Phylogeny of the sundews, Drosera (Droseraceae), based on chloroplast rbcL and nuclear 18S ribosomal DNA Sequences

The sundew genus Drosera consists of carnivorous plants with active flypaper traps and includes nearly 150 species distributed mainly in Australia, Africa, and South America, with some Northern Hemisphere species. In addition to confused intrageneric classification of Drosera, the intergeneric relationships among the Drosera and two other genera in the Droseraceae with snap traps, Dionaea and Aldrovanda, are problematic. We conducted phylogenetic analyses of DNA sequences of the chloroplast rbcL gene for 59 species of Drosera, covering all sections except one. These analyses revealed that five of 11 sections, including three monotypic sections, are polyphyletic. Combined rbcL and 18S rDNA sequence data were used to infer phylogenetic relationships among Drosera, Dionaea, and Aldrovanda. This analysis revealed that all Drosera species form a clade sister to a clade including Dionaea and Aldrovanda, suggesting that the snap traps of Aldrovanda and Dionaea are homologous despite their morphological differences. MacClade reconstructions indicated that multiple episodes of aneuploidy occurred in a clade that includes mainly Australian species, while the chromosome numbers in the other clades are not as variable. Drosera regia, which is native to South Africa, and most species native to Australia, were clustered basally, suggesting that Drosera originated in Africa or Australia. The rbcL tree indicates that Australian species expanded their distribution to South America and then to Africa. Expansion of distribution to the Northern Hemisphere from the Southern Hemispere occurred in a few different lineages.     

Glandular hairs in the genusDrosera (Droseraceae)

On the leaves and sepals of 52 species, representing all sections of the genusDrosera except one, 14 different types of glandular hairs were found: two-celled papillae, peltate scales, several types with unbranched, bi- or multiseriate stalk with a two- or multicellular gland, and one type with a multiseriate stalk and a two-armed gland. The combination of these hairs and the presence of non-glandular hairs confirm the actual classification of the genus. In combination with simple morphological characters (e.g., the type of insertion of the petiole) glandular hairs facilitate the identification of species even in the pharmaceutically important cut crude drug.     

Chemical evidence for hybridity in Drosera (Droseraceae)

Naphthoquinone patterns found in Drosera hybrids between quinone-heterogenous parent species are reported here for the first time. Quinone patterns are constant in and characteristic for all taxa investigated. Each investigated parent species contains only one quinone isomer (either plumbagin or 7-methyljuglone), whereas all investigated hybrids between quinone-heterogenous parent species contain both isomers at almost equal concentrations, which indicates co-dominant heredity resulting from expression of both parental loci affecting regioselectivity in the biosynthesis of these acetogenic metabolites. This allows predictions on hybridity (and possibly on parentage) in some taxa of the genus.     

Coproduction and ecological significance of naphthoquinones in carnivorous sundews (Drosera)

While the 1,4-naphthoquinone derivatives 7-methyljuglone (1) and plumbagin (2) possess a diverse and well documented array of biological activities, relatively little remains known about the functional significance of these compounds in planta and, in particular, their possible relation to carnivorous syndromes. In addition, the chemotaxonomic distribution of naphthoquinones (NQs) amongst species of Drosera L. is of phytopharmaceutical interest. Following the quantitative assessment of interspecific variation of 1 and 2 in 13 species and cultivars of Drosera, our findings demonstrate that these NQs are ubiquitously coproduced in, generally, species-specific ratios, and that 1 appears negatively associated with the occurrence of pigmentation in sundews. The prospective antifeedant function of 1 was evaluated in relation to allocation in various organs and ontogenetic phases of D. capensis L., revealing that significantly higher levels were accumulated in young and reproductive organs, most likely for defensive purposes. Investigation into the relationship between the biosynthesis of NQs and carnivory showed that production of 1 is optimally induced and localized in leaves in response to capture of insect prey. As a whole, these findings reveal the clear importance of this secondary metabolite in ecological interactions as well as holding implication for future bioactivity studies on the genus.     

