Low genetic variation of invasive Fallopia spp. in their northernmost European distribution range

Knowledge about the reproduction strategies of invasive species is fundamental for effective control. The invasive Fallopia taxa (Japanese knotweed s.l.) reproduce mainly clonally in Europe, and preventing spread of vegetative fragments is the most important control measure. However, high levels of genetic variation within the hybrid F. × bohemica indicate that hybridization and seed dispersal could be important. In Norway in northern Europe, it is assumed that these taxa do not reproduce sexually due to low temperatures in the autumn when the plants are flowering. The main objective of this study was to examine the genetic variation of invasive Fallopia taxa in selected areas in Norway in order to evaluate whether the taxa may reproduce by seeds in their most northerly distribution range in Europe. Fallopia stands from different localities in Norway were analyzed with respect to prevalence of taxa, and genetic variation within and between taxa was studied using amplified fragment length polymorphism (AFLP). Taxonomic identification based on morphology corresponded with identification based on simple sequence repeats (SSR) and DNA ploidy levels (8× F. japonica, 6× F. × bohemica and 4× F. sachalinensis). No genetic variation within F. japonica was detected. All F. × bohemica samples belonged to a single AFLP genotype, but one sample had a different SSR genotype. Two SSR genotypes of F. sachalinensis were also detected. Extremely low genetic variation within the invasive Fallopia taxa indicates that these taxa do not reproduce sexually in the region, suggesting that control efforts can be focused on preventing clonal spread. Climate warming may increase sexual reproduction of invasive Fallopia taxa in northern regions. The hermaphrodite F. × bohemica is a potential pollen source for the male‐sterile parental species. Targeted eradication of the hybrid can therefore reduce the risk of increased sexual reproduction under future warmer climate.     

Herbivore resistance of invasive <Emphasis Type="Italic">Fallopia</Emphasis> species and their hybrids

Hybridization has been proposed as a mechanism by which exotic plants can increase their invasiveness. By generating novel recombinants, hybridization may result in phenotypes that are better adapted to the new environment than their parental species. We experimentally assessed the resistance of five exotic Fallopia taxa, F. japonica var. japonica, F. sachalinensis and F. baldschuanica, the two hybrids F. × bohemica and F. × conollyana, and the common European plants Rumex obtusifolius and Taraxacum officinale to four native European herbivores, the slug Arion lusitanicus, the moth Noctua pronuba, the grasshopper Metrioptera roeselii and the beetle Gastrophysa viridula. Leaf area consumed and relative growth rate of the herbivores differed significantly between the Fallopia taxa and the native species, as well as among the Fallopia taxa, and was partly influenced by interspecific variation in leaf morphology and physiology. Fallopia japonica, the most abundant Fallopia taxon in Europe, showed the highest level of resistance against all herbivores tested. The level of resistance of the hybrids compared to that of their parental species varied depending on hybrid taxon and herbivore species. Genotypes of the hybrid F. × bohemica varied significantly in herbivore resistance, but no evidence was found that hybridization has generated novel recombinants that are inherently better defended against resident herbivores than their parental species, thereby increasing the hybrid’s invasion success. In general, exotic Fallopia taxa showed higher levels of herbivore resistance than the two native plant species, suggesting that both parental and hybrid Fallopia taxa largely escape from herbivory in Europe.     

Unexpected genetic diversity of Fallopia japonica from Central Europe revealed after AFLP analysis

