Apomictic Lineages Research Articles

Effects of ploidy variation on promoter DNA methylation and gene expression in rice (Oryza sativa L.)

BackgroundPolyploidy, or whole-genome duplication (WGD) promotes genetic diversification in plants. However, whether WGD is accompanied by epigenetic regulation especially DNA methylation remains yet elusive. Methylation of different region in genomic DNA play discrete role in gene regulation and developmental processes in plants.ResultsIn our study, we used an apomictic rice line (SARII-628) that produces twin seedlings of different ploidy for methylated DNA immunoprecipitation sequencing (MeDIP-seq). We compared the level of methylation and mRNA expression in three different (CG, CHG, and CHH) sequence contexts of promoter region among haploid (1X), diploid (2X), and triploid (3X) seedling. We used MeDIP-Seq analysis of 14 genes to investigate whole genome DNA methylation and found that relative level of DNA methylation across different ploidy was in following order e.g. diploid > triploid > haploid. GO functional classification of differentially methylated genes into 9 comparisons group of promoter, intergenic and intragenic region discovered, these genes were mostly enriched for cellular component, molecular function, and biological process. By the comparison of methylome data, digital gene expression (DGE), mRNA expression profile, and Q-PCR findings LOC_ Os07g31450 and LOC_ Os01g59320 were analyzed for BS-Seq (Bisulphite sequencing).ConclusionsWe found that (1) The level of the promoter DNA methylation is negatively correlated with gene expression within each ploidy level. (2) Among all ploidy levels, CG sequence context had highest methylation frequency, and demonstrated that the high CG methylation did reduce gene expression change suggesting that DNA methylation exert repressive function and ensure genome stability during WGD. (3) Alteration in ploidy (from diploid to haploid, or diploid to triploid) reveals supreme changes in methylation frequency of CHH sequence context. Our finding will contribute an understanding towards lower stability of CHH sequence context and educate the effect of promoter region methylation during change in ploidy state in rice.

The classification of asexual organisms: Old myths, new facts, and a novel pluralistic approach

AbstractOrganisms reproducing via asexuality harbor a great diversity of lineages, morphotypes and ecotypes. However, classification of asexual taxa does not fit into contemporary species concepts, and hence the diversity of apomictic plant complexes is not well reflected in taxonomy. Plants reproducing via apomixis (i.e., asexual seed formation = agamospermy) exemplify the theoretical and practical problems of classification. Obligately asexual organisms do not form reproductive communities, but they do constitute ancestor‐descendant lineages. From the conceptual side, evolutionary lineage concepts would fit best for species delimitation. Recent research showed that these lineages are not necessarily threatened by rapid extinction and do have persistence in time and space. Facultative sexuality and low levels of residual recombination counteract the accumulation of deleterious mutations due to the lack of recombination (Muller’s ratchet). Apomictic lineages do have adaptive potential, which is demonstrated by the ability to occupy large distribution areas and to experience ecological niche shifts. The challenge for classification of asexual lineages, however, is to find operational criteria for species delimitation. Current practices of species delimitation can be grouped into four main principles: (1) the sexuals‐first principle means that obligate sexual progenitor species are classified separately from their apomictic derivatives. (2) The all‐in‐one principle merges sexual progenitors and highly facultative apomictic derivatives into one species, whereby the apomicts often represent autopolyploids without differentiated phenotypes. (3) The cluster concept applies to allopolyploid complexes with facultative apomixis and a huge diversity of genotypes and morphotypes; here the main genetic clusters are treated as species. (4) Almost obligate apomictic lineages are being classified as agamospecies. The four principles reflect quite well evolutionary traits and diversity of lineages. Finally, a recommendation for a workflow is given, following this gradient from obligate sexuality to obligate apomixis.

Deciphering the sexual diploid members of the Boechera suffrutescens complex (Brassicaceae, Boechereae).

