Sexual Diploids Research Articles

Cytotaxonomic study of Plagiogyria (Plagiogyriaceae) from China

The chromosome numbers and reproductive biology of eight species from fern genus Plagiogyria (Plagiogyriaceae) from China were investigated, finding seven of the eight species (P. adnate, P. assurgens, P. euphlebia, P. glauca, P. japonica, P. pycnophylla, and P. stenoptera) had chromosomal complements of n = 66 (66II), while P. falcata had a chromosomal complement of n = 62 (31II + 31I). The chromosome numbers of three species—P. assurgens, P. falcata, and P. pycnophylla—are here reported for the first time, while other assayed species revealed new cytotypes. Based on observations of homologous chromosome pairing in diakinesis stage meiosis I of spore mother cells, P. falcata is an agamospermous triploid with 64 haploid spores per sporangium. The remaining species are sexual diploids. Three basic chromosome numbers (i.e., x = 62, 65, 66) are found in Plagiogyria. The distribution of species with different basic chromosome numbers indicates the basic chromosome number x = 66 was plesiomorphic, while x = 62 and x = 65 are apomorphic, indicating aneuploidy events have occurred in this genus and showing an evolutionary trend of decreasing chromosome numbers. The distribution of the sexual diploid and tetraploid species and agamospermous triploid species confirmed the origin of this genus to be southwest China, with apparent diffusion into northeast Asia (e.g., Taiwan) and Japan. However, a few species appear to have originated in America.

Intraspecific ecological niche divergence and reproductive shifts foster cytotype displacement and provide ecological opportunity to polyploids.

Niche divergence between polyploids and their lower ploidy progenitors is one of the primary mechanisms fostering polyploid establishment and adaptive divergence. However, within-species chromosomal and reproductive variability have usually been neglected in community ecology and biodiversity analyses even though they have been recognized to play a role in the adaptive diversification of lineages. We used Paspalum intermedium, a grass species with diverging genetic systems (diploidy vs. autopolyploidy, allogamy vs. autogamy and sexuality vs. apomixis), to recognize the causality of biogeographic patterns, adaptation and ecological flexibility of cytotypes. Chromosome counts and flow cytometry were used to characterize within-species genetic systems diversity. Environmental niche modelling was used to evaluate intraspecific ecological attributes associated with environmental and climatic factors and to assess correlations among ploidy, reproductive modes and ecological conditions ruling species' population dynamics, range expansion, adaptation and evolutionary history. Two dominant cytotypes non-randomly distributed along local and regional geographical scales displayed niche differentiation, a directional shift in niche optima and signs of disruptive selection on ploidy-related ecological aptitudes for the exploitation of environmental resources. Ecologically specialized allogamous sexual diploids were found in northern areas associated with higher temperature, humidity and productivity, while generalist autogamous apomictic tetraploids occurred in southern areas, occupying colder and less productive environments. Four localities with a documented shift in ploidy and four mixed populations in a zone of ecological transition revealed an uneven replacement between cytotypes. Polyploidy and contrasting reproductive traits between cytotypes have promoted shifts in niche optima, and increased ecological tolerance and niche divergence. Ecologically specialized diploids maintain cytotype stability in core areas by displacing tetraploids, while broader ecological preferences and a shift from sexuality to apomixis favoured polyploid colonization in peripheral areas where diploids are displaced, and fostered the ecological opportunity for autotetraploids supporting range expansion to open southern habitats.

A new taxonomic treatment for the apogamous counterpart of Pteris terminalis (Pteridaceae)

An Asia-Pacific fern species Pteris terminalis, formerly known as ‘Pteris excelsa’ is variable in terms of frond morphology as well as cytological characters. In particular, the results of previous cytological studies raised question on naturalness of currently accepted infraspecific taxa—‘P. excelsa var. simplicior’ (not yet combined with P. terminalis) consists of apogamous diploid and triploid, but these cytotypes are shared by the typical form of ‘P. excelsa’ (= P. terminalis), which is most widely distributed as sexual diploid. In the present study, the two varieties are re-circumscribed chiefly based on reproductive modes. Morphological characters including the length of apical pinna segments and the dissection degree of acroscopic side of pinna often, but not always, help their identification. After examination and lectotypification of type specimens of related taxa, correct names at varietal rank, two varieties P. terminalis var. terminalis and P. terminalis var. fauriei are proposed for the sexual form and the apogamous form, respectively.

