Comparative FISH analysis of C-positive blocks of centromeric chromosomal regions of pygmy wood mice <Emphasis Type="Italic">Sylvaemus uralensis</Emphasis> (Rodentia,Muridae)

The composition and homology of centromeric heterochromatin DNA has been compared in representatives of the Asian race and two chromosomal forms (Eastern European and Southern European) of the European race of the pygmy wood mouse Sylvaemus uralensis by means of in situ hybridization with metaphase chromosomes of microdissection DNA probes obtained from centromeric C-blocks of mice of the Southern European chromosomal form and the Asian race. Joint hybridization of both DNA probes yielded all possible variants of centromeric regions in terms of the presence of repetitive sequences homologous to those of some or another dissection region, which indicates a diversity of centromeric regions differing in DNA composition. However, most variations of the fluorescent in situ hybridization (FISH) patterns are apparently related to quantitative differences of repetitive elements of the genome. Experiments with the DNA probe obtained from the genome of the Southern European form of the pygmy wood mouse have shown that the number of intense FISH signals roughly corresponds to the number of large C-segments in representatives of the European race, which is characterized by a large amount of the centromeric C-heterochromatin in the karyotype. However, intense signals have been also detected in experiments on hybridization of this probe with chromosomes of representatives of the Asian race, which has no large C-blocks in the karyotype; thus, DNA sequences homologous to heterochromatic ones are also present in nonheterochromatic regions adjacent to C-segments. Despite the variations of the numbers of both intense and weak FISH signals, all chromosomal forms/races of S. uralensis significantly differ of the samples from one another in these characters. The number of intense FISH signals in DNA in pygmy wood mice of the samples from eastern Turkmenistan (the Kugitang ridge) and southern Omsk oblast (the vicinity of the Talapker railway station) was intermediate between those in the European and Asian races, which is apparently related to a hybrid origin of these populations (the hybridization having occurred long ago in the former case and recently in the latter case).     

Variability in size of the nuclear genome in pygmy wood mouse Sylvaemus uralensis (Rodentia, Muridae)

Earlier, in an integral genetic study, the Asian and European races were distinguished within the species Sylvaemus uralensis (pygmy wood mouse) and the European race was divided into the East European and South European forms. Each of these groups differed from the others, in particular, in the quantity of the centromeric heterochromatin in karyotypes of the animals. To establish the pattern of its changes in S. uralensis, in the present study the DNA content in splenocyte nuclei in all races and forms of pygmy wood mice was assessed using DNA flow cytometry. The heterochromatin amount in karyotypes and genome size were shown to be correlated. The East European chromosomal race of S. uralensis (Central Chernozem and Non-Chernozem regions of Russia, Crimea Peninsula, Middle Volga region, and Southern Ural) and the Asian race of this species (East Kazakhstan, Uzbekistan, and East Turkmenistan), which have respectively the highest and the lowest amounts of centromeric heterochromatin in the karyotype, exhibit the greatest difference in the DNA content in the genome. On average, the difference is approximately 8% in males and 6.7% in females; in both cases, the ranges of variability were distinctly different. Against the general background of the trait variation, the Asian race, whose members have the smallest DNA amount in their cells, looks homogeneous. The genome of the South European chromosomal form of S. uralensis (Caucasus, Transcaucasia, Carpathians, and Balkan Peninsula), which exhibits an intermediate content of the centromeric heterochromatin in the karyotype, is smaller that the genome of the East European race (by 3.2% in the group of males and by 1.9%, in the group of females), but larger than that of the Asian race (by 5% in either sex). Thus, the variability of size of centromeric C-blocks in pygmy wood mouse is likely to be associated with elimination (or, conversely, an increase in the amount) of the genetically inert chromatin. It is suggested that a significant contribution to the variability of genome size in S. uralensis is made by heterochromosomes, or, more precisely, their variable regions, which seem to be largely heterochromatic.     

