SUMMARY: Hybridization is a widespread phenomenon in the evolution of plants and exploring its role is crucial to understanding diversification processes of many taxonomic groups. Recently, more attention is focused on the role of ancient hybridization that has repeatedly been shown as triggers of evolutionary radiation, although in some cases, it can prevent further diversification. The causes, frequency, and consequences of ancient hybridization remain to be explored. Here, we present an account of several events of ancient hybridization in turmeric, the economically important plant genusCurcuma(Zingiberaceae), which harbors about 130 known species. We analyzed 1094 targeted low‐copy genes and plastomes obtained by next‐generation sequencing of 37 species ofCurcuma, representing the known genetic diversity and spanning the geographical distribution of the genus. Using phylogenetic network analysis, we show that the entire genusCurcumaas well as its most speciose lineage arose via introgression from the genusPyrgophyllumand one of the extinct lineages, respectively. We also document a single event of ancient hybridization, withC. vamanaas a product, that represents an evolutionary dead end. We further discuss distinct circumstances of those hybridization events that deal mainly with (in)congruence in chromosome counts of the parental lineages.

The genus Anthoxanthum (sweet vernal grass, Poaceae) represents a taxonomically intricate polyploid complex with large phenotypic variation and its evolutionary relationships still poorly resolved. In order to get insight into the geographic distribution of ploidy levels and assess the taxonomic value of genome size data, we determined C- and Cx-values in 628 plants representing all currently recognized European species collected from 197 populations in 29 European countries. The flow cytometric estimates were supplemented by conventional chromosome counts. In addition to diploids, we found two low (rare 3x and common 4x) and one high (~16x–18x) polyploid levels. Mean holoploid genome sizes ranged from 5.52 pg in diploid A. alpinum to 44.75 pg in highly polyploid A. amarum, while the size of monoploid genomes ranged from 2.75 pg in tetraploid A. alpinum to 9.19 pg in diploid A. gracile. In contrast to Central and Northern Europe, which harboured only limited cytological variation, a much more complex pattern of genome sizes was revealed in the Mediterranean, particularly in Corsica. Eight taxonomic groups that partly corresponded to traditionally recognized species were delimited based on genome size values and phenotypic variation. Whereas our data supported the merger of A. aristatum and A. ovatum, eastern Mediterranean populations traditionally referred to as diploid A. odoratum were shown to be cytologically distinct, and may represent a new taxon. Autopolyploid origin was suggested for 4x A. alpinum. In contrast, 4x A. odoratum seems to be an allopolyploid, based on the amounts of nuclear DNA. Intraspecific variation in genome size was observed in all recognized species, the most striking example being the A. aristatum/ovatum complex. Altogether, our study showed that genome size can be a useful taxonomic marker in Anthoxathum to not only guide taxonomic decisions but also help resolve evolutionary relationships in this challenging grass genus.

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.

Aim: Plant invasions are a global problem that requires studying plants and their environmental associations across native and introduced ranges.Location: 2000 km transects in China, Europe and North America.Time Period: June 2019–July 2020.Major Taxa Studied: Japanese knotweed (Reynoutria japonica).Methods: We surveyed 150 populations of Japanese knotweed, a noxious invader of the temperate zone, along 2000 km transects in native China and the introduced ranges of Europe and North America.Results: We found that larger plants and denser populations in the introduced ranges were associated with shifts in leaf economy and chemical defences. Introduced knotweed populations had higher SLA but reduced leaf chlorophyll, lignin, C:N ratio and leaf toughness along with altered leaf tannins, flavonoids and alkaloids. We found three distinct multivariate knotweed phenotypes primarily in the introduced ranges, and two multivariate knotweed phenotypes mainly in native populations.Main Conclusions: Decreased herbivore and pathogen impacts in introduced populations and changes in environmental associations indicate that enemy release and novel habitat conditions might have driven the emergence of novel ecological strategies in this global plant invader.