on wood (e.g., dead shrubs), which was not examined for lichens during this study. The number of 61 reported lichen species for the reference region is dated and therefore likely a conservative estimate of the potential number of species to be found in the study area.
Given the diverse local flora, and the increasing prevalance of biological studies at MDRS, our primary objective for this study was to collect and identify the vascular plants, lichens, fungi, and endolithic cyanobacteria and algae (sub-surface photosynthetic life) at MDRS. These endolithic taxa are of particular interest to astrobiologists as model systems in the search for life on Mars (Direito et al. 2011). A secondary objective of our fieldwork was to practice and evaluate the techniques needed to collect biological samples during simulated Martian fieldwork.

Fieldwork
From November 15-30, 2014, Paul Sokoloff participated in MDRS Expedition 143 (http:// mdrs.marssociety.org/home/crew-143) as Crew Biologist, and was part of a six-person crew staying at MDRS for an 11-day simulated mission to Mars. Over the course of five extra-vehicular activities (EVAs: all activities that take place outside the "hab" while in simulation), representing approximately 20 hours of collecting time, all vascular plant, lichen, fungi, and endolithic cyanobacteria and algae species encountered (except for completely dead, unidentifiable vascular plants), were collected by Paul Sokoloff with the assistance of other crew members (typically one other crew member per trip). In each area visited, as many microhabitats as possible were explored for unique plants and lichens. EVA teams wore simulated spacesuits, consisting of overalls, hiking boots with gaiters, thick gloves, a backpack containing a fan (the simulated oxygen supply), and a clear bubble helmet. These simulated suits let field teams practice standard field work activities while having to cope with restricted vision and movement, both obstacles that would have to be overcome on a real mission to Mars (Fig. 3).
While on EVAs we used standard collection techniques: plant samples were dug out at the roots or clipped from larger trunks, crustose lichens and cyanobacteria were chiseled away from rocky substrates, material was placed in numbered sample bags, coordinates were logged using a standard GPS receiver, and collection site notes were recorded. Owing to their fragile nature and the requirement for special collecting techniques, no effort was made to collect any of the soil crust lichens that might be found at MDRS. Specimens were MDRS Expedition 143 Commander Paul Knightly walking through stands of Ericameria nauseosa (Sokoloff 284, large yellow shrubs) and Ephedra viridis (wiry green shrub at centre of photo) at Kent's Reservoir while wearing a simulated spacesuit. Photo by P.C. Sokoloff. pressed and processed as appropriate inside the lab at MDRS (where simulated spacesuits were not required).
Where possible, photographs of the specimen in situ and of the habitat were taken at the time of collection. These photos are included in the species accounts below. Photos by C.E. Freebury, P.B. Hamilton, and those in Figures 8 and 10 by P.C. Sokoloff were taken under laboratory conditions in Ottawa. All other photographs were taken in the field. Photographs of vouchered lichen and vascular plant specimens include the collection number, while photographs of plants that were not collected include the location at which the photo was taken and the date.
In total, we collected 46 vascular plant specimens, 18 lichen samples (some of which were subdivided upon return to Ottawa), three rock samples containing endolithic cyanobacteria and algae, and one fungus from 10 collection sites during Expedition 143 (Fig. 2). These collection sites were chosen based on satellite images and topographical maps as representatives of the common habitat types around MDRS, so as to maximize the number of different species collected. The Mars Desert Research Station is situated in the southwest corner of this study area: our furthest north (five km from the "hab") and east (two km from the "hab") collection sites delimit an approximately 10 km2 area covered by this study.
lichen specimens at CAN and CANL were scanned and/or photographed, and are presented here as supplemental files, as cited in the species descriptions.

Algae and Cyanobacteria Identification
Selected fractured rock samples (Sokoloff 249,290,301) were examined at the Canadian Museum of Nature lab with an Olympus SZX12 dissecting microscope. Observed zones of endolithic algae and cyanobacteria were sampled by selectively isolating the algae from associated granular stone particles. Stone fragments with algae and/or cyanobacteria were picked and either cultured or placed on a microscope slide and squashed for direct examination. Culturing was conducted using 5 ml of sterile BBM Medium in 50 ml falcon tubes held at 22°C under natural and ambient light during the day. After two weeks the cultures were examined. Compound microscope examinations of original and cultured squash samples were initiated after stone fragments were removed from the slides before a semi-permanent slide mount was prepared. A Leica DMR HC microscope with differential interference contrast (DIC), phase contrast and bright field optics was used with a 100x Plan Apo (NA 1.35) objective for all microscopic examinations. Identifications were primarily based on the taxonomic treatments of Komárek and Anagnostidis (1999) and Ettl and Gärtner (2014).

