2C DNA variation and relationships among New World species of the genus Lupinus (Fabaceae)

The 2C DNA values in 38 species and accessions of the genus Lupinus (Fabaceae) from the New World have been analysed using flow cytometry. They are representatives of North and South American species (the Atlantic and the Andean regions). Estimated 2C DNA values ranged from 1.08 pg in L. pusillus to 2.68 pg in L. albicaulis (both from North America), that is a variation of more than 2.5-fold. The variation for North American lupins was much higher than that for South American ones. Statistical analysis of the data resulted in a grouping that showed for North American lupins some correlation with the length of life cycle. Discussion concerns some aspects of the evolution of the genus.     

Variation in chromosomal DNA associated with the evolution of Arachis species.

The 2C nuclear DNA amounts were determined for 99 accessions, representing 23 Arachis species from 8 of 9 taxonomic sections, and two synthetic amphidiploids. Mean 2C DNA amounts varied by 15.20%, ranging from 10.26 to 11.82 pg, between accessions of Arachis hypogaea (2n = 4x = 40). Nuclear DNA content variation (5.33-5.91 pg) was also detected among Arachis duranensis (2n = 2x = 20) accessions. The intraspecific variation in the two species may have resulted from indirect selection for favourable genome sizes in particular environmental conditions. The accessions belonging to A. hypogaea ssp. hypogaea (mean value 11.27 pg) with longer life cycle had significantly larger mean DNA content than the accessions of A. hypogaea ssp. fastigiata (mean value 10.97 pg). For 20 diploid (2n = 2x = 20) species of the genus, 2C nuclear DNA amounts ranged from approximately 3 to 7 pg. The diploid perennial species of section Arachis have about 12% more DNA than the annual species. Comparisons of DNA amounts show that evolutionary rating is not a reliable guide to DNA amounts in generic sections of the genus; lower DNA values with evolutionary advancement were found in sections Heteranthae and Triseminatae, but the same was not true for sections Arachis and Caulorrhizae. Similarly, there is evidence of significant differences in DNA content between 4 ancient sections (Procumbentes, Erectoides, Rhizomatosae, and Extranervosae) of the genus. The occurrence of genome size plasticity in both A. duranensis and A. hypogaea provides evidence that A. duranensis could be one of the diploid progenitors of A. hypogaea. The DNA content in the two synthetic amphidiploids corresponded to the sum value estimated for parental species. Key words : Arachis species, genome size, Arachis hypogaea, Arachis duranensis, intraspecific variation.     

Molecular phylogeny and phylogeography ofLupinus (Leguminosae) inferred from nucleotide sequences of therbcL gene and ITS 1 + 2 regions of rDNA

Total DNA was extracted from 55 species of theLeguminosae (including 29 species ofLupinus). The chloroplast generbcL and the ITS 1 + 2 regions of nuclear RNA genes were amplified by polymerase chain reaction (PCR) and sequenced directly. The sequences obtained were evaluated with character state (Maximum Parsimony) and distance methods (Neighbour Joining). Phylogenetic trees obtained with both data sets and methods are mostly congruent.Genisteae andCrotalarieae are sister groups and share ancestry with theThermopsideae/Podalyrieae. The genusLupinus, which forms a monophyletic clade within theGenisteae, shows a distinct Old-New World disjunction and appears to be divided into several more or less distinct groups: (1) The species from the eastern part of South America. (2) The homogeneous rough-seeded group (Scabrispermae) of the Old World species which is well distinguished from the smooth-seeded group (Malacospermae). (3) Within the rather heterogeneous smooth-seeded lupins a smaller subgroup withL. angustifolius, L. hispanicus andL. luteus is recognized. (4) Also separated are North American lupins and South American species with a western distribution. Genetic distances imply that the genusLupinus evolved during the last 12–14 million years, ruling out the hypothesis that the present Old-New World disjunction can be interpreted as a result of the continental drift. The genetic data suggest an origin in the Old World and an independant colonisation of the Eastern parts of South America as opposed to North America and the Western parts of South America.     

