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The remarkable capacity of bryophytes to tolerate extremely challenging abiotic conditions allows us to enhance our understanding of the diversity of molecular mechanisms involved in plant stress response. Here, we used next generation sequencing to study DNA methylation and gene expression changes in plants from four populations of the metallophyte moss Scopelophila cataractae experimentally exposed to either Cd or Cu. These populations previously showed differences in tolerance to both metals, so here, we aimed to investigate the molecular basis of this phenotypic differentiation. We found no evidence of genetic differentiation among the populations studied. The epigenetic data, however, showed limited but significant population-specific changes in DNA methylation in response to both metals. Exposure to acute Cu stress in the laboratory led to the downregulation of genes involved in heavy metal tolerance in both the more and the less tolerant populations, but this response was quantitatively higher in the most tolerant. We propose that chronic exposure to varying levels of heavy metals in the field led to potentially non-genetically-based intraspecific differentiation for heavy metal tolerance in S. cataractae. The most tolerant plants invested more in constitutive protection and were more efficient at entering a conservative state when faced with acute Cu stress

Plant metabolic pathways and gene networks involved in the response to herbivory are well-established, but the impact of epigenetic factors as modulators of those responses is less understood. Here, we use the demethylating agent 5-azacytidine to uncover the role of DNA cytosine methylation on phenotypic responses after short-term herbivory in Thlaspi arvense plants that came from two European populations with contrasting flowering phenotypes expected to differ in the response to experimental demethylation. The experimental design followed a 2 × 3 factorial design, that was replicated for each flowering-type. First, half the seeds were submerged in a water solution of 5-azacytidine and the other half only in water, as controls. Then, we assigned control and demethylated plants to three herbivory categories (i) insect herbivory, (ii) artificial herbivory, and (iii) undamaged plants. The effects of the demethylation and herbivory treatments were assessed by quantifying genome-wide global DNA cytosine methylation, concentration of leaf glucosinolates, final stem biomass, fruit and seed production, and seed size. For most of the plant traits analysed, individuals from the two flowering-types responded differently. In late-flowering plants, global DNA methylation did not differ between control and demethylated plants but it was significantly reduced by herbivory. Conversely, in early-flowering plants, demethylation at seed stage was still evident in leaf DNA of reproductive individuals whereas herbivory did not affect their global DNA methylation. In late-flowering plants, artificial herbivory imposed a stronger reduction than insect herbivory in global DNA methylation and final stem biomass, and induced higher concentration of aliphatic glucosinolates. In early-flowering plants, the effects of herbivory were non-significant for the same traits. Finally, the effect of herbivory on reproductive parameters varied with the level of demethylation and the plant flowering-type

The way in which taxonomic diversity relates to functional diversity is important for understanding the mechanisms that sustain ecosystem function and services. We investigated how an explicit consideration of plant-pollinator interactions influences our view of plant diversity. We studied three plant species-rich communities located in different biodiversity hotspot regions: two soil-specific plant communities with Mediterranean-climate, sandy dolomite outcrops in Andalusia (Spain) and serpentine seeps in California (USA), and a third community in the sub-tropical dry scrublands in Yucatan (Mexico). Sampling at three spatial scales (region, site, plot) and rarefaction analyses were used to characterize and compare spatial and temporal variation of entomophilous plant diversity based on species presence (“static plant diversity”), flower display sizes along the season (“dynamic flower diversity”), and pollinator visitation (“interaction-effective diversity”). The studied communities differed in the static diversity of plants, with sub-tropical dry scrublands being less diverse than the two Mediterranean communities. Reduction of static diversity at local scale was stronger in the richest Mediterranean communities and, thus, static diversity was similar among regions when considering finer (site-level) spatial scales. In addition, the two Mediterranean communities displayed more seasonal variation, thus reducing differences in dynamic diversity among regions, i.e. when considering finer temporal scales. These results suggested that, at finer spatio-temporal scales expected to be relevant for interactions with pollinators, plant communities are not necessarily as diverse as the region where they occur. Accordingly, interaction-effective diversity based on pollinator visitation was in all cases lower than expected relative to the diversity of flowers. Thus, diversity of visited flowers does not perfectly track diversity of flowering species but instead reaches asymptot

Yeasts frequently colonise floral nectar, where they can reach high densities. Recent investigations have further shown that yeast metabolism alters nectar properties by decreasing its total sugar content, modifying sugar composition, or raising nectar local temperature. However, the distribution patterns of nectar yeasts remain poorly investigated at multiple spatial and temporal scales. Here, we study natural variation of the nectar yeasts in a single host plant, Helleborus foetidus, in a mountainous region. We quantified spatio-temporal variation in the frequency and abundance of yeast species across six populations located along an altitudinal gradient. Variance partitioning techniques were used to estimate the relative magnitude of variation in yeast abundance between individual plants, flowers within plants, and nectaries within flowers. Although yeast frequency and abundance varied widely across sites and dates, the largest part of total variance occurred at the sub-individual level (i.e., flowers on the same plant). Pollinator composition and activity seemed the main factors explaining the observed patterns of yeast frequency and abundance across floral nectar samples

