Epioblasma rangiana

This taxon was previously recognized as a subspecies of Epioblasma torulosa but was elevated to species status by Williams et al. (2017). They noted that "Turgeon et al. (1998) recognized eight subspecies of Epioblasma in three nominal species: florentina (three), obliquata (two), and torulosa (three). A conclusive assessment of the taxonomic status of these taxa may be impossible at this time because half are considered extinct (E. florentina florentina, E. f. curtisii, E. torulosa torulosa, and E. t. gubernaculum). Cummings and Berlocher (1990) found no evidence of intergradation between E. t. torulosa and E. t. rangiana and both taxa co-occurred at many sites; based on this evidence, we elevate these subspecies to species status."

This once widespread species historically occurred throughout much of the Ohio River watershed, but its range has been dramatically reduced to eight to ten populations dispersed across four states and one province; some of these populations may have low viability. Chief factors in decline are the damming of rivers, which floods habitat and fragments populations; erosion and siltation from strip mining, logging, and farming; and pollution from agricultural and industrial runoff. Invasive mussels pose an additional serious threat.

The species' range centers around the U.S. Midwest and the Ohio River drainage. Range states include Illinois, Indiana, Kentucky, Michigan, New York, Ohio, Pennsylvania, and West Virginia. Additionally, it occurs in the Canadian province of Ontario within the Lake Huron drainage. As with most naiads, the species' present range is a remnant of its former distribution. E. rangiana was once thought to be a subspecies of E. torulosa that replaced Epioblasma t. torulosa in the headwaters of the Ohio River drainage. However, Cummings and Berlocher (1990) found that both taxa co-occurred at many sites (without intergradation).

NOTE: the following pre-2008 summary contains useful information but was written before E. rangiana was elevated to species status; it therefore may include data for E. torulosa and hence should be reevaluated.
Historically, this entity was recorded from the mainstem of the Ohio River (Stansbery and Cooney, 1985) but has apparently been extirpated from there. The Ohio State University Museum of Zoology has records for the White and Wabash Rivers in Indiana but it has not been collected there in recent times (Clark, 1976; Cummings et al., 1991). Taylor and Hughart (1981) presumed that it was no longer present in the Elk River of West Virginia. Currently extant in only seven streams: the Green River in Kentucky, French and LeBoeuf Creeks and the Allegheny River in Pennsylvania, the Detroit River in Michigan (possibly extirpated - see below), Big Darby Creek in Ohio (USFWS, 1993), and at least one additional river in Ontario (Metcalfe-Smith et al., 1998). Staton et al. (2000) lists historical and present distribution. Recently found in Conewanto Creek near Warren, Warren Co., Pennsylvania, where it was previously thought to be extirpated (Evans and Smith, 2005). In Illinois, it formerly occupied the Vermilion, Wabash, and Ohio rivers but is now extirpated in the state (Cummings and Mayer, 1997). Recently this species has been confirmed to be likely extirpated from the main channel of the Detroit River between Lake St. Clair and Lake Erie, Michigan/Ontario, due to zebra mussel invasion (Schloesser et al., 2006).

Once widespread in the Ohio River basin and into southern Canada in the Lake Huron drainage, this species now exists in eight to ten isolated populations, most of which are small and peripheral and with few signs of reproduction.

NOTE: the following paragraph was written prior to 2010 when the taxon was still considered a subspecies of E. torulosa. It is retained here for its detailed notes on occurrence in multiple river systems.