Historical evidence for a pre-Columbian presence of Datura in the Old World and implications for a first millennium transfer from the New World

Datura (Solanaceae)is a small genus of plants that,for long, was thought to occur naturally in both the New and Old Worlds. However, recent studies indicate that all species in the genus originated in the Americas. This finding has prompted the conclusion that no species of Datura could have been present in the Old World prior to its introduction there by Europeans in the early 16th century CE. Further, the textual evidence traditionally cited in support of a pre-Columbian Old World presence of Datura species is suggested to be due to the misreading of classical Greek and Arabic sources. As a result, botanists generally accept the opinion that Datura species were transferred into the Old World in the post-Columbian period. While the taxonomic and geographic evidence for a New World origin for all the Datura species appears to be well supported, the assertion that Datura species were not known in the Old World prior to the 16th century is based on a limited examination of the pre-Columbian non-Anglo sources.We draw on old Arabic and Indic texts and southern Indian iconographic representations to show that there is conclusive evidence for the pre-Columbian presence of at least one species of Datura in the Old World. Given the systematic evidence for a New World origin of the genus, the most plausible explanation for this presence is a relatively recent but pre-Columbian (probably first millennium CE) transfer of at least one Datura species, D. metel, into the Old World. Because D. metel is a domesticated species with a disjunct distribution,this might represent an instance of human-mediated transport from the New World to the Old World, as in the case of the sweet potato (Ipomoea batatas).     

Chromosome numbers and DNA?C values in the genus Lippia (Verbenaceae)

The genus Lippia comprises herbs, shrubs, and small trees, including many species with medicinal properties. The species are distributed throughout South and Central America and Tropical Africa, but the majority of them occur in Brazil, Paraguay, and Argentina. The DNA?C value of 28 Brazilian species has been estimated by flow cytometry. Estimated DNA?C values ranged from 0.825?pg (L. corymbosa) to 2.150?pg (L.?brasiliensis). In addition, new chromosome numbers of 12 species have also been described, and meiotic cells with 12, 13, and 14 chromosome pairs were observed. A straightforward correlation between chromosome number and DNA?C value was not observed, probably due to two outlier species of Lippia that have been transferred from the genus Lantana. In general, the data confirm previous reports regarding the variation within the taxonomic sections and also suggest a new revision in section Zapania. Aspects of karyotypic evolution of the genus are also discussed.     

Conifer genome sizes of 172 species,covering 64 of 67 genera,range from 8 to 72 picogram

Nuclear genome size of conifers as measured by flow cytometry with propidium iodide was investigated, striving to collect at least a single species from each genus. 64 out of 67 genera and 172 species were measured. Of the 67 genera, 21 are reported here for the first time and the same is true for 76 species. This nearly doubles the number of measured genera and adds 50% to the number of analyzed species. Conifers have chromosome numbers in the range of n = (7)10–12(19). However, the nuclear DNA content (2C‐value) is shown here to range from 8.3 to 71.6 picogram. The largest genome contains roughly 6 × 10¹⁰ more base pairs than the smallest genome. Genome sizes are evaluated and compared with available taxonomic treatments. For the mainly (sub)tropical Podocarpaceae small genome sizes were found with a 2C‐value of only 8–28 pg, with 13.5 pg on average. For the Taxaceae 2C‐values from 23–60 pg were determined. Not surprisingly, the genus Pinus with 97 species (39 species measured here) has a broad range with 2C = 38–72 pg. A factor of 2 difference is also found in the Cupressaceae (136 species) with nuclear DNA contents in the range 18–35 pg. Apart from the allohexaploid Sequoia, ploidy plays a role only in Juniperus and some new polyploids are found. The data on genome size support conclusions on phylogenetic relationships obtained by DNA sequencing. Flow cytometry is applicable even to young plants or seeds for the monitoring of trade in endangered species.     

