Can plants build their niche through modulation of soil microbial activities linked with nitrogen cycling? A test with Arabidopsis thaliana.

In natural systems, different plant species have been shown to modulate specific nitrogen (N) cycling processes so as to meet their N demand, thereby potentially influencing their own niche. This phenomenon might go beyond plant interactions with symbiotic microorganisms and affect the much less explored plant interactions with free-living microorganisms involved in soil N cycling, such as nitrifiers and denitrifiers. Here, we investigated variability in the modulation of soil nitrifying and denitrifying enzyme activities (NEA and DEA, respectively), and their ratio (NEA : DEA), across 193 Arabidopsis thaliana accessions. We studied the genetic and environmental determinants of such plant-soil interactions, and effects on plant biomass production in the next generation. We found that NEA, DEA, and NEA : DEA varied c. 30-, 15- and 60-fold, respectively, among A. thaliana genotypes and were related to genes linked with stress response, flowering, and nitrate nutrition, as well as to soil parameters at the geographic origin of the analysed genotypes. Moreover, plant-mediated N cycling activities correlated with the aboveground biomass of next-generation plants in home vs away nonautoclaved soil, suggesting a transgenerational impact of soil biotic conditioning on plant performance. Altogether, these findings suggest that nutrient-based plant niche construction may be much more widespread than previously thought.

AraDiv: a dataset of functional traits and leaf hyperspectral reflectance of Arabidopsis thaliana.

Data from functional trait databases have been increasingly used to address questions related to plant diversity and trait-environment relationships. However, such databases provide intraspecific data that combine individual records obtained from distinct populations at different sites and, hence, environmental conditions. This prevents distinguishing sources of variation (e.g., genetic-based variation vs. phenotypic plasticity), a necessary condition to test for adaptive processes and other determinants of plant phenotypic diversity. Consequently, individual traits measured under common growing conditions and encompassing within-species variation across the occupied geographic range have the potential to leverage trait databases with valuable data for functional and evolutionary ecology. Here, we recorded 16 functional traits and leaf hyperspectral reflectance (NIRS) data for 721 widely distributed Arabidopsis thaliana natural accessions grown in a common garden experiment. These data records, together with meteorological variables obtained during the experiment, were assembled to create the AraDiv dataset. AraDiv is a comprehensive dataset of A. thaliana's intraspecific variability that can be explored to address questions at the interface of genetics and ecology.

Strong stabilizing selection on timing of germination in a Mediterranean population of Arabidopsis thaliana.

PREMISE: Timing of germination can strongly influence plant fitness by affecting seedling survival and by having cascading effects on later life-history traits. In seasonal environments, the period favorable for seedling establishment and growth is limited, and timing of germination is likely to be under stabilizing selection because of conflicting selection through survival and fecundity. Moreover, optimal germination time may vary among genotypes because of inherent differences in later life-history traits. METHODS: To examine how germination time affects survival, fecundity, and the relative fitness of two genotypes differing in time to first flower, we conducted a field experiment in an Italian population of the winter annual Arabidopsis thaliana, in which seedling establishment occurs mainly in November. We transplanted seedlings of the local genotype and of a Swedish genotype monthly from August to December and monitored survival and fecundity. RESULTS: Only seedlings transplanted in November and December survived until reproduction, and fitness of the November cohort was 35 times higher than that of the December cohort, indicating strong stabilizing selection on timing of germination. There was no evidence of conflicting selection: seedling survival, adult survival, and fecundity were all highest in the November cohort. Moreover, the relative fitness of the two genotypes did not differ significantly between cohorts. CONCLUSIONS: The very narrow window of opportunity for seedling establishment was related to rapid seasonal changes in soil moisture and temperature, suggesting that rate of seasonal change is an important aspect to consider for understanding spatiotemporal variation in selection on phenological traits.