Comparison of growth, photosynthesis and phenotypic plasticity between invasive and native Bidens species under different light and water conditions.
To explore the traits related to the invasiveness of exotic Bidens species in China, we compared the morphology, growth, biomass allocation, photosynthesis, and phenotypic plasticity of two invasive Bidens species (B. pilosa and B. frondosa) with two native congeners (B. biternata and B. tripartita) under different light and water conditions in a common garden. The results showed that the invasive and native species displayed similar plant heights and total biomass under unfavorable conditions (i.e. low light and low water treatment). However, under favorable light and water conditions (i.e. high light and high water treatment), the invasive species showed significantly greater plant height and total biomass than the native congeners. Furthermore, in high light treatments, the relative growth rate of the invasive species was higher than that of the native species. The invasive species allocated more resources to root biomass at high light levels compared to low light levels, while they allocated more resources to leaf biomass at low light levels compared to high light levels. Specific leaf area of the invasive species was greater than that of the native congeners under low light conditions. These traits may enhance the abilities of invasive species to capture and utilize resources, enabling them to withstand adverse environmental conditions or to respond more positively to favorable conditions. The phenotypic plasticity indices of invasive and native species for morphology, growth, and photosynthetic parameters were low for water availability and high for light intensity. However, for most variables, invasive species showed a higher phenotypic plasticity index than native congeners, and this may contribute to their invasion success. In addition, there were no significant differences for photosynthetic parameters between invasive and native Bidens species under any treatment. In conclusion, this study shows that morphology, growth, biomass allocation, and phenotypic plasticity may play more important roles than photosynthetic parameters in the success of invasive Bidens species.