Linkages between riparian forest composition and shredder voltinism

Abstract

Life history patterns and seasonal growth rates of eleven shredder species inhabiting an Appalachian mountain stream (Pennsylvania, U.S.A.) were determined and conceptually linked to the species composition of the riparian forest. Thirty-two woody plant species were represented in the riparian forest, with a near-equal compliment of foliage cover within each of the three leaf processing categories (slow, medium, fast). Relative cover of individual species was highly correlated with the proportions of standing stock biomass of individual species of stream leaf detritus. With two exceptions, each shredder species was univoltine; Tallaperla maria exhibited a semivoltine life cycle, while Pteronarcys proteus appeared to require four years to complete nymphal development. Paracapnia angulata, Taeniopteryx maura, Tallaperla maria, Lepidostoma (Nosopus) modestum group sp., Pycnopsyche gentilis, P. luculenta, and Brillia flavifrons exhibited either autumn and/or winter growth. In contrast, Amphinemura nigritta, A. wui, and L. (Mormomyia) sp. displayed either spring and/or summer growth. Overall, the study stream appears to be an appropriate system for analyzing the riparian-shredder link because (1) the riparian assemblage is diverse within a broad range of leaf-processing rates, and (2) the shredder guild is correspondingly diverse with a wide array of seasonal growth patterns.