Algae and Cyanobacteria Collections Phylum Chlorophyta and Phylum Cyanobacteria
Notes: Six taxa of endolithic and endophytic algae and cyanobacteria were identified in this study. Two taxa independently (Trebouxia sp. 1 & Gloeocapsa sp.) formed a mixed layer (predominantly Gloeocapsa sp.) 1-4 mm below the surface within one sandstone sample (Sokoloff 290,Figs 4,5). In a quartz sample (Sokoloff 301), Gloeocapsa sp. was the dominant taxon growing on the underside of a quartz rock found embedded in desert sand, along with an unknown chlorophyte (Chaetophorales) within crevices of the rock. In another sample, Trebouxia sp. 1 was also observed as a distinct layer 1-4 mm below the sandstone surface (Sokoloff 249). On average, there was 1-6 sand grains of varying shapes, sizes and orientation between the outer surface and the endolith. The algae layer varied from 0.5 to 1.5 mm in thickness and ranged from disrupted to continuous. In the three samples collected, the expanse of these layers ranged from 0.5 cm to 2.5 cm . In two samples (Sokoloff 249,290) lichens (Lecanora cf. garovaglii, Acarospora strigata) were scattered across the surface with subsurface expansions of the fungi into the sandstone (Fig. 6d, Fig. 7). Scattered fungi were also observed within the endolithic algae layers (Fig. 5). In two lichen samples examined for photobionts, Heteroplacidium compactum (Sokoloff 296) and Placidium acarosporoides (Sokoloff 305), the alga Myrmecia sp. was observed within the lichens.    In culture cells were spherical, up to 19 μm in diameter, the cell wall sheath <0.5 μm. Chloroplast plate-like, sometimes lobed, covering most of the cell. One pyrenoid present, at times difficult to distinguish. In the natural population the cell wall sheath was thick, up to 1.5 μm. Colonies of daughter cells tightly packed, forming wedgeshaped colonies in spherical to elliptical clusters. Endolithic, forming a fine linear layer (flake-like) 0.1-0.4 mm below surface of sandstone. Notes: Cells elliptical to spherical, 7-21.0 μm in diameter (Fig. 7 a-f). In culture cells were spherical, up to 19-22 μm in diameter and the cell wall sheath was <0.5 μm. Chloroplast large, plate-like to lobed, covering most of the cell. One pyrenoid present, at times difficult to distinguish. In the natural population, the cell wall sheath was <1.5 μm. Colonies of daughter cells tightly packed, forming wedge-shaped colonies in spherical to elliptical clusters. This was found in two lichen species (Acarospora strigata and Lecanora cf. garovaglii) forming a fine linear layer 5-100 μm thick, approximately 75-100 μm below the lichen surface. Notes: Cells spherical to weakly elliptical, 7.0-15.0 μm in diameter (Fig. 8 a-c). Chloroplast plate-like, covering most of the cell. Culturing of this taxon was not successful. Pyrenoid difficult to distinguish. Cell wall sheath 1-2+ μm thick. Small clusters of cells, or colonies of daughter cells. Endophytic within an unidentified lichen (brown-black spheres) from the Verrucariaceae family (Fig. 8). Notes: Cells spherical to weakly elliptical, 12-15.0 μm in diameter (Fig. 4 e-f). Chloroplast lobed, covering most of the cell. One to many pyrenoids present, at times difficult to distinguish. In the natural population the cell wall sheath was thin <0.8 μm. Small colonies of daughter cells tightly packed in forming broad wedge-shaped colonies in spherical to elliptical clusters. Endolithic, scattered with Gloeocapsa sp. 0.1-0.4 mm below the sandstone surface. Notes: Cells elliptical, length 6.5-15.5 μm, width 5-12 μm (Fig. 9). Chloroplast platelike (1-many), covering most of the cell. Pyrenoid absent. Cell mucilage 0.5-1.5 μm thick. Endophytic, within two species of lichen in family Verrucariaceae (Fig. 9). Earlier descriptions of M. biatorellae indicated a broad range in cell size, however a more recent treatment of the genus (Ettl and Gärtner 2014) suggests that cells of M. biatorellae are larger than the cells observed here.   Notes: Cells small ovals, found as single cells, two cell clusters or in small clusters of daughter cells within thin firm colourless sheaths. Length 2.5-5(6) μm by 1.5-3 μm wide, cell wall sheath thickness 0.8-1.6 μm. Mats of cells form as a collection of single cells or clusters of daughter cells closely packed together. Layer occurring 0.1-0.4 mm below the sandstone surface, or on the underside of quartzite rocks (Fig. 10).