Recently much attention has been paid to genetic aspects of invasive success in Japanese knotweed s.l. One hypothesis to explain the invasive spread of these species is a multiple introduction, which leads to a higher level of genetic diversity in the invaded range. Fallopia japonica is considered to be genetically uniform in Europe, introduced as a single female clone. However, there is some evidence suggesting that invasion history and dynamics differ between Western and Central-Eastern Europe. We used AFLP markers to characterize genetic diversity of three Fallopia taxa that occur in Poland: F. japonica, F. sachalinensis and their hybrid Fallopia × bohemica, growing in so-called ‘homogeneous’ populations, consisting of one taxon and ‘heterogeneous’ populations, composed of the three taxa cohabiting together. No polymorphism, resp. an insignificantly low variability was observed in the ‘homogeneous’ populations. In the ‘heterogeneous’ stands polymorphism was detected within each taxa, with one exception that concerns individuals of F. sachalinensis from a riparian habitat. The highest level of polymorphism was found among individuals of F. × bohemica. The most striking result of our study is the observation of polymorphism between individuals of F. japonica. The AFLP data also showed that F. × bohemica is most diverse when occurring in a heterogeneous configuration with F. japonica and F. sachalinensis in the same habitat. Our results are the first evidence of genetic diversity in F. japonica populations in Central Europe and can implicate the possibility of its multiple introduction in this region or the existence of sexual reproduction of this species.     

The potential role of polyploidy and hybridisation in the further evolution of the highly invasive <Emphasis Type="Italic">Fallopia</Emphasis> taxa in Europe

Japanese knotweed s.l. comprises Fallopia japonica, F. sachalinensis, F. × bohemica and any F2s or backcrosses. The parental taxa were introduced from the East to the West as garden ornamentals in the nineteenth century, and soon spread beyond the confines of the garden to become widespread and persistent weeds. Since only female F. japonica var. japonica was introduced, its impressive spread has occurred solely by vegetative means. However, the initial lack of genetic variability has been complemented by an extensive series of hybridisations in the adventive range. We examine the history, spread, reproductive biology and ecological impact of these species in the West. The role and importance of polyploidy and hybridisation in their invasion of the West is discussed, as are the implications of these factors for the potential further evolution of the group.     

Variation of growth and functional traits of invasive knotweeds (<Emphasis Type="Italic">Fallopia</Emphasis> spp.) in Belgium

Three invasive Fallopia taxa are present in Belgium: F. japonica (FJ), F. sachalinensis (FS) and their hybrid F. × bohemica (FB). FS is the least invasive of the three taxa. In this study, we compared the taxa, in sites where they co-occur, for differences in functional traits that might influence their competitive ability and invasiveness—shoot height and ramification, leaf size, specific leaf area (SLA) and foliar nitrogen (N) concentration. The three taxa exhibited similar growth kinetics and similar SLA. However, FS differed in its architecture and allocation of leaf area, having less ramified shoots and a steeper gradient of decreasing leaf size along the main shoot. Also, FS had greater foliar N and less efficient N resorption from senescing leaves. These traits values may result in lower competitive ability of FS for light and nitrogen. For the same traits, FB was generally intermediate between FS and FJ, but often closer to the latter. FB was more variable than FS and FJ, possibly due to larger genetic variation. SLA and ramification varied greatly amongst sites for all taxa, due in part to plastic response to contrasting light regimes. Variation in functional traits values may in part explain the variation in invasiveness amongst the members of the Fallopia complex in Belgium.     

Effects of climatic factors on Fallopia japonica s.l. seedling establishment: evidence from laboratory experiments

The highly invasive Fallopia complex (Fallopia japonica s.l., Fallopia japonica var. japonica, Fallopia sachalinensis and the hybrid Fallopia × bohemica) is known to spread primarily vegetatively by rhizomes and stem fragments in its adventive range. Sexual reproduction has rarely been shown in Europe, despite a high production of germinable seeds. To elucidate this contradiction the aim of the present study was to determine which environmental conditions prevent seed germination or seedling establishment. Several laboratory experiments were conducted focusing on water and light supply as well as the influence of frost. According to morphological and cytological analyses of the parental plants paired with morphological analyses of the seedlings, the seeds used for these experiments were assumed to belong predominantly to the hybrid Fallopia × bohemica. Laboratory experiments revealed that seedling establishment is hampered by severe drought or strong late frost, which are, however, rare events in the study region and could not be crucial in explaining the rarity of seedlings in the field. We discuss the possible role of weather conditions that might lead to a loss of seeds or seedlings under field conditions and include a comparison of several other cited studies carried out in the adventive range of Fallopia japonica s.l. that observed either the presence or the absence of Fallopia seedlings in the field.     