Boechera is a model genus that is of particular interest for understanding apomixis due to the presence of numerous apomictic diploid lineages that are tightly correlated with hybridisation events. Boechera includes many narrowly distributed endemics and apomictic hybrid lineages that obscure morphological boundaries amongst taxa. In this study, we focus on the Boechera suffrutescens complex, a phylogenetically well-supported but taxonomically complex north-western United States clade whose diploid species currently include the widespread B. suffrutescens and two narrowly distributed serpentine endemics, B. constancei and B. rollei. Using a 15-locus microsatellite dataset, we infer ploidy and sexual vs. apomictic reproduction for all individuals and then assess species limits for all sexual diploid samples. Our results support the recognition of B. rollei and B. constancei as distinct species and reveal three divergent sexual diploid lineages within B. suffrutescens sensu lato. The latter three lineages exhibit geographic, genetic and morphological coherence and consequently warrant recognition at the species rank. These include Boechera suffrutescens s.s., which is restricted to Idaho and eastern Oregon, Boechera botulifructa, a newly described species distributed along the Cascade Mountain Province from Lassen County, California north to Deschutes County, Oregon and the heretofore dismissed species Boechera duriuscula (basionym ≡ Arabis duriuscula), which occurs along the Sierra Nevada Province from Plumas County southwards to Fresno County, California. Our data also reveal substructure in B. constancei that is likely attributable to the highly fragmented distribution of its serpentine habitat. This refined taxonomic framework for the B. suffrutescens complex enhances Boechera as a model system, adds to our knowledge of speciation in edaphically extreme environments and provides information on ongoing conservation efforts for these taxa.

Increased transgenerational epigenetic variation, but not predictable epigenetic variants, after environmental exposure in two apomictic dandelion lineages.

DNA methylation is one of the mechanisms underlying epigenetic modifications. DNA methylations can be environmentally induced and such induced modifications can at times be transmitted to successive generations. However, it remains speculative how common such environmentally induced transgenerational DNA methylation changes are and if they persist for more than one offspring generation. We exposed multiple accessions of two different apomictic dandelion lineages of the Taraxacum officinale group (Taraxacum alatum and T. hemicyclum) to drought and salicylic acid (SA) treatment. Using methylation‐sensitive amplified fragment length polymorphism markers (MS‐AFLPs) we screened anonymous methylation changes at CCGG restriction sites throughout the genome after stress treatments and assessed the heritability of induced changes for two subsequent unexposed offspring generations. Irrespective of the initial stress treatment, a clear buildup of heritable DNA methylation variation was observed across three generations, indicating a considerable background rate of heritable epimutations. Less evidence was detected for environmental effects. Drought stress showed some evidence for accession‐specific methylation changes, but only in the exposed generation and not in their offspring. By contrast, SA treatment caused an increased rate of methylation change in offspring of treated plants. These changes were seemingly undirected resulting in increased transgenerational epigenetic variation between offspring individuals, but not in predictable epigenetic variants. While the functional consequences of these MS‐AFLP‐detected DNA methylation changes remain to be demonstrated, our study shows that (1) stress‐induced transgenerational DNA methylation modification in dandelions is genotype and context‐specific; and (2) inherited environmental DNA methylation effects are mostly undirected and not targeted to specific loci.

Small RNAs Reflect Grandparental Environments in Apomictic Dandelion.

Plants can show long-term effects of environmental stresses and in some cases a stress “memory” has been reported to persist across generations, potentially mediated by epigenetic mechanisms. However, few documented cases exist of transgenerational effects that persist for multiple generations and it remains unclear if or how epigenetic mechanisms are involved. Here, we show that the composition of small regulatory RNAs in apomictic dandelion lineages reveals a footprint of drought stress and salicylic acid treatment experienced two generations ago. Overall proportions of 21 and 24 nt RNA pools were shifted due to grandparental treatments. While individual genes did not show strong up- or downregulation of associated sRNAs, the subset of genes that showed the strongest shifts in sRNA abundance was significantly enriched for several GO terms including stress-specific functions. This suggests that a stress-induced signal was transmitted across multiple unexposed generations leading to persistent changes in epigenetic gene regulation.

Mutation Accumulation in an Asexual Relative of Arabidopsis.

