Ploidy influences rarity and invasiveness in plants

1. The factors associated with plant species ’ endangerment and (conversely) invasiveness are of broad interest due to their potential value in explaining the causes and consequences of population status.While most past work has focussed on ecological variables, recent work suggests that genetic attributesmay be strongly associated with plant species status. 2. We collated data on chromosome numbers for 640 endangered species (worldwide) and their 9005 congeners, and for 81 invasive species and their 2356 congeners. We related ploidy (diploid versus polyploid) to endangerment and invasiveness. We also related chromosome number (abso-lute number and relative to the minimum recorded for the genus) to endangerment and invasiveness with a randomization test, taking the variation of reported chromosome numbers into account. All analyses considered the relatedness of the taxa. 3. We found that endangered plants are disproportionately likely to be diploid and to have lower ploidy ratios, whilst invasive plant species are generally found to have high chromosome counts and to be polyploid. 4. While considering the effect of relatedness, being endangered is c. 8 % less likely as ploidy ratio doubles and 14 % less likely for polyploids compared with diploids. Being invasive is 12 % mor