共查询到20条相似文献,搜索用时 812 毫秒
1.
M. Galbany‐Casals P. Carnicero‐Campmany J. M. Blanco‐Moreno R. D. Smissen 《Plant biology (Stuttgart, Germany)》2012,14(5):789-800
Hybridisation is considered an important evolutionary phenomenon in Gnaphalieae, but contemporary hybridisation has been little explored within the tribe. Here, hybridisation between Helichrysum orientale and Helichrysum stoechas is studied at two different localities in the islands of Crete and Rhodes (Greece). Using three different types of molecular data (AFLP, nrDNA ITS sequences and cpDNA ndhF sequences) and morphological data, the aim is to provide simultaneous and direct comparisons between molecular and morphological variation among the parental species and the studied hybrid populations. AFLP profiles, ITS sequences and morphological data support the existence of hybrids at the two localities studied, shown as morphological and genetic intermediates between the parental species. Chloroplast DNA sequences show that both parental species can act either as pollen donor or as maternal parent. Fertility of hybrids is demonstrated by the viability of seeds produced by hybrids from both localities, and the detection of a backcross specimen to H. orientale. Although there is general congruence of morphological and molecular data, the analysis of morphology and ITS sequences can fail to detect backcross hybrids. 相似文献
2.
Treena I. Burgess 《PloS one》2015,10(8)
Most Phytophthora hybrids characterized to date have emerged from nurseries and managed landscapes, most likely generated as a consequence of biological invasions associated with the movement of living plants and germplasm for ornamental, horticultural and agricultural purposes. Presented here is evidence for natural hybridization among a group of five closely related indigenous clade 6 Phytophthora species isolated from waterways and riparian ecosystems in Western Australia. Molecular characterization of hybrids consisted of cloning and sequencing two nuclear genes (ITS and ASF), sequencing of two further nuclear loci (BT and HSP) and of two mitochondrial loci (COI and NADH). Additionally, phenotypic traits including morphology of sporangia and optima and maxima temperatures for growth were also determined. In most cases the nuclear genes were biparentally and in all cases the mtDNA were uniparentally inherited, indicating hybrid formation through sexual crosses. Some isolates bear the molecular signature of three parents suggesting additional hybrid events, although it cannot be determined from the data if these were sequential or simultaneous. These species and their hybrids co-exist in riparian ecosystems and waterways where their ability for rapid asexual proliferation would enable them to rapidly colonize green plant litter. The apparent ease of hybridization could eventually lead to the merging of species through introgression. However, at this point in time, species integrity has been maintained and a more likely scenario is that the hybrids are not stable evolutionary lineages, but rather transient hybrid clones. 相似文献
3.
Pablo Vargas Hugh A. McAllister Cynthia Morton Stephen L. Jury Mike J. Wilkinson 《Plant Systematics and Evolution》1999,219(3-4):165-179
Variation in chromosome number and internal transcribed sequences (ITS) of nrDNA is used to infer phylogenetic relationships of a wide range ofHedera species. Polyploidy was found to be frequent inHedera, with diploid, tetraploid, hexaploid and octoploid populations being detected. Nucleotide additivity occurs in the ITS sequences of one tetraploid (H. hibernica) and two hexaploid species (H. maderensis, H. pastuchovii), suggesting that all three species originated by allopolyploidisation. ITS sequence polymorphism and nucleotide characters may indicate the presence of an ancient genome persistent only in some allopolyploid species. Phylogenetic analyses of ITS sequence data reveal two lineages ofHedera: one containing all sequences belonging to extant diploids plus the tetraploidH. algeriensis, and a second that includes this ancient ITS type and others exclusive to several polyploid species. The origin of the polyploids is evaluated on the basis of morphology, chromosome counts, ITS sequence polymorphism, and phylogenetic analyses. Reconstruction of reticulate evolution inHedera agrees with two allopolyploid areas on both sides of the Mediterranean basin. Morphological, molecular and cytological evidence also suggests an active dispersal ofHedera populations that may account for three independent introductions in Macaronesia. 相似文献
4.