Asexual populations experience weaker responses to natural selection, which causes deleterious mutations to accumulate over time. Additionally, stochastic loss of individuals free of deleterious mutations can lead to an irreversible increase in mutational load in asexuals (the “click” in Muller’s Ratchet). Here we report on the genomic divergence and distribution of mutations across eight sympatric pairs of sexual and apomictic (asexual) Boechera (Brassicaceae) genotypes. We show that apomicts harbor a greater number of derived mutations than sympatric sexual genotypes. Furthermore, in phylogenetically constrained sites that are subject to contemporary purifying selection, the ancestral, conserved allele is more likely to be retained in sexuals than apomicts. These results indicate that apomictic lineages accumulate mutations at otherwise conserved sites more often than sexuals, and support the conclusion that deleterious mutation accumulation can be a powerful force in the evolution of asexual higher plants.

Recent and dynamic transposable elements contribute to genomic divergence under asexuality.

BackgroundTransposable elements (TEs) are mobile pieces of genetic information with high mutagenic potential for the host genome. Transposition is often neutral or deleterious but may also generate potentially adaptive genetic variation. This additional source of variation could be especially relevant in non-recombining species reproducing asexually. However, evidence is lacking to determine the relevance of TEs in plant asexual genome evolution and their associated effects. Here, we characterize the repetitive fraction of the genome of the common dandelion, Taraxacum officinale and compare it between five accessions from the same apomictic lineage. The main objective of this study is to evaluate the extent of within-lineage divergence attributed to TE content and activity. We examined the repetitive genomic contribution, diversity, transcription and methylation changes to characterize accession-specific TEs.ResultsUsing low-coverage genomic sequencing, we report a highly heterogeneous TE compartment in the triploid apomict T. officinale representing up to 38.6 % of the homoploid genome. The repetitive compartment is dominated by LTR retrotransposon families accompanied by few non-LTR retrotransposons and DNA transposons. Up to half of the repeat clusters are biased towards very high read identity, indicating recent and potentially ongoing activity of these TE families. Interestingly, the five accessions are divided into two main clades based on their TE composition. Clade 2 is more dynamic than clade 1 with higher abundance of Gypsy Chromovirus sequences and transposons. Furthermore, a few low-abundant genomic TE clusters exhibit high level of transcription in two of the accessions analysed. Using reduced representation bisulfite sequencing, we detected 18.9 % of loci differentially methylated, of which 25.4 and 40.7 % are annotated as TEs or functional genes, respectively. Additionally, we show clear evidence for accession-specific TE families that are differentially transcribed and differentially methylated within the apomictic lineage, including one Copia Ale II LTR element and a PIF-Harbinger DNA transposon.ConclusionWe report here a very young and dynamic repetitive compartment that enhances divergence within one asexual lineage of T. officinale. We speculate that accession-specific TE families that are both transcriptionally and epigenetically variable are more prone to trigger changes in expression on nearby coding sequences. These findings emphasize the potential of TE-induced mutations on functional genes during asexual genome evolution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3234-9) contains supplementary material, which is available to authorized users.

A current perspective on apomixis in ferns

AbstractThis review provides a synopsis of apogamous reproduction in ferns and highlights important progress made in recent studies of fern apomixis. First, a summary of the apomictic fern life cycle is provided, distinguishing between two pathways to diploid spore production that have been documented in apomictic ferns (premeiotic endomitosis and meiotic first division restitution) and briefly discussing the evolutionary implications of each. Next, recent trends in fern apomixis research are discussed, exposing a shift in focus from the observation and characterization of apomixis in ferns to more integrated studies of the evolutionary and ecological implications of this reproductive mode. Peer‐reviewed contributions from the past decade are then summarized, spanning the identification of new apomictic lineages through to the developmental, phylogenetic, and population genetic insights that have been made in studies of fern apomixis during that time. Gaps in our understanding are also discussed, including the extent and implications of recombinant apomixis in ferns, the possible reversibility of reproductive mode (from apomictic to sexual) in ferns, and the genomic causes and consequences of apomixis in seed free vascular plants. To conclude, future directions for fern apomixis research are proposed in the context of modern technological advances and recent insights from studies of apomixis in other groups.

