ESTIMATES OF MALE DISPERSAL IN YPONOMEUTA-PADELLUS (LEPIDOPTERA, YPONOMEUTIDAE), THE SMALL ERMINE MOTH, BY MEANS OF SIMULATION

A model of male dispersal is described which simulates the observed re captures from a series of mark-release-recapture experiments. The mode l aims to obtain an unbiased estimate of the dispersal parameter, sigm a, for males of Yponomeuta padellus (Lepidoptera: Yponomeutidae). Five parameters, each considered to be potentially important in an analysi s of the dispersal patterns of Y. padellus, were incorporated into the model. Parameter values were varied individually in a stepwise fashio n to create a large number of simulated data sets. The method of maxim um likelihood was used to test the goodness of fit of each simulated d ata set against the observed distribution of recaptures to determine t he optimal combination of parameter values. Using these same parameter values, the model was then modified by examining the movement of male moths in the absence of traps to obtain an estimate of sigma. The 'be st' estimate of sigma was found to be 2.9 m gen(-1/2), with an approxi mate upper confidence limit of 6.4 m gen(-1/2). The results suggest th at dispersal in Y. padellus is extremely restricted relative to the ar ea occupied by the total population and that Y. padellus is characteri zed by an extremely fine-scale population structure.