Lenka Záveská Drábková Jan Kirschner Jan Štěpánek Luděk Záveský Čestmír Vlček 《Plant Systematics and Evolution》2009,278(1-2):67-85
Nuclear sequences of ITS1-5.8S-ITS2 region of rDNA may be an important source of phylogenetically informative data provided that nrDNA is cloned and the character of sequence variation of clones is properly analyzed. nrDNA of selected Taraxacum sections was studied to show sequence variation differences among diploid sexual, tetraploid sexual and polyploid agamospermous species. We examined nucleotide characteristics, substitution pattern, secondary structure, and the phylogenetic utility of ITS1-5.8S-ITS2 from 301 clones of 32 species representing 11 sections. The most divergent sequences of ITS1&2 differed by 17.1% and in 5.8S only by 3.7%. The ITS1-5.8S-ITS2 characteristics, integrity and also stability of secondary structures confirmed that pseudogenes are not responsible for the above variation. The within-individual polymorphism of clones implies that the concerted evolution of ITS cistron of agamospermous polyploid Taraxacum is remarkably suppressed. Sequences of ITS clones proved to be a useful tool for mapping pathways of complex reticulation (polyploid hybridity) in agamospermous Taraxacum. 相似文献
5.
It is becoming increasingly evident that interspecific hybridization is a common event in phytophthora evolution. Yet, the fundamental processes underlying interspecific hybridization and the consequences for its ecological fitness and distribution are not well understood. We studied hybridization events in phytophthora clade 8b. This is a cold-tolerant group of plant pathogenic oomycetes in which six host-specific species have been described that mostly attack winter-grown vegetables. Hybrid characterization was done by sequencing and cloning of two nuclear (ITS and Ypt1) and two mitochondrial loci (Cox1 and Nadh1) combined with DNA content estimation using flow cytometry. Three different mtDNA haplotypes were recovered among the presumed hybrid isolates, dividing the hybrids into three types, with different parental species involved. In the nuclear genes, additivity, i.e. the presence of two alleles coming from different parents, was detected. Hybrid isolates showed large variations in DNA content, which was positively correlated with the additivity in nuclear loci, indicating allopolyploid hybridization followed by a process of diploidization. Moreover, indications of homeologous recombination were found in the hybrids by cloning ITS products. The hybrid isolates have been isolated from a range of hosts that have not been reported previously for clade 8b species, indicating that they have novel pathogenic potential. Next to this, DNA content measurements of the non-hybrid clade 8b species suggest that polyploidy is a common feature of this clade. We hypothesize that interspecific hybridization and polyploidy are two linked phenomena in phytophthora, and that these processes might play an important and ongoing role in the evolution of this genus. 相似文献
6.
Jian Zeng Xing Fan Hai-Qin Zhang Li-Na Sha Hou-Yang Kang Li Zhang Rui-Wu Yang Chun-Bang Ding Yong-Hong Zhou 《Genes & genomics.》2012,34(5):499-507
Interspecies hybridization has been frequently observed in the tribe Triticeae. Natural hybridization between Kengyilia and Roegneria or Elymus species has not been reported as yet. Several sterile wheatgrass individuals exhibiting intermediately morphological traits between Kengyilia and Roegneria or Elymus species were identified in the meadow of Sichuan and Gansu provinces in China, suggesting their natural hybrid origin. The putative hybrids were analyzed by using the sequences of ITS and trnH-psbA together with cytological observation in order to assess the origin of hybrids. Both ITS and cytological data revealed the evidence of allopolyploid origin and confirmed the presence of StStYYP and StStYYHP genomes in the putative natural hybrids. The data suggest that the StStYYP hybrid originated from hybridization between Kengyilia and Roegneria and the hybrid with StStYYHP originated from hybridization between Kengyilia and Elymus. Chloroplast sequence data demonstrated that K. rigidula and K. melanthera were the likely maternal donors in the hybridization events. 相似文献
7.
Natural hybridization is common in the genus Lespedeza. No hybrids between Lespedeza leptostachya Englem. and Lespedeza capitata Michx. are formally recognized in any of the current floras, however observations in the field suggest that hybridization
might occur in many of their shared habitats. Putative hybrids were compared to L. leptostachya and L. capitata using morphological measurements and screened for the presence of species-specific trnL-F gene region (cpDNA) and the ITS gene region (nrDNA). A discriminate analysis of 10 morphological measurements identified
the hybrids as intermediate to both parents with two PCA axes explaining 99% of the variation between taxa. The presence of
hybrids was confirmed by genetic markers with individuals morphologically identified as hybrids having cpDNA trnL-F genotypes identical to L. leptostachya and the ITS (nrDNA) phenotypes in most cases contain the ITS genotype of both parents, however, some putative hybrid individuals
contained the ITS genotype of only one parents. Those individuals with L. leptostachya ITS and trnL-F could be a case of misclassification, but the presence of both L. capitata ITS genotypes and L. leptostachya
trnL-F genotypes suggest segregation has occurred, which may result from either selfing or backcrossing. 相似文献
8.