Fungus Collections Family Agaricaceae
Tulostoma sp. Notes: This is a diverse woody mushroom genus common in deserts of the southwestern United States (Hernandez Caffot et al. 2011). This specimen was found growing on sandy soils on top of the plateau immediately southwest of MDRS. Unfortunately, the specimen was too old and degraded for anything other than a generic determination (Scott A. Redhead, personal communication) (Fig. 11). Gloeocapsa sp ( Sokoloff 301). A blue-green layer of cyanobacteria (and an unknown chorophyte) growing on the underside of quartzite stone (stone has been flipped and the surface previously exposed is at the bottom of this photograph). Photo by P.C. Sokoloff.

Lichen Collections
Family Acarosporaceae Acarospora peliscypha Th. Fr. Notes: Acarospora peliscypha is an epruinose species; the whitish material on this specimen, as shown on the right side of Fig. 12, is not pruina but represents an accumulation of necrotic material. Although we were unable to find previous published reports of this species from Utah, we did examine one previous collection from that Tulostoma sp. (Sokoloff 308). Photo by P.C. Sokoloff. state. This species has been described from the Sonoran Desert as growing on granite only (Knudsen 2007), however we found the species on partially calcareous sandstone.  Acarospora peliscypha (Sokoloff 286 Notes: This lichen was encountered growing on sandstone and parasitically on Caloplaca trachyphylla (Fig. 13) in the shade of a large rock due northeast of MDRS. Acarospora stapfiana has been previously reported from Capitol Reef National Park (St. Clair et al. 1995).   Notes: This greyish-white crustose lichen was commonly encountered growing on sandstone rocks surrounding MDRS (Fig. 14). The species was previously reported from eastern Wayne County by St. Clair et al. (1991).    Notes: Small sample, ca. 2 cm diam.; on sandy soil. Enchylium tenax (syn. Collema tenax (Sw.) Ach.) (Otálora et al. 2013) is a cosmopolitan species that is widely variable in terms of habit, color and isidia (Schultz et al. 2004). This particular specimen ( Fig.  17) has somewhat ascending lobes and lacks apothecia. The species was previously reported as Collema tenax from the San Rafael Swell by Rajvanshi et al. (1998).  Notes: Cortex KC+ gold (usnic & isousnic acids). Lecanora garovaglii (Fig. 18) is common throughout the semi-arid regions of central North America (Brodo et al. 2001). It has been previously reported from Boulder Mt. Plateau, Wayne County by Leavitt and St. Clair (2008).  Notes: Buellia abstracta has sometimes been treated incorrectly as Buellia sequax (Nyl.) Zahlbr. (Bungartz et al. 2007, Giralt et al. 2011, and it has been reported as such from southwestern Utah (Bungartz et al. 2004). We have been unable to find reports of the species from the San Rafael Swell or other nearby areas. Notes: This species was one of the most conspicuous lichens encountered on EVAs (Fig. 19). One specimen (Sokoloff 252) was collected on a rock inside the passageway connecting the MDRS "hab" with the Musk Observatory. Though we follow Brodo et al. (2001) in treating this species as a member of Caloplaca, some authors treat this species as Xanthomendoza trachyphylla (Tuck.) Frödén, Arup & Søchting (Arup et al. 2013). Caloplaca trachyphylla is common in western North America (Brodo et al. 2001 St. Clair et al. (1991). This lichen begins as a parasite on other lichens, and then grows independently. Fig. 20 shows our specimen growing partly scattered among and likely parasitic on Caloplaca trachyphylla. Notes: Placidium acarosporoides was found growing on calcareous sandstone in the vicinity of MDRS (Fig. 21). It has been reported previously from eastern Wayne County by Thomson (1987) as Catapyrenium acarosporoides (   Notes: This soil crust lichen is common in the Great Basin desert shrub lands and on the Colorado Plateau (St. Clair et al. 1991). The lower cortex is comprised of a distinct layer of globular cells, 20-70 μm high, with the lowermost cells brown to black. Breuss (2002) describes the lower cortex with angular cells in distinct vertical columns.

