Basic Chromosome Number Research Articles

Chromosome Number and Genome Size Evolution in Brasolia and Sobralia (Sobralieae, Orchidaceae).

Despite the clear circumscription of tribe Sobralieae (Orchidaceae), its internal relationships are still dubious. The recently delimited genus Brasolia, based on previous Sobralia species, is now assumed to be paraphyletic, with a third genus, Elleanthus, nested in it. The morphology of these three genera is significantly different, indicating the necessity of new data for a better genera delimitation. Though morphology and molecular data are available, cytogenetics data for Sobralieae is restricted to two Sobralia and one Elleanthus species. Aiming to evaluate the potential of cytogenetic data for Brasolia-Elleanthus-Sobralia genera delimitation, we present chromosome number and genome size data for 21 and 20 species, respectively, and used such data to infer the pattern of karyotype evolution in these genera. The analysis allowed us to infer x = 24 as the base chromosome number and genome size of average 1C-value of 5.0 pg for the common ancestor of Brasolia-Elleanthus-Sobralia. The recurrent descending dysploidy in Sobralieae and the punctual genome upsize suggest a recent diversification in Sobralieae but did not allow differing between Brasolia and Sobralia. However, the basal position of tribe Sobralieae in the subfamily Epidendroideae makes this tribe of interest to further studies clarifying the internal delimitation and pattern of karyotype evolution.

Molecular and Cytogenetic Analysis of rDNA Evolution in Crepis Sensu Lato.

Although Crepis was the first model plant group in which chromosomal changes were considered to play an important role in speciation, their chromosome structure and evolution have been barely investigated using molecular cytogenetic methods. The aim of the study was to provide a better understanding of the patterns and directions of Crepis chromosome evolution, using comparative analyses of rDNA loci number and localisation. The chromosome base number and chromosomal organisation of 5S and 35S rDNA loci were analysed in the phylogenetic background for 39 species of Crepis, which represent the evolutionary lineages of Crepis sensu stricto and Lagoseris, including Lapsana communis. The phylogenetic relationships among all the species were inferred from nrITS and newly obtained 5S rDNA NTS sequences. Despite high variations in rDNA loci chromosomal organisation, most species had a chromosome with both rDNA loci within the same (usually short) chromosomal arm. The comparative analyses revealed several independent rDNA loci number gains and loci repositioning that accompanied diversification and speciation in Crepis. Some of the changes in rDNA loci patterns were reconstructed for the same evolutionary lineages as descending dysploidy.

CYTOMORPHOLOGICAL STUDIES OF SOME NIGERIAN ASTERACEAE (COMPOSITAE) - TRIBE EUPATORIEAE

Cytological, seed and epidermal studies were carried out of 9 taxa belonging to 4 genera and 6 species of the tribe Eupatorieae. Chromosome counts of 2 species-Adenostemma caffrum (n=10) and A. mauritianum (n=10) are reported for the first time from the Nigerian flora and the report of Ageratum conyzoides (n=18) differed from earlier reports. The report of 2 cytotypes in Ageratum conyzoides is reported for the first time from the Nigerian flora. The pollen fertility test of all the plants studied were high and this revealed that meiosis was normal with regular bivalent pairing and the plants were stable. The achene morphology of all the taxa studied have been drawn and described for the first time. Distribution maps of all the taxa studied have been drawn and described for the first time and this revealed that the plants were of widespread occurrence in the country. The epidermal walls of all the species studied were sinuously walled and their mature stomata was anomocytic in their amphistomatic leaves except for Adenostemma perrottetii that was hypostomatic. The ontogeny of all the plants studied was agenous and this has been presented for the first time. Eglandular multicellular trichomes were present in Chromoleana odorata and Ageratum conyzoides. Contiguous stomata was observed in (Adenostemma mauritianum, A. caffrum, Ageratum conyzoides, Chromoleana odorata and stomata with only one guard cell was observed in Mikania chenopodifolia were the only stomatal abnormality found in the tribe. The stomatal size of Mikania chenopodiifolia was the highest with 46?m x 20?m x 20?m x 4?m. There was no correlation between chromosome number and habit or between achene morphology and their growth habit in the tribe. A probable pathway of the evolution of basic chromosome number in the tribe has been suggested. The results from this study has confirmed the correct placement of the genera in the tribe Eupatorieae.