Species Delimitation in Tetraploid, Apomictic Amelanchier (Rosaceae)

Diversification in Amelanchier tetraploid apomicts differs from that of diploid sexuals and produces groups that are taxonomically difficult. Apomixis facilitates expansion of ecologically successful genotypes into numerous, narrowly distributed, and often minimally distinct microspecies. Residual sexuality in tetraploids creates hybrid swarms and intergradation of taxa. This gene flow is evident in DNA sequences from nuclear and chloroplast regions that record mostly allotetraploid, convoluted histories. Ongoing apomixis in successful tetraploid genotypes fosters their expansion into geographically widespread phenotypic clusters.We delimit such clusters as species and deny species status to microspecies.We demonstrate polyploid complexity and our approach to species delimitation in three taxa of Amelanchier. The tetraploid microspecies A. “rubra” of southeastern Maine, while morphologically distinct, hybridizes with sympatric congeners. Eastern North American A. bartramiana contains diploids and polyploids (tetraploids and a few triploids) that are sometimes morphologically semi-cryptic. We group all ploidy levels in the A. bartramiana agamic complex and recognize as a species the diploid (A. bartramiana). The tetraploid is not given species status because it intergrades extensively with tetraploid congeners, as exemplified by the nothospecies named here, A. ×neglecta. Western North American A. cusickii is tetraploid, mostly distinct morphologically and ecologically, distinct genetically, and merits species status.

Genome size variation among common dandelion accessions informs their mode of reproduction and suggests the absence of sexual diploids in North America

Apomixis is the ability of plants to produce asexual seeds, which are clones of the mother plant. The phenomenon of apomixis is tightly linked to ploidy, where diploids lack apomixis and reproduce sexually, while higher ploidy levels can exhibit apomixis. Taraxacum F.H.Wigg. species (dandelions) commonly exhibit apomixis; however, only limited studies have evaluated genome size variation of the iconic weedy dandelion, Taraxacum officinale F.H.Wigg. (common dandelion), particularly in North America. To evaluate the ploidy and reproductive biology of common dandelion, we created a global collection, with an emphasis on North America and determined genome size by evaluating seeds with flow cytometry. A total of 635 accessions were screened, and with the exception of two accessions from Germany and Austria, all were found to exclusively contain polyploid seed. The mode of reproduction of a sample of 96 of these accessions was observed by conducting emasculations. Our results indicate that the diploid, sexual cytotype of common dandelion may be absent in North America, while diploids were found in previously described areas of Central Europe. This suggests that the clonal lineages of common dandelion in North America may largely be derivative from apomictic plants introduced from abroad. Furthermore, if all North American common dandelion is apomictic, it may be unreceptive to pollen, which may isolate it from other dandelion species and inform the potential for gene flow.

Sexy males and sexless females: the origin of triploid apomicts.

Apomixis and polyploidy are closely associated in angiosperms, but the evolutionary reason for this association is unknown. Taraxacum officinale, the common dandelion, exists both as diploid sexuals and triploid apomicts. Here, in the context of T. officinale, we provide a model of the evolution of triploid apomicts from diploid sexuals. We posit an apomictic allele that arrests female meiosis in diploids, so that the plant produces diploid egg cells that can develop without fertilization, but haploid pollen. We propose occasional fertilization of diploid egg cells by haploid pollen, resulting in triploid apomicts that produce triploid egg cells but largely nonfunctional pollen. The irreversibility of this process renders diploid partial apomicts evolutionarily short-lived, and results in fixation of triploid apomicts except when they suffer extreme selective disadvantages. Our model can account for the high genetic diversity found in T. officinale triploid populations, because recombinant haploid pollen produced by diploids allows the apomictic allele to spread onto many genetic backgrounds. This leads to multiple clonal lineages in the newly apomictic population, and thereby alleviates some of the usual pitfalls of asexual reproduction.

Hieracium mrazii (Asteraceae), a new hybridogenous species from Romania

Hieracium mrazii, a new, apomictic, tetraploid (x = 9) species of presumably hybrid origin between sexual diploids, H. transylvanicum and H. umbellatum, is described from the Retezat Mountains, Southern Carpathians, Romania, and illustrated by a photo of the holotype.

