|Scientific Name:||Pisidium walkeri|
|Species Authority:||Sterki, 1895|
|Taxonomic Notes:||The species has been placed in the family Sphaeriidae, although some authors regard Pisidium as worthy of listing as a distinct family Pisidiidae; traditionally, however, it is still placed as a subfamily of the Sphaeriidae.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Bogan, A. & Cordeiro, J.|
|Reviewer(s):||Bohm, M., Collen, B. & Seddon, M.|
|Contributor(s):||Richman, N., Dyer, E., Soulsby, A.-M., Whitton, F., Kasthala, G., McGuinness, S., Milligan, HT, De Silva, R., Herdson, R., Thorley, J., McMillan, K., Collins, A., Offord, S. & Duncan, C.|
Pisidium walkeri has been assessed as Least Concern. This species has a large geographical range that extends across a large part of North America. Pisidium walkeri is able to tolerate a wide variety of habitats, does not appear to be affected by any major threats at present and has not been recognized as a species of concern by any federal or state legislation.
|Range Description:||This species occurs in the United States and Canada. The range of this species in the United States extends from the eastern coast, south to a disjunct population in the upper Mississippi drainage, Arizona (Guralnick 2005). In Canada, it is recorded from the north, towards the border with the United States (Guralnick 2005), and from New Brunswick northwest to Quebec and Labrador, and west to the Northwest Territories as far as Great Slave Lake (Mackie 2007). This species has a scattered distribution in subarctic eastern Canada, and in the United States from New Brunswick to Massachusetts, and Illinois (Clarke 1981, Guralnick 2005).|
Native:Canada (Alberta, Manitoba, New Brunswick, Northwest Territories, Ontario, Québec, Saskatchewan); United States (Arizona, Illinois, Iowa, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, New Hampshire, North Dakota, Ohio, Pennsylvania, South Dakota, Virginia, Wisconsin)
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is widespread and abundant although uncommon in certain parts of its range. This species is more frequently documented in eastern areas of the United States than the west (Guralnick 2005). On a global scale, this species is believed to be secure under present conditions (Ontario Natural Heritage Information Centre 2008).|
|Habitat and Ecology:||
This species is found in permanent rivers, streams, lakes and ponds. Within the Colorado River this species was found to be abundant in clear water, and in the wide downstream areas, but absent in the backwaters (Stevens et al. 1997). The study area encompassed a 367 km stretch from the Glen Canyon Dam to Diamond Creek, Arizona (Clarke 1981). This species is most frequently found among vegetation, and occurs on a variety of substrates (Clarke 1981).
This species breeds twice a year, with recruitment of the first (over-wintering) generation beginning in July. The second generation of juveniles is recruited in October. The maximum life expectancy is ten months for the over-wintering adults, and four months for the summer adults (Burky and Burky 1976).
|Use and Trade:||This species is not utilised.|
|Major Threat(s):||It is unlikely that there are major threats imapcting this species. This species is able to tolerate short-term habitat disturbance and is believed to be secure on a global scale (Ontario Natural Heritage Information Centre 2008, Montana Field Guide 2008). However, this source states there is some cause for concern in the long-term due to declines resulting from habitat degradation and destruction.|
|Conservation Actions:||This species has been assigned a NatureServe Global Heritage Status Rank of G5 - Secure, a National Status Rank of N5 - Secure for the US, and N4N5 - Apparently Secure or Secure for Canada, a State/Province Status Rank of S4 - Apparently Secure for Ontario, Canada, and S3 - Vulnerable for Virginia, and has not been assessed in Massachusetts, Michigan, Montana and Wisconsin in the US and Manitoba and Quebec in Canada (NatureServe 2009). There are no specific conservation measures in place for this species.|
|Citation:||Bogan, A. & Cordeiro, J. 2012. Pisidium walkeri. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 01 March 2015.|
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