Mechanisms of Phragmites australis invasion: feedbacks among genetic diversity, nutrients, and sexual reproduction : Mechanisms of Phragmites invasion

Biological invasions are gaining attention as a major threat to biodiversity and an important element of global change. Recent research indicates that other components of global change, such as increases in nitrogen deposition and atmospheric CO2 concentration, favor groups of species that share certain physiological or life history traits. New evidence suggests that many invasive species share traits that will allow them to capitalize on the various elements of global change. Increases in the prevalence of some of these biological invaders would alter basic ecosystem properties in ways that feed back to affect many components of global change.

Cryptic invasions are a largely unrecognized type of biological invasion that lead to underestimation of the total numbers and impacts of invaders because of the difficulty in detecting them. The distribution and abundance of Phragmites australis in North America has increased dramatically over the past 150 years. This research tests the hypothesis that a non-native strain of Phragmites is responsible for the observed spread. Two noncoding chloroplast DNA regions were sequenced for samples collected worldwide, throughout the range of Phragmites. Modern North American populations were compared with historical ones from herbarium collections. Results indicate that an introduction has occurred, and the introduced type has displaced native types as well as expanded to regions previously not known to have Phragmites. Native types apparently have disappeared from New England and, while still present, may be threatened in other parts of North America.

Abstract Microsatellites are powerful molecular markers, used commonly to estimate intraspecific genetic distances. With the exception of band sharing similarity index, available distance measures were developed specifically for diploid organisms and are unsuited for comparisons of polyploids. Here, we present a simple method for calculation of microsatellite genotype distances, which takes into account mutation processes and permits comparison of individuals with different ploidy levels. This method should provide a valuable tool for intraspecific analyses of polyploid organisms, which are widespread among plants and some animal taxa. An illustration is given using data from the planarian flatworm Schmidtea polychroa (Platyhelminthes).