A comparative study reveals the key biological traits causing bioinvasion difference among four alien species of genus Veronica in China

The four alien farmland weeds of genus Veronica (i.e., V. arvensis, V. didyma, V. hederifolia, and V. persica) have successfully colonized in China, but caused different ecological consequences in the colonized habitats. However, the key biological traits conferring to bio-invasion differences under different light conditions among the four alien species of Veronica remain unknown. A comprehensive contrastive analysis experiment was conducted to assess the contribution intensity of photosynthetic and sexual and asexual reproductive traits of the four alien Veronica weeds to their invasion level in both field trial and laboratory. The field survey results showed that V. persica had the highest invasion level, V. didyma, V. hederifolia and V. arvensis in turn. Their invasiveness were mainly attributed to photosynthetic-related parameters (LMA) and asexual reproduction traits (the ratio of adventitious root) out of all the 22 tested indexes. The photosynthetic-related and some asexual reproduction indexes from separated determinations under both sun and shade conditions showed that V. persica was able to adapt strong illumination but more tolerant to the shade than the other species. This adaptive differentiation to illumination conferred the four alien Veronica weeds to different competitiveness to crops through allocating resource to the biomass of each organ in farmland. It may conclude that the adaptability to illumination conditions and the asexual reproduction traits may endow their successful invasion and become different important farmland weeds.