Material
McCune and Rosentreter (2007) provide a photo that shows +/-globular cells in a nonaligned pattern. Brodo et al. (2016) describe the cells of the lower cortex as spherical and sometimes in vertical columns, which corresponds well with our specimen (Fig.  20b). Other key characteristics of Placidium lachneum include the presence of marginal pycnidia and hyphal wefts that help to attach the lichen to the soil, as shown in Fig.  22c.  (Stutz 1978), both of which are found in the study area. This species is known from the nearby San Rafael Swell (Harris 1983  Notes: This was one of the most commonly encountered species in the vicinity of MDRS (Fig. 23), and was seen on sandy desert flats throughout the study area. This species displays a great deal of phenotypic plasticity throughout its range, and hybridizes readily wth other sympatric species of Atriplex, complicating taxonomic delimitation (Stutz 1978). Previously recorded in the nearby San Rafael Swell as Atriplex cuneata A. Nelson (Harris 1983), here we follow Welsh (2003)  Notes: This introduced species is highly invasive in the western United States, flourishing in disturbed habitats and alkaline soils (Holmgren 2003). It was commonly encountered along Cow Dung Road, and has flourished in the disturbed areas immediately surrounding MDRS (Fig. 24). This species was previously recorded for the nearby San Rafael Swell (Harris 1983   noxious weed found throughout the southwestern United States (Welsh et al. 1993 Notes: Common on the plateau just west of the MDRS (Fig. 26) this species is abundant on sandy substrates of the region (Shultz 2006), and was previously reported for the nearby San Rafael Swell (Harris 1983).   (Harris 1983). Urbatshc et al. (2006), whose treatment we follow here, accept 21 varieties in North America; however we were unable to identify our specimen to variety as the diagnostic phyllaries were missing. Notes: Abundant on the rocky outcrops, desert shrub communities (Fig. 28), and plateaus surrounding MDRS, this species is well adapted to disturbance in Utah's desert rangelands (Welsh et al. 1993). Gutierrezia sarothrae was previously reported from the nearby San Rafael Swell as Xanthocephalum sarothrae (Pursh) Shinners (Harris 1983). Gutierrezia is now segregated into a distinct genus (Nesom 2006 (2006), who had previously placed this species in Scabrethia (Weber 1998). We were unable to identify this specimen to subspecies as the diagnostic phyllaries were missing (Fig. 29) .       Notes: This species was common along the banks of a seasonally wet stream crossing due northeast of MDRS (Fig. 32). This species was previously recorded from the nearby San Rafael Swell as Opuntia basilaris (without infraspecific rank) (Harris 1983). Morphological variability and hybridization have hindered infraspecific delineation in this species, and many named varieties appear in the literature, including four in Welsh et al. (1993), and a different set of four in Pinkava (2003); here we follow the latter treatment.  Notes: Opuntia polyacantha was the more common of the two Opuntia species recorded near the station, and was frequently encountered in the Ephedra-Atriplex-Achnatherum shrubland deserts north of MDRS (Fig. 33)  Opuntia polyacantha var. polyacantha (Sokoloff 293). Habitat. Photo by P.C. Sokoloff. Notes: A common species of dry hills and desert slopes (Stevensen 1993), we collected this species along mesa tops and desert scrub communities north of MDRS along Cow Dung Road (Fig. 34). This species was previously reported for the nearby San Rafael Swell (Harris 1983  Notes: This species was common on sandy soil in Atriplex-Ephedra communities due north of MDRS (Fig. 35). Harris (1983) reported two varieties of this species from the nearby San Rafael Swell: Astragalus amphioxys var. amphioxys and Astragalus amphioxys var. vespertinus (E. Sheld.) M.E. Jones. Both varieties are recognized in Barneby (1964) and Welsh (2006), which follow a nearly identical taxonomy, however we were unable to determine these collections to variety as the plants were neither flowering nor fruiting.

Figure 35.
Astragalus amphioxys (Sokoloff 276 Notes: This species was only encountered once in the MDRS vicinity, due northwest of MDRS (Fig. 36). Harris (1983) reported two varieties of this species from the nearby San Rafael Swell: Astragalus lentiginosus var. araneosus (E. Sheld.) Barneby and Astragalus lentiginosus var. palans (M.E. Jones) M.E. Jones. Both of these varieties are accepted in both Barneby (1964) and Welsh (2006) however, we were unable to determine our collection to variety as this specimen was vegetative.

