Effective control methods and the genetic and phenetic differences of European dewberry (Rubus caesius) among locations in the Finger Lakes Region of New York

Abstract

The colonization of invasive species is rapidly increasing due to human travel, trade, and disturbance. An area of focus in invasive species control efforts is in riparian zones, which are often highly invaded and disturbed systems. Rubus caesius (European dewberry) is a nonnative invasive woody shrub that has recently been observed to grow densely and spread through riparian ecosystems in western New York. Multiple locations have been noted, but it is not clear if all locations of Rubus caseius are correctly identified, as morphological and reproductive characteristics vary among them. Rubus caeisus is a relatively understudied invasive plant and it is not known how R. caesius is dispersing or how to effectively control extant locations. To understand the dispersal mechanisms of R. caesius I conducted a greenhouse cutting experiment and quantified the fruiting characteristics among six locations across western New York. I found that R. caesius is capable of reproducing via fragmentation regardless of source location, while only some locations produce large numbers of seeds. I investigated location differences through vegetative morphometrics and microsatellite fragment analysis. I found that all locations are identified correctly as R. caesius but there is some evidence for differentiation among the locations. Contrary to my expectations the most similar locations are not always the closest geographically. To evaluate effective control measures, I conducted a control experiment in a randomized block design at one located at Ganondagan State Historic Site in Victor, NY. I compared mechanical and herbicide treatments in different combinations of frequency, control method, and herbicide type. Treatments using chemicals were most effective in reducing the cover of R. caesius across a variety of environmental conditions. I also provide tentative evidence that repeated mechanical treatments are effective in reducing the cover of R. caesius. My determination of potential dispersal mechanisms and effective control methods will be useful for land managers as management strategies may need to differ based on reproductive traits among locations.