Athearnia anthonyi

Athearnia anthonyi is treated as a full species by some (e.g., Dillon and Ahlstedt 1997, Mirarchi et al. 2004, Garner and Johnson 2017, FMCS 2021) and as a subspecies of Athearnia crassa by others (Turgeon et al. 1998, Minton and Savarese 2005). In this database, we follow the former treatment. Two studies have confirmed that Athearnia anthonyi is a distinct species from Leptoxis praerosa (Dillon and Ahlstedt 1997, Minton and Savarese 2005).

Because of pollution, heavy siltation, and habitat modification or destruction (e.g., inundation by reservoirs), this snail has been extirpated from almost its entire historic range (greater than 80% decline), with most of the decline occurring historically as the result of impoundment. Currently populations remain stable as far back as 1996. Currently it is known from five or perhaps a few more occurrences (3 rivers) in a range extent of less than 250 square km and area of occupancy less than 100 square km although a captive breeding and reintroduction program is underway and has shown some success.

Historically distributed from the lower French Broad and Clinch rivers to the vicinity of Muscle Shoals, this species was originally described from the Holston River near Knoxville, Tennessee (USFWS, 1996). It was once widespread in the Tennessee River system, where it was associated with shoal areas in the main stem of the Tennessee River from Knoxville (Knox Co., Tennessee) downstream to Muscle Shoals (Colbert and Lauderdale Cos., Alabama) and lower reaches of its tributaries in eastern Tennessee, northern Alabama, and northwestern Georgia (USFWS, 1996). Extirpated from much of the Tennessee River and tributaries following impoundment. Presently known from the extreme lower sections of only four streams: a stretch of the Sequatchie and Little Sequatchie Rivers, Marion County, Tennessee; Limestone Creek, Limestone County, Alabama, and in the main channel of the Tennessee River near the Alabama and Tennessee state line (Mirarchi et al., 2004; Minton and Savarese, 2005). Populations all found to be genetically distinct from one another (Minton and Savarese, 2005; TN NHP, pers. comm., 2007).

At present, 5 occurrences are known in three streams. There is a very slight possibility for a few others. Known from the extreme lower sections of only three streams: a single stretch of the Sequatchie River, Marion County, Tennessee; Limestone Creek, Limestone County, Alabama, and in the main channel of the Tennessee River near the Alabama (Jackson Co.) and Tennessee (Marion Co.) state line (Mirarchi et al., 2004; Minton and Savarese, 2005). Populations all found to be genetically distinct from one another each with unique haplotype and all individuals from a population sharing the same haplotype (Minton and Savarese, 2005). Also reintroduction efforts in Tennessee River, downstream of Wilson Dam. A new site with good viability was reported in 2007 in the Little Sequatchie River where the species may have been documented historically (D. Withers, TN NHP, pers. comm., 2007).

The former mainstream habitat for this species has been eliminated by the impoundment of the Tennessee River (Bogan and Parmalee, 1983). Most historical populations were lost when much of the Tennessee River was impounded as the species is not tolerant of impoundment. Historical impoundments resulted in current fragmentation and isolation of populations. Additional population losses and declines are attributable to general deterioration of water quality due to inadequate erosion and sedimentation control during mining, agricultural, timbering, and construction activities; run-off and discharge of agricultural, municipal, and industrial point and nonpoint source pollution; and habitat alteration from channelization and dredging (USFWS, 1996). Increasing urbanization within the Limestone Creek watershed may pose a future threat (Garner and Haggerty, 2010).