Nuclear DNA Content, Selected Morphological and Anatomical Traits of Narcissus Cultivars and Breeding Clones

The genus Narcissus belongs to the family Amaryllidaceae. This genus has been the subject of numerous cytological and cytometric studies and have shown enormous variation in terms of genome size, ploidy level, and even the basic chromosome number. The basic chromosome numbers are 5 or 7, but 10, 11, and 12 have been recorded as well. Most narcissus cultivars are euploid tetraploids. There are also numerous triploids. Some cultivars are aneuploid such as tetraploids or triploids, with missing chromosomes or possessing additional chromosomes. Due to their very complex parentage, cultivars have various numbers of chromosomes not found in the species. In this publication, we present a study on the genome size and assessment of the likely ploidy level of 38 cultivars and breeding clones of Narcissus in relation to their selected morphological traits and information on their parental forms. For the first time, 12 Polish cultivars and breeding clones of narcissus were the subject of such an evaluation. Perianth diameter, leaf length, and width were evaluated and rated with notes according to the descriptor of the International Union for the Protection of New Varieties of Plants. Stomatal density and stomata length were measured using light microscopy. Analysis of genome size was carried out using flow cytometry. For three selected genotypes, the chromosome number was counted. Our results lead to the general conclusion that the morphological traits studied and nuclear DNA content can be useful for determining the possible ploidy level of narcissi. The information on the origin and parental forms of narcissi can be helpful in determining the ploidy level of narcissi. However, clear confirmation of ploidy level requires verification of chromosome number and preferably karyotyping. The results obtained are a prelude to further studies.

Genome Sizes, Ploidy Levels, and Base Compositions of Styrax Species and Cultivars

Styrax L. is a genus of ≈130 species, many with horticultural traits of interest, though sparsely represented in cultivation. Previous studies reporting chromosome counts have established a base chromosome number of x = 8 and provided evidence of diploid, tetraploid, pentaploid, and hexaploid levels within the genus, including the more commonly cultivated Styrax japonicus Siebold & Zucc. being reported as pentaploid. Little has been reported relative to genome size within the Styracaceae. We conducted flow cytometry using fluorochromes propidium iodide (PI) and 4′,6-diamidino-2-phenylindole (DAPI) to estimate relative 2C genome size and ploidy of 47 accessions representing 15 species of Styrax and base composition of a subset of 9 accessions representing 6 species. Cytologic analysis of chromosomes was completed on Styrax confusus Hemsl. for ploidy calibration to genome size. Diploids, tetraploids, pentaploids, hexaploids, and octoploids were identified. Relative 2C genome size ranged from 1.38 to 6.61 pg. This survey confirms published ploidy for Styrax americanus Lam., Styrax obassia Siebold & Zucc., Styrax redivivus (Torr.) L.C.Wheeler (diploid), and S. japonicus (pentaploid); suggests alternate ploidy levels and/or ploidy series for Styrax grandifolius Aiton (diploid) and Styrax hookeri C.B.Clarke (octoploid); and establishes ploidy levels for Styrax glabrescens Benth., Styrax odoratissimus Champ. ex Benth., Styrax officinalis L., Styrax platanifolius Engelm. ex Torr., Styrax ramirezii Greenm., Styrax wilsonii Rehder (diploid), Styrax confusus, Styrax hemsleyanus Diels (tetraploid), and Styrax fortunei Hance (diploid and hexaploid).

Niche conservatism, divergence and polyploidy inSennaseriesAphyllae(Fabaceae: Caesalpinioideae) from arid zones of South America

AbstractThis paper aims to integrate cytogenetic and ecological approaches into a phylogenetic framework to better understand the evolution and systematics of Senna series Aphyllae, an endemic group of arid and semi-arid regions of South America. We counted the chromosome numbers at the population level in three species of series Aphyllae using a conventional technique (GIEMSA) and in situ hybridization (FISH). Phylogenetic reconstructions and inference of chromosome evolution were based on four plastid DNA regions and one nuclear marker. A principal component analysis was carried out using environmental data. Finally, ecological niche models (ENM) were implemented: (1) to identify the abiotic factors that constraint the potential geographical distribution of series Aphyllae and (2) to understand the ecological drivers for species diversification. The basic chromosome number is x = 12. Senna aphylla showed three cytotypes with (2n = 24, 48 and 60) and S. pachyrrhiza has two cytotypes (2n = 24 and 48). Senna crassiramea appeared to be polyploid with 2n = 48. In diploid S. pachyrrhiza, two 45S and three 5S rDNA sites were reported. In tetraploid S. crassiramea, four 45S and four 5S rDNA sites were detected. The ENM and ecological speciation tests suggest that in series Aphyllae speciation was sometimes associated with conservatism and sometimes with niche divergence. Our results contribute to the evolutionary knowledge of Neotropical legumes and understanding of drivers of diversification in arid regions in South America.