Heritable gene expression differences between apomictic clone members in Taraxacum officinale: Insights into early stages of evolutionary divergence in asexual plants.

BackgroundAsexual reproduction has the potential to enhance deleterious mutation accumulation and to constrain adaptive evolution. One source of mutations that can be especially relevant in recent asexuals is activity of transposable elements (TEs), which may have experienced selection for high transposition rates in sexual ancestor populations. Predictions of genomic divergence under asexual reproduction therefore likely include a large contribution of transposable elements but limited adaptive divergence. For plants empirical insight into genome divergence under asexual reproduction remains limited. Here, we characterize expression divergence between clone members of a single apomictic lineage of the common dandelion (Taraxacum officinale) to contribute to our knowledge of genome evolution under asexuality.ResultsUsing RNA-Seq, we show that about one third of heritable divergence within the apomictic lineage is driven by TEs and TE-related gene activity. In addition, we identify non-random transcriptional differences in pathways related to acyl-lipid and abscisic acid metabolisms which might reflect functional divergence within the apomictic lineage. We analyze SNPs in the transcriptome to assess genetic divergence between the apomictic clone members and reveal that heritable expression differences between the accessions are not explained simply by genome-wide genetic divergence.ConclusionThe present study depicts a first effort towards a more complete understanding of apomictic plant genome evolution. We identify abundant TE activity and ecologically relevant functional genes and pathways affecting heritable within-lineage expression divergence. These findings offer valuable resources for future work looking at epigenetic silencing and Cis-regulation of gene expression with particular emphasis on the effects of TE activity on asexual species’ genome.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2524-6) contains supplementary material, which is available to authorized users.

An apomixis-linked ORC3-like pseudogene is associated with silencing of its functional homolog in apomictic Paspalum simplex.

Apomixis in plants consists of asexual reproduction by seeds. Here we characterized at structural and functional levels an apomixis-linked sequence of Paspalum simplex homologous to subunit 3 of the ORIGIN RECOGNITION COMPLEX (ORC3). ORC is a multiprotein complex which controls DNA replication and cell differentiation in eukaryotes. Three PsORC3 copies were identified, each one characterized by a specific expression profile. Of these, PsORC3a, specific for apomictic genotypes, is a pseudogene that was poorly and constitutively expressed in all developmental stages of apomictic flowers, whereas PsORC3b, the putative functional gene in sexual flowers, showed a precise time-related regulation. Sense transcripts of PsORC3 were expressed in the female cell lineage of both apomictic and sexual reproductive phenotypes, and in aposporous initials. Although strong expression was detected in sexual early endosperm, no expression was present in the apomictic endosperm. Antisense PsORC3 transcripts were revealed exclusively in apomictic germ cell lineages. Defective orc3 mutants of rice and Arabidopsis showed normal female gametophytes although the embryo and endosperm were arrested at early phases of development. We hypothesize that PsORC3a is associated with the down-regulation of its functional homolog and with the development of apomictic endosperm which deviates from the canonical 2(maternal):1(paternal) genome ratio.

Plant Breeding: Surprisingly, Less Sex Is Better

Introduction of apomixis, asexual reproduction through seeds, into crop species has the potential to dramatically transform plant breeding. A new study demonstrates that traits can be stably transferred between generations in newly produced apomictic lines, and heralds a breeding revolution needed to increase food production for the growing planet.

Natural epigenetic variation contributes to heritable flowering divergence in a widespread asexual dandelion lineage.

