Seagrass genomes reveal ancient polyploidy and adaptations to the marine environment.

We present chromosome-level genome assemblies from representative species of three independently evolved seagrass lineages: Posidonia oceanica, Cymodocea nodosa, Thalassia testudinum and Zostera marina. We also include a draft genome of Potamogeton acutifolius, belonging to a freshwater sister lineage to Zosteraceae. All seagrass species share an ancient whole-genome triplication, while additional whole-genome duplications were uncovered for C. nodosa, Z. marina and P. acutifolius. Comparative analysis of selected gene families suggests that the transition from submerged-freshwater to submerged-marine environments mainly involved fine-tuning of multiple processes (such as osmoregulation, salinity, light capture, carbon acquisition and temperature) that all had to happen in parallel, probably explaining why adaptation to a marine lifestyle has been exceedingly rare. Major gene losses related to stomata, volatiles, defence and lignification are probably a consequence of the return to the sea rather than the cause of it. These new genomes will accelerate functional studies and solutions, as continuing losses of the 'savannahs of the sea' are of major concern in times of climate change and loss of biodiversity.

Cryptic invasion suggested by a cytogeographic analysis of the halophytic Puccinellia distans complex (Poaceae) in Central Europe.

Introduction: Despite the wealth of studies dealing with the invasions of alien plants, invasions of alien genotypes of native species (cryptic invasions) have been vastly neglected. The impact of cryptic invasions on the biodiversity of plant communities can, however, be significant. Inland saline habitats and halophytes (i.e., salt-tolerant plant species) are especially threatened by this phenomenon as they inhabit fragmented remnants of largely destroyed habitats, but at the same time some of these halophytic species are rapidly spreading along salt-treated roads. To study potential cryptic invasion of halophytes, the patterns of genome size and ploidy variation in the Puccinellia distans complex (Poaceae), the most rapidly spreading roadside halophyte in Central Europe, were investigated. Methods: DNA flow cytometry with confirmatory chromosome counts were employed to assess ploidy levels of 1414 individuals from 133 populations of the P. distans complex. In addition, climatic niche modelling was used to predict the distributions of selected cytotypes. Results: Eight groups differing in ploidy level and/or genome size were discovered, one diploid (2x; 2n = 14), two tetraploid (4xA, 4xB; 2n = 28), one pentaploid (5x; 2n = 35), three hexaploid (6xA, 6xB, 6xC; 2n = 42), and one heptaploid (7x; 2n = 49). The hexaploids (mostly the 6xC cytotype) were widespread through the study area, spreading intensively in both anthropogenic and natural habitats and probably hybridizing with the natural habitat dwelling tetraploids. In contrast, the non-hexaploid cytotypes rarely spread and were predominantly confined to natural habitats. Discussion: The extensive spread of the hexaploid cytotypes along roadsides has most likely facilitated their incursion into natural habitats. The colonization of new natural habitats by the hexaploids may pose a threat to the indigenous Puccinellia populations by compromising their genetic integrity and/or by outcompeting them.

PADAPT 1.0 - the Pannonian Dataset of Plant Traits.

The existing plant trait databases' applicability is limited for studies dealing with the flora and vegetation of the eastern and central part of Europe and for large-scale comparisons across regions, mostly because their geographical data coverage is limited and they incorporate records from several different sources, often from regions with markedly different climatic conditions. These problems motivated the compilation of a regional dataset for the flora of the Pannonian region (Eastern Central Europe). PADAPT, the Pannonian Dataset of Plant Traits relies on regional data sources and collates data on 54 traits and attributes of the plant species of the Pannonian region. The current version covers approximately 90% of the species of the region and consists of 126,337 records on 2745 taxa. By including species of the eastern part of Europe not covered by other databases, PADAPT can facilitate studying the flora and vegetation of the eastern part of the continent. Although data coverage is far from complete, PADAPT meets the longstanding need for a regional database of the Pannonian flora.

Karyotypes and Physical Mapping of Ribosomal DNA with Oligo-Probes in Eranthis sect. Eranthis (Ranunculaceae).

A comparative karyotype analysis of four species of yellow-flowered Eranthis sect. Eranthis, i.e., E. bulgarica, E. cilicica, E. hyemalis, and E. longistipitata from different areas, has been carried out for the first time. All the studied specimens had somatic chromosome number 2n = 16 with basic chromosome number x = 8. Karyotypes of the investigated plants included five pairs of metacentric chromosomes and three pairs of submetacentric/subtelocentric chromosomes. The chromosome sets of the investigated species differ mainly in the ratio of submetacentric/subtelocentric chromosomes, their relative lengths, and arm ratios. A new oligonucleotide probe was developed and tested to detect 45S rDNA clusters. Using this probe and an oligonucleotide probe to 5S rDNA, 45S and 5S rDNA clusters were localized for the first time on chromosomes of E. cilicica, E. hyemalis, and E. longistipitata. Major 45S rDNA clusters were identified on satellite chromosomes in all the species; in E. cilicica, minor clusters were also identified in the terminal regions of one metacentric chromosome pair. The number and distribution of 5S rDNA clusters is more specific. In E. cilicica, two major clusters were identified in the pericentromeric region of a pair of metacentric chromosomes. Two major clusters in the pericentromeric region of a pair of submetacentric chromosomes and two major clusters in the interstitial region of a pair of metacentric chromosomes were observed in E. longistipitata. E. hyemalis has many clusters of different sizes, localized mainly in the pericentromeric regions. Summarizing new data on the karyotype structure of E. sect. Eranthis and previously obtained data on E. sect. Shibateranthis allowed conclusions to be formed about the clear interspecific karyological differences of the genus Eranthis.

