Shade tolerance as a key trait in invasion success of submerged macrophyte over .

The synergy between climate change, eutrophication, and biological invasion is threatening for native submerged plants in many ways. The response of submerged plants to these changes is a key factor that determines the outcome of biological invasion. In order to explain the invasion successes, we investigated the combined effects of climate change and eutrophication-related environmental factors (temperature, light, and nutrients) on the trait responses of a native () and an alien () submerged species. In a factorial design, we cultivated the two species in aquaria containing low (0.5 mg N L, 0.05 mg P L) and high (2 mg N L, 0.2 mg P L) nutrient concentrations, incubated at four light intensities (average 25, 67, 230, and 295 μmol m s PAR photon flux density) under two temperature levels (21.5 and 27.5 ± 0.5°C). We used four invasion-related functional traits (relative growth rate (RGR), specific leaf area (SLA), leaf dry matter content (LDMC), and nitrogen to carbon ratio (N:C molar ratio)) to measure the environmental response of the species. We calculated plasticity indexes to express the trait differences between species. showed significantly higher RGR and SLA than especially under low light intensity indicating that is much more shade tolerant. Elevated temperature resulted in higher SLA and reduced LDMC for indicating that may have higher invasion success. showed higher LDMC than . Chemical analyses of the plant tissue revealed that although showed significantly higher N:C molar ratio, nonetheless, the daily nitrogen uptake of was more than three times faster than that of . Results supported the idea that due to its higher shade tolerance and nitrogen uptake capacity, likely has greater invasion success with increasing temperature combined with low light levels.