Synthesis of Nuclear and Chloroplast Data Combined With Network Analyses Supports the Polyploid Origin of the Apple Tribe and the Hybrid Origin of the Maleae-Gillenieae Clade.

Plant biologists have debated the evolutionary origin of the apple tribe (Maleae; Rosaceae) for over a century. The “wide-hybridization hypothesis” posits that the pome-bearing members of Maleae (base chromosome number x = 17) resulted from a hybridization and/or allopolyploid event between progenitors of other tribes in the subfamily Amygdaloideae with x = 8 and x = 9, respectively. An alternative “spiraeoid hypothesis” proposed that the x = 17 of Maleae arose via the genome doubling of x = 9 ancestors to x = 18, and subsequent aneuploidy resulting in x = 17. We use publicly available genomic data—448 nuclear genes and complete plastomes—from 27 species representing all major tribes within the Amygdaloideae to investigate evolutionary relationships within the subfamily containing the apple tribe. Specifically, we use network analyses and multi-labeled trees to test the competing wide-hybridization and spiraeoid hypotheses. Hybridization occurred between an ancestor of the tribe Spiraeeae (x = 9) and an ancestor of the clade Sorbarieae (x = 9) + Exochordeae (x = 8) + Kerrieae (x = 9), giving rise to the clade Gillenieae (x = 9) + Maleae (x = 17). The ancestor of the Maleae + Gillenieae arose via hybridization between distantly related tribes in the Amygdaloideae (i.e., supporting the wide hybridization hypothesis). However, some evidence supports an aspect of the spiraeoid hypothesis—the ancestors involved in the hybridization event were likely both x = 9, so genome doubling was followed by aneuploidy to result in x = 17 observed in Maleae. By synthesizing existing genomic data with novel analyses, we resolve the nearly century-old mystery regarding the origin of the apple tribe. Our results also indicate that nuclear gene tree-species tree conflict and/or cytonuclear conflict are pervasive at several other nodes in subfamily Amygdaloideae of Rosaceae.

Chromosome restructuring and number change during the evolution of Morus notabilis and Morus alba.

Mulberry (Morus spp.) is an economically important plant as the main food plant used for rearing domesticated silkworm and it has multiple uses in traditional Chinese medicine. Two basic chromosome numbers (Morus notabilis, n = 7, and Morus alba, n = 14) have been reported in the genus Morus, but the evolutionary history and relationship between them remain unclear. In the present study, a 335-Mb high-quality chromosome-scale genome was assembled for the wild mulberry species M. notabilis. Comparative genomic analyses indicated high chromosomal synteny between the 14 chromosomes of cultivated M. alba and the six chromosomes of wild M. notabilis. These results were successfully verified by fluorescence in situ hybridization. Chromosomal fission/fusion events played crucial roles in the chromosome restructuring process between M. notabilis and M. alba. The activity of the centromere was another key factor that ensured the stable inheritance of chromosomes. Our results also revealed that long terminal repeat retrotransposons were a major driver of the genome divergence and evolution of the mulberry genomes after they diverged from each other. This study provides important insights and a solid foundation for studying the evolution of mulberry, allowing the accelerated genetic improvement of cultivated mulberry species.

