Do Reproductive Traits of Invasive Populations of Scotch Broom, Cytisus scoparius (Fabaceae), Outperform Native Populations?

Abstract

Reproductive traits are among the most important factors in determining the success of species establishment and invasion in a new area. Studies on transcontinental invasions have revealed that invasive species perform better in the invasive range than in their native ranges. We assumed that the same regularity exists in intracontinental invasions and thus investigated whether the reproductive traits of Scotch broom, Cytisus scoparius, perform better in the alien invasive range in Europe compared to its native range in the same continent. The aim of this research was to reveal the potential and realised fecundity of C. scoparius in its native and invasive ranges, as well as relationships with the size of pods, habitat type, and how these traits vary at the same site in different years. The results of this study were not able to unambiguously confirm our hypothesis that C. scoparius in the invasive range in Lithuania, specifically in the southern part of the Boreal biogeographical region, outperform plants in the native range with regard to the analysed reproductive traits. Potential fecundity of C. scoparius in the native range was significantly higher than in the invaded range; however, realised fecundity was not significantly different between the native and invasive ranges. The pod length was similar in both ranges, whereas the pod width was significantly greater in the invasive range than in the native range. The results suggest that the number of ovules per pod, number of matured seeds, and the size of pods are related with the type of habitat and local environmental conditions in the habitat. Although many studies on other species have confirmed higher fecundity and overall better performance of plants in the invasive range than in the native range on other continents, this rule probably cannot be applied for intracontinental invasive species occurring in relatively close geographical regions to their native ranges.