Abstract

Local adaptation is an important mechanism underlying the adaptation of plants to environmental heterogeneity, and the toxicity of salt results in strong selection pressure on salt tolerance in plants and different ecotypes. Solidago canadensis, which is invasive in China, has spread widely and has recently colonized alkali sandy loams with a significant salt content. A common greenhouse experiment was conducted to test the role of local adaptation in the successful invasion of S. canadensis into salty habitats. Salt treatment significantly decreased the growth of S. canadensis, including rates of increase in the number of leaves and plant height; the root, shoot, and total biomass. Furthermore, salt stress significantly reduced the net photosynthetic rate, stomatal conductance, transpiration rate and relative chlorophyll content but significantly increased peroxidase activity and the proline content of S. canadensis and the root/shoot ratio. Two-way analysis of variance showed that salt treatment had a significant effect on the physiological traits of S. canadensis, except for the intercellular CO2 concentration, whereas the population and the salt × population interaction had no significant effect on any physiological traits. Most of the variation in plasticity existed within and not among populations, excep for the root/shoot ratio. S. canadensis populations from soil with moderate/high salt levels grew similarly to S. canadensis populations from soils with low salt levels. No significant correlation between salt tolerance indices and soil salinity levels was observed. The plasticity of the proline content, intercellular CO2 concentration and chlorophyll content had significant correlations with the salt tolerance index. These findings indicate a lack of evidence for local adaption in the existing populations of invasive S. canadensis in China; instead, plasticity might be more important than local adaptation in influencing the physiological traits and salt tolerance ability across the S. canadensis distribution.

Highlights

  • Invasive species are considered the second greatest threat to native biodiversity following habitat destruction and are a hotspot in the study of ecology and the environment [1]

  • It has been well documented that invasive plants have stronger adaptation ability to heterogeneous environments than native species [4, 5], yet there is evidence showing that invasive and native plants have equal ability to adapt to heterogeneous environments [6]

  • Nonparametric correlations analysis showed no significant correlation between salt tolerance indices and soil salinity levels (Table 2)

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Summary

Introduction

Invasive species are considered the second greatest threat to native biodiversity following habitat destruction and are a hotspot in the study of ecology and the environment [1]. Phenotypic plasticity, the ability of a single genotype to produce different phenotypes in response to environmental variation [14,15,16], contributes to the success of an invasive plant species by allowing increased fitness across a range of habitats [3, 17,18,19,20,21,22] and plays an important role in successful establishment under novel conditions [19, 23]. A central issue in invasion ecology is determining the importance of phenotypic plasticity and local adaptation in the adaption of invasive plant to novel heterogeneous environments across its distribution. More attention should be paid to invasive plants to explore the mechanisms underlying invasion success [24]

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