Family Juncaceae
Juncus bufonius L.  Sphaeralcea coccinea (Sokoloff 260 Notes: Common in Atriplex-Ephedra communities (Welsh et al. 1993), this species was found growing in the disturbed sandy areas immediately surrounding MDRS (Fig. 37). This species was previously recorded in the nearby San Rafael Swell (Harris 1983 Notes: This species was previously reported for the nearby San Rafael Swell (Harris 1983 ), and is common in desert shrub communities (Welsh et al. 1993). Notes: Common on disturbed sands and desert shrub communities in the vicinity of MDRS (Fig. 38), this species was previously recorded in the nearby San Rafael Swell as Oenothera caespitosa Nutt. (Harris 1983). Here we follow Welsh et al. (1993) and treat these specimens as var. navajoensis, based on the characteristic fringe of trichomes on the leaf margin.  (2007) who recognize the taxon in Achnatherum. Common across our study area, we encountered this species throughout the deserts surrounding MDRS (Fig. 39). Notes: Though not previously reported in a survey of the nearby San Rafael Swell flora (Harris 1983 ), this species was recorded for nearby Capitol Reef National Park (Fertig 2009). This species was collected once in an old, dried wash northeast of MDRS, and photographed in the vicinity of the Burpee Dinosaur quarry at the northern end of Cow Dung Road (Fig. 40). Varieties in B. barbata are recognized by both Wipff (2005)  Notes: A noxious weed common throughout the southwestern United States (Pavlick and Anderton 2007), this species was previously reported for the nearby San Rafael Swell (Harris 1983 ), and was common in the immediate vicinity of MDRS.  (Harris 1983), recent work has placed this species in the monotypic genus Dasyochloa (Caro 1981, Valdés-Reyna 2003.  2005), and was common in the vicinity of MDRS (Fig. 41). This species was previously reported for the nearby San Rafael Swell (Harris 1983 Notes: This species was previously reported for the San Rafael Swell (Harris 1983 ), and was encountered on sandy soils north of MDRS (Fig. 42). Welsh et al. (1993) recognize two varieties in S. airoides, however Peterson et al. (2003) do not. We follow the latter treatment here. Notes: Common in the desert shrub communities near MDRS (Fig. 43), and typical of sandy soils and salt deserts (Peterson et al. 2003), this species was previously reported for the nearby San Rafael Swell (Harris 1983 (Harris 1983). These two varieties have been differentiated by substrate (fine textured shales on the Colorado Plateau in var. fusiforme, vs. coarse sandstone in var. inflatum), root and caudex size, and annual vs. perennial life history (Harris 1983). Reveal (2005), who we follow here, ascribe var. fusiforme to an "annual phase", and do not recognize these varieties. Eriogonum inflatum was common in the deserts surrounding MDRS (Fig. 44).  Eriogonum inflatum (Sokoloff 262). Habit. Photo by P.C. Sokoloff.  Eriogonum shockleyi (Sokoloff 315 Notes: A common species on alkaline habitats (Hils et al. 1993), Sarcobatus vermiculatus was found in greatest abundance along the banks of a seasonally wet stream crossing due northeast of MDRS (Fig. 46). Previously placed within the Chenopodiaceae, Sarcobatus is now recognized as the sole genus within the Sarcobataceae (Behnke 1997;APG III 2009). This species was previously recorded for the nearby San Rafael Swell (Harris 1983).

Material
Supplemental File: CAN 607490 (Suppl. material 69). Sarcobatus vermiculatus (Sokoloff 274 Figure 47. Tamarix ramosissima (Sokoloff 285). Habit and habitat. The large shub to the centre-right of the photo is Tamarix ramosissima, the yellow shrubs to the left are Ericamerica nauseosa. Photo by P.C. Sokoloff. This species has previously been reported for the nearby San Rafael Swell (Harris 1983). Only one population was encountered in the vicinity of MDRS, consisting of three shrubby trees and multiple seedlings, around Kent's Reservoir -a pond on the west side of Cow Dung Road north of MDRS (Fig. 47).

Vascular Plants
The most species-rich vascular plant families reported from MDRS included the Asteraceae (nine species), and the Poaceae (eight species). These two plant families were also the largest reported for nearby Capitol Reef National Park (Heil et al. 1993). The most species-rich genera in the study area were Atriplex and Astragalus, both of which are extremely diverse throughout the southwestern states (Stutz 1978, Welsh et al. 1993). We recorded three species in each of these two genera at the site. Crews at MDRS often must balance multiple research, habitat maintenance, and outreach activities while in simulation. Time spent on EVA is therefore tightly controlled to accomplish these diverse goals, to simulate realistic work pacing, and because radiation exposure will likely limit EVA time on an actual mission to Mars. Therefore, many studies at MDRS take place within close proximity to the hab, and the species present at the hab are likely of primary interest to most investigators. spathulata, Gutierrezia sarothrae, and Hymenoxys cooperi. We observed higher vascular plant diversity, and many examples of completely dead, unidentifiable (and therefore not collected) plant species on this plateau than on the desert flats surrounding the station. Therefore researchers at MDRS should take care when identifying vascular plant species from the plateau, as they may not be treated here.
