The effects of genetic bottlenecks
Genetic bottlenecks play an important role in the establishment of invasive species (Dlugosch & Parker, 2008; Suarez & Tsutsui, 2008), with numerous examples of instances where multiple introductions have been important for overcoming propagule pressures (Kolbe et al., 2004; Lavergne & Molofsky, 2007; Simberloff, 2009) and even an example of how bottlenecks may have aided the establishment of an invasive species (Tsutsui, Suarez, Holway, & Case, 2000). Interestingly, here we find evidence for multiple introductions of winter moth to North America, and that all four invasive populations have experienced dramatic bottlenecks in terms of the reductions of their effective population sizes (Supplemental Appendix S1 Table S3). Yet, we find no evidence for reductions in genetic diversity of these populations, as all invasive populations had as great or greater allelic diversity than populations found from across Europe (Supplemental Appendix S1 Table S2). As such, winter moth represents an ideal system to conduct comparative analyses on factors that influence establishment and ecological impact as each introduced population represents a unique and independent data point.