On the taxonomic rank of <Emphasis Type="Italic">ciscaucasicus</Emphasis> and its relationships with the pygmy wood mouse <Emphasis Type="Italic">Sylvaemus uralensis</Emphasis> inferred from the mtDNA cytochrome b gene sequence

To specify the taxonomic rank of form ciscaucasicus (independent species Sylvaemus ciscaucasicus, or intraspecific form of pygmy wood mouse, S. uralensis), a 402-bp the mtDNA cytochrome b gene fragment (402 bp) was examined in ciscaucasicus individuals from six geographic localities of the Caucasus and Ciscaucasus (Krasnodar krai and Adygeya Republic) and 17 S. uralensis individuals from seven localities of the Russian Plain (Saratov oblast, Smolensk oblast, Voronezh oblast, Tula oblast, Moscow oblast, Tver’ oblast, and northern Krasnodar krai). For comparison, the cytochrome b gene was partly sequenced in the samples of yellow necked, S. flavicollis (n = 2, Samara oblast), and Caucasian, S. ponticus (n = 6, Krasnodar krai), wood mice. One Mus musculus specimen from Western Europe, whose nucleotide sequences were deposed in the GenBank, was used as intergeneric outgroup. Phylogenetic trees for the forms examined were constructed based on the mtDNA sequence variation and using the neighbor joining and maximum parsimony methods. The network of the cytochrome b haplotypes was also constructed. The level of genetic divergence was evaluated using Kimura’s two-parameter algorithm. Based on the data on the sequence variation in a 402-bp mtDNA cytochrome b gene fragment, the hypothesis on the species status of the ciscaucasicus form was. The mean intergroup distances (d) between the geographic groups of S. uralensis varied from 0.0036 to 0.0152. At the same time, the distances between the pygmy wood mice and the group of S. flavicollis-S. ponticus varies in the range from 0.0860 to 0.0935, and the level of intergeneric genetic differentiation (Sylvaemus-Mus) is higher than the latter index (d = 0.142). Ciscaucasicus should be considered as geographic substitution form of S. uralensis. Furthermore, the Caucasian populations of S. uralensis (= ciscaucasicus) were characterized by a threefold lower value of intergroup genetic divergence (d = 0.0062) than the East European populations (d = 0.0179). This finding pointed to some isolation of Caucasian populations of pygmy wood mouse and depletion of their gene pool. However other molecular genetic data (similarity of nucleotide composition and consistence of the levels of intra-and intergroup distances) suggest the absence of geographic subdivision between Caucasian and East European populations of S. uralensis relative to the molecular marker examined.     

Allozyme Variation of the Pygmy Wood Mouse Sylvaemus uralensis (Rodentia,Muridae) and Estimation of the Divergence of Its Chromosome Forms

The genetic divergence between the eastern European, southern European, and Asian chromosome forms of the pygmy wood mouse Sylvaemus uralensis, whose karyotypes differ from one another in the amount of centromeric heterochromatin, has been reevaluated using allozyme analysis. In general, Asian chromosome forms in S. uralensis living in eastern Kazakhstan, eastern Turkmenistan (the Kugitang Ridge), and Uzbekistan are more monomorphic than European populations of this species. However, the allozyme differences between all chromosome forms of the pygmy wood mouse are comparable with the interpopulation differences within each form and are an order of magnitude smaller than those between good species of the genus Sylvaemus. Thus, the chromosome forms of S. uralensis cannot be considered to be separate species. The concept of races as large population groups that have not diverged enough to regard them as species but differ from one another in some genetic characters is used to describe the differentiation of S. uralensis forms more adequately. The currently available evidence suggests the existence of two S. uralensis races, the Asian and the European ones, and two chromosome forms (eastern and southern) of the European race. The possible historical factors that have determined the formation of the races of the pygmy wood mouse are considered. According to the most plausible hypothesis, the shift and fragmentation of the broad-leaved forest zone during the most recent glacial period (late Pleistocene) were the crucial factors of the formation of these races, because they resulted in a prolonged isolation of the European and Asian population groups ofS. uralensis from each other.     

Localization of repetitive DNA in the chromosomes of <Emphasis Type="Italic">Microtus agrestis</Emphasis> by means of <Emphasis Type="Italic">in situ</Emphasis> hybridization

Heterochromatin in the European field vole, Microtus agrestis, was studied using a special staining technique and DNA/RNA in situ hybridization. The heterochromatin composed the proximal 1/4 of the short arm and the entire long arm of the X chromosome, practically the entire Y chromosome and the centromeric areas of the autosomes. By using the DNA/RNA in situ hybridization technique, repeated nucleotide sequences are shown to be in the heterochromatin of the sex chromosomes.     

