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Elliptio downiei

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA MOLLUSCA BIVALVIA UNIONOIDA UNIONIDAE

Scientific Name: Elliptio downiei
Species Authority: (Lea, 1858)
Common Name(s):
English Satilla Elephantear
Taxonomic Notes: The classification of the Atlantic Slope species of Elliptio is currently in a state of uncertainty. Johnson (1970) grouped many named taxa under a single name. Current research is finding many of these synonomized taxa to be valid species. This research is in progress and will result in the recognition of numerous additional taxa in this genus. This species is often confused with Elliptio crassidens. Johnson (1970) recognized Elliptio downiei as a subspecies of Elliptio crassidens, although subsequent authors have given downiei species-level status (e.g., Turgeon et al. 1998, Graf and Cummings 2007).

A list of synonyms for this species can be found on The MUSSEL project web site (Graf and Cummings 2011).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2011
Date Assessed: 2011-07-22
Assessor(s): NatureServe (Jay Cordeiro)
Reviewer(s): Böhm, M. & Collen, B.
Contributor(s): Dyer, E., Soulsby, A.-M., Whitton, F., McGuinness, S., De Silva, R., Milligan, H.T., Kasthala, G., Thorley, J., Herdson, R., McMillan, K. & Collins, A.
Justification:
Elliptio downiei has been assessed as Least Concern as populations appear to be stable. This species is endemic to a single river (Satilla) system in Georgia with a very small area of occupancy where populations are reported to be stable. Because threat information and long term trends are not known, further research is necessary in order to effectively respond should this species become more threatened.
History:
1996 Lower Risk/near threatened (Baillie and Groombridge 1996)

Geographic Range [top]

Range Description: This species is restricted to the Satilla River system in Georgia (Butler 1994). There is some speculation that this species may also occur in the St. Marys River system, which lies directly south of the Satilla River, but this species has been listed at times as Elliptio crassidens (Johnson 1970). Williams et al. (1993) also list this species from South Carolina and Florida.
Countries:
Native:
United States (Florida, Georgia, South Carolina)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Although historically known from few occurrences, these occurrences were often represented by an abundance of individuals and despite a lack of comprehensive survey effort of the river, periodic recent survey efforts have not documented any site extirpations. Number of occurrences can only be estimated, since a comprehensive survey of the Satilla River basin has not been completed. Johnson (1970) lists only four historical occurrences, three from the main stem of the Satilla River, and one from Buck Lake, a bayou of the Satilla River. Heard (1975) reported Elliptio downiei from only a few occurrences in the Satilla River, but noted that populations could be locally abundant. Butler (1994) lists the species as endemic to the Satilla River in Georgia. If the Elliptio in the St. Mary's River, Georgia, is indeed this species and not Elliptio crassidens, occurrences would include the St. Mary's River east of St. George and south-southeast of Folkston, and Spanish Creek in West Folkston, all in Charleton Co. (Johnson, 1970). Elliptio downiei is still extant at the type locality, Buck Lake (G. Keferl pers. comm. 2000).

This species is currently considered stable (G. Keferl pers. comm. 2000). Long term trends are not really known as the occupied habitat was not well surveyed historically.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: This species is found in sandy/muddy to sandy substrates in medium-sized streams in swift to moderate currents (Heard 1975). It is also found in the main channel of rivers, backwaters and even lakes (G. Keferl pers. comm. 2000).
Systems: Freshwater

Threats [top]

Major Threat(s): This species is restricted to a single river system in Georgia (although it has also been recorded from South Carolina and Florida). Threats include bank destabilization due to urbanization, eutrophication, chemical pollution, and extreme low water conditions induced by water withdrawals.

Conservation Actions [top]

Conservation Actions: No widespread conservation actions have been undertaken for this species. Further research regarding the taxonomy, population trends, threats and ecology of this species is required.

Citation: NatureServe (Jay Cordeiro) 2011. Elliptio downiei. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 30 July 2014.
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