Alpine spiders and harvestmen of Mount Rainier, Washington, U.S.A.: taxonomy and bionomics

Abstract

Resident spiders and harvestmen were collected (largely by pitfall trap) at eight sites from 1930 to 3230 m elevation on Mount Rainier (4392 m), Cascade Mountains, ranging in environment from subalpine heath shrub meadow to essentially unvegetated aeolian zone. Records and taxonomic and ecological notes are given for the 31 species taken. Two new linyphiid spiders are described in the genera Scotinotylus and Meioneta; Scotinotylus autor (Chamberlin) and Coreorgonal petulcus (Millidge) are proposed as new combinations. The female of Scotinotylus bicavatus Millidge is redescribed and a description of the male is given, with a report of a gynandromorph specimen and new synonymy of Scotinotylus bipoculatus Millidge. Several other linyphiid species are illustrated. Variation is discussed in the linyphiids Erigone paradisicola Crosby and Bishop, S. bicavatus, and Tennesseellum formicum Emerton and the gnaphosid Micaria constricta Emerton. Included are the first valid North American records of the linyphiid Walckenaeria vigilax (Blackwall) and the first United States records of the phalangiid harvestman Liopilio glaber Schenkel. Samples from 1930 to 2250 m showed similar species richness; above 2250 m, numbers of species decreased but abundance of trapped individuals did not. At the highest site, 3230 m, two species exploit windblown arthropod fallout: the nocturnal L. glaber and the diurnal lycosid spider Pardosa rainieriana Lowrie and Dondale.

Elevational variation of spider and insect communities in the Swedish mountains

“…Such an interpretation is supported by the observed taxonomic distribution of spiders, where we found a larger proportion of actively hunting spiders (e.g., Lycosidae) at lower elevations and conversely mainly passively hunting web‐weaving spiders (primarily Linyphiidae) at high elevations. The low primary productivity in high‐elevation environments may favor passive hunting modes, since spiders need to rely to a large extent on windblown fallout (Crawford & Edwards, 1989; Swan, 1992). Indeed, the catching of windblown food by spiders has been suggested as an important source of nutrient entrapment in low‐productivity ecosystems (Hodkinson et al, 2001), and we therefore propose that spiders may play a key role in maintaining biodiversity in low‐productivity/high‐elevation environments.…”