• colonization cycle;
  • dispersal;
  • invertebrate drift;
  • metapopulation;
  • population persistence


  • 1
    Recent explanations for the persistence of freshwater invertebrates in the face of downstream drift (the so-called ‘drift paradox’) have centred largely on recolonization by upstream flight by preovipositing adults.
  • 2
    Such explanations do not cover the many important species often found in the drift that lack an aerial phase. Here we demonstrate conclusively that long-range aerial movements are not required to explain the drift paradox.
  • 3
    We show that small-scale movements along the streambed of the order of centimetres, combined with density dependence at some stage of the lifecycle, are sufficient to maintain populations over geological timescales.
  • 4
    Further, we demonstrate that the principal previous modelling study of the drift paradox was parameterized in a way that is more compatible with such small-scale movements than the long-range flight for which it was intended.