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An accumulating body of evidence indicates that natural plant populations harbour a large diversity of transposable elements (TEs). TEs, which are especially mobilized under genomic and/or environmental stress, provide genetic and epigenetic variation that can substantially translate into a diversity of plant phenotypes within populations. However, it remains unclear what the potential ecological effects of diversity in TEs within an otherwise genetically uniform population are in terms of phenotypic diversity's effects on coexistence and ecosystem functioning. Using Arabidopsis thaliana as a proof-of-concept model, we assembled populations from individuals differing in the number and positions of ONSEN retrotransposon and tested whether the increasing diversity created by the ONSEN retrotransposon increased the phenotypic diversity of populations and enhanced their functioning under different environmental conditions. We demonstrate that TE-generated variation creates differentiation in ecologically important traits connected to different axes of the plant ‘economics’ spectrum. In particular, we show that Arabidopsis populations with increasing diversity of individuals differing in the ONSEN retrotransposon had higher phenotypic and functional diversity in resource use-related traits. Such increased diversity enhanced population productivity and reduced the performance of interspecific competitors. Synthesis. We conclude that TE-generated phenotypic and functional diversity can have similar effects on ecosystems as are usually documented for other biological diversity effects. The results of our experiment open up new fields of investigation, highlighting the ecological relevance of unexplored sources of phenotypic variability and hopefully inspiring functional trait ecologists and evolutionary biologists to begin exploring new questions at the intersection of their fields.

Biomass data for Arabidopsis thaliana populations. Each row refers to a pot in the pot experiment and shows: the population code treatment (competition, drought, their combination, or control) diversity, i.e. the number of different TE lines that a population was composed of number of individuals at time of biomass harvest total pot biomass average individual biomass (pot biomass/number of individuals) weight of competitors in the pot (0 if no competitors were present)

The phenotypes of plants can be influenced by the environmental conditions experienced by their parents. However, there is still much uncertainty about how common and how predictable such parental environmental effects really are. We carried out a comprehensive experimental test for parental effects, subjecting plants of multiple Arabidopsis thaliana genotypes to 24 different biotic or abiotic stresses, or combinations thereof, and comparing their offspring phenotypes in a common environment. The majority of environmental stresses caused significant parental effects, with −35% to +38% changes in offspring fitness. The expression of parental effects was strongly genotype-dependent, and multiple environmental stresses often acted nonadditively when combined. The direction and magnitude of parental effects were unrelated to the direct effects on the parents: Some environmental stresses did not affect the parents but caused substantial effects on offspring, while for others, the situation was reversed. Our study demonstrates that parental environmental effects are common and often strong in A. thaliana, but they are genotype-dependent, act nonadditively, and are difficult to predict. We should thus be cautious with generalizing from simple studies with single plant genotypes and/or only few individual environmental stresses. A thorough and general understanding of parental effects requires large multifactorial experiments.

Phenotypic plasticity, within and across generations (transgenerational plasticity), allows organisms and their progeny to adapt to the environment without modification of the underlying DNA. Recent findings suggest that epigenetic modifications are important mediators of such plasticity. However, empirical studies have, so far, mainly focused on plasticity in response to abiotic factors, overlooking the response to competition. We tested for within-generation and transgenerational phenotypic plasticity triggered by plant–plant competition intensity, and we tested whether it was mediated via DNA methylation, using the perennial, apomictic herb Taraxacum brevicorniculatum in four coordinated experiments. We then tested the consequences of transgenerational plasticity affecting competitive interactions of the offspring and ecosystem processes, such as decomposition. We found that, by promoting differences in DNA methylation, offspring of plants under stronger competition developed faster and presented more resource-conservative phenotypes. Further, these adjustments associated with less degradable leaves, which have the potential to reduce nutrient turnover and might, in turn, favour plants with more conservative traits. Greater parental competition enhanced competitive abilities of the offspring, by triggering adaptive phenotypic plasticity, and decreased offspring leaf decomposability. Our results suggest that competition-induced transgenerational effects could promote rapid adaptations and species coexistence and feed back on biodiversity assembly and nutrient cycling.

[Background and Aims] The observed positive diversity effect on ecosystem functioning has rarely been assessed in terms of intraspecific trait variability within populations. Intraspecific phenotypic variability could stem both from underlying genetic diversity and from plasticity in response to environmental cues. The latter might derive from modifications to a plant’s epigenome and potentially last multiple generations in response to previous environmental conditions. We experimentally disentangled the role of genetic diversity and diversity of parental environments on population productivity, resistance against environmental fluctuations and intraspecific phenotypic variation. [Methods} A glasshouse experiment was conducted in which different types of Arabidopsis thaliana populations were established: one population type with differing levels of genetic diversity and another type, genetically identical, but with varying diversity levels of the parental environments (parents grown in the same or different environments). The latter population type was further combined, or not, with experimental demethylation to reduce the potential epigenetic diversity produced by the diversity of parental environments. Furthermore, all populations were each grown under different environmental conditions (control, fertilization and waterlogging). Mortality, productivity and trait variability were measured in each population. [Key Results] Parental environments triggered phenotypic modifications in the offspring, which translated into more functionally diverse populations when offspring from parents grown under different conditions were brought together in mixtures. In general, neither the increase in genetic diversity nor the increase in diversity of parental environments had a remarkable effect on productivity or resistance to environmental fluctuations. However, when the epigenetic variation was reduced via demethylation, mixtures were less productive than monocultures (i.e. nega