Asexual spread versus sexual reproduction and evolution in Japanese Knotweed s.l. sets the stage for the “Battle of the Clones”

The invasion of NW Europe by a single clone of male-sterile Fallopia japonica var. japonica by purely vegetative reproduction has demonstrated that reproduction by seed and the genetic diversity associated with it may not be an essential feature of plant invasions, at least in the short term. What is less well known is that a significant proportion of the Japanese Knotweed s.l. involved is not F. japonica var. japonica, but the hybrid between it and F. sachalinensis–F. × bohemica. This hybrid is able to backcross to either parent with the potential to replace the missing male F. japonica; by the same process, the hybrid is generating the genetic diversity so conspicuously lacking in F. japonica. In terms of understanding the population structure in a particular country, it is important to be able to identify hybrids and putative back-crosses. We bring together a mixture of published and unpublished information to provide a comprehensive section on morphological and anatomical aids to identification. Regeneration of plants from stem and rhizome fragments varies by taxon, as do responses to control techniques, underlining the importance of correct identification of these plants. In this paper we look closely at this group of taxa, with special emphasis on the role played by hybridization, with an examination of the genetic make up of seedlings produced in the wild or by artificial hybridizations, and the implications that this will have on the future directions of the invasion process.     

Factors influencing the production of stilbenes by the knotweed, <Emphasis Type="Italic">Reynoutria</Emphasis> × <Emphasis Type="Italic">bohemica</Emphasis>

Background  

Japanese knotweed, Reynoutria japonica, is known for its high growth rate, even on adverse substrates, and for containing organic substances that are beneficial to human health. Its hybrid, Reynoutria × bohemica, was described in the Czech Republic in 1983 and has been widespread ever since. We examined whether Reynoutria × bohemica as a medicinal plant providing stilbenes and emodin, can be cultivated in spoil bank substrates and hence in the coalmine spoil banks changed into arable fields. We designed a pot experiment and a field experiment to assess the effects of various factors on the growth efficiency of Reynoutria × bohemica on clayish substrates and on the production of stilbenes and emodin in this plant.     

Reynoutria niche modelling and protected area prioritization for restoration and protection from invasion: A Southeastern Europe case study

An important step in managing invasive species is determining the factors responsible for their current and potential distribution, especially when species distribution is climatically determined like in Reynoutria taxa case. The main aim of this paper was to integrate all available distribution data of the Reynoutria taxa in SE Europe and to predict in which habitats and along which corridors its future spread can be expected. Distribution data of the Reynoutria taxa were obtained from extensive field studies in the period from 2006 to 2016, as well as from the literature and herbarium sources. A total of 4081 localities in Serbia and the Kosovo region, Montenegro, Slovenia, Croatia, Bosnia and Herzegovina, Bulgaria and Romania have been recorded, most frequently in riparian and human-made habitats. Ecologically suitable ranges for the Reynoutria taxa were predicted using the MaxEnt program and 19 bioclimatic variables which were derived from the WorldClim data set. Results of this study showed that the most frequent Reynoutria taxa in SE Europe are R. japonica var. japonica and hybrid R. × bohemica. The most suitable geographical areas for R. japonica and R. sachalinensis are mostly located in the north, while for R. × bohemica the central part of SE Europe is suitable. The precipitation of the warmest quarter had a high influence on the potential distribution modelling of these closely related species. Potential distribution modelling revealed R. × bohemica’s high temperature tolerance in different seasons with high durability of drought (up to 60 mm per year less precipitation than parental species). Moreover, this research predicts which areas are most likely to be invaded, and makes suggestions where to focus management efforts for survey and removal of these invaders, especially in protected areas. According to the future climate analysis R. japonica and R. × bohemica could expand their range in riparian habitats up to 30–40%. Consequently, invasion in Slovenia’s and Croatia’s rivers requires urgent preventative measures. This study provides empirical evidence that these plants could become widespread throughout SE Europe within 25 years under the current trend and emphasizes that regionally specific management plans should be implemented to prevent further spread of these taxa.     

