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Adaptive differentiation among populations of the Mediterranean dry grassland species Brachypodium retusum : The role of soil conditions, grazing, and humidity
Author(s) -
Vidaller Christel,
Dutoit Thierry,
Ibrahim Yosra,
Hanslin Hans Martin,
Bischoff Armin
Publication year - 2018
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/ajb2.1116
Subject(s) - biology , local adaptation , grazing , population , ecology , adaptation (eye) , grassland , ecological succession , mediterranean climate , agronomy , demography , neuroscience , sociology
Premise of the Study Genetic differentiation in plant species may result from adaptation to environmental conditions, but also from stochastic processes. The drivers selecting for local adaptation and the contribution of adaptation to genetic differentiation are often unknown. Restoration and succession studies have revealed different colonization patterns for Brachypodium retusum , a common Mediterranean grass. In order to understand these patterns, we tested population differentiation and adaptation to different environmental factors. Methods Structured sampling of 12 populations from six sites and two soil types within site was used to analyze the spatial and environmental structure of population differentiation. Sampling sites differ in grazing intensity and climate. We tested germination and growth in a common garden. In subsets, we analyzed the differential response to stone cover, grazing and soil moisture. Key Results We found significant differences among populations. The site explained population differentiation better than soil, suggesting a dominant influence of climate and/or genetic drift. Stone cover had a positive influence on seedling establishment, and populations showed a differential response. However, this response was not related to environmental differences between collection sites. Regrowth after clipping was higher in populations from the more intensively grazed Red Mediterranean soils suggesting an adaptation to grazing. Final germination was generally high even under drought, but germination response to differences in soil moisture was similar across populations. Conclusions Adaptive population differentiation in germination and early growth may have contributed to different colonization patterns. Thus, the provenance of B. retusum needs to be carefully considered in ecological restoration.