The metabolome represents an important functional trait likely important to plant invasion success, but we have a limited understanding of whether the entire metabolome or targeted groups of compounds confer an advantage to invasive as compared to native taxa. We conducted a lipidomic and metabolomic analysis of the cosmopolitan wetland grass Phragmites australis. We classified features into metabolic pathways, subclasses, and classes. Subsequently, we used Random Forests to identify informative features to differentiate five phylogeographic and ecologically distinct lineages: European native, North American invasive, North American native, Gulf, and Delta. We found that lineages had unique phytochemical fingerprints, although there was overlap between the North American invasive and North American native lineages. Furthermore, we found that divergence in phytochemical diversity was driven by compound evenness rather than metabolite richness. Interestingly, the North American invasive lineage had greater chemical evenness than the Delta and Gulf lineages but lower evenness than the North American native lineage. Our results suggest that metabolomic evenness may represent a critical functional trait within a plant species. Its role in invasion success, resistance to herbivory, and large-scale die-off events common to this and other plant species remain to be investigated.

• Keywords
• Common Reed, Ecological Omics, Invasion Ecology, Invasive Plant Species, Liquid Chromatography–Mass Spectrometry (LC–MS), Phytochemistry,
• MeSH
• Phenotype MeSH
• Phytochemicals MeSH
• Poaceae * MeSH
• Wetlands * MeSH
• Plants MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phytochemicals MeSH

Among the traits whose relevance for plant invasions has recently been suggested are genome size (the amount of nuclear DNA) and ploidy level. So far, research on the role of genome size in invasiveness has been mostly based on indirect evidence by comparing species with different genome sizes, but how karyological traits influence competition at the intraspecific level remains unknown. We addressed these questions in a common-garden experiment evaluating the outcome of direct intraspecific competition among 20 populations of Phragmites australis, represented by clones collected in North America and Europe, and differing in their status (native and invasive), genome size (small and large), and ploidy levels (tetraploid, hexaploid, or octoploid). Each clone was planted in competition with one of the others in all possible combinations with three replicates in 45-L pots. Upon harvest, the identity of 21 shoots sampled per pot was revealed by flow cytometry and DNA analysis. Differences in performance were examined using relative proportions of shoots of each clone, ratios of their aboveground biomass, and relative yield total (RYT). The performance of the clones in competition primarily depended on the clone status (native vs. invasive). Measured in terms of shoot number or aboveground biomass, the strongest signal observed was that North American native clones always lost in competition to the other two groups. In addition, North American native clones were suppressed by European natives to a similar degree as by North American invasives. North American invasive clones had the largest average shoot biomass, but only by a limited, nonsignificant difference due to genome size. There was no effect of ploidy on competition. Since the North American invaders of European origin are able to outcompete the native North American clones, we suggest that their high competitiveness acts as an important driver in the early stages of their invasion.

• Keywords
• Europe, North America, common reed, genome size, intraspecific competition, native populations, plant invasion, ploidy level,
• Publication type
• Journal Article MeSH

Identifying the factors that influence spatial genetic structure among populations can provide insights into the evolution of invasive plants. In this study, we used the common reed (Phragmites australis), a grass native in Europe and invading North America, to examine the relative importance of geographic, environmental (represented by climate here), and human effects on population genetic structure and its changes during invasion. We collected samples of P. australis from both the invaded North American and native European ranges and used molecular markers to investigate the population genetic structure within and between ranges. We used path analysis to identify the contributions of each of the three factors-geographic, environmental, and human-related-to the formation of spatial genetic patterns. Genetic differentiation was observed between the introduced and native populations, and their genetic structure in the native and introduced ranges was different. There were strong effects of geography and environment on the genetic structure of populations in the native range, but the human-related factors manifested through colonization of anthropogenic habitats in the introduced range counteracted the effects of environment. The between-range genetic differences among populations were mainly explained by the heterogeneous environment between the ranges, with the coefficient 2.6 times higher for the environment than that explained by the geographic distance. Human activities were the primary contributor to the genetic structure of the introduced populations. The significant environmental divergence between ranges and the strong contribution of human activities to the genetic structure in the introduced range suggest that invasive populations of P. australis have evolved to adapt to a different climate and to human-made habitats in North America.

• Keywords
• Phragmites, biological invasions, common reed, evolution, human activities, isolation by distance, isolation by environment, landscape genetics, spatial genetic structure,
• Publication type
• Journal Article MeSH