M. Ajmal Ali 《Saudi Journal of Biological Sciences》2018,25(7):1298-1301
The deciduous habit and tendency to produce flowers prior to developing leaves, and a predominantly dioecious system of breeding in the genus Commiphora leads to difficulties in its taxonomic identification at species level. The characteristics of easy amplification by universal primer, shorter length and higher discrimination power at the species level makes the internal transcribed spacer (ITS) sequence of nuclear ribosomal DNA (nrDNA) to a smart gene for generating species-specific phylogenetic inferences in most of the plants groups. The present study deals the ITS sequence of nrDNA based molecular genotyping of seven species of the genus Commiphora of Saudi Arabia. The molecular phylogenetic analysis of ITS sequences of nrDNA of Commiphora species distributed in Saudi Arabia reveals the the occurrence of C. madagascariens in Saudi Arabia. 相似文献
9.
Facultative asexual reproduction is a trait commonly found in invasive species. With a
combination of sexual and asexual reproductive modes, such species may adapt to new
environments via sexual recombination during range expansion, while at the same time
having the benefits of asexuality such as the maintenance of fitness effects that depend
upon heterozygosity. In the Western United States, native species of Rubus
(Rosaceae) reproduce sexually whereas exotic naturalized Rubus species reproduce
by pseudogamous apomixis. We hypothesized that new asexual lineages of Rubus
could arise from hybridization in this range. To detect hybridization between native and
exotic Rubus, we genotyped 579 individuals collected across California, Oregon
and Washington with eight nuclear microsatellites and two chloroplast markers. Principal
Coordinate Analysis and Bayesian clustering revealed a limited amount of hybridization of
the native R. ursinus with the exotic R. armeniacus and R.
pensilvanicus, as well as cultivated varieties. Genetic distances between these
hybrids and their offspring indicated that both R. ursinus × R.
armeniacus and R. ursinus × R. pensilvanicus produced a mix
of apomictic and sexual seeds, with sexual seeds being more viable. Although neither of
these hybrid types is currently considered invasive, they model the early stages of
evolution of new invasive lineages, given the potential for fixed heterosis and the
generation of novel genotypes. The hybrids also retain the ability to increase their
fitness via sexual recombination and natural selection. Mixed reproductive systems such as
those described here may be an important step in the evolution of asexual invasive
species. 相似文献
10.
11.
Carolyn J. Ferguson Donald A. Levin Robert K. Jansen 《Plant Systematics and Evolution》1999,218(1-2):153-158
Natural F1 hybrids between the outcrossingPhlox drummondii and the predominantly selfingP. cuspidata were examined to ascertain the proportion of hybrid individuals mothered by each species. Species-specific restriction fragment patterns (both nrDNA and cpDNA) were established as markers, and synthetic hybrids of known parentage were utilized to determine that the chloroplast genome is maternally inherited. Of 89 mature natural hybrids examined, approximately two thirds were mothered byP. drummondii, the outcrosser. That the outcrosser should mother most hybrids is expected since it is dependent upon incoming pollen for fertilization, and hybrids may result when heterospecific pollen is received. The fact that the highly selfingP. cuspidata mothered nearly one third of the hybrids is surprising, and may be related to both pre-zygotic and post-zygotic factors. Which species mothers hybrids has important implications for the potential for introgression as well as its direction. 相似文献
12.
ITS sequence variation and concerted evolution in the natural hybrid species Malus toringoides
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Liang Tang Jian‐Min Tang Si Tan Ju Li Xiang Ma Zhi‐Qin Zhou 《Nordic Journal of Botany》2015,33(1):109-119
The internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) is one of the most used molecular characters in plant systematics. Our previous studies based on morphological analysis and ITS sequence variation suggested that Malus toringoides (Rehd.) Hughes is derived from hybridization between M. transitoria (Batal.) Schneid. and M. kansuensis (Batal.) Schneid. To further understand the variation pattern of ITS sequences in M. toringoides, and to elucidate the evolutionary processes that affect ITS sequence variation after hybridization, we sampled 99 accessions from multiple populations of the hybrid and parental species, and then obtained totally 254 ITS sequences by cloning and sequencing. Our ITS variation data demonstrates three outcomes of ITS repeats after hybrid speciation. ~ 27–41% of M. toringoides have only M. transitoria type ITS sequence, ~ 40–70% have M. transitoria type ITS sequence plus one or two chimeric ITS sequences generated by recombination between parental ITS sequences, and six accessions retain both parental type ITS sequences. The plausible evolutionary processes that created the observed ITS variations were inferred to be the joint actions of recombination, concerted evolution, pseudogenization and backcrossing. Our study provides further understandings of the variation model of ITS repeats after hybridization as well as the evolution of M. toringoides after its hybrid speciation. 相似文献
13.