Future floristic work at MDRS should focus on collecting in warmer seasons, when vascular plants are flowering, as this will undoubtedly yield new records for the station. This would also ensure that geophytes, if present, would be recorded. Geophytes are vascular plant species which die back each year and lay dormant underground (Dafni et al. 1981), and are therefore unlikely to be found during a fall/winter survey such as ours. Several geophyte species, notably the sego lily (Calochortus nuttallii) have been recorded from both the San Rafael Swell (Harris 1983), and Capitol Reef National Park (Fertig 2009), and thus may be present at MDRS.

Lichens
Overall, we collected 13 lichen species from nine genera. Given the lichen diversity documented from nearby sites (i.e. Rajvanshi et al. 1998, St. Clair et al. 1991, these 13 species likely represent a small sample of the true lichen diversity at MDRS. Further exploration will be required to generate a more comprehensive local checklist.
The following ten species were collected from the desert flats and outcrops within a 500meter radius of the research station: Acarospora rosulata, A. stapfiana, A. strigata, Buellia abstracta, Caloplaca trachyphylla, Candelariella rosulans, Enchylium tenax, Placidium acarosporoides, P. lachneum, and Polysporina gyrocarpa. Acarospora strigata was also collected on the rim of the plateau about 400 meters southwest of, and about 34 meters in altitude above the station. Another three species, Acarospora peliscypha, Heteroplacidium compactum and Polysporina gyrocarpa, were collected along Cow Dung Road between 1.5 and two kilometres north of the station. Ten species were growing on rock, while Enchylium tenax and Placidium lachneum were collected on sandy soil. Two species, Acarospora stapfiana and Heteroplacidium compactum, were found growing independently on rock and parasitically on other lichens. We were unable to find previous published reports of Acarospora peliscypha for Utah, and the two specimens reported here may represent new records for the state.
The gypsiferous soils of southeastern Utah are well-known habitats for lichen soil crusts (St. Clair et al. 1991) and provide future opportunities to add to the flora of the research area and practice the techniques required to collect delicate species on fragile substrates. As well, lower sagebrush (Artemisia) branches on desert flats, and soil in protected, shaded microhabitats should also offer good possibilities of adding to the checklist list of species. Care should be taken to collect good-sized samples with fruiting bodies to aid in making determinations.

Algae and Cyanobacteria
The rarity of eplithic algae in the Utah desert is not surprising due to the high-to-extreme level of desiccation and light exposure (Rahmonov and Piatek 2007); however the relative abundance of endolithic (cryptoendolithic and chasmoendolithic) algae and photobiont algae was notable from three endolithic samples and two lichen samples. Environmental DNA (eDNA) markers have shown a wide diversity of life forms, from bacteria to eutrophs, in MDRS sub-terrestrial habitats (Direito et al. 2011). This abundance of diversity has also been observed genetically in extreme dry and cold environments (de la Torre et al. 2003, Pointing et al. 2009) and hot thermal environments (Walker et al. 2005). In the Utah desert, endolithic algae layers were close to the substrate surface (<4mm), allowing for adequate light penetration (Matthes et al. 2001). In addition, periods of long dormancy in endolithic microenvironments could further stabilize species-rich communities and niche diversity (Knoll and Grotzinger 2006).
In sandstone microhabitats, the majority of the cells did not show signs of desiccation or stress. Trebouxia sp. (Chlorophyceae) had well developed chloroplasts extending across most of the cell. The lobed or plate-like structures of the chloroplasts were often difficult to discern, but occasionally observed. Cultures of these algae from samples Sokoloff 249 and Sokoloff 290 also showed well developed chloroplasts that were also difficult to identify (Fig. 4). The central pyrenoid, lobed plate-like chloroplast and thickened cell wall distinguished these Trebouxia from other genera, such as Neochloris and Myrmecia; these latter two genera have similar valve morphologies and genetically similar 18S sequences. Therefore a definitive identification even to the genus is problematic Fott 1983, Friedl andBüdel 2008 The number of Trebouxia taxa was difficult to discern in this study; four possible taxa were observed based on size, wall sheath thickness, general chloroplast structure and the number of pyrenoids. These taxa likely belong to the Trebouxia anticipata/gelatinosa ITS rDNA clade Fott 1983, Friedl andBüdel 2008). Lobe and parietal plate-like chloroplast, cell size, wall thickness, and number of pyrenoids are diagnostic for this clade. Zoospores were not observed for any of the chlorophytes.
