Lampsilis rafinesqueana

This is a declining regional endemic that is undergoing range contraction and continues to decline through most of its range. It has been extirpated from nearly 70% of its historic range. Through most of its current range (although fairly large), it is rare, has very few viable populations (show no signs of recruitment), and faces major threats. Changes rank to a G1, downgraded from a G2 ranked in 2007, and in danger of becoming extinct because of low population numbers and minimal viabile populations with very high threats.

Found in isolated watersheds across Arkansas, Kansas, Oklahoma and Missouri. The Neosho mucket is endemic to the Neosho and Verdigris basins of the Arkansas River system in Kansas, Missouri, Oklahoma and Arkansas. Distribution of relic shell material indicates that the species was once widespread throughout these basins. It was historically reported from the Illinois River in Oklahoma and Arkansas; the Neosho River in Oklahoma and Kansas; Neosho River tributaries, including the Elk River in Missouri, Cottonwood River in Kansas, and the Spring River in Oklahoma, Kansas, and Missouri, and Spring River tributaries, North Fork Spring River and Indian Creek in Missouri, and Shoal and Center Creeks in Kansas and Missouri; the Verdigris River in Oklahoma and Kansas, and its tributaries, Caney River in Oklahoma and Kansas, and Fall River in Kansas (USFWS, 2003). Recent status surveys conducted throughout this area indicate that the species has been extirpated from much of its range. In the Neosho River basin the species now survives in the Neosho River (KS), Elk River (MO), Spring River (MO, KS, possibly OK), North Fork Spring River (MO), Illinois River (OK, AR), and Shoal, Indian and Center creeks (MO). In the Verdigris basin the species survives in the Verdigris River (KS) and Fall River (KS) (USFWS, 2003). Listed as an endangered species by the United States Fish and Wildlife Service.

Currently, approximately 70 occurrences are known, of which ca. 15% are of good to excellent viability, and the remainder are mostly low to no viability. Historically, many 100s of occurrences were estimated. In Arkansas, the Neosho mucket was found at 19 of 22 survey sites in the Illinois River, Washington/Benton Counties (USFWS, 2003) and it was once considered locally abundant in second order streams of the system downstream to the Oklahoma line (Harris and Gordon, 1987). The species has not been found in surveys of other tributaries of the Arkansas River in Arkansas. In Oklahoma, living Neosho muckets were found to be locally common in about 92 km (55 mi) of the Illinois River from the Oklahoma/Arkansas state line (Harris et al., 1997),

The present or threatened destruction, modification, or curtailment of its habitat or range is the most serious threat to continued survival of Lampsilis rafinesqueana. The reduction of habitat and range of Lampsilis rafinesqueana has been attributed to impoundment, sedimentation, agricultural pollutants (Mather, 1990; Obermeyer et al., 1997b), and mining (Obermeyer et al., 1997b). At least 11 major dams have been constructed that have impounded significant portions of the historic range of Lampsilis rafinesqueana, effectively resulting in fragmented Lampsilis rafinesqueana populations and habitats. The species does not tolerate lentic conditions and has not been collected from those portions of its historic habitat that have been impounded. Other contributions to habitat loss include pollution, sedimentation, eutrophication, pesticide residues, and sand and gravel mining.