Chromosome numbers and genome size data on species of the genus Petrorhagia(Caryophyllaceae) from Turkey

Genome size, i.e. the total amount of DNA in an unreplicated somatic nucleus is considered an important character in the biology of organisms, and it is especially relevant for land plants given the extraordinary diversity reported. Despite the continuous growth of data and the efforts aimed at increasing our understanding of plant genome size diversity, more data are needed to have an evenly representation across lineages. With this premise in mind, in this work, we investigated genome size, complemented with chromosome data in eight species of the genus Petrorhagia (Caryophyllaceae) from Turkey. Chromosome counts made indicate that the species studied are diploid except for one species, P. saxifraga, which is probably a tetraploid, based on previously published estimations of nuclear DNA contents. The presence of both basic chromosome numbers x = 15 and x = 13 is confirmed, the latter being restricted to the species P. hispidula and P. cretica. The counts carried out for the Turkish endemic species, in P. hispidula (2n = 26), P. pamphylica (2n = 30) and P. peroninii (2n = 30) represent novel data for the genus. Nuclear DNA contents ranged from 1.24 to 2.32 pg/2C (varying 1.87-fold). Based on available data, genome expansions in the genus seem to have occurred through different evolutionary mechanisms, such as polyploidy and differential repetitive DNA activation, evidencing contrasting genomic trajectories between closely related taxa

The chromosomal evolution and analyses of Turkish Cousinia species

In this study, Turkish Cousinia species were examined in point of chromosome number and morphology. To our knowledge, this work is the first comprehensive chromosomal study regarding Turkish Cousinia as a whole, especially for endemics. As consistent with previous reports, the chromosome numbers are mostly 2n = 26 and have been determined also as 2n = 24 for only the members of Cynaroideae and Sphaerocephalae sections. An interesting result of this paper is that there is not any polyploid species in this taxonomic group and all of them are diploids. Concerning the chromosome evolution of the Cousinia species, we concluded that merely dysploidy is effective within the genus and evolutionally a unipolar reduction goes on in the basic chromosome number in speciation (from 13 to 12). In terms of general chromosomal information, the chromosomes of the genus consist of metacentric and submetacentric types and they could be categorized in small category according to Lima De Faria classification (0.67?3.43). According to chromosomal indices used in this paper, while most species have symmetrical chromosomes, fewer have asymmetrical ones. From this point, it could be said that Cousinia stapfiana could be assessed as the most evolved taxa in karyomorphology according to the average of all indexes used in here. Besides, Cousinia bicolor, Cousinia birandiana, and Cousinia sintenisii are species having the most primitive chromosome within the genus.

Karyotype and genome size variation in white-flowered Eranthis sect. Shibateranthis (Ranunculaceae).

Comparative karyomorphological analyses of six out of the eight white-flowered species of Eranthissect.Shibateranthis have been carried out. All studied specimens of E.byunsanensis, E.lobulata, E.pinnatifida, and E.stellata had a somatic chromosome number 2n = 16 with basic chromosome number x = 8. On the contrary, E.tanhoensis and E.sibirica had a basic chromosome number x = 7. The specimens of E.tanhoensis were diploid with 2n = 14, while the specimens of E.sibirica were polyploid with 2n = 42. Monoploid chromosome sets of the investigated diploid species had 4–5 metacentric chromosomes and 2–4 submetacentric/subtelocentric/acrocentric chromosomes. The highest level of interchromosomal asymmetry, estimated via CVCL, was found in E.byunsanensis and E.pinnatifida. The highest levels of intrachromosomal asymmetry (MCA) and heterogeneity in centromere position (CVCI) were found in E.lobulata and E.byunsanensis, while E.sibirica had the most symmetric karyotype. A multivariate PCoA analysis of basic karyotype parameters (2n, x, THL, CVCL, MCA, and CVCI) highlighted no overlap among species accessions, which was also confirmed by LDA. The average absolute monoploid DNA content (1Cx) of the 23 investigated samples of six Eranthis species varied from 9.26 ± 0.25 pg in E.sibirica to 15.93 ± 0.32 pg in E.stellata. Overall karyological affinity was highlighted between E.lobulata and E.stellata, on one side, and between E.byunsanensis and E.pinnatifida, on the other side. Interestingly, there was no significant correlation between total haploid (monoploid) chromosome length (THL) and 1Cx values in these species.

Karyomorphological Studies of Six Species of Turkish <i>Muscari</i> (Asparagaceae)

In this study, chromosome length, karyomorphology and chromosome asymmetry of six Turkish Muscari species; Muscari muglaensis, M. nazimiyensis, M. pallens, M. pamiryigidii, M. inundatum and M. fatmaceranie were evaluated. The somatic chromosome number of all examined taxa was determined as 2n=18. The basic chromosome number was x=9. Chromosomes consist of metacentric, submetacentric, and subtelocentric chromosomes. This is the first report on chromosome number and morphology for five of the six taxa studied. Studies on the karyotype and chromosomal diversity of Muscari may provide insight into taxonomic relationships and differences within the genus.