Biogeographical, ecological and ploidy variation in related asexual and sexualLimoniumtaxa (Plumbaginaceae)

Limonium is a widespread genus of halophytes and taxa found on the Atlantic coast include sexual diploids of the L. ovalifolium complex, agamospermous tetraploids of the L. binervosum complex and the triploid L. algarvense. In this study, we investigated: (1) cytotype distribution and diversity within and among populations in an overlapping region of diploid and polyploid Limonium spp. in south-western Iberia and north-western Morocco; and (2) patterns of geographical parthenogenesis and ecological preferences across a latitudinal gradient on the Atlantic coast. We show here for the first time that L. nydeggeri and L. algarvense are found further south in Morocco than previously reported. Genome size and ploidy estimates showed that the distribution of these species is not random at the overlapping region studied: tetraploid apomicts tend to be found at higher latitudes than the sexual diploids and L. algarvense grows in sympatry at the southern boundaries of the diploids. Natural populations showed a constancy in ploidy in these complexes. However, we report for the first time the occurrence of mixed-ploidy populations of L. ovalifolium s.l., euploid triploids in L. algarvense and aneuploids in the L. binervosum complex. On the Atlantic coasts, L. algarvense followed by L. ovalifolium complexes occur significantly more frequently in thermomediterranean and dry ombrotype habitats than the L. binervosum complex. Significant differences were also observed among taxa in the frequency of occurrences on the most common lithological groups. In conclusion, this work presents the first biogeographical insights for the group based in a coarse-scale analysis of data and it provides evidence of ecological differentiation between the studied Limonium complexes.

Attack of the clones: reproductive interference between sexuals and asexuals in the Crepis agamic complex.

Negative reproductive interactions are likely to be strongest between close relatives and may be important in limiting local coexistence. In plants, interspecific pollen flow is common between co‐occurring close relatives and may serve as the key mechanism of reproductive interference. Agamic complexes, systems in which some populations reproduce through asexual seeds (apomixis), while others reproduce sexually, provide an opportunity to examine effects of reproductive interference in limiting coexistence. Apomictic populations experience little or no reproductive interference, because apomictic ovules cannot receive pollen from nearby sexuals. Oppositely, apomicts produce some viable pollen and can exert reproductive interference on sexuals by siring hybrids. In the Crepis agamic complex, sexuals co‐occur less often with other members of the complex, but apomicts appear to freely co‐occur with one another. We identified a mixed population and conducted a crossing experiment between sexual diploid C. atribarba and apomictic polyploid C. barbigera using pollen from sexual diploids and apomictic polyploids. Seed set was high for all treatments, and as predicted, diploid–diploid crosses produced all diploid offspring. Diploid–polyploid crosses, however, produced mainly polyploidy offspring, suggesting that non‐diploid hybrids can be formed when the two taxa meet. Furthermore, a small proportion of seeds produced in open‐pollinated flowers was also polyploid, indicating that polyploid hybrids are produced under natural conditions. Our results provide evidence for asymmetric reproductive interference, with pollen from polyploid apomicts contributing to reduce the recruitment of sexual diploids in subsequent generations. Existing models suggest that these mixed sexual–asexual populations are likely to be transient, eventually leading to eradication of sexual individuals from the population.

Heterozygote Advantage Is a Common Outcome of Adaptation in Saccharomyces cerevisiae.

Adaptation in diploids is predicted to proceed via mutations that are at least partially dominant in fitness. Recently, we argued that many adaptive mutations might also be commonly overdominant in fitness. Natural (directional) selection acting on overdominant mutations should drive them into the population but then, instead of bringing them to fixation, should maintain them as balanced polymorphisms via heterozygote advantage. If true, this would make adaptive evolution in sexual diploids differ drastically from that of haploids. The validity of this prediction has not yet been tested experimentally. Here, we performed four replicate evolutionary experiments with diploid yeast populations (Saccharomyces cerevisiae) growing in glucose-limited continuous cultures. We sequenced 24 evolved clones and identified initial adaptive mutations in all four chemostats. The first adaptive mutations in all four chemostats were three copy number variations, all of which proved to be overdominant in fitness. The fact that fitness overdominant mutations were always the first step in independent adaptive walks supports the prediction that heterozygote advantage can arise as a common outcome of directional selection in diploids and demonstrates that overdominance of de novo adaptive mutations in diploids is not rare.