Isoenzyme diversity in Reynoutria (Polygonaceae) taxa: escape from sterility by hybridization

The genus Reynoutria is represented by four taxa in the Czech Republic – R. japonica var. japonica and compacta, R. sachalinensis and R. × bohemica. Using isoenzyme analysis, we determined the degree of genotype variability in all taxa and compared clones of R. japonica var. japonica from the Czech Republic with those from Great Britain. While the rarely occurring tetraploid variety R. japonica var. compacta possesses low variability, the octoploid female clone of R. japonica var. japonica is genetically uniform in the 93 clones sampled and belongs to the same genotype that is present in the whole Europe. R. japonica var. japonica can be fertilized by the pollen of tetraploid R. sachalinensis and a hexaploid hybrid R. × bohemica is produced. In R. sachalinensis, 16 genotypes were found in the 50 clones sampled. R. × bohemica is genetically the most diverse taxon in the study area, with 33 genotypes recorded among 88 clones sampled.     

Facilitation in multiple life-history stages: evidence for nucleated succession in coastal dunes

Garden experiments focused on vegetative regeneration were carried out with four invasive taxa of the genus Reynoutria (R. japonica var. japonica, R. japonica var. compacta, R. sachalinensis and a hybrid between R. sachalinensis and R. japonica var. japonica, R. ×bohemica). Regeneration ability of stems and rhizomes, timing of shoot emergence and biomass production were studied under the following treatments: laid horizontally on the soil surface; placed upright; buried in the soil; floating in water. Two different soils (sand and garden loam) representing contrasting nutrient levels were applied. Differences were found in the capability and speed of regeneration, as well as in the quality of shoots produced. Regeneration from stems was less efficient than that from rhizomes in all taxa except R. sachalinensis. R. ×bohemica exhibits higher regeneration potential (61%) than all other taxa and can be considered as the most successful taxon of the Czech representatives of the genus Reynoutria in terms of regeneration and establishment of new shoots. High regeneration capacity was also exhibited by R. japonica var. compacta (52%). Other taxa showed generally lower regeneration rates (R. japonica var. japonica 39% and R. sachalinensis 21%), but under some treatments the percentage of regenerated segments was high, too. R. japonica var. japonica rhizomes regenerated successfully in all three soil treatments but not in the water. An opposite pattern was found for its stems: they regenerated well if exposed to water treatment but in the soil, they did not regenerate at all. Particular taxa responded to the soil type in a contrasting way. R. sachalinensis and R. ×bohemica regenerated better in loam while the opposite was true in R. japonica var. japonica. R. japonica var. compacta produced the tallest and R. ×bohemica the heaviest and most robust shoots. It is concluded that rhizomes are more crucial than stems for the spread of knotweeds through fragmentation and clonal growth, suggesting the importance of soil disturbance.     

Genetic population structure of <Emphasis Type="Italic">Osmunda japonica</Emphasis>, rheophilous <Emphasis Type="Italic">Osmunda lancea</Emphasis> and their hybrids

Rheophilous Osmunda lancea often hybridizes with a dryland ally, Osmunda japonica, to produce O. × intermedia, forming zonation in riverbanks and the adjacent dryland along flooding frequency clines. This study examined the genetic structure of populations consisting of O. × intermedia and the two parental species by analyzing ten nuclear DNA markers [six cleaved amplified polymorphic sequence (CAPS) markers and three simple sequence repeat (SSR) markers developed from an expressed sequence tag (EST) library, and the sequence of the glyceraldehyde-3-phosphate dehydrogenase gene GapCp] and chloroplast DNA sequences. The results suggest that the nuclear genes of O. japonica and O. lancea are genetically differentiated despite shared polymorphism in their chloroplast DNA sequences. This discrepancy may be attributable to natural selection and recent introgression, although it is not evident if introgression occurs between O. japonica and O. lancea in the examined populations. Our findings of putative F2 hybrids in O. × intermedia support its partial reproducibility, and also suggest that formation of later-generation hybrids generates morphological variation in O. × intermedia. O. lancea plants collected from geographically distant localities were genetically very similar, and it is suggested that O. lancea originated monotopically.     