Cytological Study of <i>Begonia</i> Sect. <i>Diploclinium</i> (Begoniaceae)

Previous chromosome information is restricted to 13 species in the Asian Begonia sect. Diploclinium. Here we present the first chromosome counts of three species, as well as confirmed their chromosome numbers of five species. Among three species investigated for the first time, the chromosome number of 2n=18 and 2n=32 are new counts in the section. Additionally, we provide the karyotypes of eight species for the first time. Among ca. 135 species in sect. Diploclinium, chromosome numbers of 16 species are available together with the present and previous reports. Among 16 species, they show diverse chromosome numbers with 2n=18, 22, 24, 26, 30, 32, 36, 46, and 54. B. wenshanensis with 2n=18 is the lowest chromosome number in the section and the third lowest chromosome number in Begonia. We suggest that B. coptidimontana with 2n=32 is tetraploid origin with the basic chromosome number of x=8. We discussed the chromosome evolution in Begonia sect. Diploclinium.

Chromosome-specific painting unveils chromosomal fusions and distinct allopolyploid species in the Saccharum complex.

Karyotypes provide key cytogenetic information on the phylogenetic relationships and evolutionary origins in related eukaryotic species. Despite our knowledge of the chromosome numbers of sugarcane and its wild relatives, the chromosome composition and evolution among the species in the Saccharum complex have been elusive owing to the complex polyploidy and the large numbers of chromosomes of these species. Oligonucleotide-based chromosome painting has become a powerful tool of cytogenetic studies especially for plant species with large numbers of chromosomes. We developed oligo-based chromosome painting probes for all 10 chromosomes in Saccharum officinarum (2n = 8x = 80). The 10 painting probes generated robust fluorescence in situ hybridization signals in all plant species within the Saccharum complex, including species in the genera Saccharum, Miscanthus, Narenga and Erianthus. We conducted comparative chromosome analysis using the same set of probes among species from four different genera within the Saccharum complex. Excitingly, we discovered several novel cytotypes and chromosome rearrangements in these species. We discovered that fusion from two different chromosomes is a common type of chromosome rearrangement associated with the species in the Saccharum complex. Such fusion events changed the basic chromosome number and resulted in distinct allopolyploids in the Saccharum complex.

Molecular cytogenetics of Dictyoloma vandellianum A. Juss. and the ancestral karyotype of Rutaceae

Determination of the chromosome base number of a taxon is fundamental to understanding karyotypic variation and its implications for the evolution of that group. This usually requires careful evaluation of cytological literature and robust phylogenetic support. The base number for the family Rutaceae (x = 9 or x = 18) has long been the subject of debate. Here, we analyzed the banding pattern, rDNA sites, and genome size of Dictyoloma vandellianum, subfamily Cneoroideae, the sister group of the remaining Rutaceae, and revised critical points about the chromosome base number of the family. We found that this species has n = 9, which differs from the n = 18 possessed by other cytologically known Cneoroideae species. Thus, n = 9 occurs in the main clades of Rutaceae and is the most probable base number of the family. The hypothesis of x = 18 as the base number is no longer sustainable, although n = 18 is very common in Rutaceae. Moreover, the fluorescent banding pattern and the relatively large genome size (1C = 1.3 pg) of D. vandellianum suggest that its chromosomal organization is highly divergent from Aurantieae, the only large Rutaceae clade where species with n = 9 are greatly dominant.

Chromosome and Genome Diversity in the Genus Trifolium (Fabaceae).

Trifolium L. is an economically important genus that is characterized by variable karyotypes relating to its ploidy level and basic chromosome numbers. The advent of genomic resources combined with molecular cytogenetics provides an opportunity to develop our understanding of plant genomes in general. Here, we summarize the current state of knowledge on Trifolium genomes and chromosomes and review methodologies using molecular markers that have contributed to Trifolium research. We discuss possible future applications of cytogenetic methods in research on the Trifolium genome and chromosomes.