Genome Size and Pollen Viability as Taxonomic Criteria: Application to the Genus Hosta

Abstract: Genome size (C values) and pollen viability staining were applied as new criteria to investigate the taxonomy of the genus Hosta Tratt. (Hostaceae). Nearly all species of the genus Hosta have the same basic chromosome number (2n = 2x = 60). However, the nuclear DNA contents, as measured by flow cytometry with propidium iodide, could be demonstrated to range between 17.2 to 26.6 pg. This implies that the largest genome contains roughly 10¹⁰ more base pairs than the smallest. Therefore, nuclear DNA content is a very relevant taxonomic trait that can be measured simply by flow cytometry. In addition, differences in overall DNA composition were demonstrated by comparing to DAPI fluorescence. In general, genome size data confirmed the division into three subgenera. The geographical distribution of genome sizes indicates the migration pattern of Hosta throughout East Asia. The species belonging to the mainly Korean subgenus Bryocles, with a low nuclear DNA content (17.2 - 19.3 pg), can now largely be distinguished from the mainly Japanese species of the subgenus Giboshi (21.3 - 26.5 pg). The exception is H. longissima, that with only 19.6 pg provides a nice example of a decrease in DNA content. On the mainland, as well as on Honshu, species with increased and decreased DNA content have evolved independently. The usefulness of pollen viability to detect hybrids in Hosta was demonstrated in a large series of artificial crosses between bona fide species. Consequently, pollen viability was measured in all available Hosta described as species. Several had low pollen viability and were concluded to be hybrids. Morphology and DNA content confirmed this in most cases. The resulting 23 species approximate the number of Hosta species that follows from the combined studies by Fujita (1976¹⁸) on the Japanese species and Chung (1991 a¹¹) on the Korean species.     

Phylogenetic relationships of North American Antirrhinum (Veronicaceae)

Species of the genus Antirrhinum (Veronicaceae) provide excellent opportunities for research on plant evolution given their extensive morphological and ecological diversity. These opportunities are enhanced by genetic and developmental data from the model organism Antirrhinum majus. The genus Antirrhinum includes 15 New World species in section Saerorhinum and 21 Old World species in sections Antirrhinum and Orontium. Phylogenetic analyses of sequences of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA were conducted for 19 Antirrhinum species, including all species from the New World, and 13 related genera in the tribe Antirrhineae. These analyses confirm the monophyly of Antirrhinum given the inclusion of the small genus Mohavea and exclusion of A. cyathiferum. The New World species, all of which are tetraploid, form a clade that is weakly supported as sister to the Old World sect. Orontium. The Old World species in sect. Antirrhinum form a well-supported clade that is sister to the remainder of the genus. In addition, both molecular and morphological data are used in the most comprehensive effort to date focused on recovering the phylogenetic relationships among the extremely diverse species in section Saerorhinum.     

The genus Sorex (Mammalia, Soricidae)–distribution and evolutionary aspects of Eurasian species

There are about 60 species of shrews of the genus Sorex distributed over the Nearctic and Palaearctic regions; these are usually divided into the subgenera Sorex, Otisorex and Microsorex . The Old World species are listed and their phylogeny discussed, with special emphasis laid on the karyotypes. It is proposed that the Old World forms should be divided into the subgenera Homalurus, Sorex and Otisorex . It is also suggested that the subgenus Sorex could be divided into at least three taxonomic units.     

Quantitative karyology of some species ofLuzula

The dimensions of metaphase chromosomes and nuclear DNA contents were measured in eight species ofLuzula. The 2 C DNA contents ranged from 8.51 pg inL. purpurea to 0.55 pg inL. pilosa. Total chromosome volume shows a linear relationship with DNA content; however, the total chromosome length of the complement of the different species is approximately constant. Nucleolar volume and the number of chromocentres in the different species also show a relationship with DNA content. Taken together, these data suggest that while chromosome fragmentation could have generated the present-day range of chromosome numbers in the genus, there have also been changes in the total quantity of DNA with the result that species with similar chromosome numbers have different DNA contents. The relationships of DNA content with chromosome volume inLuzula and other genera are compared and the differences discussed.     

