Shrub management is the principal driver of differing population sizes between native and invasive populations of Rosa rubiginosa L.

Abstract

An essential step in understanding biological invasions is the comparison of species' performance in the native and introduced ranges, especially for long lived woody exotics. We explored causes for the higher density and abundance of invasive Rosa rubiginosa L. populations by comparing plant performance and habitat attributes in both ranges. Native shrubs in Spain and Germany were, on average, taller than introduced shrubs in Central and Southern Argentina. Inside 100 m2 plots rose-cover in Spain and Germany was significantly higher than in Central Argentina but comparable to that found in Southern Argentina. Growth rates of marked branches did not differ between ranges, but marked shrubs indicated that native R. rubiginosa stems are cut regularly, with the oldest rose stems being found in Argentina. Seeds from the introduced range did not have higher germination rates overall, and low seedling numbers in the field underline the general importance of vegetative growth for the species. Leaf damage did not differ between regions and soil analyses proved that R. rubiginosa tolerate a wide range of soil conditions without necessarily benefiting from any one in particular. No differences were observed in vegetation structure, pointing to favorable conditions in the introduced range, and greenhouse experiments showed that plants of invasive origin do not outgrow native roses. The smaller population sizes and lower abundance in the native range can therefore be attributed to management actions along with a lower level of viable habitat.