Seed shape supports phylogenetic relationships and adaptive radiation in the genusPinguicula(Lentibulariaceae)

AbstractRecent phylogenetic analyses call into question the morphology-based classification of Pinguicula. Although considerable floral morphological diversity among taxa in the genus is present within a geographical region, the phylogenetic analyses suggest that in many cases the taxa in any such region form a monophyletic group. Floral morphology may well have masked phylogenetic relationships and further evidence is required to clarify the issue. In this study, seed shape and size in Pinguicula from Mexico and higher latitudes of the Northern Hemisphere (Northern) belonging to subgenera Isoloba and Pinguicula, a total of 38 taxa, were compared. Results showed that the seed of Mexican taxa was significantly narrower than that of the Northern taxa. The study suggests that the morphology-based subgeneric division was not supported by statistical analyses of seed characters, whereas the geographical division was supported. The Northern and Mexican taxa can, therefore, be separated by their seed shape and size, and consequently the adaptive radiation inferred by the phylogenetic analyses was strongly supported by seed shape, in addition to life-form and basic chromosome number. The shape of seed remains similar within a lineage in each region with relation to the evolutionary history of the genus.

Molecular Phylogeny of Trifolium L. Section Trifolium with Reference to Chromosome Number and Subsections Delimitation.

The genus Trifolium is one of the largest genera of the legume family Fabaceae with ca. 255 species. The genus is divided into eight sections; the section Trifolium is a major section of the genus, comprising 73 species mainly distributed in the Mediterranean region. We used nuclear ribosomal DNA internal transcribed spacer (ITS) and morphological variation to reconsider the delimitation and phylogenetic relationships of species in the section Trifolium with reference to chromosomal variations. Bayesian analysis of ITS data delimited the species as three clades based on the analysis of ITS sequence and informative indels in combination with morphological variation. The phylogeny of the species by different analyses methods does not support their current delimitation in 17 subsections. The basic chromosome number x = 8 is the number for the genus Trifolium, from which x = 7, 6 and 5 were derived through successive aneuploidy events. With reference to the distribution of these numbers in the species of the section Trifolium, species in clade III and clade II are more evolved than species in clade I.

Cytological Study of Cypripedium japonicum Thunb. (Orchidaceae Juss.): An Endangered Species from Korea.

Changes in chromosome number and karyotype evolution are important to plant diversification, as they are both major drivers of speciation processes. Herein, chromosome number, karyotype, and genome size of the Korean lady’s slipper orchid Cypripedium japonicum Thunb., an endangered species, were investigated in natural populations. Furthermore, all cytological data from this species are reported herein for the first time. The chromosome number of all investigated C. japonicum plants was diploid (2n = 2x = 22), with x = 11 as base chromosome number, whereby the species can now be clearly distinguished from the Japanese lady’s slipper orchid. The karyotypes of all studied individuals were of similar length, symmetrical, and rather unimodal. Flow cytometry of the C. japonicum revealed that the genome size ranged from 28.38 to 30.14 pg/1C. Data on chromosome number and karyotypes were largely consistent with previous results indicating that Korean (x = 11) populations of C. japonicum are more closely related to Chinese populations (x = 11) compared to Japanese (x = 10) populations. These comprehensive cytological results will benefit the efforts to discriminate the geographically isolated and endangered Eastern Asian (China, Japan, and Korea) lady’s slipper orchid species.

Descending Dysploidy and Bidirectional Changes in Genome Size Accompanied Crepis (Asteraceae) Evolution.

The evolution of the karyotype and genome size was examined in species of Crepis sensu lato. The phylogenetic relationships, inferred from the plastid and nrITS DNA sequences, were used as a framework to infer the patterns of karyotype evolution. Five different base chromosome numbers (x = 3, 4, 5, 6, and 11) were observed. A phylogenetic analysis of the evolution of the chromosome numbers allowed the inference of x = 6 as the ancestral state and the descending dysploidy as the major direction of the chromosome base number evolution. The derived base chromosome numbers (x = 5, 4, and 3) were found to have originated independently and recurrently in the different lineages of the genus. A few independent events of increases in karyotype asymmetry were inferred to have accompanied the karyotype evolution in Crepis. The genome sizes of 33 Crepis species differed seven-fold and the ancestral genome size was reconstructed to be 1C = 3.44 pg. Both decreases and increases in the genome size were inferred to have occurred within and between the lineages. The data suggest that, in addition to dysploidy, the amplification/elimination of various repetitive DNAs was likely involved in the genome and taxa differentiation in the genus.