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Sunday, September 22, 2013

Species of concern on the Colorado Plateau: Mosses & Lichens

Preface: nearly a decade ago I was asked to contribute to a book about species of concern in the Colorado Plateau ecoregion focusing on all taxa. I drafted up a section about mosses and lichens, focusing on gypsiferous species of biocrusts, which is a rare habitat. There are no federally listed mosses or lichens, not because they don't exist, but rather because the Endangered Species Act categorically excludes them. 

I asked Roger Rosentreter (lichenologist), and Lloyd Stark (bryologist) for tips on other non-gypsiferous species I ought to mention. 

Having heard nothing about the book in many years, I think I can assume the project is dead. In the meantime, I reckon its more useful here than on an old hard drive in an obsolete file format. I've supplemented it with links to images from the web, if they exist.

Regarding status, vulnerable means that it could conceivably be extirpated. For example rarity of habitat would render something vulnerable. At risk refers to a vulnerable species that is threatened by a stressor. 



Status in region: At risk

Status elsewhere: At risk in the Americas

DESCRIPTION ~ Nodule cracked lichen was first encountered in the Americas in the mid-1980's, and has been found to be locally common species confined to the gypsiferous soils of the Colorado Plateau. Although it is has a widespread distribution around the world, its preference for a very rare habitat type in North America makes it a species of concern. This lichen is composed of many scales of ~3-5 mm diameter with lobed margins. Generally the appearance of the lichen is white due to a covering of oxalate salts, but the thallus underneath is actually pale brown. It has black fruiting bodies immersed in the thallus that lack any kind of rim around them. Colonies are irregularly shaped and generally less than 5 cm in diameter.

Vulnerability Factors: Habitat specialist, restricted range


Status in Region: At risk

Status in other regions: At risk

DESCRIPTION~ This rare moss was recently described in 1995 as a result of morphologically well-developed collections made during California bearpoppy studies. Nevada gypsum moss appears to be a widely but sparsely distributed species of western North America, almost exclusively on gypsiferous soils. It is distinguished by other mosses of the same habitat by its lack of an awn (hair-like projection) on its leaf tips, and its dark green to black leaves that tend to spiral around the stem near the top. Its small stature (usually < 2mm tall) makes a handlens a must to observe these features. Many desert mosses have skewed sex ratios, but to date a male individual of this species has yet to be found making it one of the champions.

Vulnerability Factors: Habitat specialist, restricted range, possible low genetic diversity due to lack of sexual reproduction



Status elsewhere: Widespread and stable

DESCRIPTION ~ Desert crater lichen is found on several continents but on the Colorado Plateau it is strongly restricted to the rare gypsiferous soils where large white populations can be visually impressive. This lichen forms rather large colonies often exceeding 5cm in diameter and is pure white. It tends to have a rugose, undulating surface and has large (~ 2mm) black fruiting bodies which are bowl shaped and sunken into the thallus surface like a crater. This species tends to have a very clumped distribution, so if you find some you are likely to find a lot.

Vulnerability factors: habitat specialist, restricted range


Status in region: At risk

Status elsewhere: At risk globally

DESCRIPTION ~ Largeleaf gypsum lichen has been confusing lichenologists since the 1920's, and was not discovered in the US until 1990. Its unique fruiting body which grades into the vegetative thallus afforded it a designation as a new genus solely representing a new family, Gypsoplacaceae. It is a squamulose lichen with olive - tan squamules (scale-like mini thalli) usually about 0.5 - 1 cm in diameter. The fruiting bodies, when present, look like upraised brick red swellings on the squamules and may be irregular to dome shaped. Although fairly large in the soil lichen world, colonies are usually less than 5cm in diameter. This species is a rare one even within its specialized habitat which is also rare.

Vulnerability Factors: Low population density, habitat specialist, restricted range.


Status in region: At risk

Status elsewhere: At risk globally

DESCRIPTION ~ This lichen was unknown to science until collected in the San Rafael Swell in 1998, and has since been observed at scattered locations around the Colorado Plateau. Gypsum-loving rim lichen is chalky white to ashy gray and forms a tightly adhering crust on the soil surface. Its thallus (vegetative portion) is divided into small partitions called areoles. It bears black disk shaped fruiting bodies (1-2 mm dia.) with a white margin that are flush with or sitting slightly atop the thallus. A typical specimen is about 3 - 5 cm in diameter and irregularly shaped.

Vulnerability Factors: Habitat specialist, restricted range.

Habitat: These species are strongly restricted to arid and semi-arid sites with gypsiferous soils such as those derived from gypsum-bearing portions of the Carmel  Formation, the Paradox Formation, and the Moenkopi Formation (most of which occur at 5000 - 6500 ft). Such sites are found across southern Utah and in southwestern Colorado. They occur as components of the conspicuously well developed biological soil crusts generally found on these soils.

Threats and Concerns: On the Colorado Plateau, these species are endemic to an inherently rare habitat type, and are uncommon to rare within that habitat type even when undisturbed. Largeleaf gypsum lichen is a rare species even within this special habitat type. Most of the gypsum soils of the plateau are degraded to some extent by livestock activity and off road vehicle use, and truly undisturbed examples may be lacking. As population growth continues in the region, economical exploitation of the more pure gypsum deposits may occur to satisfy demand for products such as drywall. Gypsum areas are particularly popular with users of dirt bikes and all-terrain vehicles.

Conservation: When planning road and trail construction, gypsum areas should be avoided whenever possible. Enforcement of off-road vehicle regulations should be prioritized in these areas. Plant cover is poor on gypsum soils, therefore they offer relatively little forage value to livestock. Grazing of these fragile habitats could and should be phased out without creating major economic impacts. Because gypsiferous soils generally occur in relatively small patches, a network of small fenced reserves could potentially maintain the endemic biota.