Response of plant and gastropod species to knotweed invasion

Invasive species of the knotweed complex (Fallopia sp.) have repeatedly been shown to decrease diversity of native local biota. While effects on plant species richness are well established, effects on invertebrate and in particular gastropod species richness are less well understood. We recorded cover of plant species and diversity and abundance of gastropod species in four plots (1 m × 1 m) with Fallopia japonica and compared these to paired control plots without F. japonica at 15 sites along the river Birs (Switzerland) in early summer (June) and autumn (September). Knotweed and control plots did not differ in site characteristics and soil parameters.Average plant species richness in F. japonica plots was 50% lower compared to control plots. This reduction was significant for woody species as well as for herbaceous species. However, species richness of early flowering annuals did not differ significantly. Among the species most affected by knotweed were hop (Humulus lupulus) and European spindle tree (Euonymus europaeus) but also stand-forming species such as nettle (Urtica dioica) or ground elder (Aegopodium podagraria).Average snail species richness was significantly reduced in F. japonica plots. The reduction was pronounced in large (≥5 mm shell size) and long-lived (>2 years) snail species but not in slugs or small and short-lived snails. For example, large snails such as the Roman snail (Helix pomatia, ?85%) or the red-listed species Bradybaena fruticum (?93%), showed reduced abundances in F. japonica compared to control plots. In contrast, the red-listed but small Vertigo pusilla (+92%) had higher abundances in F. japoinca plots. Principal component analyses revealed little overlap in plant communities or community composition of large snail species between F. japonica and control plots. Taken together, knotweed invasion decreased the cover of most plant species and abundance of large and long-lived gastropods.     

Morphological and chromosomal variation in Fallopia section Reynoutria (Polygonaceae) in Korea

We have examined morphological and chromosomal variation inFallopia sect.Reynoutria in Korea to clarify their taxonomic identities and to determine whether their morphological variability is associated with ploidy levels. Principal components analysis (PCA) of individuals from 21 populations, using major distinguishing characters, revealed the presence of four major entiries of sect.Reynoutria in Korea; these includeF. sachalinensis, F. japonica var.japonica, F. forbesii, and the Nonsan population consisting of presumed hybrids. Based on morphology, it is hypothesized that the Nonsan population was probably derived from multiple hybridization events involving the three named taxa. The results also indicate thatF. forbesii is distinct fromF. japonica var.japonica. Polyploidy is more prevalent in sect.Reynoutria than has been previously recognized.Fallopia sachalinensis in Korea occurs as dodecaploids with 2n=132; our count is the first dodecaploid count for the species, and represents the highest chromosome number known in the genus.Fallopia japonica var.japonica occurs as tetraploids (2n=44), hexaploids (2n=66), and octoploids (2n=88), whileF. forbesii occurs as hexaploids (2n=66) and octoploids (2n=88); our counts appear to be the first reported chromosome numbers forF. forbesii. Morphological analysis indicates that there is no apparent correlation between the ploidy levels in these taxa and the morphological characters that we have considered in this study except that the tetraploids ofF. japonica var.japonica tend to have somewhat thicker leaves.     