Genome evolution in the genus Sorghum (Poaceae)

BACKGROUND AND AIMS: The roles of variation in DNA content in plant evolution and adaptation remain a major biological enigma. Chromosome number and 2C DNA content were determined for 21 of the 25 species of the genus Sorghum and analysed from a phylogenetic perspective. METHODS: DNA content was determined by flow cytometry. A Sorghum phylogeny was constructed based on combined nuclear ITS and chloroplast ndhF DNA sequences. KEY RESULTS: Chromosome counts (2n = 10, 20, 30, 40) were, with few exceptions, concordant with published numbers. New chromosome numbers were obtained for S. amplum (2n = 30) and S. leiocladum (2n = 10). 2C DNA content varies 8.1-fold (1.27-10.30 pg) among the 21 Sorghum species. 2C DNA content varies 3.6-fold from 1.27 pg to 4.60 pg among the 2n = 10 species and 5.8-fold (1.52-8.79 pg) among the 2n = 20 species. The x = 5 genome size varies over an 8.8-fold range from 0.26 pg to 2.30 pg. The mean 2C DNA content of perennial species (6.20 pg) is significantly greater than the mean (2.92 pg) of the annuals. Among the 21 species studied, the mean x = 5 genome size of annuals (1.15 pg) and of perennials (1.29 pg) is not significantly different. Statistical analysis of Australian species showed: (a) mean 2C DNA content of annual (2.89 pg) and perennial (7.73 pg) species is significantly different; (b) mean x = 5 genome size of perennials (1.66 pg) is significantly greater than that of the annuals (1.09 pg); (c) the mean maximum latitude at which perennial species grow (-25.4 degrees) is significantly greater than the mean maximum latitude (-17.6) at which annual species grow. CONCLUSIONS: The DNA sequence phylogeny splits Sorghum into two lineages, one comprising the 2n = 10 species with large genomes and their polyploid relatives, and the other with the 2n = 20, 40 species with relatively small genomes. An apparent phylogenetic reduction in genome size has occurred in the 2n = 10 lineage. Genome size evolution in the genus Sorghum apparently did not involve a 'one way ticket to genomic obesity' as has been proposed for the grasses.     

Intra- and interspecific variation in DNA content in Cistus (Cistaceae)

Flow cytometry, using propidium iodide and 4',6-diamidano-2-phenylindole staining, was used to estimate the nuclear DNA content (2C) and the proportion of A-T base pairs in 16 species of the Mediterranean genus Cistus. Genome sizes were shown to be constant within species, since no significant intraspecific variation in 2C DNA content was detected. At the genus level, up to about 1.5-fold differences in absolute DNA amounts were observed, ranging from 3.92 pg in C. crispus to 5.88 pg in C. monspeliensis. The (AT) : (GC) ratio was close to 1, and was similar for all species examined, ranging from 47.87% A-T content in C clusii, to 50.67% in C. populifolius. Pink-flowered species (subgenus Cistus) had lower DNA amounts than white-flowered species (subgenera Leucocistus and Halimioides). However, the distribution of DNA amounts in Cistus appeared to be continuous and did not permit a clear separation of infra-generic ranks in the genus.     

MONOPHYLY OF ANEUPLOID ASTRAGALUS (FABACEAE): EVIDENCE FROM NUCLEAR RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACER SEQUENCES

Evolutionary relationships within Astragalus L. (Fabaceae) were inferred from nucleotide sequence variation in nuclear ribosomal DNA of both New World and Old World species. The internal transcribed spacer regions (ITS) of 18S–26S nuclear ribosomal DNA from representatives of 26 species of Astragalus, three species of Oxytropis DC., and two outgroup taxa were analyzed by polymerase chain reaction amplification and direct DNA sequencing. The length of the ITS 1 region within these taxa varied from 221 to 231 bp, while ITS 2 varied in length from 207 to 217 bp. Of the aligned, unambiguous positions, approximately 34% were variable in each spacer region. In pairwise comparisons among Astragalus species and outgroup taxa, sequence divergence at these sites ranged from 0 to 18.8% in ITS 1 and from 0 to 21.7% in ITS 2. Parsimony analyses of these sequences resulted in a well-resolved phylogeny that is highly concordant with previous cytogenetic and chloroplast DNA evidence for a major phylogenetic division in the genus. These data suggest that the New World aneuploid species of Astragalus form a monophyletic but morphologically cryptic group derived from euploid species of Old World (Eurasian) origin, which are consequently paraphyletic.     

