Villosa ortmanni (Mussels of the Upper Green River, KY)

Villosa ortmanni

Distribution ²

Global Range: (250-1000 square km (about 100-400 square miles)) What is considered "classic" Villosa ortmanni is a lienosa-like species with orange nacre occurring in the Green River in and around Munfordville, Kentucky. But beyond that, V. ortmanni quickly becomes something else. In the Nolin and Gasper Rivers, moving away from the Green River, populations begin to show smaller, chunkier individuals, some having purple nacre as well as orange. At the periphery of the species' range in the Red River and the middle Gasper Rivers, the entire population has purple nacre. These look very different from the "classic" V. ortmanni yet are part of a continuum of shell characteristics linking the two. This species is endemic to the Green River system in Kentucky (Cicerello and Schuster, 2003) where it inhabits a few sites in the Green River and in a direct tributary, as well as a limited number of tributaries of the Nolin, Gasper, Rough, and Barren rivers (R. Cicerello, KY NHP, pers. comm., 1998; Cicerello and Hannan, 1990). Historically specimens were also collected in Beaver Creek but there is no recent evidence of the species there (R. Cicerello, KY NHP, pers. comm., 1998).

Habitat ³

Habitat Type: Freshwater

Comments: This species is primarily found in large rivers with gravel cobble bottoms. The portion of the Green river in Kentucky where this species was collected had "deep flowing riffles and runs with substrates composed of sand, gravel, and some cobble" (Cicerello and Hannan, 1990). More recently, this mussel has been found in smaller to medium-sized streams and rivers in sand, mud, or gravel (Cicerello and Schuster, 2003).

Nature serve conservation status ⁴

Rounded Global Status Rank: G2 - Imperiled

Reasons: This species is endemic to two river systems with less than 20 extant populations. Further examination of these populations may allow for lumping of occurrences into larger populations. Suitable habitat is fragmented although the species appears to be declining slightly within its extremely limited range.

Intrinsic Vulnerability: Unknown

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Comments: This species is primarily found in large rivers with gravel cobble bottoms. The portion of the Green river in Kentucky where this species was collected had "deep flowing riffles and runs with substrates composed of sand, gravel, and some cobble" (Cicerello, 1990). More recently, this mussel has been found in smaller to medium-sized streams and rivers in sand, mud, or gravel (Cicerello and Schuster, 2003).