William J. Gerth, Judith L. Li, and Richard Van Driesche. Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331
We sampled macroinvertebrates from 18 summer-dry, agriculturally-influenced streams during winter and spring. All of these streams flowed for 6 months or more per year and their watersheds had 55-98% of land used for agriculture. Surber samples collected in March contained high relative abundances of non-insects and few mayflies, stoneflies and caddisflies. Nonetheless, combining qualitative and quantitative samples, we found limnephilid caddisflies (Heperophylax sp. and several Limnephilus species) at over 90% of sites. Limnephilus larval morphospecies were lab-reared to obtain adults for species identifications. Limnephilus species included L. nogus, L. occidentalis, and L. flavastellus, and a fourth morphospecies that may consist of more than 1 species. Limnephilus nogus was most ubiquitous, occurring at 67% of sites; Hesperophylax sp. was least common, found at only 3 sites. Limnephilus nogus was common in the more agriculturally-influenced sites east of the Willamette River and the undetermined Limnephilus morphopsecies was common in the less agricultural sites west of the Willamette; these types only co-occurred at 3 sites. Limnephilus flavastellus and L. occidentalis were also segregated, co-occurring at only 2 sites. Species identifications allowed us to document the regional limnephilid diversity that persists despite extensive agricultural land use and to better understand within-region caddisfly distributions.
Web Page:
Limnephilidae, summer–dry streams, agriculture