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Diploid Species (diploid + species)
Selected AbstractsKaryotype analysis and polyploidy in Palaua and a comparison with its sister group Fuertesimalva (Malvaceae)JOURNAL OF SYSTEMATICS EVOLUTION, Issue 3 2010Julio V SCHNEIDER Abstract,Palaua (Malveae, Malvaceae) comprises 15 species endemic to the hyperarid coastal desert of Chile and Peru. So far, chromosome counts have been known for two diploid species (2n= 2x= 10) only. Here we report new chromosome numbers for 12 species of Palaua and four of its sister group Fuertesimalva. Karyotypes including 4,,6,-diamidino-2-phenylindole dihydrochloride (DAPI)/chromomycin (CMA3) fluorescent banding are presented for selected species representative of each of the main clades of Palaua. An important finding is the discovery of polyploids in one exclusively tetraploid species (P. trisepala) and four species with mixed diploid and tetraploid cytotypes (P. dissecta, P. mollendoensis, P. moschata, and P. tomentosa). The diploid and tetraploid karyotypes are all unimodal, symmetrical and show one or two pairs of satellite chromosomes with their associated CMA+/DAPI, band depending on the cytotype. For some of the tetraploids an autopolyploid origin is suggested. [source] Segregation patterns of AFLP markers in F1 hybrids of a cross between tetraploid and diploid species in the genus MalusPLANT BREEDING, Issue 4 2004Y. H. Li Abstract Malus xiaojinensis, one of the most important wild genotypes in the genus Malus, is resistant to a variety of stresses such as Fe deficiency chlorosis, drought and cold. However, lack of knowledge of its genetic background prevents using genetic analysis to study those agronomic traits and corresponding gene functions. Here, as the first step towards construction of the linkage map of M. xiaojinensis, genetic analysis of the F1 triploid hybrids (M. xiaojinensis × M. baccata) was performed with amplified fragment length polymorphism (AFLP) markers. Using 15 EcoRI- MseI primer combinations, 1110 AFLPs were identified, with 31.3% of M. xiaojinensis -, 12.7% of M. baccata-specific markers, 54.9% of common markers, and 1.2% of non-parental markers; 93.3% of the AFLP markers exhibit the expected segregation ratio. Thirty-two M. xiaojinensis -specific markers and 47 common markers display a 5 : 1 and 11:1 segregation ratios, respectively, suggesting that M. xiaojinensis is an autotetraploid, or at least an isosyndetic allotetraploid. [source] Modes and mechanisms of speciation in pteridophytes: Implications of contrasting patterns in ferns representing temperate and tropical habitatsPLANT SPECIES BIOLOGY, Issue 3 2000Christopher H. Haufler Abstract Discovering how biological diversification results in species is one of the primary challenges facing evolutionary biologists. In the ferns, evidence indicates that dissimilar speciation modes and mechanisms may differentiate some temperate and tropical groups. The Polypodium sibiricum group contains three related diploid species that all inhabit rock outcrops in temperate forests. Although differing lettle in gross leaf morphology and joined by the distinctive morphological synapomorphy of sporangiasters, these three species have an average interspecific genetic identity developed from isozymic com-parisons of only 0.460. A likely mode of speciation is that periodic glaciation pushed Po. sibiricum populations south and, with the retreat of the glaciers, southern populations persisted, evolved diagnostic traits, and ultimately erected postzygotic barriers to interbreeding. This hypothesis follows a classic allopatric speciation model and interspecific distinctions may have been reinforced through contact mediated by subsequent ice ages. In contrast, a monophyletic group of four diploid, epiphytic Pleopeltis species centered in Mexico has an isozymically-determined average interspecific genetic identity value of 0.849. In spite of this high value, these species show greater morphological discrimination than do the Polypodium species. Although the species ranges overlap, they appear to occupy ecologically discrete habitats. These Pleopeltis species may have originated through adaptation to different ecological zones and developed individual morphologies in the process. The high interspecific genetic identity values among the Pleopeltis species suggest a relatively recent and/or rapid process. These hypotheses should be tested by further biosystematic investigations and the discovery of additional monophyletic assemblages with similar patterns of speciation. [source] Chromosome arrangement and nuclear architecture but not centromeric sequences are conserved between Arabidopsis thaliana and Arabidopsis lyrataTHE PLANT JOURNAL, Issue 5 2006Alexandre Berr Summary In contrast to the situation described for mammals and Drosophila, chromosome territory (CT) arrangement and somatic homologous pairing in interphase nuclei of Arabidopsis thaliana (n = 5) are