Habitat niche specialization in an understory species in a warm temperate forest

Relationships between microhabitat variables; understory light conditions in summer and winter, altitude, slope inclination and topographic categories (valley, ridge, and slope) and the distribution of Aucuba japonica Thunb. (Cornaceae), a common understory shrub species in Japan were examined using non-contagious 66, 20 × 20 m² quadrats. The Morishita’s I _δ suggested that A. japonica distributions were strongly heterogeneous among the quadrats. Therefore positive spatial autocorrelation of A. japonica at a within-quadrat level (≤20 m) was obvious. Moran’s I statistics showed a significant positive spatial autocorrelation in A. japonica abundance within the distance shorter than 60 m. But the partial Mantel tests suggested that the mass effect from neighboring quadrats would little explain A. japonica abundance in a quadrat. The partial Mantel tests also clearly showed that A. japonica distributions were strongly structured by topography and understory light conditions. Using Monte Carlo randomization tests, we found that A. japonica was aggregately distributed in quadrats in valley which were covered by deciduous canopies. Better understory light conditions in winter together with valley edaphic conditions may increase the abundance of A. japonica there. It is concluded that habitat niche specialization is important in structuring distribution of A. japonica in this forest community.     

A molecular phylogeny of the genus Gagea (Liliaceae) in Germany inferred from non-coding chloroplast and nuclear DNA sequences

The systematics of the mainly yellow flowered Gagea species complex (Liliaceae) has long been considered difficult because only a few phenotypic features within this genus and as a result of hypothesized interspecific hybridisation. A molecular phylogenetic study of seven Gagea species (G. bohemica, G. lutea, G. minima, G. pomeranica, G. pratenis, G. spathacea and G. villosa) from Germany has been undertaken, based on plastid DNA sequences (trnL(UAA)-trnF(GAA), psbA-trnH) and on the nuclear ribosomal internal transcribed spacer (ITS). Sequence divergence within the Gagea species ranges up to 15.5% for psbA-trnH, 22.0% for trnL-trnF and 23.7% for ITS (ITS1 + 5.8S rRNA + ITS2). Two subspecies of Gagea bohemica: G. bohemica subsp. saxatilis and G. bohemica subsp. bohemica are characterized by trnL-trnF data and morphological features. Analysis of the ITS region shows that G. pomeranica represents a hybrid of G. pratensis and G. lutea. Lloydia serotina was initially used as an outgroup species, but it was placed within the investigated Gagea species in the psbA-trnH and the trnL-trnF phylogenetic tree.     

Multiple invasions in urbanized landscapes: interactions between the invasive garden ant <Emphasis Type="Italic">Lasius neglectus</Emphasis> and Japanese knotweeds (<Emphasis Type="Italic">Fallopia</Emphasis> spp.)

Urbanized landscapes are the theater of multiple simultaneous biological invasions likely to affect spread dynamics when co-occurring introduced species interact with each other. Interactions between widespread invaders call for particular attention because they are likely to be common and because non-additive outcomes of such associations might induce negative consequences (e.g., enhanced population growth increasing impacts or resistance to control). We explored the invasions of two widespread invasive taxa: the Japanese knotweed species complex Fallopia spp. and the invasive garden ant Lasius neglectus, in the urban area of Lyon (France). First, we investigated landscape habitat preferences as well as co-occurrence rates of the two species. We showed that Fallopia spp. and L. neglectus had broadly overlapping environmental preferences (measured by seven landscape variables), but their landscape co-occurrence pattern was random, indicating independent spread and non-obligatory association. Second, as Fallopia spp. produce extra-floral nectar, we estimated the amount of nectar L. neglectus used under field conditions without ant competitors. We estimated that L. neglectus collected 150–321 kg of nectar in the month of April (when nectar production is peaking) in a 1162 m² knotweed patch, an amount likely to boost ant population growth. Finally, at six patches of Fallopia spp. surveyed, herbivory levels were low (1–6% loss of leaf surface area) but no relationship between ant abundance (native and invasive) and loss of leaf surface was found. Co-occurrences of Fallopia spp. and L. neglectus are likely to become more common as both taxa colonize landscapes, which could favor the spread and invasion success of the invasive ant.     

