• expanding populations;
  • isolated colonies;
  • Lymantria dispar;
  • protandry;
  • stochastic diffusion model


  • 1
    Understanding why invading populations sometimes fail to establish is of considerable relevance to the development of strategies for managing biological invasions.
  • 2
    Newly arriving populations tend to be sparse and are often influenced by Allee effects. Mating failure is a typical cause of Allee effects in low-density insect populations, and dispersion of individuals in space and time can exacerbate mate-location failure in invading populations.
  • 3
    Here we evaluate the relative importance of dispersal and sexual asynchrony as contributors to Allee effects in invading populations by adopting as a case study the gypsy moth (Lymantria dispar L.), an important insect defoliator for which considerable demographic information is available.
  • 4
    We used release–recapture experiments to parameterize a model that describes probabilities that males locate females along various spatial and temporal offsets between male and female adult emergence.
  • 5
    Based on these experimental results, we developed a generalized model of mating success that demonstrates the existence of an Allee threshold, below which introduced gypsy moth populations are likely to go extinct without any management intervention.