Chromosome size and DNA content of species of anemone L. and related genera (Ranunculaceae)

Relative amounts of DNA were determined by Feulgen cytophotometry in 22 diploid species of Ranunculaceae (n=7, 8, 9) representing six genera, and exhibiting large differences in chromosome size, but no marked differences in karyotype pattern. Chemical determination of absolute amounts of DNA for six of these species, allowed conversion of all the photometric data into absolute units of DNA. The mean DNA content per nucleus varied from.13×10^–11gm in Aquilegia to 5.25×10^–11gm in species of Anemone in the section Homalocarpus. The DNA values obtained appeared to be quantized, and data for the majority of species fitted a non-geometrical series with the observed relative terms: 1—8—12—16—20—24—40. The magnitude of these variations in DNA content, the preservation of the karyotype and the tendency towards a simple numerical progression in DNA values, lead us to prefer an interpretation of the evolution of DNA content in terms of differential polynemy to one postulating changes in size of genetic units in an unchanging number of strands per chromosome.     

Chromosome number,morphology, pairing,and DNA values of species and hybrids in the genusFallopia (Polygonaceae)

The taxa in this study have in the past been treated together in sect.Tiniaria Meissner ofPolygonum L. s.l., and more recently the large erect rhizomatous herbaceous perennials have been separated from the twining annuals and perennials as the generaReynoutria andFallopia respectively. These taxa range in ploidy level from diploid to octoploid, with base numbers of both 10 and 11 present. The plants are primarily Asiatic in distribution, although many of the large erect perennials are now naturalized in many parts of Europe. Cytological examination has revealed the presence of a number of previously unknown hybrid taxa in the British Isles. The readiness with which hybridisation occurs between taxa of differing base number and ploidy level, and similarities revealed in chromosome morphology, meiotic pairing and in DNA C-value, suggest to the authors that these two genera are best amalgamated underFallopia.     

Chromosome studies in Hippeastrum (Amaryllidaceae): variation in genome size

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.     

Chromosome number and genome size variation in Colocasia (Araceae) from China

Journal of Plant Research - Chromosome number and genome size are important cytological characters that significantly influence various organismal traits. We investigated chromosome number and...     

Flowering phenology and reproductive biology of Drosera anglica (Droseraceae)

Prompted by the sparse knowledge of the reproductive biology of carnivorous plants, compared with studies of their trapping habits, we investigated the flowering phenology and pollination biology of Drosera anglica Huds. in two fens in mid-western Canada. Seed set and germination were used to compare the effectiveness of a series of pollination treatments, including single insect visits to virgin flowers. Flowers opened during mid-morning but closed by early afternoon, and exhibited pseudo-cleistogamic behaviour in cool, overcast weather. D. anglica was found to be self-compatible, and able to self-pollinate and self-fertilize. Geitonogamy was an uncommon mode of self-reproduction because plants typically possessed a lone inflorescence upon which a single, short-lived flower opened, a few days before the next bud reached anthesis. Insect visits to the fragrance-lacking, nectarless flowers, chiefly by flies (Diptera: Syrphidae), were infrequent (one visit per 1 h 40 min of observation), and the low frequency of seed set and low numbers of seeds per fruit in pollination treatments involving insects, suggest the species does not rely on insects to effect pollination. Self-pollination, with or without the aid of a vector (insects, wind) was as effective as natural pollination; ultimately, autogamy is chiefly responsible for natural seed set. Thus, the species exhibits characteristics of facultative autogamy.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 417–426.     

DNA values in the genus Phalaris (Gramineae)

In the genus Phalaris diploid species with 2n=12 have approximately twice the DNA content per cell found in species with 2n=14; i. e. the first group has chromosomes about twice the size of the other group. DNA content per unit length suggests that the difference is reflected more in the diameter of the metaphase chromosome than in the lengths. The trend in evolution seems to be towards increase in DNA content.     

