Origins and distribution of invasive Rubus fruticosus L. agg. (Rosaceae) clones in the Western United States

In facultatively asexual invasive species, an understanding of the origins and diversity of clones can reveal introduction and invasion pathways and inform management efforts. In this study, we use microsatellite and chloroplast DNA markers to infer clonal diversity of the Rubus fruticosus agg. invasion in the Western United States, determine the relationship of these clones to clones found in other exotic ranges, and determine the geographic and genetic origins of the invasive clones. We found two invasive clones in the Western United States, where the invasion had previously been thought to consist of a single asexual lineage. The most common clone was genetically identical to the microspecies R. armeniacus from the native range of Germany, while the second clone was identical to the microspecies R. anglocandicans in the invaded range of Australia and closely related to samples from the native ranges of England and Serbia. A third distinct clone was identified in a collection from the exotic range of Chile. Our results demonstrate that cryptic genetic diversity may be present in asexual invasions that are thought to be homogeneous. However, the asexual relationships between R. fruticosus agg. clones in the native and multiple exotic ranges indicate that preadaptation has played an important role in invasion success in this species aggregate.