Testing models for equilibrium distribution and abundance of insects

The Kean–Barlow model predicts how the equilibrium distribution and abundance of a population may be affected by local rates of increase, dispersal, colonisation, and extinction. Here, the model is parameterised for three insects: the Glanville fritillary Melitaea cinxia in Åland, Finland, the ribbonwood aphid Paradoxaphis plagianthi in Christchurch, New Zealand, and the coxella weevil Hadramphus spinipennis in the Chatham Islands, New Zealand. The model was modified for the weevil to accommodate its unusual habit of overexploiting local resources. For the butterfly and the weevil, parameters estimated from the literature suggest high patch occupancy with low to moderate relative local population sizes. For the aphid, the model suggested low distribution and abundance. These predictions appear to match field observations, at least qualitatively, suggesting that the model captures sufficient biological detail to be a valid tool for exploring the relative effects of population-level processes on rarity and commonness.