predominantly random except for a more frequent association of the chromosomes bearing a homologous nucleolus organizer region. To find out whether this chromosome arrangement is also characteristic for other species of the genus Arabidopsis, we investigated Arabidopsis lyrata ssp. lyrata (n = 8), one of the closest relatives of A. thaliana. First, we determined the size of each chromosome and chromosome arm, the sequence type of centromeric repeats and their distribution between individual centromeres and the position of the 5S/45S rDNA arrays in A. lyrata. Then we demonstrated that CT arrangement, homologous pairing and sister chromatid alignment of distinct euchromatic and/or heterochromatic regions within A. lyrata interphase nuclei are similar to that in A. thaliana nuclei. Thus, the arrangement of interphase chromosomes appears to be conserved between both taxa that diverged about 5 million years ago. Since the chromosomes of A. lyrata resemble those of the presumed ancestral karyotype, a similar arrangement of interphase chromosomes is also to be expected for other closely related diploid species of the Brassicaceae family. [source] Allopolyploidy and homoploid hybridization in the Sphagnum subsecundum complex (Sphagnaceae: Bryophyta)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010MARIANA RICCA Several complexes of species in Sphagnum (peat mosses) originated through hybridization and allopolyploidy, suggesting that these processes have played a major evolutionary role in this genus. The Sphagnum subsecundum complex includes gametophytically haploid and diploid species in North America. Analyses of 12 microsatellite loci and sequences from two plastid DNA markers show that the evolutionary history of this group is substantially more complex than previously thought. Two taxonomic species, Sphagnum lescurii and Sphagnum inundatum, include both haploid and diploid populations. Within each ploidal level, S. lescurii and S. inundatum are not genetically differentiated. The diploid taxa show patterns of fixed heterozygosity for the microsatellite markers, consistent with an allopolyploid origin. Diploid S. lescurii is an allopolyploid between haploid S. lescurii and (haploid) S. subsecundum. Sphagnum carolinianum is an allopolyploid between haploid S. lescurii and an unknown parent. We detected homoploid hybridization between the haploids Sphagnum contortum and S. subsecundum. Finally, we report three samples of diploid Sphagnum platyphyllum (otherwise haploid) that have an allopolyploid origin involving north-eastern haploid S. platyphyllum and an unidentified taxon. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 135,151. [source] A new species of Allium (Alliaceae) from Dalmatia, CroatiaBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2008SANDRO BOGDANOVI Allium croaticum, a new species from the island of Vis in Central Dalmatia (Croatia) is described and illustrated. Its relationships with allied species belonging to the A. stamineum group (Allium section Codonoprasum) are discussed. It is a diploid species (2n = 16), colonizing calcareous screes and flowering in early summer. Its morphology, leaf anatomy, karyology, palynology, ecology and taxonomic position are examined. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158, 106,114. [source] Chromosome studies in Hippeastrum (Amaryllidaceae): variation in genome sizeBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2007LIDIA POGGIO This paper presents the karyotype and DNA content of 12 diploid species of Hippeastrum from South America. The variation in genome size is compared with the karyotype and DNA content of Amaryllis belladonna from South Africa. The Hippeastrum species present a uniform and bimodal basic karyotype formula, but significant differences are found in the total chromosome volume (TCV) and nuclear DNA content. A positive correlation between the DNA content and TCV is also observed. The karyotype's constancy is a product of changes in DNA content occurring in the whole chromosome complement. The DNA addition to the long and short sets of chromosomes varies independently. In species with higher DNA contents, the short chromosomes add equal DNA amounts to both arms, maintaining their metacentric morphology, whereas the long chromosomes add DNA only to the short arm, increasing the chromosome symmetry. These data show that the evolutionary changes in DNA amount are proportional to chromosome length, maintaining the karyotypic uniformity. A. belladonna has a larger DNA content and possesses a karyotype different from that of Hippeastrum spp., supporting the distinction between the two genera and upholding the name Amaryllis for the South African entity against Hippeastrum for the South American genus. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 171,178. [source] Molecular evidence for the hybrid origin of a new endemic species of Stylosanthes Sw. (Fabaceae) from the Mexican Yucatán PeninsulaBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2002JACQUELINE VANDER STAPPEN Stylosanthes aff. calcicola is a formally undescribed tetraploid species from the Mexican Yucatán Peninsula, showing morphological similarities to the diploid species S. calcicola, but distinct in a number of characters. We used uni- and biparentally inherited molecular markers to infer the hybrid origin of this species in relation to known diploid species of Stylosanthes. Molecular characterization was based on length and/or DNA sequence variation of nuclear sequence-tagged site (STS) markers, the internal transcribed spacer (ITS) region of nuclear rDNA and the trnL intron of chloroplast DNA (cpDNA). Stylosanthes aff. calcicola contains a distinct cpDNA haplotype and nuclear DNA fragment, with closest relationship to the diploid species S. calcicola. In contrast, the DNA sequences of two nuclear loci reveal a closer relationship to the diploid species S. angustifolia, S. hispida, S. humilis, S. leiocarpa and S. viscosa. The majority of the STS markers showed additivity of PCR fragments in S. aff. calcicola, representing the combination of two genetically different genomes. We postulate that S. aff. calcicola is a distinct species of allotetraploid origin that appears to have originated once from hybridization between two divergent genomes, of which the maternal and paternal parent are closely related to, or derived from, a member of the lineages represented by S. calcicola and S. viscosa, respectively. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society, 140, 1,13. [source] A phylogenetic analysis of the monogenomic Triticeae (Poaceae) based on morphologyBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2001OLE SEBERG FLS A cladistic analysis, primarily based on morphology, is presented from 40 diploid taxa representing the 24 monogenomic genera of the Triticeae. General problems related to the treatment of hybrids and supposedly allopolyploid heterogenomic taxa are highlighted. Special emphasis is given to taxa not traditionally included in Aegilops s.J. Most of the 33 characters used in the analysis are coded as binary. The only four multistate characters in the matrix are treated as unordered. Three diploid species of Bromus are used as outgroup. The number of equally parsimonious trees found is very large (approx. 170000; length = 107, ci = 0.36, ri = 0.75) and the strict consensus tree has an expectedly low level of resolution. However, most of the equally parsimonious trees owe their existence to an unresolved Aegilops clade. If this clade is replaced by its hypothetical ancestor, the number of equally parsimonious trees drops dramatically (48; length = 78, ci = 0.45, ri = 0.76). When trees for which more highly resolved compatible trees exist are excluded, only two trees remain. Bremer support is used as a measure of branch support. The trees based on morphology and on molecular data are largely incongruent. [source] Genome redundancy and plasticity within ancient and recent Brassica crop speciesBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2004LEWIS N. LUKENS The crop species within the genus Brassica have highly replicated genomes. Three base ,diploid' species, Brassica oleracea, B. nigra and B. rapa, are likely ancient polyploids, and three derived allopolyploid species, B. carinata, B. juncea and B. napus, are created from the interspecific hybridization of these base genomes. The base Brassica genome is thought to have hexaploid ancestry, and both recent and ancient polyploidization events have been proposed to generate a large number of genome rearrangements and novel genetic variation for important traits. Here, we revisit and refine these hypotheses. We have examined the B. oleracea linkage map using the Arabidopsis thaliana genome sequence as a template and suggest that there is strong evidence for genome replication and rearrangement within the base Brassicas, but less evidence for genome triplication. We show that novel phenotypic variation within the base Brassicas can be achieved by replication of a single gene, BrFLC, that acts additively to influence flowering time. Within the derived allopolyploids, intergenomic heterozygosity is associated with higher seed yields. Some studies have reported that de novo genomic variation occurs within derived polyploid genomes, whereas other studies have not detected these changes. We discuss reasons for these different findings. Large translocations and tetrasomic inheritance can explain some but not all genomic changes within the polyploids. Transpositions and other small-scale sequence changes probably also have contributed to genomic novelty. Our results have shown that the Brassica genomes are remarkably plastic, and that polyploidy generates novel genetic variation through gene duplication, intergenomic heterozygosity and perhaps epigenetic change. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 665,674. [source] | ||||||||||||||||||||||