Gloeocapsa sp. (Chroococcales, Microcystaceae) was prominent as a fine layer within the sandstone of Sokoloff 290 (Fig. 5a, b, c). This cyanobacterium was also dominant as a sub-surface crust (along with a small, prostrate, thallus-forming epiphytic chlorophyte in the Chaetophorales) on the bottom of a quartzite rock found embedded in desert sand near MDRS (Sokoloff 301, Fig. 10). Quartzite rocks were infrequently encountered in the deserts surrounding MDRS, and the stone collected likely provided a protected habitat for the cyanobacterial crust while still allowing light transmittance through the translucent mineral of the quartz. Similar stones around MDRS may harbour similar microbial communities.
Gloeocapsa colonies form by cell division and binary fusion (Komárek and Anagnostidis 1999). In the two samples collected here (endolithic and epilithic), colonies were densely packed often forming rectangular masses. The multilayered wall sheath characteristic for Gloeocapsa was evident in isolated cell clusters (Fig. 5. Cell morphology is very similar to genera within the family Xenococcaceae, but distinguished from them by the absence of multiple fission and baeocyte formation (Komárek and Anagnostidis 1999). Early 16S rDNA results show that Gloeocapsa is separated from Myxosarcina and Xenococcus, which is further separated from Chroococcidiopsis (Friedl and Büdel 2008). We did not observe baeocytes (motile or nonmotile), and this combined with the general rectangular-cube formation of the colonies, widely separated cells in the colonies, layers of surrounding sheath and single cells with thick sheaths, leads us to identify this taxon as Gloeocapsa sp. This differentiation and identification is subject to challenge with recent DNA studies suggesting that the other genera Myxosarcina and Chroococcidiopsis are somewhat related (Friedl and Büdel 2008). The DNA results further highlight potential problematic identifications in cultures used for the study, indicating the difficulty in determining differences between taxa in Gloeocapsa, Chroococcidiopsis and Myxosarcina. A number of studies have identified Chroococcidiopsis sp. (sensu lato) in addition to Gloeocapsa sp. as prominent endolithic or epilithic genera (Friedmann 1961, Friedmann 1971, Friedmann et al. 1967, Friedmann and Ocampo-Friedmann 1984, Dor and Danin 1996. In the present study, colony morphology, cell size and form would indicate that we have Gloeocapsa sp. Many taxa within Gloeocapsa are classified as sub-areal and epilithic. Comparable species include Gloeocapsa coracina, G. decorticans (A. Braun) Richter, G. caldariorum Raben., G. atrata Kütz. and G. bituminosa (Bory) Kütz..
Two lichen species had hyphae associated with endolithic Trebouxia algae layers in our samples (Lecanora cf. garovaglii, Acarospora strigata). Two other lichen taxa (Placidium acarosporoides and Heteroplacidium compactum) had Myrmecia sp. as the associated alga with endolithic algae layers and endolithic hyphae in proximity to the surface lichens. The subsurface penetration and sporadic association of fungal threads with the endolithic algae support the observation that biological interactions within the sandstone are part of the ongoing development of lichen taxa (de la Torre et al. 1991). In addition, Heteroplacidium compactum is partly parasitic on other crustose lichens, as well as growing independently on rock (Breuss 2007, Prieto et al. 2012).
The primary survival mechanism displayed by endolithic algae in hot conditions is to "hide" from the extreme environment. Like other plant groups, extreme heat causes cellular water loss, which at some point will cause the cell to die. Xeric algae typically have thick sheaths to minimize water loss and environmental abrasion. Many studies have shown the effective tolerance of plant, fungi, and algae cells to desiccation, and the ability to remain viable for long periods of drought in both extreme hot and cold conditions (e.g. Beckett et al. 2008 and references within). Most xeric plants, fungi, and algae have thick cuticles, or protective carbon based coverings for water retention as well as UV protection. The rate of water loss is also critical, if cells are not able to adapt to the environment and their cellular structure (e.g. leaky membranes) cannot control the water loss. In addition to water loss heat can denature functional proteins, while light and heat can induce the cellular production of reactive oxygen species (ROS). Beckett et al. (2008) define many of the ROS as free oxygen radicals. ROS are unstable and a threat to all cellular macromolecules (Fridovich 1999). At least eight ROS species (eg. superoxide O and hydrogen peroxide H O ), are potentially harmful to cellular structure. For an excellent review of general ROS damaging processes to cells refer to Beckett et al. (2008). The endolithic algae observed here do not appear to be stressed and there is no visual evidence of membrane and micro-molecule damage. These algae have either created adapted processes to combat ROH stress or have selected a perfect microhabitat for survival and growth.
