Strong divergence in quantitative traits and plastic behavior in response to nitrogen availability among provenances of a common wetland plant

• Genetic variation in quantitative traits is assessed for a common wetland plant.
• Strong divergence among populations in traits probably related to nitrogen removal in wetlands.
• Trait expression is related to soil N availability of plant origin suggesting adaptation.

Wetland ecosystems provide important ecosystem services such as the degradation and retention of excessive nutrient loadings. Plants may affect these processes directly or indirectly via the interaction with the rhizosphere community. Many studies on the impact of plant functional traits on ecosystem processes in wetlands focused on variability among species, neglecting the importance of intraspecific variability. Here we assessed the intraspecific genetically based variability of a common wetland plant for traits, potentially relevant for the removal of nitrogen compounds from the soil. We asked whether and how quantitative genetic variation is expressed differently depending on nitrogen availability and how it is structured within and among natural European populations of Juncus effusus. We partitioned the observed genetic variation into within- (broad-sense heritability) and among (QST) population components for mean traits and plasticities. We found a strong plastic behavior for all measured traits in response to nitrogen availability. Genetic variation for mean traits differed strongly among populations but was very low at population level. We could not demonstrate a general effect of nitrogen availability on genetic trait expression. Our results suggest that basic and applied studies on wetland ecosystem processes will benefit from a deeper understanding of intraspecific genetic variation for traits and plastic behavior which is also fundamental for breeding approaches or to predict evolutionary responses.