Systematics of the Adiantum philippense complex (Pteridaceae, Polypodiales) in Taiwan

Adiantum philippense s.l. is a member of once-pinnate Adiantum but comprise several cytotaxa with different ploidies and reproductive modes. According to the differences of cytotypes, the up-to-date revision had identified three subspecies under the A. philippense complex. In Taiwan, different ploidies and reproductive modes had also been found in this species complex, and existence of (a) cryptic species among these cytotypes had been suggested. The current study focuses on taxonomical revision of Taiwanese A. philippense complex. We sampled not only different Taiwanese cytotypes/populations but also all subspecies under A. philippense and the closely related species of them. By re-examining their phylogeny, ploidies, and reproductive modes, we confirmed that the sexual diploids in Taiwan belong to Adiantum menglianense, and this species is phylogenetically separated from A. philippense. We further approved that A. menglianense can be morphologically distinguished from A. philippense by their frond features and spore numbers in sporangia. Another taxon of Taiwanese A. philippense complex is A. philippense subsp. philippense, which is an apomictic and triploidy subspecies. Additionally, we assigned lectotypes of A. menglianense, and revised the hybrid combination of A. × meishanianum. We also provided a key in order to identify two taxa under Taiwanese A. philippense complex and the other once-pinnate Adiantum species in Taiwan.

Asplenium pifongiae (Aspleniaceae: Polypodiales), a New Species from Taiwan

Abstract We describe and illustrate a new species, Asplenium pifongia., currently known only from Taiwan. Although superficially similar to A. monanthe., this species is a sexual diploid and has little perforation on its spore surfaces. Phylogenetic analyses demonstrate that A. pifongia. is not closely related to A. monanthe., and is instead sister to the A. normal. complex. Asplenium pifongia. differs from A. normal. in having sori mostly only on, and parallel to, the basiscopic side of pinnae, a common feature in A. monanthes.

Searching for Diamonds in the Apomictic Rough: A Case Study Involving <I>Boechera lignifera</I> (Brassicaceae)

Abstract The genus Boechera is one of the most difficult species complexes in North America, with about 70 sexual diploids and hundreds of apomictic taxa representing diverse combinations of nearly every known sexual genome. In this study, we set out to clarify the taxonomy of Boechera lignifera, which currently includes a small number of sexual diploid populations in addition to the widespread apomictic diploid upon which the name is based. Using data from cytological studies, microsatellite DNA analyses, geography, and morphology, we demonstrate that the apomictic populations are genetically quite divergent from the sexual diploids. We propose the name Boechera kelseyana to accommodate the sexual diploid taxon, which occurs entirely south of the geographic range of B. lignifera. Boechera kelseyana is consistently separable from B. lignifera based on pollen and seed morphology, the length and proximal orientation of fruiting pedicels, differences in the branching and orientation of trichomes on the lower...

Hybridization in natural mixed populations of sexual diploid and apomictic triploid dandelions (Taraxacum sect. Taraxacum): Why are the diploid sexuals not forced out?

In agamic complexes, the ‘minority cytotype exclusion principle’ can be modified to the ‘sexual cytotype exclusion principle’: Apomicts produce polyploid progeny of maternal genotype without the need for pollination, but still produce pollen. Outcrossing sexuals thus suffer from unsuccessful hybridizations – they produce reduced amounts of progeny. This causes a decrease in the relative frequency of sexuals and later leads to their exclusion from the population. However, in the agamic complex Taraxacum sect. Taraxacum, diploid sexuals coexist with triploid apomicts in stabilized mixed populations. This paper deals with hybridizations in natural populations, the possibilities of new triploid apomicts originating and investigates why the 'sexual cytotype exclusion principle' does not work in Taraxacum sect. Taraxacum. The progeny of diploids from natural populations screened by the flow-cytometric seed screening method consisted only of diploids. Different simulations of natural pollinations were carried experimentally. When the flowers of a diploid received different mixtures of pollen of surrounding diploids and triploids, pollination was successful and only diploid progeny was produced, probably due to the preference of high-quality compatible pollen of diploids by diploid maternal plants. Therefore, the 'sexual cytotype exclusion principle' cannot work in Taraxacum sect. Taraxacum, and diploids and triploids can coexist in common populations. Polyploid progeny was produced by a diploid plant surrounded only by triploid apomicts to a certain distance. This suggests that new polyploid apomicts can be produced only in places where isolated diploids can occur among triploids. Newly formed apomicts further spread their progeny to both areas of apomicts and areas of mixed populations.

Correlations of polyploidy and apomixis with elevation and associated environmental gradients in an alpine plant.

