Genetic analysis of native and introduced populations of Taeniatherum caput-medusae (Poaceae): implications for biological control

摘要

Genetic analysis of both native and introduced populations of invasive species can be used to examine population origins and spread. Accurate delineation of an invasive species' source populations can contribute to the search for specific and effective biological control agents. Medusahead, Tae-niatherum caput-medusae (L.) Nevski, a primarily self-pollinating Eurasian annual grass that was introduced in the western USA in the late 1800s, is now widely distributed in California, Idaho, Nevada, Oregon,Utah and Washington. The goal of our current research is to assess introduction dynamics and range expansion of this grass in the western USA, and to identify source populations in the native range to facilitate the search for potential biocontrol agents. Across introduced populations, nine multilocus genotypes were detected, and we suggest a minimum of seven separate introduction events of T. caput-medusae in the western USA. Although range expansion appears to have occurred primarily on a local level, several introduced populations appear to be composed of admixtures of introduced genotypes. None of the native populations analysed to date possess the exact multilocus genotypes detected in introduced populations. We have recently begun screening Eurasian populations using intersimple sequence repeat (ISSR) genetic markers to determine whether this polymerase chain reaction-based technique can provide a higher degree of resolution for the identification of source populations.