High Diversity of mtDNA Haplotypes Confirms Syntopic Occurrence of Two Field Mouse Species <Emphasis Type="Italic">Apodemus uralensis</Emphasis> and <Emphasis Type="Italic">A. witherbyi</Emphasis> (Muridae: <Emphasis Type="Italic">Apodemus</Emphasis>) in Armenia

Wood mice of the genus Apodemus belong to the most frequent and epidemiologically important rodents of Europe and adjacent regions. Previous studies showed that in the Middle East region species of this genus exhibit extraordinary morphological similarity precluding their proper determination without application of molecular characters. In order to determine the species of the studied populations and to obtain an insight into their phylogeographic history, we analyzed their genetic variation. We sequenced 1139 bp fragment of the mitochondrial DNA control region and flanking tRNA genes in samples collected from six localities. Phylogenetic analyses revealed presence of distinct clades corresponding to species A. uralensis and A. witherbyi. In most localities we confirmed presence of both species which suggests their large sympatric and syntopic occurrence. We recognized an extensive genetic variability, 38 specimens of A. uralensis belong to 32 distinct haplotypes, while 19 specimens of A. witherbyi to 14 haplotypes. We confirmed presence of several distinct haplotypes that may originate from multiple wood mouse colonization waves from distinct geographic regions.     

Centromeric and non-centromeric satellite DNA organisation differs in holocentric <Emphasis Type="Italic">Rhynchospora</Emphasis> species

Satellite DNA repeats (or satDNA) are fast-evolving sequences usually associated with condensed heterochromatin. To test whether the chromosomal organisation of centromeric and non-centromeric satDNA differs in species with holocentric chromosomes, we identified and characterised the major satDNA families in the holocentric Cyperaceae species Rhynchospora ciliata (2n = 10), R. globosa (2n = 50) and R. tenuis (2n = 2x = 4 and 2n = 4x = 8). While conserved centromeric repeats (present in R. ciliata and R. tenuis) revealed linear signals at both chromatids, non-centromeric, species-specific satDNAs formed distinct clusters along the chromosomes. Colocalisation of both repeat types resulted in a ladder-like hybridisation pattern at mitotic chromosomes. In interphase, the centromeric satDNA was dispersed while non-centromeric satDNA clustered and partly colocalised to chromocentres. Despite the banding-like hybridisation patterns of the clustered satDNA, the identification of chromosome pairs was impaired due to the irregular hybridisation patterns of the homologues in R. tenuis and R. ciliata. These differences are probably caused by restricted or impaired meiotic recombination as reported for R. tenuis, or alternatively by complex chromosome rearrangements or unequal condensation of homologous metaphase chromosomes. Thus, holocentricity influences the chromosomal organisation leading to differences in the distribution patterns and condensation dynamics of centromeric and non-centromeric satDNA.     

Mitochondrial Evidence of Refugial Distribution of the Pygmy Field Mouse <Emphasis Type="Italic">Sylvaemus uralensis</Emphasis> Pall. (Rodentia,Muridae) in the Northwestern Caucasus

Variation of the 838-bp fragment of the mitochondrial cytb gene was analyzed in Sylvaemus uralensis from the northern macroslope of the Western Caucasus. On the basis of two fixed nonsynonymous substitutions, cytb sequences of the population sample studied can be considered as a distinct Lago-Naki haplogroup, which is clustered in the European cytb lineage. As estimated on the basis of the known rate of substitutions per third codon position in S. sylvaticus, the population must have been isolated for all or a part of the last glaciation period (10000 to 100000 years ago). The observed differentiation of cytb haplotypes is indicative of the refugial distribution of S. uralensis in the northern macroslope of the Western Caucasus, as well as of a secondary contact between the Caucasian and the Russian Plain populations during the Holocene.     

A Comparative Study of Pygmy Hippopotamus (<Emphasis Type="Italic">Choeropsis liberiensis</Emphasis>) Karyotype by Cross-Species Chromosome Painting

The family Hippopotamidae is comprised of two genera with two living species, the common hippo (Hippopotamus amphibius) and the pygmy hippo (Choeropsis liberiensis). Unlike the common hippo, the karyotype of C. liberiensis has not yet been investigated via cross-species chromosome painting methods. We established chromosomal homologies between the pygmy hippo, pig, and cattle by fluorescence in situ hybridization using whole chromosome, arm-specific, region specific, and bacterial artificial chromosome (BAC) probes. Probes from the 18 pig autosomes painted 45 conserved chromosomal segments in the pygmy hippo genome. The pygmy hippo and cattle homology map was deduced from our hybridization results of painting probes to pygmy hippo chromosomes with a combination of previously published dromedary hybridization data. On the pygmy hippo and cattle homology map, 29 cattle autosomes revealed 39 conservative segments on pygmy hippo chromosomes. For a more detailed structural analysis of genome rearrangements and X chromosome structure, we used cattle region specific and BAC probes. Our report demonstrates that cattle probes are useful not only in comparative studies within Ruminantia, but also in more phylogenetically distant Artiodactyla species.     