With new developments in taxonomy using DNA sequencing, it would not be surprising to find that endolithic algae communities are more diverse than currently reported. This notion is in contrast to the traditional idea that only a few endolithic algae groups and species are present in the environment (Friedmann et al. 1967). Gerrath et al. (2000) for example, observed 22 endolithic taxa from 180 rock samples along the Niagara escarpment (Ontario, Canada). Already, molecular studies have shown that more than one algae species can be present in one lichen host (Kroken and Taylor 2000), thus more endolithic taxa may be present at MDRS given the number and taxonomic diversity of crustose lichen taxa reported in this study. However, the difficulty in identifying xeric algae based on cell morphology is still problematic without additional culturing and future DNA work, as observed here and in other publications (Friedmann et al. 1967, Thüs et al. 2011. The biological complexity of algae development within the rock, between the rock and surface biota, and the facultative transfer of algae taxa between species illustrates the interwoven connectivity of life in this extreme environment.

Biological Sampling at MDRS
While we found it unnecessary to modify standard collection techniques for vascular plant and lichen species, we did note several improvements that would streamline biological sample collection while wearing a simulated spacesuit.
The thick gloves that simulate pressurized material made it difficult to write notes in a fieldbook and operate a handheld GPS receiver. We improvised better collecting workflows during the expedition by using a clipboard and paper datasheets instead of a fieldbook. We kept the GPS receiver on continuously, rather than attempting to operate the touchpad, which was not designed for heavy gloves.
While digital cameras were relatively easy to operate while wearing gloves, it was not possible to use the viewfinder on a DLSR camera while wearing a helmet; we used live view mode on the rear screen of the camera body to compose photographs. Future expeditions may benefit from technological data capture methods, like the voice operated "Mobile Agents" of Clancey et al. (2004), for example.
The presence of an on-site laboratory at MDRS greatly assisted in the processing of plant and lichen samples in a clean, controlled environment, and the availability of microscopes and electronic literature databases allowed us to accurately identify a subset of the vascular plant species during the simulation. The in situ facilities allowed us to share preliminary data with mission control, and to decide if follow-up collections at the same site would be required during our mission. This highlights the importance of the laboratory to 2 2 2 MDRS, and the utility of including a well-designed laboratory space on a future manned mission to Mars, where efficient execution of a field science program would be of paramount importance.

Conclusions
In the deserts surrounding MDRS and throughout the southwestern United States of America, the diversity and distribution of vascular plants, lichens, fungi, algae and cyanobacteria are dependent on various factors, including underlying geology (Schenk et al. 2003), the availability of water (Ehleringer et al. 1991) and nutrients (Schlesinger et al. 1996), and the presence of other biological organisms, including vascular plant (Schlesinger and Pilmanis 1998) and soil crust communities (Harper and Belnap 2001). The taxonomic groups treated in this study all possess various adaptations to life in this harsh desert environment, including (but not limited to) thick, moisture retaining cell walls (Holzinger and Karsten 2013) and an endolithic habit (Thielen and Garbary 1999) in algae and cyanobacteria, resistance to UV radiation and dessication in lichens (de Vera et al. 2002), and C4 carbon fixation in vascular plants (Mulroy and Rundel 1977). These adaptations have allowed a diverse floristic comunity to thrive in various microhabitats throughout southeastern Utah, and continued exploration will undoubtedly yield many species not documented here.
Therefore, while our present checklist is not an exhaustive inventory of the MDRS site (greater sampling effort would be necessary to capture all local diversity), it can serve as a first-line reference for identifying vascular plants and lichens at MDRS, and serves as a starting point for future floristic and ecological work at the station. Other useful field references to the MDRS flora include the Desert Plants of Utah (Andersen 1996), and A Field Guide to Biological Soil Crusts of the Western U.S. Drylands ).