DISTRIBUTION PATTERNS OF INTERSTITIAL FRESH-WATER MEIOFAUNA OVER A RANGE OF SPATIAL SCALES, WITH EMPHASIS ON ALLUVIAL RIVER AQUIFER SYSTEMS

Spatial distribution patterns of the interstitial meiobenthos are exam ined across a range of scales, A global interstitial highway model is presented with the alluvial aquifer system as its central core. Spatia lly discontinuous hypogean entities, such as karstic aquifers, springs , anchialine waters and the psammolittoral, have limited interconnecti ons except through the alluvial aquifer system and are contiguous with epigean waters. The global interstitial highway is viewed as an evolu tionary pathway and long-term dispersal route for meiobenthic forms. T he distribution of interstitial animals in alluvial river-aquifer syst ems is examined at longitudinal (altitudinal), reach, floodplain, grav el bar, and vertical (depth) scales. Geomorphic and hydrogeologic feat ures and interactions emerge as major determinants of the spatially he terogeneous nature of alluvial aquifers that structure the patchy dist ribution patterns of hypogean fauna across a range of scales.