Phenotypic plasticity, within and across generations (transgenerational plasticity), allows organisms and their progeny to adapt to the environment without modification of the underlying DNA. Recent findings suggest that epigenetic modifications are important mediators of such plasticity. However, empirical studies have, so far, mainly focused on plasticity in response to abiotic factors, overlooking the response to competition. We tested for within‐generation and transgenerational phenotypic plasticity triggered by plant–plant competition intensity, and tested whether it was mediated via DNA methylation, using the perennial, apomictic herb Taraxacum brevicorniculatum in four coordinated experiments. We then tested the consequences of transgenerational plasticity affecting competitive interactions of the offspring and ecosystem processes such as decomposition. We found that, by promoting differences in DNA methylation, offspring of plants under stronger competition developed faster and presented more resource‐conservative phenotypes. Further, these adjustments associated with less degradable leaves which have the potential to reduce nutrient turnover and might, in turn, favour plants with more conservative traits. Greater parental competition enhanced competitive abilities of the offspring by triggering adaptive phenotypic plasticity, and decreased offspring leaf decomposability. Our results suggest that competition‐induced transgenerational effects could promote rapid adaptations and species coexistence, and feed back on biodiversity assembly and nutrient cycling.

Many plant species are able to tolerate severe disturbance leading to removal of a substantial portion of the body by resprouting from intact or fragmented organs. Resprouting enables plants to compensate for biomass loss and complete their life cycles. The degree of disturbance tolerance, and hence the ecological advantage of damage tolerance (in contrast to alternative strategies), has been reported to be affected by environmental productivity. In our study, we examined the influence of soil nutrients (as an indicator of environmental productivity) on biomass and stored carbohydrate compensation after removal of aboveground parts in the perennial resprouter Plantago lanceolata. Specifically, we tested and compared the effects of nutrient availability on biomass and carbon storage in damaged and undamaged individuals. Damaged plants of P. lanceolata compensated neither in terms of biomass nor overall carbon storage. However, whereas in the nutrient-poor environment, root total non-structural carbohydrate concentrations (TNC) were similar for damaged and undamaged plants, in the nutrient-rich environment, damaged plants had remarkably higher TNC than undamaged plants. Based on TNC allocation patterns, we conclude that tolerance to disturbance is promoted in more productive environments, where higher photosynthetic efficiency allows for successful replenishment of carbohydrates. Although plants under nutrient-rich conditions did not compensate in terms of biomass or seed production, they entered winter with higher content of carbohydrates, which might result in better performance in the next growing season. This otherwise overlooked compensation mechanism might be responsible for inconsistent results reported from other studies.

Transgenerational effects can modify phenotypes of offspring generations playing thus a potentially important role in ecology and evolution of many plant species. These effects have been studied mostly across generations of sexually reproducing species. A substantial proportion of plant species are however reproducing asexually, for instance via clonal growth. Transgenerational effects are thought to be enabled by heritable epigenetic modification of DNA, although unambiguous evidence is still scarce. On the clonal herb white clover (Trifolium repens), we tested the generality of clonal transgenerational effects across five genotypes and five parental environments including soil contamination and above-ground competition. Moreover, by genome wide-methylation variation analysis we explored the role of drought, one of the parental environments that triggered the strongest transgenerational effects. We tested the induction of epigenetic changes in offspring generations using several intensities and durations of drought stress. We found that transgenerational effects of different environments were highly genotype specific and all tested environments triggered transgenerational effects at least in some genotypes. In addition, parental drought stresses triggered epigenetic change in T. repens and most of the induced epigenetic change was maintained across several clonal offspring generations. We conclude that transgenerational effects are common and genotype specific in clonal plant T. repens and potentially under epigenetic control.

Background and Aims There is currently much speculation about the role of epigenetic variation as a determinant of heritable variation in ecologically important plant traits. However, we still know very little about the phenotypic consequences of epigenetic variation, in particular with regard to more complex traits related to biotic interactions. Methods Here, a test was carried out to determine whether variation in DNA methylation alone can cause heritable variation in plant growth responses to jasmonic acid and salicylic acid, two key hormones involved in induction of plant defences against herbivores and pathogens. In order to be able to ascribe phenotypic differences to epigenetic variation, the hormone responses were studied of epigenetic recombinant inbred lines (epiRILs) of Arabidopsis thaliana - lines that are highly variable at the level of DNA methylation but nearly identical at the level of DNA sequence. Key Results Significant heritable variation was found among epiRILs both in the means of phenotypic traits, including growth rate, and in the degree to which these responded to treatment with jasmonic acid and salicylic acid. Moreover, there was a positive epigenetic correlation between the responses of different epiRILs to the two hormones, suggesting that plant responses to herbivore and pathogen attack may have a similar molecular epigenetic basis. Conclusions This study demonstrates that epigenetic variation alone can cause heritable variation in, and thus potentially microevolution of, plant responses to defence hormones. This suggests that part of the variation of plant defences observed in natural populations may be due to underlying epigenetic, rather than entirely genetic, variation