Genetic Allee effects on performance, plasticity and developmental stability in a clonal plant

Negative effects of small population size on fitness, so-called Allee effec ts, may threaten population persistence even in intact habitat remnants. We studied genotypes of 14 isolated populations of the clonal plant Ranunculu s reptans, for which molecular genetic (RAPD-) variability is higher for la rge than for small populations. In a competition-free greenhouse environmen t vegetative offspring of genotypes from large populations produced more ro settes and flowers, indicating higher fitness. Within-genotype coefficients of variation in performance traits, indicating developmental instability, were lower for genotypes from populations with higher RAPD-variability. In competition with a taller grass, we found relative reduction in leaf length less pronounced for plants from large populations, suggesting higher adapt ive plasticity. Our experimental study of a plant with predominantly vegeta tive reproduction suggests, that negative genetic effects of recent. habita t fragmentation, which so far rather were expected in plants with frequent sexual reproduction, are more severe and more common than previously acknow ledged.