Chromosome banding and genome size differentiation inProspero (Hyacinthaceae): Diploids

Prospero is a Mediterranean autumn-flowering genus ofHyacinthaceae commonly classified inScilla asS. autumnalis andS. obtusifolia. Extensive dysploid and polyploid variation has been reported. In the present study 77 diploid accessions from the western to the eastern part of the area of distribution, the major part being from continental Greece and Crete, have been analysed for karyotype structure and, in part, for genome size. Methods employed were acetocarmine staining, Giemsa C-banding, fluorochrome staining mainly with chromomycin A₃/DAPI, silver impregnation, and Feulgen densitometry. Banded idiograms were established with a computer assisted karyotype analysis procedure. Chromosome numbers were 2n = 8 inP. obtusifolium, and 2n = 12 and 14 inP. autumnale s. l. Dispensable euchromatic chromosome segments and different types of B chromosomes occurred. Among the cytotypes with 2n = 14 two karyotypes from Turkey differed from each other and from the rest in form, position of the nucleolar constriction, and in genome size. The remaining accessions were similar in karyotype shape but three levels of genome size could be discerned, the highest (1C = 7.50 pg) being found on the Iberian Peninsula, an intermediate one on Corsica and Malta, and the lowest (4.27 pg) in the Aegean. The karyotype with 2n = 12 had an intermediate genome size, and that ofP. obtusifolium a relatively low one. Heterochromatin amount was generally low, but some karyotypes showed characteristic banding patterns. The relationship between the chromosome complements with 2n = 14, 12 and 8 is discussed on the basis of idiograms and DNA amounts.The authors respectfully dedicate this papers to emer. o. Prof. Dr.Elisabeth Tschermak-Woess on the occasion of her 80th birthday.     

Chromosome numbers and genome size variation in Indian species of Curcuma (Zingiberaceae)

BACKGROUND AND AIMS: Genome size and chromosome numbers are important cytological characters that significantly influence various organismal traits. However, geographical representation of these data is seriously unbalanced, with tropical and subtropical regions being largely neglected. In the present study, an investigation was made of chromosomal and genome size variation in the majority of Curcuma species from the Indian subcontinent, and an assessment was made of the value of these data for taxonomic purposes. METHODS: Genome size of 161 homogeneously cultivated plant samples classified into 51 taxonomic entities was determined by propidium iodide flow cytometry. Chromosome numbers were counted in actively growing root tips using conventional rapid squash techniques. KEY RESULTS: Six different chromosome counts (2n = 22, 42, 63, >70, 77 and 105) were found, the last two representing new generic records. The 2C-values varied from 1.66 pg in C. vamana to 4.76 pg in C. oligantha, representing a 2.87-fold range. Three groups of taxa with significantly different homoploid genome sizes (Cx-values) and distinct geographical distribution were identified. Five species exhibited intraspecific variation in nuclear DNA content, reaching up to 15.1 % in cultivated C. longa. Chromosome counts and genome sizes of three Curcuma-like species (Hitchenia caulina, Kaempferia scaposa and Paracautleya bhatii) corresponded well with typical hexaploid (2n = 6x = 42) Curcuma spp. CONCLUSIONS: The basic chromosome number in the majority of Indian taxa (belonging to subgenus Curcuma) is x = 7; published counts correspond to 6x, 9x, 11x, 12x and 15x ploidy levels. Only a few species-specific C-values were found, but karyological and/or flow cytometric data may support taxonomic decisions in some species alliances with morphological similarities. Close evolutionary relationships among some cytotypes are suggested based on the similarity in homoploid genome sizes and geographical grouping. A new species combination, Curcuma scaposa (Nimmo) Skornick. & M. Sabu, comb. nov., is proposed.     

Chromosome size in salmon and trout

The chromosomes of the Atlantic salmon, Salmo salar (2n=58) are, on average, larger than those of the trout, S. trutta (2n=80). If the difference in chromosome size represents a permanent change in chromosome structure as between the two species the expectation is that the size difference between salmon and trout chromosomes will be maintained in the hybrid. If, alternatively, the size difference between salmon and trout chromosomes is genotypically determined the difference will not be maintained in nuclei of hybrid genotype. Measurements of a specific chromosome, S, of the salmon complement and of another, S ¹, of the trout complement in nuclei of parent species and of the hybrid show that the difference in size is maintained in hybrid nuclei. It is concluded therefore that the size difference between salmon and trout chromosomes is due to structural change rather than to genotypic control.     