Epigenetic variation has been proposed to contribute to the success of asexual plants, either as a contributor to phenotypic plasticity or by enabling transient adaptation via selection on transgenerationally stable, but reversible, epialleles. While recent studies in experimental plant populations have shown the potential for epigenetic mechanisms to contribute to adaptive phenotypes, it remains unknown whether heritable variation in ecologically relevant traits is at least partially epigenetically determined in natural populations. Here, we tested the hypothesis that DNA methylation variation contributes to heritable differences in flowering time within a single widespread apomictic clonal lineage of the common dandelion (Taraxacum officinale s. lat.). Apomictic clone members of the same apomictic lineage collected from different field sites showed heritable differences in flowering time, which was correlated with inherited differences in methylation-sensitive AFLP marker profiles. Differences in flowering between apomictic clone members were significantly reduced after invivo demethylation using the DNA methyltransferase inhibitor zebularine. This synchronization of flowering times suggests that flowering time divergence within an apomictic lineage was mediated by differences in DNA methylation. While the underlying basis of the methylation polymorphism at functional flowering time-affecting loci remains to be demonstrated, our study shows that epigenetic variation contributes to heritable phenotypic divergence in ecologically relevant traits in natural plant populations. This result also suggests that epigenetic mechanisms can facilitate adaptive divergence within genetically uniform asexual lineages.

Variability of biometric indices of plants of breeding forms of sweet pepper under condition of sexual and combined apomictically-sexual reproduction

The actual problem in sweet pepper breeding is working out alternative methods for speeded genetic stabilization of valuable genotypes unlike those using sexual hybridization. The aim and tasks of the study. The aim of investigation is to evaluate efficiency of genetic stabilization of sweet pepper population when using sexual and combined apomictically-sexual hybridization. The task of investigation is to study manifestation of quantitative traits of plants that belong to populations of apomictic lines and original forms. Material and methods. In the work were used 4 original forms and 7 apomictic lines derivates thereof. In the period of biological ripeness of fruits there were compared such quantitative traits: “plant height”, “leaf length”, “leaf width”, “quantity of fruits on a plant”, “productivity of a plant”. The scope pf traits variation was determined with the help of coefficient of variation (CV). Investigation were conducted according to conventional methods for carrying out sweet pepper breeding under field conditions. Results and discussion. Two-year biometric measurements of plants of apomictic lines revealed the scope of 3 qualitative traits variation: “plant height”, “leaf length”, “leaf width” within the range of CV up to 33 %. In comparison with the original forms there was noted a lover value of CV simultaneously by two-three traits in 4 apomictic lines. The greatest instability of manifestation was in the trait “quantity of fruits on a plant” in original forms and apomictic lines. In apomictic lines the scope of variation of CV by the trait “plant height” was 18-38,1 %, “leaf length” – 15,1-31,9 %, “leaf width” – 22,0-31,3 %, “quantity of fruits on a plant” – 22,1-55,7 %. The line Velikan (d271, AA) had the greatest productivity – 676,8 g. Conclusions. Comparative analysis of two methods of sweet pepper breeding samples reproduction the stable tendency to greater stability of quantitative traits manifestation when using combined apomictically-sexual reproduction.

Emergence of apospory and bypass of meiosis via apomixis after sexual hybridisation and polyploidisation.

Hybridisation and polyploidy are major forces contributing to plant speciation. Homoploid (2x) and heteroploid (3x) hybrids, however, represent critical stages for evolution due to disturbed meiosis and reduced fertility. Apomixis – asexual reproduction via seeds – can overcome hybrid sterility, but requires several concerted alterations of developmental pathways to result in functional seed formation.Here, we analyse the reproductive behaviours of homo- and heteroploid synthetic hybrids from crosses between sexual diploid and tetraploid Ranunculus auricomus species to test the hypothesis that developmental asynchrony in hybrids triggers the shift to apomictic reproduction.Evaluation of male and female gametophyte development, viability and functionality of gametes shows developmental asynchrony, whereas seed set and germinability indicate reduced fitness in synthetic hybrids compared to sexual parents. We present the first experimental evidence for spontaneous apospory in most hybrids as an alternative pathway to meiosis, and the appearance of functional apomictic seeds in triploids. Bypassing meiosis permits these triploid genotypes to form viable seed and new polyploid progeny.Asynchronous development causes reduced sexual seed set and emergence of apospory in synthetic Ranunculus hybrids. Apomixis is functional in triploids and associated with drastic meiotic abnormalities. Selection acts to stabilise developmental patterns and to tolerate endosperm dosage balance shifts which facilitates successful seed set and establishment of apomictic lineages.

