Small-scale phenotypic differentiation along complex stream gradients in a non-native amphipod

摘要: Selective landscapes in rivers are made up by an array of selective forces that vary from source to downstream regions or between seasons, and local/temporal variation fitness maxima can result gradual spatio-temporal phenotypic traits. This study aimed at establishing freshwater amphipods as future model organisms adaptive diversification (evolutionary divergence and/or plasticity) along stream gradients. We collected Gammarus roeselii 16 sampling sites the Rhine catchment during two consecutive seasons (summer winter). Altogether, we dissected n = 1648 individuals quantified key parameters related morphological life-history diversification, including naturally selected (e.g., gill surface areas) well primarily sexually traits male antennae). Acknowledging complexity regimes streams interrelated nature selection factors, assessed several abiotic temperature, flow velocity) biotic ecological conspecific densities, sex ratios) condensed them into four principal components (PCs). Generalized least squares models revealed pronounced differentiation most investigated herein, gradient (PCs) explained parts observed differences. Depending on trait under investigation, could be ascribed conditions, anthropogenic disturbance (influx thermally polluted water), population parameters. For example, female fecundity showed altitudinal decreased with increasing while sexual dimorphism length antennae—used for mate finding assessment—increased densities towards female-biased ratios. provide a comprehensive protocol comparative analyses intraspecific life history amphipods. Whether over small geographical distances reflects evolutionary plasticity (or both) remains studies. Independent mechanisms involved, is likely have consequences ecosystem functions. leaf-shredding G. strongly depends body size, which varied dependence