Variation of Nuclear DNA Content in the Biflorus Species of Lonchocarpus (Leguminosae)

This represents the first study of nuclear DNA content in alarge sample (135 spp.) from a tropical arboreal genus, in whicha large proportion of the species were examined (42 spp., 31.1%).Somatic chromosome numbers and 4C-DNA values for 51 taxa ofLonchocarpus are reported. All taxa were diploid with 2 n =22,but their DNA content ranged from 1.92 to 2.86 pg 4C nucleus,corresponding to a 48.95% variation in genome size. In the 74collections studied, no correlation was observed between DNAcontent and habitat altitude. Variation in nuclear DNA contentwas analysed at the level of genus, subgenus, section and subsection.Variation in genome size was also studied within some species,either among widely separated populations or among differentintraspecific taxa. Very little variation in genome size wasdetected between populations, subspecies, and varieties of thesame species. The taxonomic implications of variation in nuclearDNA content are discussed.Copyright 2000 Annals of Botany Company Lonchocarpus (Leguminosae), DNA content, chromosome number.     

Chromosome counts and genome size of Leontopodium species (Asteraceae: Gnaphalieae) from south‐western China

Chromosome counts and genome sizes are reported from six species of Leontopodium: five from the centre of diversity in south‐western China, and L. japonicum from cultivation. Previously published chromosome counts for the genus are also compiled. Genome size (1C) in diploids ranges from 0.93 pg (L. dedeckensii) to 1.14 pg (L. cf. stracheyi) and 1.93 pg for tetraploid L. sinense. Leontopodium artemisiifolium had one pair of heteromorphic chromosomes. Leontopodium japonicum accessions showed variation in ploidy levels. Polyploidy, including autopolyploidy, is frequent in the genus. Variation is seen in basic chromosome number, including between species in the centre of diversity of the genus, where x = 12 or 13, but also within species among previously published counts. This variation does not correspond to currently inferred infrageneric groupings, and indicates both the importance of large‐scale chromosome evolution and the need for more in‐depth taxonomic work in a genus that shows little DNA sequence variation. © 2013 The Linnean Society of London     

Historical evidence for a pre-Columbian presence of <Emphasis Type="Italic">Datura</Emphasis> in the Old World and implications for a first millennium transfer from the New World

Datura (Solanaceae) is a small genus of plants that, for long, was thought to occur naturally in both the New and Old Worlds. However, recent studies indicate that all species in the genus originated in the Americas. This finding has prompted the conclusion that no species of Datura could have been present in the Old World prior to its introduction there by Europeans in the early 16th century CE. Further, the textual evidence traditionally cited in support of a pre-Columbian Old World presence of Datura species is suggested to be due to the misreading of classical Greek and Arabic sources. As a result, botanists generally accept the opinion that Datura species were transferred into the Old World in the post-Columbian period. While the taxonomic and geographic evidence for a New World origin for all the Datura species appears to be well supported, the assertion that Datura species were not known in the Old World prior to the 16th century is based on a limited examination of the pre-Columbian non-Anglo sources. We draw on old Arabic and Indic1 texts and southern Indian iconographic representations to show that there is conclusive evidence for the pre-Columbian presence of at least one species of Datura in the Old World. Given the systematic evidence for a New World origin of the genus, the most plausible explanation for this presence is a relatively recent but pre-Columbian (probably first millennium CE) transfer of at least one Datura species, D. metel, into the Old World. Because D. metel is a domesticated species with a disjunct distribution, this might represent an instance of human-mediated transport from the New World to the Old World, as in the case of the sweet potato (Ipomoea batatas).     