Asexual genome evolution in the apomictic Ranunculus auricomus complex: examining the effects of hybridization and mutation accumulation

Asexual lineages are thought to be prone to extinction because of deleterious mutation accumulation (Muller's ratchet). Here, we analyse genomic effects of hybridity, polyploidy and allelic divergence in apomictic plants, and identify loci under divergent selection among sexual/apomictic lineages. RNAseq was used to sequence the flower-specific transcriptomes of five genotypes of the Ranunculus auricomus complex, representing three sexual and two apomictic reproductive biotypes. The five sequence libraries were pooled and de novo assembly performed, and the resultant assembly was used as a backbone for a subsequent alignment of each separate library. High-quality single-nucleotide (SNP) and insertion-deletion (indel) polymorphisms were mined from each library. Annotated genes for which open reading frames (ORF) could be determined were analysed for signatures of divergent versus stabilizing selection. A comparison between all genotypes supports the hypothesis of Pleistocene hybrid origin of both apomictic genotypes from R.carpaticola and R.cassubicifolius, with subsequent allelic divergence of apomictic lineages (Meselson effect). Pairwise comparisons of nonsynonymous (dN) to synonymous (dS) substitution rate ratios between apomictic and sexual genotypes for 1231 genes demonstrated similar distributions for all comparisons, although 324 genes demonstrated outlier (i.e. elevated) dN/dS ratios. Gene ontology analyses of these outliers revealed significant enrichment of genes associated with reproduction including meiosis and gametogenesis, following predictions of divergent selection between sexual and apomictic reproduction, although no significant signal of genome-wide mutation accumulation could be identified. The results suggest that gene function should be considered in order to understand effects of mutation accumulation in asexual lineages.

Copy Number Variation in Transcriptionally Active Regions of Sexual and Apomictic Boechera Demonstrates Independently Derived Apomictic Lineages

In asexual (apomictic) plants, the absence of meiosis and sex is expected to lead to mutation accumulation. To compare mutation accumulation in the transcribed genomic regions of sexual and apomictic plants, we performed a double-validated analysis of copy number variation (CNV) on 10 biological replicates each of diploid sexual and diploid apomictic Boechera, using a high-density (>700 K) custom microarray. The Boechera genome demonstrated higher levels of depleted CNV, compared with enriched CNV, irrespective of reproductive mode. Genome-wide patterns of CNV revealed four divergent lineages, three of which contain both sexual and apomictic genotypes. Hence genome-wide CNV reflects at least three independent origins (i.e., expression) of apomixis from different sexual genetic backgrounds. CNV distributions for different families of transposable elements were lineage specific, and the enrichment of LINE/L1 and long term repeat/Copia elements in lineage 3 apomicts is consistent with sex and meiosis being mechanisms for purging genomic parasites. We hypothesize that significant overrepresentation of specific gene ontology classes (e.g., pollen-pistil interaction) in apomicts implies that gene enrichment could be an adaptive mechanism for genome stability in diploid apomicts by providing a polyploid-like system for buffering the effects of deleterious mutations.

On the origin and evolution of apomixis in Boechera

The genetic mechanisms causing seed development by gametophytic apomixis in plants are predominantly unknown. As apomixis is consistently associated with hybridity and polyploidy, these confounding factors may either (a) be the underlying mechanism for the expression of apomixis, or (b) obscure the genetic factors which cause apomixis. To distinguish between these hypotheses, we analyzed the population genetic patterns of diploid and triploid apomictic lineages and their sexual progenitors in the genus Boechera (Brassicaceae). We find that while triploid apomixis is associated with hybridization, the majority of diploid apomictic lineages are likely the product of intra-specific crosses. We then show that these diploid apomicts are more likely to sire triploid apomictic lineages than conspecific sexuals. Combined with flow cytometric seed screen phenotyping for male and female components of apomixis, our analyses demonstrate that hybridization is an indirect correlate of apomixis in Boechera.

