Early View
Research Article

Natural variation on whole‐plant form in the wild is influenced by multivariate soil nutrient characteristics: natural selection acts on root traits

Courtney J. Murren

Corresponding Author

E-mail address: murrenc@cofc.edu

Department of Biology, College of Charleston, Charleston, SC, 29424 USA

Author for correspondence (e‐mail:

murrenc@cofc.edu

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Claudia H. S. Alt

Department of Biology, College of Charleston, Charleston, SC, 29424 USA

Department of Earth Sciences, University of Bristol, Bristol, UK

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Clare Kohler

Department of Biology, College of Charleston, Charleston, SC, 29424 USA

Environmental Sciences Initiative, CUNY ASRC, New York, NY, 10031 USA

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Gorka Sancho

Department of Biology, College of Charleston, Charleston, SC, 29424 USA

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First published: 30 January 2020

Abstract

Premise

In the complex soil nutrient environments of wild populations of annual plants, in general, low nutrient availability restricts growth and alters root–shoot relationships. However, our knowledge of natural selection on roots in field settings is limited. We sought to determine whether selection acts directly on root traits and to identify which components of the soil environment were potential agents of selection.

Methods

We studied wild native populations of Arabidopsis thaliana across 4 years, measuring aboveground and belowground traits and analyzing soil nutrients. Using multivariate methods, we examined patterns of natural selection and identified soil attributes that contributed to whole‐plant form. In a common garden experiment at two field sites with contrasting soil texture, we examined patterns of selection on root and shoot traits.

Results

In wild populations, we uncovered selection for above‐ and belowground size and architectural traits. We detected variation through time and identified soil components that influenced fruit production. In the garden experiment, we detected a distinct positive selection for total root length at the site with greater water‐holding capacity and negative selection for measures of root architecture at the field site with reduced nutrient availability and water holding capacity.

Conclusions

Patterns of natural selection on belowground traits varied through time, across field sites and experimental gardens. Simultaneous investigations of above‐ and belowground traits reveal trait functional relationships on which natural selection can act, highlighting the influence of edaphic features on evolutionary processes in wild annual plant populations.

DATA AVAILABILITY

Data available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.dncjsxkv6 (Murren et al., 2019).