Apomictic plants expand their geographical distributions more to higher elevations compared to their sexual progenitors. It was so far unclear whether this tendency is related to mode of reproduction itself or represents a side effect of polyploidy. Apomixis is advantageous for range expansions as no mating partners and pollinators are needed (Baker's rule). Polyploidy is thought to infer fitness advantages and a higher vigour that would enable plants to adjust better to more extreme climatic conditions. However, little is known about actual performance of plants at higher elevations. We analyzed 81 populations of Ranunculus kuepferi from the whole distribution area in the European Alps to quantify apomictic versus sexual seed formation via flow cytometric seed screening. Seed set and vegetative growth were measured as fitness parameters. All parameters were correlated to geographical distribution, elevation, temperature and precipitation. Flow cytometric seed screening revealed predominantly obligate sexuality (88.9 %) and facultative apomixis in diploid populations, while tetraploid populations are predominantly facultative (65.4 %) to obligate apomictic. Apomictic seed formation correlated significantly to higher elevations, which explains also the observed niche shift to lower temperatures. However, within the tetraploid range, there is no apparent correlation of degree of facultative apomixis to geographical distance. Apomixis appeared in diploids three times independently in separated, otherwise sexual populations in the southwestern refugial areas of the Alps. Diploid apomixis was not successful in range expansions, and obligate sexual polyploids were not observed. Polyploidy may relate to cold tolerance as an adaptation to conditions at high elevations, where diploid sexuals have no fitness advantage. Instead, facultative apomixis may have aided colonization of higher elevations and range expansions in the Alps without mate and pollinator limitation, but did not necessarily involve long-distance dispersal. A direct influence of low temperatures on unreduced gamete formation cannot be ruled out.

Hybrid origin of gynogenetic clones and the introgression of their mitochondrial genome into sexual diploids through meiotic hybridogenesis in the loach, Misgurnus anguillicuadatus.

In a few Japanese populations of the loach Misgurnus anguillicaudatus (Teleostei: Cobitidae), clonal diploid lineages produce unreduced diploid eggs that normally undergo gynogenetic reproduction; however the origin of these clones remains elusive. Here, we show the presence of two diverse clades, A and B, within this loach species from sequence analyses of two nuclear genes RAG1 (recombination activating gene 1) and IRBP2 (interphotoreceptor retinoid-binding protein, 2) and then demonstrate heterozygous genotypes fixed at the two loci as the evidence of the hybrid nature of clonal lineages. All the clonal individuals were identified by clone-specific mitochondrial DNA haplotypes, microsatellite genotypes, and random amplified polymorphic DNA fingerprints; they commonly showed two alleles, one from clade A and another from clade B, whereas other wild-type diploids possessed alleles from either clade A or B. However, we also found wild-type diploids with clone-specific mitochondrial DNA and nuclear genes from clade B. One possible explanation is an introgression of a clone-specific mitochondrial genome from clonal to these wild-type loaches. These individuals likely arose by a cross between haploid sperm from bisexual B clade males and haploid eggs with clone-specific mtDNA and clade B nuclear genome, produced by meiotic hybridogenesis (elimination of unmatched A genome followed by meiosis after preferential pairing between two matched B genomes) in clone-origin triploid individual (ABB).

When sexual meets apomict: genome size, ploidy level and reproductive mode variation of Sorbus aria s.l. and S. austriaca (Rosaceae) in Bosnia and Herzegovina.

Allopolyploidy and intraspecific heteroploid crosses are associated, in certain groups, with changes in the mating system. The genus Sorbus represents an appropriate model to study the relationships between ploidy and reproductive mode variations. Diploid S. aria and tetraploid apomictic S. austriaca were screened for ploidy and mating system variations within pure and sympatric populations in order to gain insights into their putative causalities. Flow cytometry was used to assess genome size and ploidy level among 380 S. aria s.l. and S. austriaca individuals from Bosnia and Herzegovina, with 303 single-seed flow cytometric seed screenings being performed to identify their mating system. Pollen viability and seed set were also determined. Flow cytometry confirmed the presence of di-, tri- and tetraploid cytotype mixtures in mixed-ploidy populations of S. aria and S. austriaca. No ploidy variation was detected in single-species populations. Diploid S. aria mother plants always produced sexually originated seeds, whereas tetraploid S. austriaca as well as triploid S. aria were obligate apomicts. Tetraploid S. aria preserved sexuality in a low portion of plants. A tendency towards a balanced 2m : 1p parental genome contribution to the endosperm was shared by diploids and tetraploids, regardless of their sexual or asexual origin. In contrast, most triploids apparently tolerated endosperm imbalance. Coexistence of apomictic tetraploids and sexual diploids drives the production of novel polyploid cytotypes with predominantly apomictic reproductive modes. The data suggest that processes governing cytotype diversity and mating system variation in Sorbus from Bosnia and Herzegovina are probably parallel to those in other diversity hotspots of this genus. The results represent a solid contribution to knowledge of the reproduction of Sorbus and will inform future investigations of the molecular and genetic mechanisms involved in triggering and regulating cytotype diversity and alteration of reproductive modes.

