Comparison of Lythrum salicaria L. study sites in the midwest US and central Europe

Lythrum salicaria L. is a generalist species that can grow under a wide ran ge of habitat conditions, both in its native distribution (Eurasia) and in Worth America, where it is a successful invader of temperate wetlands. Comp arison of the European and U.S. habitats was a preliminary part of a larger project studying the life history traits of native and invasive population s of L. salicaria, when growing under different environmental conditions, M ultivariate statistical analyses, using relativized Bray-Curtis ordinations , found that the sites separate along environmental gradients. This allowed for the establishment of experiments under natural settings; geographic ef fects were studied for populations growing under similar habitat conditions but in different regions of the species distribution in North America. The U.S. and European populations were measured during different growing pe riods. In order for comparisons to be meaningful, they must be done when cl imatic conditions were similar. Statistical analyses, using non-randomized nested designs for daily high and low temperatures and bimonthly precipitat ion amounts, showed that the European sites had similar temperature regimes as those in the U.S. Also, a more rainy growing season followed a drier on e on both continents.