Chromosome length values in digenomic buttercups [Ranunculaceae] and the relation to DNA content

Root-tip chromosome complement length ratios were determined in F1 hybrids combinining two haploid (n = 8) genomes each from different species, to form a series AB, AC, AD, ... AI. The observed values, for the length ratios B/A, C/A, etc., ranged from 0.53 to 1.0. It is noted that the values form a quasilinear distribution, with a slope of 1.0, when plotted against the known 4C DNA values of the species having a range from appr. 1.1 to 2.2 × 10^?11 g. Also observed, but not numerically evaluated was some apparently related variation in chromosome “width”. DNA-related variation in root-tip chromosome size in these buttercups may be three-dimensional; however, the magnitude of the observed length differentials and the 1∶1 correlation with DNA content suggest that it occupies predominantly the first dimension.     

Floral and reproductive biology of Drosophyllum lusitanicum (L.) Link (Droseraceae)

We studied the floral and reproductive biology of Drosophyllym lusitanicum (Droseraceae), a species endemic to the western Iberian Peninsula and northwest Morocco. Flowering lasted from March to August, peaking in April. The species is clearly homogamous, with pollen germination and stigma receptivity occurring even in preanthesis. This was reflected in the high rates of fruit set and seed set in bagged inflorescences. Fructification did not differ significantly between different pollination treatments, although we did find differences between some treatments in the numbers of viable seeds per flower and fruit. However, seed weight did not differ significantly. The importance of self-pollination over cross-pollination was also supported by the low percentages of fructification (24.67%) after emasculation and open pollination. Metameric deviations were seen in flowers, although this abnormality was not translated as any reproductive benefit or disadvantage (fructification, number or weight of seeds) in comparison with normal flowers.     

Modes of Self-Pollination and Absence of Cryptic Self-Incompatibility in Drosophyllum lusitanicum (Droseraceae)

We show experimentally that several types of selfing occur simultaneously in Drosophyllum lusitanicum: prior, competitive, insect-facilitated, delayed and geitonogamous. In addition, we report evidence of cleistogamy in the flower bud. All types of selfing were successful in producing fruits and seeds; however, geitonogamy did not occur uniformly throughout the flowering period in this species. We also report the absence of cryptic self-incompatibility: the germination rate and pollen tube growth rate of cross pollen were no greater than those of self pollen when both types were placed on stigmas of the same flower (mixed pollination). There was a tendency for self pollen to be more vigorous than cross pollen but it just failed to reach significance.     

Chromosome length and DNA loop size during early embryonic development of Xenopus laevis

The looped organization of the eukaryotic genome mediated by a skeletal framework of non-histone proteins is conserved throughout the cell cycle. The radial loop/scaffold model envisages that the higher order architecture of metaphase chromosomes relies on an axial structure around which looped DNA domains are radially arranged through stable attachment sites. In this light we investigated the relationship between the looped organization and overall morphology of chromosomes. In developing Xenopus laevis embryos at gastrulation, the bulk of the loops associated with histone-depleted nuclei exhibit a significant size increase, as visualized by fluorescence microscopy of the fully extended DNA halo surrounding high salt treated, ethidium bromide stained nuclei. This implies a reduction in the number of looped domains anchored to the supporting nucleoskeletal structure. The cytological analysis of metaphase plates from acetic acid fixed whole embryos, carried out in the absence of drugs inducing chromosome condensation, reveals a progressive thickening and shortening of metaphase chromosomes during development. We interpret these findings as a strong indication that the size and number of DNA loops influence the thickness and length of the chromosomes, respectively. The quantitative analysis of chromosome length distributions at different developmental stages suggests that the shortening is timed differently in different embryonic cells.     

DNA values in somatic tissues of Dermestes (Dermestidae: Coleoptera)

The organisation of the male Malpighian tubule has been investigated in the coleopteran genus Dermestes. Nuclear number is found to be more or less constant between species. However, the DNA values of these nuclei do not, in general, reflect the germ-line DNA value of the species since many of them do not conform with members of a doubling series. These phenomena may be interpreted as aspects of the control of tissue and organ size, the final dimensions of the Malpighian tubules being similar in spite of presumed differences in 2C cell size in the different species.     

New species ofBeaufortia andChamaelaucium (Myrtaceae),Drosera (Droseraceae) andPultenaea (Fabaceae) from SW. Australia

Four new species of the generaBeaufortia, Chamaelaucium, Drosera, andPultenaea are described based on the author's collections from SW. Australia. Their affinities are discussed and full illustrations are provided.Dedicated to Hofrat Univ.-Prof.K. H. Rechinger on the occasion of his 80th birthday.