Notes: Because several soil crust species and some vascular plant species are rare gypsum endemics, and gypsum soils cover very little area, it is practical and possible to conserve them all by conserving the habitat in small reserves. We thank Dr. Larry St. Clair of BYU for sharing his expertise on gypsiferous lichens, and Dr. Lloyd Stark of UNLV for information pertaining to Didymodon nevadensis.

Crossidium seriatum

Status in region: Unknown

Status elsewhere: At risk globally

DESCRIPTION ~ This little fringe moss is an extremely rare western North American soil moss with a primarily hot desert distribution. It has never been collected in the Colorado Plateau but likely occurs in the more xeric portions, albeit very rarely. Although this species cannot be separated from lookalikes in the field, perhaps its best identifying characteristic is its extremely small size. A typical field specimen is frequently less than 0.5 mm tall and although it does generally have a white hairlike point on its leaf tips, it never appears as a white hairy cushion. With the naked eye, individuals look like little black dots.

Vulnerability Factors: Low population density, restricted range

Habitat: This moss occurs on sandy or gypsiferous soils of aridlands. Dr. Lloyd Stark suggests that this species is primarily centered around the gypsiferous soils near Lake Mead, thus its most likely habitat on the Colorado Plateau includes the more xeric gypsiferous substrates at the margins of the Colorado Plateau ecoregion such as those near St. George, Utah. Other possible localities include exposures of the Paradox formation in Cataract Canyon and adjacent side canyons.

Threats and concerns: Soil disturbances of various sorts are the most likely stressors: foot traffic, livestock grazing, and off road vehicles.

Conservation: Initially, the best strategy is simply to determine that the species does indeed occur on the Colorado Plateau so that the habitat characteristics can be better defined and stressors better identified. As a preemptive strategy, gypsiferous habit reserves should be developed as described previously. Fortunately, the most likely localities for this species happen to be in protected areas (Canyonlands National Park, and Glen Canyon National Recreation Area), but they could potentially be impacted by river users.

Entosthodon planoconvexus

Status in region: Vulnerable

Status elsewhere: Globally vulnerable

DESCRIPTION ~ This exceedingly rare moss is known on the Colorado Plateau from only one location in Canyonlands (deposited by the author at the National Park Service Southeast Utah Group's herbarium in Moab, Utah), and is known from only four other collections worldwide. Entosthodon planoconvexus is a short moss with rather large yellowish green leaves that are spreading when moist and shriveled when dry. Its sporophyte, when present, consists of an upside-down pear-shaped capsule borne on a reddish stalk.

Vulnerability factors: Low population density

Habitat: Because of its rarity, the habitat of this species is poorly defined although it tends to occur on dry soil at the base of rocks. The Canyonlands specimen grew in a dry sandy soil layer over rock and adjacent to a rock outcrop. It is an occasional associate of liverworts of the genus Targionia.

Threats and Concerns: The main concerns with Entosthodon planoconvexus are its naturally highly isolated small populations. Because it tends to grow in at least partially protected habitats, the population is likely stable, however stochastic events or disturbance could easily drive this species locally extinct. Livestock and recreation impacts are the most likely anthropogenic stressors of this species.

Conservation: It is difficult to recommend conservation strategies for this species without knowing what potential stressors are. Perhaps the best strategy is simply to determine where the species occurs so that the habitat characteristics can be better defined and stressors identified. Currently, bryophytes are not generally included in inventory and monitoring projects.

Notes: Dr. Lloyd Stark of UNLV provided helpful information on this species.

Lichinella minnesotensis

Status in Region: Unknown

Status elsewhere: Possibly vulnerable in western North America

DESCRIPTION~ This rock licorice lichen is apparently a North American endemic with a primarily eastern distribution. There are some rather disjunct collections from the midwest and west including a single collection from near Kanab, Utah. This black lichen is composed of clumps of ascending convoluted lobes. It is jelly like and semi-transparent when wet. Colonies are generally only about 1 cm in diameter.

Vulnerability Factors: Isolated populations

Habitat: Minnesota rock licorice is found in shallow fissures or crevices on rock outcrops. The sole Colorado Plateau collection was from a limestone substrate of the Timpoweap member of the Moenkopi formation in Grand Staircase-Escalante National Monument. It is difficult to characterize the habitat characteristics of this species on the Colorado Plateau because only one collection has been made.

Threats and Concerns: It is unknown whether this species is threatened by anthropogenic forces, buts its rarity in the region suggest it is vulnerable. Fortunately, its habitat type affords considerable protection.

Conservation: It is difficult to recommend conservation strategies for this species without knowing what potential stressors are. Perhaps the best strategy is simply to determine where the species occurs so that the habitat characteristics can be better defined and stressors identified if they exist. Currently, lichens are not generally included in inventory and monitoring projects.

Notes: Dr. Roger Rosentreter of the BLM provided information on his Kanab-area collection of this species.

Trichostonum sweetii

Status in region: Vulnerable

Status elsewhere: Globally vulnerable

DESCRIPTION ~ Hairy mouth moss is known from only three collections on the Colorado Plateau (one a dubious identification) and only a handful more from western North America where it is endemic. This is a fairly large moss for arid regions (up to 2cm tall) and is an inhabitant of shady crevices. It has large, narrow, bright green leaves (2-3 mm long) which are spreading and widest just below the apex.  They may occur as small tufts or scattered individuals mixed with other species.

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