Ecological and evolutionary relevance of plant responses to environmental variability

Abstract

Global climate change brings not only changes in environmental means, but also trends of increasing temporal environmental variability, for instance through increased frequencies and intensities of extreme weathers and resulting changes in other environmental variables such as soil resource fluctuations. Terrestrial plants can respond to environmental change through short-term phenotypic plasticity, cross-generational responses, long-term population changes and community turnover. The latter two are driven by genetic and species differences in plant environmental responses, respectively. Albeit a few studies showing the potential effects of increasing environmental variability on plant communities and ecosystems, there are still many open questions, such as: (i) What are the effects of increased environmental variability per se on plants, and how do these effects compare to those of changes in environmental means? (ii) What is the relative importance of different components of environmental variability, in particular the timing versus frequency of environmental fluctuations? (iii) How do plants plastically respond to increased environmental variability across generations? (iv) How much variation is there among different plant species and genotypes within species, and does this variation reflect their ecological origins and evolutionary history? I tested these questions in short-lived plants, using: (1) two experiments with experimental nutrient fluctuations in which I compared the overall effects of changes in temporal nutrient variability to effects of changes in nutrient means, investigated both among- and within-species variation in a set of common European annual plants, and tested a phylogenetic signal in species responses; (2) a set of two related experiments in which I compared the effects of timing versus frequency of temperature fluctuations in different Arabidopsis thaliana genotypes across two generations, and tested for relationships between genotypes’ responses and their climate of origin, as potential indication for adaptive significance. My results show that: (i) Changes in environmental variability affect plants, but the magnitude of these effects depends on the environmental mean. (ii) Different aspects of environmental variability have different effects on plants. In the case of the temperature treatments tested in my experiments, the timing of temperature stress had much stronger impacts on plants than its frequency. (iii) The plastic responses of plants to environmental variability can be expressed in the following generation. Also here I found much stronger effects of timing of (parental) temperature stress than its frequency on offspring performance. (iv) There is significant variation in plant responses to increased environmental variability both among plant species and among genotypes within the same species. The variation among species can be partly explained by their shared phylogeny, while variation within species is related to the climatic variability of their geographic origins, indicating a possible adaptive significance. Together, my findings suggest that there is both ecological and evolutionary relevance in plant responses to increased environmental variability, and that changes in environmental variability will result in plant population and community changes.

Global climate change brings not only changes in environmental means, but also trends of increasing temporal environmental variability, for instance through increased frequencies and intensities of extreme weathers and resulting changes in other environmental variables such as soil resource fluctuations. Terrestrial plants can respond to environmental change through short-term phenotypic plasticity, cross-generational responses, long-term population changes and community turnover. The latter two are driven by genetic and species differences in plant environmental responses, respectively. Albeit a few studies showing the potential effects of increasing environmental variability on plant communities and ecosystems, there are still many open questions, such as: (i) What are the effects of increased environmental variability per se on plants, and how do these effects compare to those of changes in environmental means? (ii) What is the relative importance of different components of environmental variability, in particular the timing versus frequency of environmental fluctuations? (iii) How do plants plastically respond to increased environmental variability across generations? (iv) How much variation is there among different plant species and genotypes within species, and does this variation reflect their ecological origins and evolutionary history? I tested these questions in short-lived plants, using: (1) two experiments with experimental nutrient fluctuations in which I compared the overall effects of changes in temporal nutrient variability to effects of changes in nutrient means, investigated both among- and within-species variation in a set of common European annual plants, and tested a phylogenetic signal in species responses; (2) a set of two related experiments in which I compared the effects of timing versus frequency of temperature fluctuations in different Arabidopsis thaliana genotypes across two generations, and tested for relationships between genotypes’ responses and their climate of origin, as potential indication for adaptive significance. My results show that: (i) Changes in environmental variability affect plants, but the magnitude of these effects depends on the environmental mean. (ii) Different aspects of environmental variability have different effects on plants. In the case of the temperature treatments tested in my experiments, the timing of temperature stress had much stronger impacts on plants than its frequency. (iii) The plastic responses of plants to environmental variability can be expressed in the following generation. Also here I found much stronger effects of timing of (parental) temperature stress than its frequency on offspring performance. (iv) There is significant variation in plant responses to increased environmental variability both among plant species and among genotypes within the same species. The variation among species can be partly explained by their shared phylogeny, while variation within species is related to the climatic variability of their geographic origins, indicating a possible adaptive significance. Together, my findings suggest that there is both ecological and evolutionary relevance in plant responses to increased environmental variability, and that changes in environmental variability will result in plant population and community changes.