Conclusion

Four species were most commonly encountered. Although none of the collections made in the upper Fraser Basin employed quantitative methods, a rough idea of common versus less common species can be inferred from the frequency that species are recorded from the region (see maps). The most collected species were Euconulus fulvus, Discus whitneyi, Vitrina pellucida and Nesovitrea binneyana.

Wetlands are undersurveyed for terrestrial gastropods. Species listed in this report that are restricted to wetland habitats tend to have fewer locality records than those species that are generalists. While it is true that
exclusively wetland species will be spotty in their distribution, wetlands are usually overlooked, and species such as Vertigo ovata and Euconulus praticola are probably under recorded.

Exotic species are likely more widespread. Although well known to gardeners and “‘backyard naturalists”, exotic species are often overlooked because as everyday occurrences they may not be considered worthy to record. During the 2001 field survey, we did not especially target sites in towns of the upper Fraser Basin, so the relatively few collections of some synanthropic species, such as Limax maximus, Arion subfuscus, Cochlocopa lubrica, result from  a lack of collecting effort in urban areas. However, certain exotic species were found more frequently — the grey fieldslug, Deroceras reticulatum, was living in many roadside stops that we visited.

Species expected but not found. One species, Discus shimekii, although historically recorded from the upper Fraser Basin (Stanwell-Fletcher & Stanwell-Fletcher 1943; Map 14), has not recently been collected. My current understanding of the distribution of this species would suggest that it certainly would not be present over much of the upper Fraser Basin (particuarly the central, southern and western portions). It is possible that this literature record of D. shimekii is based on a misidentification for D. whitneyi.

Among native species of terrestrial gastropods, there are several species that have been recorded elsewhere in B.C. that were expected for the upper Fraser Basin but subsequently not found: Vallonia gracilicosta Reinhardt, 1883; Striatura pugetensis (Dall 1895); and Microphysula ingersollii (Bland, 1875). V. gracilicosta is known from scattered localities north, west and south of the upper Fraser Basin. S. pugetensis is known from the valley of the North Thompson River and from the B.C. coast (Forsyth 2001b). M. ingersollii lives in subalpine forests and avalanche tracks up to the treeline and is currently known from southeastern B.C. (south of near Field) and above Pine Pass in the Murray Range (Forsyth 2004).

Terrestrial Gastropods ...   
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