Differential Under-replication of Satellite DNAs during <Emphasis Type="Italic">Drosophila</Emphasis> Development

SATELLITE DNAs are heavily concentrated in the centromeric heterochromatin of metaphase chromosomes^1–3. Satellites and other repeated polynucleotide sequences are under-represented in the polytene, salivary gland cells of Drosophila melanogaster, D. virilis and D. hydei larvae but are fully represented in diploid cells from embryos and imaginal disks^4–6. This under-representation in polytene cells stems from the association of heterochromatin in the chromocentre and the progressive under-replication of the chromocentre during larval development^7,8.     

Hidden diversity in the <Emphasis Type="Italic">Antrodia malicola</Emphasis> group (Polyporales,Basidiomycota)

Taxonomy of the Antrodia malicola group is revised based on DNA, morphological, ecological, and geographic data. This species complex is not related to Antrodia s. str. but constitutes its own lineage within the large Fomitopsis – Daedalea clade. The A. malicola group includes five species. Antrodia malicola s. str. is distributed in North America and East Asia, and a few records of this species are reported from Azores and Africa. Its European counterpart is A. kuzyana, comb. nova, with wider pores. Infraspecific variability of A. malicola and possible gene flow between it and A. kuzyana in East Asia are detected based on tef1 sequence data. Antrodia cyclopis, sp. nova, is described as a large-spored relative of A. malicola from New Guinea. Antrodia minuta is reported here from several European countries and Siberia, and its morphological characters and host preferences are discussed. Its close relative is A. tuvensis, sp. nova, from Central Siberia, an unusual member of the group with sparse, flexuous skeletal hyphae.     

Evidence of multiple introductions and genetic admixture of the Asian brush-clawed shore crab <Emphasis Type="Italic">Hemigrapsus takanoi</Emphasis> (Decapoda: Brachyura: Varunidae) along the Northern European coast

The Asian brush-clawed shore crab Hemigrapsus takanoi is a non-indigenous species along the Northern European coast. Although the history of range expansion of European H. takanoi has been well-documented, little is known about the genetic compositions of either the introduced European populations or the native Asian ones. We therefore collected H. takanoi broadly from their native Asian sites and introduced European ranges, and genotyped them by sequencing the mitochondrial 16S RNA gene and by analyzing nuclear microsatellite loci. Our results revealed that the H. takanoi Bay of Seine (France) populations consisted of a genetic admixture between populations in Japan and those in the Yellow Sea region. These French populations should be carefully monitored in the future, since the genetic admixture of multiple source populations may accelerate range expansion in non-indigenous organisms. Our results also suggested that shipping lines from East Asia were more probable vectors than historical juvenile oyster transportations from Japan for the foundation of present European H. takanoi populations. Interestingly, gene flow between populations in Japan and those in the Yellow Sea region (i.e., domestic invasion) was not observed despite the higher potential for artificial translocations via shipping lines in the native Asian range compared with those from Asia to Europe. The lack of domestic invasions implied that intra-specific priority effects of the resident H. takanoi populations played an important role in preventing the successful colonization of artificially-transferred individuals.     

Revision of <Emphasis Type="Italic">Protohydnum</Emphasis> (Auriculariales,Basidiomycota)

Three species currently addressed to Protohydnum (Auriculariales) are studied with morphological and DNA methods. The genus Protohydnum is retained for the type species only, P. cartilagineum, recently re-collected in Brazil. The European species, P. piceicola, is not congeneric with P. cartilagineum and, therefore, placed in its own genus, Hyalodon, gen. nov. Another Hyalodon species, H. antui, is described from East Asia. The third member of Protohydnum sensu lato, P. sclerodontium from South-East Asia, is transferred to Elmerina.     