Chase MW Knapp S Cox AV Clarkson JJ Butsko Y Joseph J Savolainen V Parokonny AS 《Annals of botany》2003,92(1):107-127
Phylogenetic relationships in the genus Nicotiana were investigated using parsimony analyses of the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (nrDNA). In addition, origins of some amphidiploid taxa in Nicotiana were investigated using the techniques of genomic in situ hybridization (GISH), and the results of both sets of analyses were used to evaluate previous hypotheses about the origins of these taxa. Phylogenetic analyses of the ITS nrDNA data were performed on the entire genus (66 of 77 naturally occurring species, plus three artificial hybrids), comprising both diploid and polyploid taxa, and on the diploid taxa only (35 species) to examine the effects of amphidiploids on estimates of relationships. All taxa, regardless of ploidy, produced clean, single copies of the ITS region, even though some taxa are hybrids. Results are compared with a published plastid (matK) phylogeny using fewer, but many of the same, taxa. The patterns of relationships in Nicotiana, as seen in both analyses, are largely congruent with each other and previous evolutionary ideas based on morphology and cytology, but some important differences are apparent. None of the currently recognized subgenera of Nicotiana is monophyletic and, although most of the currently recognized sections are coherent, others are clearly polyphyletic. Relying solely upon ITS nrDNA analysis to reveal phylogenetic patterns in a complex genus such as Nicotiana is insufficient, and it is clear that conventional analysis of single data sets, such as ITS, is likely to be misleading in at least some respects about evolutionary history. ITS sequences of natural and well-documented amphidiploids are similar or identical to one of their two parents-usually, but not always, the maternal parent-and are not in any sense themselves 'hybrid'. Knowing how ITS evolves in artificial amphidiploids gives insight into what ITS analysis might reveal about naturally occurring amphidiploids of unknown origin, and it is in this perspective that analysis of ITS sequences is highly informative. 相似文献
14.
To compare morphological characters and phylogenetic placement between Japanese and European Russula, 32 specimens of 12 species were collected from Japanese subalpine forests and Northern Europe. Several sequences of nrDNA ITS region (ITS) of these Russula species were obtained. High homological similarities were shown between ITS sequences of several Russula samples collected from Japanese subalpine forests, Europe and North America. These facts show distribution of the same Russula species among these areas. From morphological observations and phylogenetic analyses, two same Russula species, R. velenovskyi, and R. decolorans are found in Japan, Europe and North America. Of these, R. velenovskyi collected from Mt. Fuji, Mt. Nyukasa and Mt. Tateshina in mountainous area of central Honshu is reported as a new Japanese record. 相似文献
15.
Modes of evolution of species classified within different sections inTaraxacum involve diverse processes, viz. primary divergence of an ancestral sexual diploid, hybridization between a tetraploid apomict and a diploid sexual hybrid, differentiation of an advanced apomictic taxon at one ploidy level, hybridization between a sexual tetraploid and a sexual diploid, formation of a polyploid series from an apomictic ancestor of a lower polyploidy level, and remote hybridization between an autumn-flowering ancestral diploid and a spring-flowering derivative diploid or apomict. Various reproduction systems of the plants involved, different environments and different timing of the processes contribute to a very varied nature of the species groups. 相似文献
16.
Viola jaubertiana Marès & Vigin. is a narrow endemic violet of the Balearic Islands, restricted to small, fragmented, and scattered populations living in inaccessible rocky places and calcareous overhangs. V. jaubertiana is entirely glabrous and morphologically very uniform. However, several authors have reported hairy individuals collected at the type locality, suggesting that these rupicolous, pubescent plants are putative hybrids with V. alba Bess. subsp. dehnhardtii (Ten.) W. Becker, a woodland violet growing in the area. Ribosomal ITS sequences of the putative hybrids analysed showed additive species-specific sites of V. alba subsp. dehnhardtii and V. jaubertiana, strongly supporting its hybrid origin from these progenitors. CpDNA sequences of all putative hybrids were uniform, and identical to those present in V. jaubertiana accessions. This suggests that the gene flow between V. alba subsp. dehnhardtii and V. jaubertiana is unidirectional and identifies the endemic V. jaubertiana as the unique ovule donor. The additivity of the ITS sequences, together with the pollen and ovule sterility, suggests that the sampled individuals are primary F1 hybrids, whereas no trace of introgressive hybridization or hybrid zone has been evidenced by the nuclear and plastid markers used. Judging from herbarium sheets, hybridization between V. alba subsp. dehnhardtii and V. jaubertiana is recurrent and dates back from the XIXth century. Hybrids between these species are not linked to disturbed environments. In fact, they have been always reported in rupicolous habitats, where the maternal species is restricted. 相似文献
17.
