Effectiveness of Seed Traps for Assessing Seed Rain in Periurban Grasslands

Landscape context plays an important role in plant community structuring, with selection pressure affecting dispersal ability. This is particularly true in cities, where land use heterogeneity and habitat fragmentation can affect plant dispersal patterns. Seed rain surveys are often used to study dispersal but involve a wide variety of methods and trap types and rarely address the urban context. This study aimed to (1) compare seed rain, especially of anemochorous seeds, in different spatial contexts in a periurban area in Angers (western France); and (2) compare seed rain captured using different trap types (funnel traps/sticky traps), trap heights, and shapes. Seven sites, each equipped with five replicates of funnel traps, were selected in a periurban area in the western part of Angers. Within one of these sites, ten types of traps (differing in trapping method, height, shape, degree of tilt, and area) were employed and their performance compared. The results show that trap height rather than trap type is responsible for differences in seed density and composition. Furthermore, the composition of collected seeds appears to be associated with surrounding land cover, in particular built areas, which has implications for urban ecology in terms of understanding the influence of landscape factors on plant dispersal

Intraspecific trait variation in grassland plant communities along urban-rural gradients

International audienceTrait-based approaches have been successfully used to demonstrate how the modified ecological conditions within urban areas filter plant species within plant communities. However, there is growing evidence that trait measurement in situ may improve knowledge of the ecological mechanisms underlying such filtering processes. This study aimed to determine the relative contribution of inter- and intraspecific trait variation in explaining the influence of urban-rural gradients on grassland plant communities. Twenty-one stations were sampled along an urban-rural gradient in two French cities. Three functional traits (specific leaf area, maximum height and phenology), chosen to represent general adaptive strategies of plants, were measured on the 26 most abundant grassland plant species. By decomposing the community-level variance of these traits into species turnover, intraspecific trait variability and covariation, we showed how important it may be to take field measurements into account when studying trait distributions in urban ecology. High intraspecific variability may reinforce trait selection effects, for example by favoring both taller species and populations of taller individuals in urban areas in comparison with rural contexts. Advanced phenology at community-level was influenced by early flowering for almost all urban populations of each species while Specific Leaf Area responses were inconsistent. Because trait distributions and ecosystem functions are closely linked, we suggest that it is now important to develop trait-based approaches at community-level, including both intra- and inter-specific trait variability, in order to improve our knowledge of ecological processes operating in urban areas

Acibenzolar-S-Methyl Reprograms Apple Transcriptome Toward Resistance to Rosy Apple Aphid

International audienceAcibenzolar-S-methyl (ASM) is a chemical compound, which is able to induce resistance in several model and non-model plants, but the end-players of this induced defense remain ill-defined. Here, we test the hypothesis that treatment with ASM can protect apple (Malus × domestica) against the rosy apple aphid (Dysaphis plantaginea) and investigate the defense molecules potentially involved in resistance. We measured aphid life traits and performed behavioral assays to study the effect of ASM on plant resistance against the aphid, and then combined transcriptomic, bioinformatics, metabolic and biochemical analyses to identify the plant compounds involved in resistance. Plants treated with ASM negatively affected several life traits of the aphid and modified its feeding and host seeking behaviors. ASM treatment elicited up-regulation of terpene synthase genes in apple and led to the emission of (E,E)-α-farnesene, a sesquiterpene that was repellent to the aphid. Several genes encoding amaranthin-like lectins were also strongly up-regulated upon treatment and the corresponding proteins accumulated in leaves, petioles and stems. Our results link the production of specific apple proteins and metabolites to the antibiosis and antixenosis effects observed against Dysaphis plantaginea, providing insight into the mechanisms underlying ASM-induced herbivore resistance