Linking a synoptic climatology model with population dynamics data to explain atmospheric transport of the gypsy moth (Lymantria dispar)

The gypsy moth is a non-native species that continues to invade new areas in North America. It generally spreads through stratified dispersal in which local growth and diffusive spread are coupled with long-distance jumps ahead of the expanding leading edge. Long-distance jumps due to the anthropogenic movement of life stages are a well-documented mechanism of dispersal. Another mechanism is through atmospheric transport of life stages, which is thought to occur over short distances. However, empirical data on male moth flight supports the possibility of long-range dispersal not explained by anthropogenic-facilitated movement. Such dispersal events seemed to occur in the 1990s when gypsy moth populations spread across Lake Michigan to previously uninhabitated areas in eastern Wisconsin. Although such dispersal events would generally be against the prevailing wind flow for the area and would have occurred despite a significant physical barrier (Lake Michigan), the wind climatology of the region shows that the area is subject to vigorous cyclones that can result in strong easterly winds at the time when life stages are present. We parameterized a synoptic climatology model coupled with population dynamics data from gypsy moth populations in Wisconsin to show an association between favorable transport events, as determined by climatic patterns, and gypsy moth annual spread rates, as ascertained by trapping records collected from 1996-2007. This work highlights the importance of atmospheric transport events relative to the invasion dynamics of the gypsy moth, and serves as a model for understanding this mechanism of spread in other related biological invasions.