Abstract
Benthic macroinvertebrate communities were sampled from five sites, over two consecutive years, within a glacial catchment in the French Pyrenees. Longitudinal patterns in 20 biological traits possessed by 36 taxa were examined using multivariate analyses. Boundary Reynolds number was used to investigate the potential resistance and resilience of individual traits to the flow forces acting on zoobenthic taxa. Using the percentage of taxa possessing individual biological traits, samples were separated along an altitudinal gradient. Traits predominant in separating samples above an altitude of 2200 m from those at 1900 m were mode of attachment to substrate, nutrition and life history strategy. The relative abundance of traits varied seasonally at lower altitude sites concurrent with snowline retreat. Small body-size and clinger-habit, traits offering resistance and/or resilience to hydraulically turbulent conditions, were present throughout the catchment. The dominance of resistant traits was extended to lower boundary Reynolds number conditions concomitant with low refugia potential. Semivoltine life history, crawler and swimmer habit and streamlined-flattened body shape were found exclusively in lower boundary Reynolds number conditions. A variable trait composition was associated with lower turbulence conditions or a range of turbulence when concomitant with high refugia availability.
Published Version
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