Typification of Names in Iris (Iridaceae) Described by Victor Janka with Taxonomic Considerations.

Viktor Janka von Bulcs described five names in Iris, i.e., I. balkana, I. cretensis, I. lorea, I. mellita, and I. sintenisii. These names are typified on specimens deposited at BP, JE, LD, and P, and taxonomical information is provided in the present report. Lectotypes are designated for I. mellita (a taxonomic synonym of I. suaveolens) deposited at Friedrich Schiller University Jena (JE), for I. sintenisii at Lund University (LD), and for I. lorea (a taxonomic synonym of I. sintenisii) at the French National Museum of Natural History (P). A neotype is designated and an image provided for the name I. balkana (a taxonomic synonym of I. reichenbachii) deposited at the Hungarian Natural History Museum (BP). The lectotype for I. cretensis (a taxonomic synonym of I. unguicularis) from JE is corrected. Images of plants of the accepted taxa are provided.

Morphological variability of Carex buekii (Cyperaceae) as a function of soil conditions: a case study of the Central European populations.

Carex buekii is a highly adaptive species showing a fairly wide ecological spectrum. It belongs to the group of river corridor plants which are vulnerable to any human activity directed at transformation of river valley habitats worldwide. This study was aimed at: determining the phenotypic variability of the species in the central part of its range, examining effects of soil conditions on the sedge's morphological traits, and finding out whether the phenotypic plasticity observed may have taxonomic implications. A total of 487 specimens from 26 populations were collected in Hungary, Poland and Slovakia and tested by univariate, bivariate, and multivariate statistical methods. The analysis involved 16 morphological traits and 7 soil parameters (organic matter, pH, potassium, phosphorus, nitrogen, magnesium, calcium). Soil conditions were shown to affect the C. buekii morphology; particularly important was potassium, the only soil parameter that was indicated as a factor affecting intra-specific variability. Sites with lower contents of bioavailable potassium hosted C. buekii individuals which were generally smaller than those at sites showing higher soil potassium contents. The relationship held true also with respect to generative traits important in sedge taxonomy, i.e. utricle and beak lengths. Consideration of morphological differences only, without analysing relationships between morphology and soil conditions, could have resulted in distinguishing new entities at the level of species, subspecies or variety. Thus, knowledge on the range of phenotypic plasticity in field populations seems to be of a key importance in taxonomic studies.

Corrigendum: Plastid Genomes of Five Species of Riverweeds (Podostemaceae): Structural Organization and Comparative Analysis in Malpighiales.

[This corrects the article DOI: 10.3389/fpls.2019.01035.].

Plastid Genomes of Five Species of Riverweeds (Podostemaceae): Structural Organization and Comparative Analysis in Malpighiales.

With the advent of next-generation sequencing technologies, whole-plastome data can be obtained as a byproduct of low-coverage sequencing of the plant genomic DNA. This provides an opportunity to study plastid evolution across groups, as well as testing phylogenetic relationships among taxa. Within the order Malpighiales (∼16,000 spp.), the Podostemaceae (∼300 spp.) stand out for their unique habit, living attached to rocks in fast-flowing aquatic habitats, and displaying highly modified morphologies that confound our understanding of their classification, biology, and evolution. In this study, we used genome skimming data to assemble the full plastid genome of 5 species within Podostemaceae. We analyzed our data in a comparative framework within Malpighiales to determine the structure, gene content, and rearrangements in the plastomes of the family. The Podostemaceae have one of the smallest plastid genomes reported so far for the Malpighiales, possibly due to variation in length of inverted repeat (IR) regions, gene loss, and intergenic region variation. We also detected a major inversion in the large single-copy region unique to the family. The uncommon loss or pseudogenization of ycf1 and ycf2 in angiosperms and in land plants in general is also found to be characteristic of Podostemaceae, but the compensatory mechanisms and implications of this and of the pseudogenization of accD, rpl22, and clpP and loss of rps16 remain to be explained in this group. In addition, we estimated a phylogenetic tree among selected species in Malpighiales. Our findings indicate that the Podostemaceae are a distinct lineage with long branches that suggest faster rates of evolution in the plastome of the group, compared with other taxa in the order. This study lays the foundations for future phylogenomic studies in the family.

Ecology, threats and conservation status of Carex buekii (Cyperaceae) in Central Europe.