Begonia × taipeiensis C.-I Peng, a naturally occurring hybrid resulting from B. formosana × B. aptera, in Taiwan. To understand the inheritance of ribosomal DNA in unidirectional hybridization, experiments were conducted using
B. formosana and B. aptera as ovule and pollen donors, respectively. The internal transcribed spacer region (ITS) of nuclear ribosomal DNA was amplified
from the artificial hybrids, parental species, and natural hybrids. In contrast to the single type of ITS in the parental
species, multiple sequences were cloned from both natural and artificial hybrids. A split decomposition network based on ITS
nucleotide variation revealed that all but one (clone B14) of the hybrid sequences were “phylogenetically” closely related
to B. formosana. Apparently, in such unidirectional hybridization, maternal DNA provided most of phylogenetic information. In the hybrid
sequences, in addition to additive polymorphisms inherited from maternal (38.1%) and paternal (30.1%) plants, a novel nucleotide
composition (31.8%) was also detected. The “new” characters are seen as noise in phylogenetic inference. They were probably
obtained via intramolecular recombination, as gene conversion was not detected. The occurrence of genetic recombination appeared
to be nonrandom, with a higher frequency in the ITS1 (3.14%) and ITS2 (3.42%) regions than in the 5.8S RNA gene (2.22%). Given
the lack of sexual recombination in B. × taipeiensis and short time span, unequal crossing-over likely contributed to the heterogeneity of the ITS composition in the nuclear
genome. Although the sterile hybrids have not attained their own lineage independent from the parental species, a high level
of genetic diversity is transmitted asexually and maintained in these plants.
Received 7 February 2001/ Accepted in revised form 31 May 2001 相似文献
18.
As a common cause of reproductive isolation in diverse taxa, hybrid incompatibilities are fundamentally important to speciation. A key question is which evolutionary forces drive the initial substitutions within species that lead to hybrid dysfunction. Previously, we discovered a simple genetic incompatibility that causes nearly complete male sterility and partial female sterility in hybrids between the two closely related yellow monkeyflower species Mimulus guttatus and M. nasutus. In this report, we fine map the two major incompatibility loci—hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2)—to small nuclear genomic regions (each <70 kb) that include strong candidate genes. With this improved genetic resolution, we also investigate the evolutionary dynamics of hms1 in a natural population of M. guttatus known to be polymorphic at this locus. Using classical genetic crosses and population genomics, we show that a 320-kb region containing the hms1 incompatibility allele has risen to intermediate frequency in this population by strong natural selection. This finding provides direct evidence that natural selection within plant species can lead to hybrid dysfunction between species. 相似文献
19.
Jan H. Nagel Marieka Gryzenhout Bernard Slippers Michael J. Wingfield Giles E.St.J. Hardy Michael J.C. Stukely Treena I. Burgess 《Fungal biology》2013,117(5):329-347
Surveys of Australian and South African rivers revealed numerous Phytophthora isolates residing in clade 6 of the genus, with internal transcribed spacer (ITS) gene regions that were either highly polymorphic or unsequenceable. These isolates were suspected to be hybrids. Three nuclear loci, the ITS region, two single copy loci (antisilencing factor (ASF) and G protein alpha subunit (GPA)), and one mitochondrial locus (cytochrome oxidase c subunit I (coxI)) were amplified and sequenced to test this hypothesis. Abundant recombination within the ITS region was observed. This, combined with phylogenetic comparisons of the other three loci, confirmed the presence of four different hybrid types involving the three described parent species Phytophthora amnicola, Phytophthora thermophila, and Phytophthora taxon PgChlamydo. In all cases, only a single coxI allele was detected, suggesting that hybrids arose from sexual recombination. All the hybrid isolates were sterile in culture and all their physiological traits tended to resemble those of the maternal parents. Nothing is known regarding their host range or pathogenicity. Nonetheless, as several isolates from Western Australia were obtained from the rhizosphere soil of dying plants, they should be regarded as potential threats to plant health. The frequent occurrence of the hybrids and their parent species in Australia strongly suggests an Australian origin and a subsequent introduction into South Africa. 相似文献
20.