Margins of distribution of plant species constitute natural areas where the impact of the antagonistic interactions is expected to be higher and where changes in the dynamics of plant-herbivore coevolution could promote intraspecific differentiation in (co)evolving plant traits. In the present study, we investigated how differences in the average herbivory level affect maternal fitness in core continuous and marginal disjunct populations of Daphne laureola in an effort to assess the role of herbivores limiting plant distribution. Furthermore, we investigated intraspecific differentiation in vegetative traits and their potential connection to divergent selection by herbivores in both groups of populations. Our results did not support increased herbivory at the species margin but did support a difference in the effect of herbivory on maternal fitness between core continuous and marginal disjunct populations of D. laureola. In addition, herbivores did not exert phenotypic selection consistent with the geographic variation in studied plant traits. Therefore, the geographic variation of vegetative traits of D. laureola seems to be consequence of environmental heterogeneity more than result of geographically divergent selection by herbivores.

Several ecological conditions and processes occurring naturally in plant populations may lead to spatial aggregation of sexes within populations of sexually polymorphic species. In addition, ecological disturbances such as forest management or fire could also affect the spatial distribution of sexes within populations. Spatial aggregation of sexes can have important consequences for the fitness of the individuals in sex-biased patches through increased pollen limitation and/or variation in the male fitness of hermaphrodites. Therefore, spatial aggregation of sexes could be relevant for the maintenance of the sexual polymorphism in plant species. Here, we used point pattern analysis to study the spatial distribution of female and hermaphrodite individuals within a single population of the gynodioecious understory shrub Daphne laureola, inhabiting a young pine reforestation and the adjacent natural undisturbed area. In the undisturbed area, we found that hermaphrodites were distributed randomly whereas females were spatially aggregated at short distances. Such aggregation could result from narrower ecological amplitude, cyto-nuclear determination of sex and limited dispersal and/or increased cloning in females. In the reforested area, females were slightly more abundant and the two sexes were randomly distributed among all plants. Recolonization processes after certain forest disturbances could thus favour the establishment of females and alter the spatial distribution of sexes in this understory species. © 2012.

Biogeographic models predict that marginal populations should be more geographically isolated and smaller than central populations, linked to more stressful conditions and likely also to a reduction in density of individuals, individual growth, survival and reproductive output. This variation in population features could have important consequences for different aspects of plant ecology such as individual reproductive success, population genetic structure or plant-animal interactions. In this study, we analyze if individuals of the evergreen shrub Daphne laureola at disjunt populations in a local border of its distribution area in southern Iberian Peninsula differ in individual size, shoot growth, reproductive output and the pollination environment from central continuous populations within the area. Plants of central continuous populations were larger and produced more flowers and fruits than plants of marginal disjunct populations suggesting more optimal conditions, although they had lower annual shoot growth. In contrast, fruit set was higher in plants at the local border, suggesting a more efficient pollinator service in these populations where the main pollinator in central continuous populations, the pollen beetle Meligethes elongatus, was not present. Our results do not support strong differences in the ecological stress between marginal disjunct and central continuous populations of D. laureola in the south of the Iberian Peninsula but indicate some changes in plant-pollinator interactions that could be relevant for the sexual polymorphism in this gynodioecious species.

— Despite year round availability of foliage, abundance of generalist noctuid larvae (Lepidoptera: Noctuidae) in evergreen- dominated Mediterranean forests has a narrow, distinct spring peak. This restricted larval period has been suggested to result in part from avoidance of the nutritionally poor mature foliage, and preference for nutritionally superior spring-produced young leaves. This study examines this hypothesis by (i) documenting differences in nutritional characteristics between expanding (April) and mature (June) young leaves of the evergreen Mediterranean shrub Daphne laureola L. (Thymelaeaceae), and (ii) experimentally studying the feeding preferences of noctuid larvae for young leaves, old leaves (≥ 1 yr old), and developing fruits of this species in one south-eastern Spanish locality. Young leaves of D. laureola declined in nutrient concentration and specific dry mass from April to June. The responses of noctuid larvae, in terms of both relative preference and total consumption, to this seasonal variation in chemical and physical features of young leaves were also investigated. When noctuid larvae were simultaneously offered young leaves, old leaves and developing fruits, they exhibited similar preferences for young leaves and developing fruits, and rejected old leaves developed during the previous year. Noctuid larvae did not modify their consumption of young leaves relative to old leaves and developing fruits in response to seasonal changes. Food selection patterns exhibited by D. laureola noctuid herbivores, notably the rejection of old leaves in favour of young ones, are consistent with the hypothesis relating restricted larval periods of these generalist consumers with the low food value of the previous season leaves of evergreen Mediterranean plants