Carex buekii is a tall sedge, forming large stands in wetlands, particularly in river floodplains across Central Europe and thus on many sites determining the typical appearance of riverine habitats. Our paper aims at increasing the knowledge on ecology of C. buekii and its role in the wetlands. Field data were collected in Poland, the Czech Republic, Slovakia, Hungary, and Italy. Carex buekii usually occurs in nutrient rich habitats, but is also capable of colonising relatively nutrient-poor ones; it grows on both acidic and alkaline soils (pH 3.3-7.4) with diverse concentrations of assimilable elements (Ca, Mg, P, K). One of the most important ecological characteristics of C. buekii is its relationship to the floodplains of watercourses. It seems to be dependent on, or at least very tolerant to regular disturbances by streaming, floods and transport of sediments. Carex buekii usually forms relatively uniform stands of its own association, Caricetum buekii. The species most frequently accompanying C. buekii are Urtica dioica, Calystegia sepium, Galium aparine, Rubus caesius, Phalaris arundinacea, and Cirsium arvense. The sedge also occurs in the understorey of forests with e.g. Alnus glutinosa, Salix fragilis, Padus avium, and Quercus robur. Carex buekii is able to colonise man-made or man-changed habitats such as railway embankments and roadsides or regulated river banks. Taking into account the IUCN Red List Criteria we propose to regard C. buekii as a least-concern (LC).

First molecular phylogenetic insights into the evolution of Eriocaulon (Eriocaulaceae, Poales).

Eriocaulon is a genus of c. 470 aquatic and wetland species of the monocot plant family Eriocaulaceae. It is widely distributed in Africa, Asia and America, with centres of species richness in the tropics. Most species of Eriocaulon grow in wetlands although some inhabit shallow rivers and streams with an apparent adaptive morphology of elongated submerged stems. In a previous molecular phylogenetic hypothesis, Eriocaulon was recovered as sister of the African endemic genus Mesanthemum. Several regional infrageneric classifications have been proposed for Eriocaulon. This study aims to critically assess the existing infrageneric classifications through phylogenetic reconstruction of infrageneric relationships, based on DNA sequence data of four chloroplast markers and one nuclear marker. There is little congruence between our molecular results and previous morphology-based infrageneric classifications. However, some similarities can be found, including Fyson's sect. Leucantherae and Zhang's sect. Apoda. Further phylogenetic studies, particularly focusing on less well sampled regions such as the Neotropics, will help provide a more global overview of the relationships in Eriocaulon and may enable suggesting the first global infrageneric classification.

Growth-form and spatiality driving the functional difference of native and alien aquatic plants in Europe.

Trait-based approaches are widely used in community ecology and invasion biology to unravel underlying mechanisms of vegetation dynamics. Although fundamental trade-offs between specific traits and invasibility are well described among terrestrial plants, little is known about their role and function in aquatic plant species. In this study, we examine the functional differences of aquatic alien and native plants stating that alien and native species differ in selected leaf traits. Our investigation is based on 60 taxa (21 alien and 39 native) collected from 22 freshwater units of Hungarian and Italian lowlands and highlands. Linear mixed models were used to investigate the effects of nativeness on four fundamental traits (leaf area, leaf dry matter content, specific leaf area, and leaf nitrogen content), while the influence of growth-form, altitude, and site were employed simultaneously. We found significantly higher values of leaf areas and significantly lower values of specific leaf areas for alien species if growth-form was included in the model as an additional predictor.We showed that the trait-based approach of autochthony can apply to aquatic environments similar to terrestrial ones, and leaf traits have relevance in explaining aquatic plant ecology whether traits are combined with growth-forms as a fixed factor. Our results confirm the importance of traits related to competitive ability in the process of aquatic plant invasions. Alien aquatic plants can be characterized as species producing soft leaves faster. We argue that the functional traits of alien aquatic plants are strongly growth-form dependent. Using the trait-based approach, we found reliable characteristics of aquatic plants related to species invasions, which might be used, for example, in conservation management.

Flood induced phenotypic plasticity in amphibious genus Elatine (Elatinaceae).

Vegetative characters are widely used in the taxonomy of the amphibious genus Elatine L. However, these usually show great variation not just between species but between their aquatic and terrestrial forms. In the present study we examine the variation of seed and vegetative characters in nine Elatine species (E. brachysperma, E. californica, E. gussonei, E. hexandra, E. hungarica, E. hydropiper, E. macropoda, E. orthosperma and E. triandra) to reveal the extension of plasticity induced by the amphibious environment, and to test character reliability for species identification. Cultivated plant clones were kept under controlled conditions exposed to either aquatic or terrestrial environmental conditions. Six vegetative characters (length of stem, length of internodium, length of lamina, width of lamina, length of petioles, length of pedicel) and four seed characters (curvature, number of pits / lateral row, 1st and 2nd dimension) were measured on 50 fruiting stems of the aquatic and on 50 stems of the terrestrial form of the same clone. MDA, NPMANOVA Random Forest classification and cluster analysis were used to unravel the morphological differences between aquatic and terrestrial forms. The results of MDA cross-validated and Random Forest classification clearly indicated that only seed traits are stable within species (i.e., different forms of the same species keep similar morphology). Consequently, only seed morphology is valuable for taxonomic purposes since vegetative traits are highly influenced by environmental factors.