Plant adaptation to soil nitrogen: The role of microbes vs. the abiotic environment

Local adaptation is widely documented, but contributing selective agents are rarely identified or disentangled. Here we partition the effects of soil nitrogen and microbes on plant local adaptation. We experimentally manipulated both nitrogen and soil microbial communities on twelve Amphicarpaea bracteata populations from across a naturally occurring soil nitrogen gradient to investigate whether nitrogen and/or microbes contribute to local adaptation. We found that plants that had evolved in high nitrogen environments shifted resource allocation from mutualism (nitrogen-fixing rhizobia) to reproduction when grown in high nitrogen, while plants from low nitrogen sites did not, suggesting that mutualism-related traits have diverged across the nitrogen gradient. However, we detected no evidence for plant local adaptation to soil nitrogen or sympatric microbes. We also failed to find evidence for microbe-mediated adaptive plasticity (the phenomenon in which microbes from a particular habita..., , , # Plant adaptation to soil nitrogen: The role of microbes vs. the abiotic environment

[https://doi.org/10.5061/dryad.612jm64bw](https://doi.org/10.5061/dryad.612jm64bw)

## Description of the data and file structure

We grew twelve *Amphicarpaea bracteata* populations and four soil microbial communities from across a naturally occurring soil N gradient in three levels of contemporary N to investigate whether soil microbes and N availability contribute to plant local adaptation and whether rhizobium populations are adapted to local hosts and/or N availability. We found that plants with a history of elevated soil N shifted resource investment from mutualism to reproduction when grown in high contemporary N, while investment by plants from low-N sites did not change in response to contemporary N fertilization, suggesting that mutualism-related traits have diverged across the N gradient. However, we detected no evidence for plant local adaptation to microbes or to N. In contrast to plants,...,