Hybridization between Crataegus monogyna Jacq. and C. laevigata (Poiret) DC. in south-eastern England

Hybridization between C. monogyna Jacq. and C. laevigata (Poiret) DC. (c. oxyacantllOides Thuill.) has been investigated in selected populations in south-eastern England. The results show that most populations now contain hybrids and it appears that hybridization has con­ tinued long enough for a new equilibrium to be reached with the environment, resulting in a strong similiarity between populations found on similar soils. The far-reaching effects of man's activities in the past appear to have progressed to a point where further disturbance will only have a marginal effect, e.g. possibly the destruction of the last habitats at present allowing the survival of pure C. laevigata. The concept of the two species C. monogyna and C. laevigata is largely irrelevant in south­ eastern England because most of the populations now existing in this region appear to be the result of varied degrees of introgressive hybridization. However, there is a possible exception on the chalk scarps, which may provide a refuge for pure C. monogyna.