Links of ploidy with other traits and distributions of nonnative species in North American flora

Abstract Background and Aim Polyploidization is becoming an increasingly important subject in ecology and invasion biology. To date, the role of polyploidy in the success of species invasions remains unclear. Here, we explore the associations between ploidy levels and seed size, reproductive mode, life form, time after introduction, and range size of nonnative plants introduced to North America (NAM), as well as whether polyploidization is related to invasion success. Methods Using data on 1,804 nonnative plant species in continental North America, with information on chromosome numbers, we conduct comparative, correlation and regression analyses to investigate the possible links among ploidy level, multiple life history traits, and geographical distribution. Key Results Among the 1,804 species, 54% were polyploids. The proportion of plants with three or more levels of ploidy was much higher in herbaceous species than in woody species. Species in aquatic, forb, and graminoid forms had higher proportions of species that exhibit multiple ploidy levels than trees and shrubs. Range size was also positively related to levels of ploidy. We also observed clear differences in seed size among ploidy levels, but no correlation between chromosome number and seed size. Conclusions Our findings demonstrate that (1) polyploidy is linked to other life history traits at varying degrees or intensities and (2) the level of ploidy appears to be important in regulating plant traits and distribution. The relationships of levels of ploidy with other traits and range size are useful in predicting species invasiveness and spread potential. Our findings thus have strong implications for invasion biology and management.