To address this question, Jordi Figuerola, Andy J. Green, and Thomas C. Michot combined data from previous studies of genetic differences between populations of invertebrates across North America with the movements of waterfowl as quantified by band-recovery data collected by amateur and professional ornithologists. They found that, for 3 out of 4 invertebrate species studied, bird movements give the best explanation for the genetic differences between populations, suggesting that waterbirds were the main agents of dispersal. The genetic distance between two populations depended more on the likelihood of birds moving between those localities than on the geographical distance between them.
This is the most solid evidence to date that dispersal via migratory waterfowl has a major influence on the population genetics of invertebrates. Some invertebrates are better at dispersing via birds than others. If researchers can learn to identify the features that make an invertebrate a good disperser, they will improve the understanding of how the composition of native aquatic communities is determined and why some introduced species are more invasive than others.
This article will appear in the February 2005 issue of American Naturalist.