Long-Distance Dispersal of the Gypsy Moth (Lepidoptera: Lymantriidae) Facilitated Its Initial Invasion of Wisconsin

Abstract

Gypsy moth (Lymantria dispar L.) spread is dominated by stratified dispersal, and, although spread rates are variable in space and time, the gypsy moth has invaded Wisconsin at a consistently higher rate than in other regions. Allee effects, which act on low-density populations ahead of the moving population that contribute to gypsy moth spread, have also been observed to be consistently weaker in Wisconsin. Because a major cause of an Allee effect in the gypsy moth is mate-finding failure at low densities, supplementing low-density populations with immigrants that arrive through dispersal may facilitate establishment and consequent spread. We used local indicator of spatial autocorrelation methods to examine space-time gypsy moth monitoring data from 1996 to 2006 and identify isolated, low-density colonies that arrived through dispersal. We measured the distance of these colonies from the moving population front to show that long-distance dispersal was markedly present in earlier years when Wisconsin was still mainly uninfested. Recently, however, immigrants arriving through long-distance dispersal may no longer be detected because instead of invading uninfested areas, they are now supplementing high-density colonies. In contrast, we observed no temporal pattern in the distance between low-density colonies and the population front in West Virginia and Virginia. We submit that long-distance dispersal, perhaps facilitated through meteorological mechanisms, played an important role in the spread dynamics of the initial Wisconsin gypsy moth invasion, but it currently plays a lesser role because the portion of Wisconsin most susceptible to long-distance immigrants from alternate sources is now heavily infested.

The role of Allee effects in gypsy moth,Lymantria dispar(L.), invasions

“…2 Proportion of females successfully located by males and mated based upon the background male moth density in central West Virginia and Virginia, 1993-1994(solid line, Sharov et al 1995), and Wisconsin, 2000(dashed line, Tcheslavskaia et al 2002) Popul Ecol (2009 proportion of colonies that arise through atmospheric versus anthropogenic transport mechanisms. However, in general, the majority of colonies arrive in close proximity to the leading edge (Sharov and Liebhold 1998;Tobin and Blackburn 2008). These colonies vary considerably in their initial size, and while some colonies successfully establish, the majority fail to persist.…”

Dispersal Patterns of Pine Wilt Disease in the Early Stage of Its Invasion in South Korea

“…Generally, invertebrates display a stratified dispersal based on the combination of long distance dispersal (LDD) and short distance dispersal (SDD) [5]. There are many examples of stratified dispersal including gypsy moth (L. dispar) [6], Argentine ant (Linepithema humile) [7], and mountain pine beetle (Dendroctonus ponderosae) [8].…”

An autoregressive model for global vertebrate richness rankings: long-distance dispersers may have stronger spatial structures

“…At a broad spatial scale, long-range dispersal was found to be important in structuring species diversity patterns. For example, long-distance dispersal was vital to the interplay of climatic conditions in determining the spread of the gypsy moth (Tobin and Blackburn 2007).…”