Signature of positive selection of <Emphasis Type="Italic">PTK6</Emphasis> gene in East Asian populations: a cross talk for <Emphasis Type="Italic">Helicobacter pylori</Emphasis> invasion and gastric cancer endemicity

Analysis of natural selection events is an attractive strategy for identification of functional variants shaped by gene–environmental interactions and human adaptation. Here, we identified PTK6, a Src-related tyrosine kinase gene, underlying positive selection in East Asian populations. Interestingly, PTK6 variant showed significant correlation with gastric cancer incidences which was the highest in East Asian populations. The high prevalence of gastric cancer in East Asians was also believed to be strongly affected by Helicobacter pylori infection and dietary habit. Therefore, we speculated a competitive interaction of cancer-associated molecules for activation/reduction, where PTK6 likely plays a role through CagA-driven signaling pathway after H. pylori infection. This hypothesis was also supported by our gene expression analysis and the dating of the selective event which was estimated to be ~16,500 years ago, much later than H. pylori invasion in human 50,000 years ago. Establishment of cross talk between PTK6 and CagA by functional studies may further elucidate the underlying biology of H. pylori-mediated gastric cancer.     

Comparative cytogenetic analysis of four species of <Emphasis Type="Italic">Dendropsophus</Emphasis> (Hylinae) from the Brazilian Atlantic forest

We conducted a cytogenetic study of four hyline frog species (Dendropsophus elegans, D. microps, D. minutus and D. werneri) from southern Brazil. All species had 2n = 30 chromosomes, with interspecific and intraspecific variation in the numbers of metacentric, submetacentric, subtelocentric and telocentric chromosomes. C-banding and fluorochrome staining revealed conservative GC-rich heterochromatin localized in the pericentromeric regions of all species. The location of the nucleolus organizer regions, as confirmed by fluorescent in situ hybridization, differed between species. Telomeric probes detected sites that were restricted to the terminal regions of all chromosomes and no interstitial or centromeric signals were observed. Our study corroborates the generic synapomorphy of 2n = 30 chromosomes for Dendropsophus and adds data that may become useful for future taxonomic revisions and a broader understanding of chromosomal evolution among hylids.     

Tracking an invasion: community changes in hardwood forests following the arrival of <Emphasis Type="Italic">Amynthas agrestis</Emphasis> and <Emphasis Type="Italic">Amynthas tokioensis</Emphasis> in Wisconsin

Because Upper Midwest temperate forests lack native earthworms, the invasions of European and Asian earthworms can significantly alter soils and understory vegetation. Earthworms’ ability to increase leaf litter decay, alter nutrient cycling by mixing the organic layer with mineral soil, and decrease plant species richness leads to concern about the Asian ‘jumping earthworm’ (Amynthas agrestis and A. tokioensis) species that were recorded in the University of Wisconsin—Madison Arboretum in 2013. In 2015, we found A. agrestis and A. tokioensis in a distinct 8-ha region of a 23-ha hardwood forest surveyed in the Arboretum; by 2016 A. agrestis and A. tokioensis had spread over an additional 7 ha. Plots also contained the European earthworm species Lumbricus terrestris, L. rubellus, and Apporectodea spp., whose distributions decreased from 2015 to 2016. While leaf litter, plant species richness, and tree and shrub seedling abundance were generally reduced in areas with European earthworms, they were typically slightly increased in areas with A. agrestis and A. tokioensis versus those without. Although our results do not show substantial impacts of A. agrestis and A. tokioensis on vegetation in the initial years of invasion, the rapid replacement of European earthworms by A. agrestis and A. tokioensis suggests continued monitoring of these new invasive species is important to better understand their potential to change the Upper Midwest’s forests.     

Polymorphism of Human Thermoreceptor Genes <Emphasis Type="Italic">TRPV1</Emphasis> and <Emphasis Type="Italic">TRPA1</Emphasis> in Populations of the Altai-Sayan Region and the Far East

