Land Mollusks of Great Basin National Park

This article was originally published in The Midden – Great Basin National Park: Vol. 16, No. 1, Summer 2016.

Euconulus species, a land mollusk found in the park.

Photo Submitted by the author

By Mark Ports, Biology Professor (emeritus), Great Basin College, Elko, Nevada

Land snails and slugs are important invertebrate inhabitants of woodland litter and soils, boulder and talus slides, riparian meadows, and vegetation around springs throughout the Great Basin. These land-inhabiting invertebrates play critical roles in these mountain habitats such as decomposing dead plant material for use by bacteria and fungi, recycling important biological nutrients such as calcium and nitrogen, passively transporting fungal spores through litter, and providing an essential source of calcium and protein for bird and mammal predators.

Now in the last season of a three-year survey (2014-2016), the species diversity, habitat preferences, and population densities of land snails and slugs are being surveyed throughout the park. To date a total of 17 species of land snails and one species of slug have been recorded. The smallest land snail in the park is the Small Spot at only 1.5 mm in shell diameter, while the largest of the land snails is the Great Basin Mountainsnail which has a shell range of 20 to 30 mm in diameter. The columnar (elongate coiled) land snails such as the Cross Vertigo and Crestless Column range in height from 2 to 5 mm while the heliciform (round coiled) snails such as the Silky Vallonia and Quick Gloss range from 3.5 to 5.6 mm in diameter.

A sampling of land mollusks found in Great Basin National Park. To date eighteen species have been found in the park.

Photo submitted by the author

Land mollusk communities range from one species at 2,000 m in a xeric, pinyon-pine and Utah juniper woodland on Lower Lehman Creek to a maximum of nine species at 2,800 m in a mesic, mixed aspen-conifer woodland on upper Strawberry Creek. Both of these localities are dominated by a bedrock and soil of granitic schist which provides little free calcium for land snails to build their shells. However, it has been shown that land snails in such localities obtain their calcium and nutrients from the decomposing leaf material. At two other sites, limestone/dolomite bedrock provide free limestone. This bedrock, along with a mesic understory of shrubs, allows for a community of eight species found below Grey Cliffs on Baker Creek and on the South Fork of Big Wash. The highest elevations for land snails in the park occur at Stella Lake and a nearby bristlecone pine woodland at approximately 3,200 m.

While the land snail communities described above depend primarily on mesic woodland and shrub habitats, some species tend to be habitat specialists. For example, both species of Mountainsnails and the Montane Snaggletooth depend on limestone boulder and talus fields with a shrub and grass cover. Other species, such as the Meadow Slug, the two species of Amber snails, and the Cross Vertigo, are restricted to wet meadows and springs.

The species diversity and habitat preferences found in the park during this survey are similar to those found in other high elevation mountains throughout the eastern Great Basin such as the Deep Creek Range to the north along the Utah border, the Ruby Mountains to the Northwest in northeastern Nevada, and the Schell Creek Range to the west of the Snake Range.