Chromosome number and DNA ploidy level reports from Central Europe — 2

Second part of commented chromosome number and DNA ploidy level reports from Central Europe comprising the whole Carpatho-Pannonian region includes the data for following taxa: Tephroseris aurantiaca (2n = 96), T. capitata (2n = 64) and T. integrifolia (2n = 48) by J. Kochjarová from Poland and Slovakia (reports nos. 12–14); Urtica diocia and U. kioviensis (both 2n = 26) by M. Kolník & K. Goliašová from Slovakia (nos. 15–16); Viola hirta (2n = 20), V. odorata (2n = 20), V. reichenbachiana (2n = 20), V. riviniana (2n = 40, 2n ∼ 8x, based on x = 5), V. suavis (2n = 40) and V. × bavarica [V. reichenbachiana × v. riviniana] (2n ∼ 6x, based on x = 5) by P. Mereďa jun., I. Hodálová, P. Mártonfi & V. Kolarčík from Slovakia (nos. 17–22); Fallopia × bohemica [F. japonica × F. sachalinensis] (2n = 66), Thladiantha dubia (2n = 18) and Hieracium longifoliosum (2n = 36) by P. Mráz from Romania and Slovakia (nos. 23–25); Amsinckia calycina (2n = 34) by M. Perny & H. Šípošová from Slovakia (no. 26). For further details and arrangements of reports see the first part (Mráz, 2005).     

Dances with fire: Tracking metapopulation dynamics of<Emphasis Type="Italic">polygonella basiramia</Emphasis> in Florida scrub (USA)

The regional persistence of species subject to local population colonization and extinction necessarily depends on how landscape features and disturbance affect metapopulation dynamics. Here, we characterize the metapopulation structure and short-term dynamics ofPolygonella basiramia. This rare, short-lived perennial herb is endemic to Florida scrublands and lacks a seed bank. Fires create the open sand gaps within a shrub matrix that support this species but also kill established plants. Thus, persistence depends on frequent colonization of unoccupied gaps. We are monitoring population dynamics within and among 1204 gaps distributed among 19 shrub patches. Considerable subpopulation turnover is evident at the gap level with rates of gap extinction exceeding rates of colonization in the first year. Whether declines in overall abundance continue is likely to depend on patterns of disturbance and regional stochasticity in this dynamic landscape.Polygonella is more likely to occupy larger and less isolated gaps, demonstrating that landscape features and disturbance strongly affect metapopulation dynamics. BecausePolygonella basiramia displays characteristics, occupancy patterns, and turnover dynamics consistent with metapopulation theory, it represents a model system for studying plant metapopulations.     

The morphology and activity of the extrafloral nectaries in Reynoutria × bohemica (Polygonaceae)

• Reynoutria × bohemica is an invasive species causing significant damage to native ecosystems in North America and Europe.
• In this work, we performed an in‐depth micromorphological characterisation of the extrafloral nectaries (EFN), during their secretory and post‐secretory phases, in combination with field monitoring of nectary activity over time and the qualitative pool of insect visitors.
• EFN consist of secretory trichomes and vascularised parenchyma. Polysaccharides, lipids and proteins were histochemically detected in all trichome cells; phenolic substances were detected in parenchyma cells. Our data indicate that all nectary regions are involved in nectar production and release, constituting a functional unit. Moreover, the main compound classes of nectar and their transfer change over time: first, granulocrine secretion for sugars prevails, then eccrine secretion of the lipophilic fraction takes place. Active nectaries are mainly located in the apical portion of the stem during the growth phase (April–May), when we detected the highest number of individuals visited by ants; from mid‐August onwards, during flowering, the number of active nectaries declined then ceased production (September), with a concomitant decrease in visits by the ants. The spectrum of nectar‐foraging ants mainly included representatives of the genera Formica, Lasius and Camponotus.
• Reynoutria × bohemica produces an attractive secretion able to recruit local ants that may potentially act as ‘bodyguards’ for protecting young shoots, reducing secretions during the blooming stage. This defence mechanism against herbivores is the same as that displayed by the parental species in its native areas.