Karyological and morphological investigations on aHieraciumputatively endemic to the National Park “Foreste Casentinesi, M. Falterona, Campigna” (northern Apennines, central Italy)

A putatively endemic infraspecific taxon of the Hieracium villosum group from the northern Apennines was investigated from nomenclatural, morphological and karyological points of view. H. villosum Jacq. var. zangherii Vignolo-Lutati proved to be invalidly described, and for its morphological features was referred to H. dentatum Hoppe subsp. xanthostylophorum Furrer & Zahn, a taxon hitherto only known from Abruzzo (Central Apennines). Karyological investigations resulted in the first report for an Italian specimen belonging to the collective species H. dentatum. H. dentatum subsp. xanthostylophorum proved to be tetraploid, with a formula 2n = 4x = 36 = 2M + 14m + 18sm + 2st. Chromosomes were generally of large size and showed a low degree of polymorphism in their shapes. The karyological parameters of H. dentatum subsp. xanthostylophorum have been compared with some available karyological parameters from the literature, belonging to related entities of Hieracium subgen. Hieracium. The Italian Hieracium subgen. Hieracium populations proved to have the most asymmetric karyotypes with respect to other European populations. H. dentatum subsp. xanthostylophorum showed an intermediate karyotype asymmetry between Hieracium subgen. Hieracium populations of the Balkan Peninsula and those of southern Tuscany. From a broader point of view, this study confirms in the northern Apennines a trend pointed out in other central and southern European mountain areas: the core taxon (H. villosum) is surrounded by tetraploid apomictic lineages that show some morphological characters of other Hieracium species; in the case of H. dentatum subsp. xanthostylophorum (= H. villosum “var. zangherii”), characters of H. bifidum.

The Evolutionary Dynamics of Apomixis in Ferns: A Case Study from Polystichoid Ferns

The disparate distribution of apomixis between the major plant lineages is arguably one of the most paradoxical phenomena in plant evolution. Ferns are particularly interesting for addressing this issue because apomixis is more frequent than in any other group of plants. Here, we use a phylogenetic framework to explore some aspects of the evolution of apomixis in ferns and in particular in the polystichoid ferns. Our findings indicate that apomixis evolved several times independently in three different clades of polystichoid ferns. A lineage-wide perspective across ferns indicates a correlation between apomixis and the species richness of lineages; however BiSSE tests did not recover evidence for a correlation of apomixis and diversification rates. Instead, evidence was recovered supporting an association between the establishment of apomixis and reticulate evolution, especially in the establishment of triploid hybrids. Diversification time estimates supported the hypothesis of short living apomictic lineages and indicated a link between the establishment of apomixis and the strengthening of the monsoons caused by the lifting of the Qinghai-Tibetan plateau. In general our results supported the hypothesis for the rare establishment of apomictic lineages, high extinction risks, and low speciation rates.

The role of the Weberian Reform in European Rubus research and the taxonomy of locally distributed species – which species should we describe?

After Sudre published his treatment of European Rubi in the early 20th century, Rubus taxonomy in Europe suffered from a scholastic phase and a longer period of stagnation. The so‐called ‘Weberian Reform’ initiated the necessary revival of European batology. It rests on four major pillars: 1) mapping projects over larger areas, 2) evaluation of type material, 3) visits to loci classici, and 4) evaluation of the status of species by means of their distribution areas. Subsequently, it has become widely accepted in European batology that only species with a distribution area over 50 km should be described. Although this pragmatic species concept has been useful in making a continent‐wide overview of brambles, we argue that it is lacking a scientific basis, and should thus be rejected.There are at least four distinctive problems when treating locally distributed brambles: 1) primary hybrids, 2) locally distributed stabilised apomicts, 3) intraspecific variation in species with a larger distribution range, and 4) unstabilised swarms of hybridogenic biotypes and the derivates thereof (mainly in the montane regions). When facing the problems in Rubus systematics, we argue that all independently evolving lineages should be described as species, including apomictic lineages with very small distribution ranges, both from the mountain‐dwelling glandular series and from the lowlands. Neither primary hybrids (which are not stabilised by apomixis), nor biotypes without an independent and coherent distribution area are independently evolving lineages, and should thus not be described as species. We advocate a restrained attitude when describing new species with limited distribution areas.