Genotyping of TRPV1 and TRPA1 genes encoding thermoreceptors in the populations of the Altai-Sayan region and the Far East was conducted. The sample consisted of 15 populations comprising 1482 individuals. The analysis of TRPV1 rs222747 demonstrated that the frequency of M315I was closest to East Asian populations only in Nanais and Koryaks (56 and 64%, respectively). Siberian Tatars, Yakuts, and Evenks were closest to European populations. All populations of the Altai-Sayan region reported an intermediate position between the Caucasoids and the Eastern Mongoloids on the basis of the frequency of M315I. No deviations from the Hardy–Weinberg distribution were observed. The observed heterozygosity exceeded the expected one in eight populations. The analysis of TRPA1 rs13268757 revealed that Chukchi, Yukaghir, Koryak, Tuvinian, Southern Altaian, and Telengit populations were closest to the East Asian populations on the basis of the frequency of R3C substitution (3–7%). At the same time, populations of Siberian Tatars, Nanais, Evenks, Yakuts, Shorians, Khakases, and Kazakhs were intermediate between the Caucasoids (18–23%) and the Mongoloids from East Asia (3–7%) on the basis of the frequency of this polymorphism. A deviation from the Hardy–Weinberg distribution was detected only in the Yukaghir population. The observed heterozygosity was higher than the expected one in nine populations. A trans-association of TRPA1 and TRPV1 gene polymorphisms was carried out in 14 populations via regression analysis. A negative correlation of–0.545 was determined, the number of degrees of freedom (df) was 13, and the P-value was 0.048. The data obtained indicate that the analyzed polymorphisms are correlated, which confirms an earlier conclusion of the TRPA1-dependent inhibition of TRPV1 function. The results may evidence in the co-evolution of analyzed genes.     

Molecular and cytogenic analysis of pericentromeric heterochromatin in ovarian nurse cells of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> subgroup species

Evolutionary rearrangements of pericentromeric heterochromatin among Drosophila melanogaster subgroup species have been investigated. A region-specific DNA library from Drosophila orena ovarian nurse cell chromocenter was obtained by the microdissection of polythene chromosomes. The probe has been localized on chromosomes of ovarian nurse cells of Drosophila melanogaster subgroup species using fluorescent hybridization in situ. Sequences homologous to the sequences of the DNA probe were detected in the chromocenter and pericentromeric regions of D. orena polythene chromosomes, in all pericentromeric regions of other species with several exceptions. There was no labeling on one of the arms of the D. simulans chromosome 2; however, these sequences were present on the telomere of D. erecta chromosome 3 and in regions adjacent to the brightly DAPI-stained heterochromatin blocks of D. yakuba, D. santomea and D. teissieri chromosomes 2 and 3. At the S₆ stage (secondary reticulate nucleus), labeled chromatin can be found mostly within a restricted territory in D. orena nucleus; no such chromatin can be detected throughout the rest of the nucleus. On the contrary, at this stage, in nuclei of other species, labeled DNA is spread diffusely.     

Cytogenetic evidences on the evolutionary relationships between the tetraploids of the section <Emphasis Type="Italic">Rhizomatosae</Emphasis> and related diploid species (<Emphasis Type="Italic">Arachis</Emphasis>, Leguminosae)

Rhizomatosae is a taxonomic section of the South American genus Arachis, whose diagnostic character is the presence of rhizomes in all its species. This section is of particular evolutionary interest because it has three polyploid (A. pseudovillosa, A. nitida and A. glabrata, 2n?=?4x?=?40) and only one diploid (A. burkartii, 2n?=?2x?=?20) species. The phylogenetic relationships of these species as well as the polyploidy nature and the origin of the tetraploids are still controversial. The present study provides an exhaustive analysis of the karyotypes of all rhizomatous species and six closely related diploid species of the sections Erectoides and Procumbentes by cytogenetic mapping of DAPI/CMA heterochromatin bands and 5S and 18–26S rDNA loci. Chromosome banding showed variation in the DAPI heterochromatin distribution pattern, which, together with the number and distribution of rDNA loci, allowed the characterization of all species studied here. The bulk of chromosomal markers suggest that the three rhizomatous tetraploid species constitute a natural group and may have at least one common diploid ancestor. The cytogenetic data of the diploid species analyzed evidenced that the only rhizomatous diploid species—A. burkartii—has a karyotype pattern different from those of the rhizomatous tetraploids, showing that it is not likely the genome donor of the tetraploids and the non-monophyletic nature of the section Rhizomatosae. Thus, the tetraploid species should be excluded from the R genome, which should remain exclusively for A. burkartii. Instead, the karyotype features of these tetraploids are compatible with those of different species of the sections Erectoides and Procumbentes (E genome species), suggesting the hypothesis of multiple origins of these tetraploids. In addition, the polyploid nature and the group of diploid species closer to the tetraploids are discussed.