Biological traits are important characters for predicting invasiveness of species: a comparative study between invasive and native species

Life history traits that make species invasive have been of continuing interest because of their potential predictive power. This study examined the biological traits of some native and invasive weed species in Nigeria with a view to predicting the most important life traits that enhance invasiveness. Mature seeds of the selected species were collected from natural populations, and planted in perforated polyethylene pots, in replicates of ten. Five different biological traits group were studied (i.e., fecundity, physiology, biomass, longevity, and morphology). A canonical linear discriminant analysis was conducted to determine the attribute(s) that predicted invasiveness among species. Multiple correspondence analysis was performed to classify the weeds that were similar in invasiveness. Cluster analysis was performed on the plant species to determine if the biological traits were adequate enough to group the invasive species separately from the native species. The canonical linear discriminant analysis showed that the most important predictors of invasiveness were seed production (10.06) and fruit production (-10.30). Dendrogram of biological traits showed that the species were separated into three groups, with the first group bearing the strongest invasive species viz. Alternanthera brasiliana, Chromolaena odorata and Tithonia diversifolia with the weakest being Euphorbia graminea. Longevity trait of all species was significantly correlated with the fecundity trait (r = 0.43; df = 8; p = 0.002). This study concluded that the weakest invasive species, Euphorbia graminea, which exhibited the r-survival strategy might act as a facilitator for secondary invasion. Fecundity traits were the most important traits of invasiveness, and, since fecundity traits and longevity traits were significantly correlated, focus on traits such as maximum flowering period, life cycle and juvenile period of alien species is much needed for consideration in any ecosystem restoration plan.