Herbarium records, actual distribution, and critical attributes of invasive plants:: genus Crotalaria in Taiwan

Herbarium records have been widely used in biogeographical and ecological studies for decades. To test the adequacy of using herbarium records, we used residuals, calculated from the regression of the number of herbarium records on minimum residence time of Crotalaria species naturalized in Taiwan, as a predictor of species actual frequency and invasiveness. Number of positive localities (localities where a particular species is present), net infested area, maximum cover, as well as reproductive traits, were estimated for five exotic Crotalaria species with a similar minimum residence time. The tight correlation between residuals and the number of positive localities, as well as with maximum cover, confirms that herbarium records accurately reflect some aspects of the invasion success of the studied species. However, residuals were not a significant predictor of net infested area. Strong correlations between residuals and reproductive traits contributing to species fitness, including log(seeds/plant), flowers/inflorescence, inflorescences/plant, and flowers/plant supported the use of herbarium records in representing field distributions and invasiveness.