Flow cytometric measurement of nuclear DNA content inCapsicum (Solanaceae)

Nuclei were isolated from leaf tissue of differentCapsicum species and the relative fluorescence intensity was measured by flow cytometry after propidium iodide staining.Pisum sativum nuclei with known nuclear genome size (9.07 pg) were used as internal standard to determine nuclear DNA content of the samples in absolute units. The 2C DNA contents ranged between 7.65 pg inC. annuum and 9.72 pg inC. pubescens, and the general mean of the genus was 8.42 pg. These values correspond, respectively, to 1C genome size of 3.691 (C. annuum), 4.690 (C. pubescens) and 4.063 (general mean) Mbp. In general, white-flowered species proved to have less DNA, with the exception ofC. praetermissum, which displayed a 2C DNA content of 9.23 pg. It was possible to divide the studied species into three main groups according to their DNA content, and demonstrate differences in DNA content within two of the three species complexes established on the basis of morphological traits.     

Genome size and karyotype length in some interstitial polychaete species of the genus Ophryotrocha (Dorvilleidae).

Interstitial polychaetes of the genus Ophryotrocha are very small, progenetic, and morphologically very similar. These worms have been widely used in evolutionary biology and sexuality studies. To have a better insight into the karyological evolution of this genus, we measured the total karyotypic length and the 2C nuclear DNA content of the nine best-known species of this genus. No interspecific differences were observed in karyotypic lengths, apart from that of O. gracilis, which was significantly greater than the karyotypic length of five of the nine species. The genome size (i.e., 1C DNA content calculated from 2C DNA content) in eight of the nine species is about 0.4 pg, irrespective of the chromosome number. A group of four gonochoric and morphologically indistinguishable species, with 2n = 6 metacentric chromosomes, appears to be heterogeneous with regard to its DNA content, because one of the species, O. macrovifera, has a genome twice the size of that of the other three species. A hermaphroditic species, O. hartmanni, has a genome three times that size. No correlation has been observed between genome size and body size, egg cell diameter, or time interval from egg fertilization to sexual maturity. The basic genome size of 0.4 pg is among the lowest recorded in invertebrates. Hypotheses about selective pressures that maintain such a low amount of nuclear DNA in this genus are discussed.     

Tribal delimitation and phylogenetic relationships of Loteae and Coronilleae (Faboideae: Fabaceae) with special reference to Lotus: evidence from nuclear ribosomal ITS sequences

The temperate herbaceous tribes Loteae and Coronilleae have traditionally been regarded as taxonomically distinct entities. More recent morphological assessments, however, have challenged this view and suggest combining the two tribes under Loteae. Two key features used to distinguish the Coronilleae from Loteae include jointed fruits and branched root nodules. We evaluate the taxonomic utility of these characters using information derived from phylogenetic analyses of the internal transcribed spacers ITS1 + 2, and the intervening 5.8S region of nuclear ribosomal DNA. Results from this study show that neither the Loteae nor Coronilleae form individual monophyletic groups, and that key fruit and root nodule characters used to distinguish the Coronilleae are homoplastic. Given these data, we support the recognition of a single tribe, Loteae. We also find that Lotus, the largest and most morphologically complex genus in either tribe, is not monophyletic. Rather, it consists of two geographically distinct lineages, Old and New World, each of which are more closely related to other Loteae genera: Old World Lotus are more closely related to Old World Anthyllis, while New World Lotus show closer affinities to Old World Coronilla. These data also have important implications for the biogeography of New World Lotus: equally most parsimonious reconstructions suggest a complex scenario of intercontinental dispersals that involve not only Old World Lotus but Coronilla as well.     

Old World and New World Cupressus pollen: morphological and cytological remarks

The aim of this work was to collect new information about pollen morphology and pollen wall structure comparing Cupressus species from the Old World and New World. Cupressus is a nonmonophyletic genus that includes species that appear to be divided into Old World and New World clades. Observations in this study on cypress pollen indicate that grain size and composition of intine β-glucans are different between the considered Old World and New World species. Different from all the other American cypress species, pollen of C. macrocarpa reacted to dying in a similar manner to Old World species. Rehydrated pollen grains collected from 20 Asian, Afro-Mediterranean and American cypress species were measured under a light microscope. The size of the pollen grains and the percentage of intine in relation to the pollen grain diameter were significantly different between Old World and New World species. Pollen wall composition was tested after addition of different dyes to the hydration solution, and subsequent observations were carried out by light and fluorescence microscopy. Lugol and calcofluor staining showed differences in composition of the middle and inner intine layers between New World and Old World species.