Hybrid apomicts trapped in the ecological niches of their sexual ancestors

Asexual reproduction is expected to reduce the adaptive potential to novel or changing environmental conditions, restricting or altering the ecological niche of asexual lineages. Asexual lineages of plants and animals are typically polyploid, an attribute that may influence their genetic variation, plasticity, adaptive potential, and niche breadth. The genus Boechera (Brassicaceae) represents an ideal model to test the relative ecological and biogeographic impacts of reproductive mode and ploidy because it is composed of diploid sexual and both diploid and polyploid asexual (i.e., apomictic) lineages. Here, we demonstrate a strong association between a transcriptionally conserved allele and apomictic seed formation. We then use this allele as a proxy apomixis marker in 1,649 accessions to demonstrate that apomixis is likely to be a common feature across the Boechera phylogeny. Phylogeographic analyses of these data demonstrate (i) species-specific niche differentiation in sexuals, (ii) extensive niche conservation between differing reproductive modes of the same species, (iii) ploidy-specific niche differentiation within and among species, and (iv) occasional niche drift between apomicts and their sexual ancestors. We conclude that ploidy is a substantially stronger and more common driver of niche divergence within and across Boechera species although variation in both traits may not necessarily lead to niche evolution on the species scale.

Genotypic diversity of apomictic microspecies of the Taraxacum scanicum group (Taraxacum sect. Erythrosperma)

Populations of polyploid apomictic dandelions consist of a mixture of clonal genotypes that are nearly phenotypically and genetically uniform. Some apomictic taxa are widespread, but many other taxa occur locally or at a single locality. Additionally, certain Central European dandelion populations consist of both diploid sexuals and polyploid apomicts, and the gene flow expected in mixed populations obscures clear genetic and morphological borders among apomictic taxa. In the present study, we investigated genotypic diversity among seven apomictic microspecies coexisting in Central Europe. Using microsatellites, amplified fragment length polymorphism and chloroplast DNA markers, we focused on the clonal structure of apomictic taxa, i.e., whether the studied apomictic taxa are represented by one or a few related genotypes or whether they are represented by many different and unrelated genotypes. The pattern of genotypic diversity within the studied microspecies suggests both intra- and inter-specific genetic diversification. At the intra-specific level, the studied apomictic taxa consist of several related genotypes, and difference among these genotypes is the result of somatic mutations and/or the consequence of repeated origin from different lineages or recent hybridisation. The inter-specific genetic diversity is greater and may reflect a different evolutionary origin of apomictic taxa. Our results show that despite their increased genetic diversity, apomictic dandelions form definable clusters that may be characterised by both molecular markers and morphology.

How just a few makes a lot: Speciation via reticulation and apomixis on example of European brambles (Rubus subgen. Rubus, Rosaceae)

New species are generated by many means, among which hybridization plays an important role. Interspecific hybrids can form isolated evolutionary units, especially when mechanisms increasing viability and fertility, like polyploidy and apomixis, are involved. A good model system to study reticulate evolution in plants is Rubus subgen. Rubus (brambles, blackberries), which only in Europe includes 748 accepted species, out of which only four are sexual diploids and all others are polyploid apomicts. We employed two molecular markers (ITS and cpDNA) to shed light on the evolutionary history of European bramble flora and main processes generating such high species diversity. We distinguished just six ancestral diploids (including two extinct ones) for both markers, which gave rise to all European polyploid accessions, and revealed an extreme reticulation in bramble evolution. We furthermore detected hybridogenous origins and identified putative parents for several taxa (e.g. ser. Nessenses), while in other groups (e.g. ser. Discolores) we could also infer the direction of hybridization. By comparing different cp haplotypes having clear geographic patterns, we hypothesize that the origin of European brambles can be attributed to both Holocene species range expansion and Pleistocene climate fluctuations.