Population turnover and habitat dynamics in Notonecta (Hemiptera : Notonectidae) metapopulations

Simple metapopulation models assume that local populations occur in patches of uniform quality habitat separated by non-habitat. However field metapop ulations tend to show considerable spatial and temporal variation in patch quality, and hence probability of occupancy. This may have implications for the adequacy of simple metapopulation models in describing and predicting regional population dynamics of natural systems. This study investigated th e effects of habitat characteristics on landscape-scale occupancy dynamics of two species of backswimmer (Notonecta Hemiptera: Notonectidae) in small freshwater ponds. The results demonstrated clear links between habitat, pon d occupancy and population turnover, particularly local extinction. There w ere considerable changes in the habitat of individual ponds between years, but local changes were not spatially correlated and the frequency distribut ion of habitat conditions at the landscape level remained similar in differ ent years. Stable occupancy levels of Notonecta species appears to result f rom a balance of the rates of creation and loss of suitable habitat due to spatially uncorrelated habitat change. Systems such as this, where turnover is driven by habitat dynamics, demonstrate the potential value of incorpor ating the dynamics of habitat change into metapopulation models. Such devel opments are Likely to improve predictions of landscape-scale occupancy dyna mics, whilst also allowing patch-level predictions of occupancy, based on l ocal habitat conditions.