Epioblasma torulosa rangiana, the only remaining extant subspecies, was formerly widespread in the Ohio River basin (including Ohio River system in Ohio River at Cincinnati, Little Miami, Scioto and tribs., Muskingham, Auglaize, Sandusy, and Olentangy Rivers, and Big Darby Creek- a tributary of the Scioto; Beaver River in Ohio and Pennsylvania; Lake Erie drainage in Fish Creek, and Kanawha River, West Virginia; Wabash River and tributaries-Tippecanoe River and the Eel, Blue, and White Rivers) (Parmalee and Bogan, 1998) as well as having been collected historically from the Allegheny River drainage in Pennsylvania above Pittsburgh and from the West Fork River (Ortmann, 1913), a tributary of the Monongahela River, Harrison Co., West Virginia (Parmalee and Bogan, 1998; USFWS, 1994). This subspecies now exists in eight to ten isolated populations, most of which are small and peripheral and with little signs of reproduction. It is known from the Kentucky, Licking, and Green River drainages in Kentucky (Johnson, 1978), but is likely only still extant in the Upper Green. In the Maumee River drainage, it was last seen in Fish Creek (St. Joseph drainage) in Ohio and Indiana and Big Darby Creek in Ohio (Watters et al., 2009), where live individuals were very rare (Watters, 1995; Grabarkiewicz and Crail, 2006). Recently found in Conewango Creek near Warren, Warren Co., Pennsylvania, where it was previously thought to be extirpated (Evans and Smith, 2005). It also occurs in the Allegheny River, Pennsylvania (Jones, 2004). Epioblasma torulosa rangiana occurs in Muddy Creek (French Creek drainage) in the Erie NWR in Crawford Co., Pennsylvania (Mohler et al., 2006) and elsewhere in the French Creek drainage. Weathered shells are reported from the Tippecanoe River (shell only- Cummings and Berlocher, 1990), Sugar Creek (east fork White River drainage) in central Indiana (Harmon, 1992) as well as throughout most central Indiana drainages but no living specimens are known recently (USFWS, 1994) and Fisher (2006) lists it as extirpated from the Wabash drainage. As such, it is likely extirpated from the rest of Indiana (IN NHP, pers. comm., 2009) with the last remaining population in the Tippecanoe drainage (USFWS, 1994). Specimens from the Black River (St. Clair drainage), Michigan, were relocated to the Detroit River in 1992 (Trdan and Hoeh, 1993). It is historically known from the Clinton River drainage in Michigan (Strayer, 1980). In Canada, it historically occurred in the Cedar River and currently occurs in the Sydenham River in the Northern Lake Erie drainage (Metcalfe-Smith et al., 2003) and also the Ausable River in the Eastern Lake Huron drainage (Staton et al., 2000).

Members of the genus Epioblasma seem to be particularly sensitive to impoundment; most species are riffle/run inhabitants and cannot tolerate other habitats. For example, impoundment of the Clinch River in Tennessee by the Norris Reservoir resulted in the extirpation of the majority of species below the dam (Ahlstedt 1984), and construction of the Wilson Dam on the Tennessee River eliminated 20 of the original 22 Cumberlandian naiad species (Stansbery 1971). Smith (1971) ranked the causes of extirpation or declines in fish species as follows: siltation, drainage of bottomland lakes, swamps, and prairie marshes, desiccation during drought, species introductions, pollution, impoundments, and increased water temperatures. All of these factors render habitats unsuitable, cause extirpations, and lead to the isolation of populations thereby increasing their vulnerability to extirpation for many aquatic species (including mussels) throughout North America. The Zebra mussel, Dreissena polymorpha, has destroyed mussel populations in the Great Lakes and significantly reduced mussels in many of the large rivers of the eastern North America and has the potential to severely threaten other populations especially if it makes its way into smaller streams. Pollution through point (industrial and residential discharge) and non-point (siltation, herbicide and fertilizer run-off) sources is perhaps the greatest on-going threat to this species and most freshwater mussels. Lowered dissolved oxygen content and elevated ammonia levels (frequently associated with agricultural runoff and sewage discharge) have been shown to be lethal to some species of freshwater naiads (Horne and McIntosh 1979). Residential development, mineral extraction, and industrial development also pose significant threats. Destruction of habitat through stream channelization and maintenance and the construction of dams, although slowed in recent years, is still a threat in some areas. Impoundments reduce currents that are necessary for basic physiological activities such as feeding, waste removal, and reproduction. In addition, reduced water flow typically results in a reduction in water oxygen levels and a settling out of suspended solids (silt, etc.), both of which are detrimental. Dredging of streams has an immediate effect on existing populations by physically removing and destroying individuals. Dredging also affects long-term recolonization abilities by destroying much of the potential habitat by making substrates and flow rates uniform throughout a system. Rotenone, a toxin used to kill fish in bodies of water for increased sport fishery quality, has been shown to be lethal to mussels as well (Heard, 1970). Natural predators include raccoons, otter, mink, muskrats, turtles, and some birds (Simpson 1899, Boepple and Coker 1912, Evermann and Clark 1918, Coker, et al. 1921, Parmalee 1967, Snyder and Snyder 1969). Domestic animals such as hogs can root mussel beds to pieces (Meek and Clark 1912). Fishes, particularly catfish (Ictalurus spp. and Amierus spp.) and freshwater drum (Aplodinotus grunniens) also consume large numbers of unionids. USFWS (1994) lists the following reasons for mussel decline: siltation (from agriculture, construction, and forestry runoff), impoundment (including dam construction and maintenance), instream sand and gravel mining (for channelization), pollutants (pesticides and fertilizers, heavy metals, ammonia from wastewater, acid-mine runoff, and invasive species (zebra mussel, quagga mussel).