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Montana Field Guide

Montana Field Guides

Threeridge Valvata - Valvata tricarinata

Potential Species of Concern
Native Species

Global Rank: G5
State Rank: S2S3
(see State Rank Reason below)

Agency Status

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State Rank Reason (see State Rank above)
The Three-ridge valvata is currently ranked a "S2S3" Potential Species of Concern in MT and is potentially at risk because of limited and/or potentially declining population numbers, range and/or habitat, making it vulnerable. Known occurrences in Montana are widely disjunct.
General Description
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Species Range
Montana Range Range Descriptions


Range Comments
Known from several lakes in the Clark Fork and Flathead drainages and the Flathead Indian Reservation; specimens from MT sites, however, are among those that need to be rechecked to determine if speciation has occurred (Frest and Johannes 1995). Originally found in Quebec and New Brunswick west to Alberta and south to Wyoming, Arkansas, and Virginia; western occurrences are strongly disjunct and specimens from the WA and MT populations need to be compared in detail with more easterly occurrences, in view of the fact that speciation has occurred in several other genera with disjunct species swarms with both eastern and western representation. Recently, the species has been found in several lakes in the Clark Fork and Flathead drainages, Lake Roosevelt, WA, Ferry County, WA, the Flathead Indian Reservation, MT; searches in ID turned up no sites (Frest and Johannes 1995).

Observations in Montana Natural Heritage Program Database
Number of Observations: 15

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)


Threats or Limiting Factors
Modification, poisoning, and eutropification of kettle lakes, particularly nutrient enhancement due to farm animal wastes, sewage, or to irrigation runoff may so eutropify lakes to exclude this species, which is probably the case for most MT lakes where this species could potentially occur (Frest and Johannes 1995).

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Citation for data on this website:
Threeridge Valvata — Valvata tricarinata.  Montana Field Guide.  .  Retrieved on , from