首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The diversity of rhizobia that establish symbiosis with Lotus corniculatus has scarcely been studied. Several species of Mesorhizobium are endosymbionts of this legume, including Mesorhizobium loti, the type species of this genus. We analysed the genetic diversity of strains nodulating Lotus corniculatus in Northwest Spain and ten different RAPD patterns were identified among 22 isolates. The phylogenetic analysis of the 16S rRNA gene showed that the isolated strains belong to four divergent phylogenetic groups within the genus Mesorhizobium. These phylogenetic groups are widely distributed worldwide and the strains nodulate L. corniculatus in several countries of Europe, America and Asia. Three of the groups include the currently described Mesorhizobium species M. loti, M. erdmanii and M. jarvisii which are L. corniculatus endosymbionts. An analysis of the recA and atpD genes showed that our strains belong to several clusters, one of them very closely related to M. jarvisii and the remanining ones phylogenetically divergent from all currently described Mesorhizobium species. Some of these clusters include L. corniculatus nodulating strains isolated in Europe, America and Asia, although the recA and atpD genes have been sequenced in only a few L. corniculatus endosymbionts. The results of this study revealed great phylogenetic diversity of strains nodulating L. corniculatus, allowing us to predict that even more diversity will be discovered as further ecosystems are investigated.  相似文献   

2.
In this study we are concerned with the general problem of choosing from a set of endangered species T a subset S of k species to protect as a priority. Here, the interest to protect the species of S is assessed by the resulting expected phylogenetic diversity (ePD) of the set T, a widely used criterion for measuring the expected amount of evolutionary history associated with T. We consider that the survival of the protected species is assured and, on the contrary, that there is a risk of extinction for the unprotected species. The problem is easy to solve by a greedy type method if the extinction probabilities of the unprotected species are known but these probabilities are generally not easy to quantify. We show in this note that the choice of the precise values attributed to the extinction probabilities—provided it respects the rank of imperilment of each species—is not as decisive as might be feared for the considered problem. The values of these probabilities have a clear impact on the selection of the species to be protected but a little impact on the resulting ePD. More precisely, if T 1 and T 2 are the two optimal subsets of species corresponding to two scenarios (two different sets of probabilities) the ePDs of T 1 and T 2, calculated with the probabilities of the first scenario—or with the probabilities of the second scenario—are not very different.  相似文献   

3.
Wolbachia are intracellular prokaryotic endosymbionts associated with a wide distribution of arthropod and nematode hosts. Their association ranges from parasitism to mutualism, and there is growing evidence that Wolbachia can have dramatic effects on host reproduction, physiology, and immunity. Although all Wolbachia are currently considered as single species, W. pipientis, phylogenetic studies reveal about a dozen monophyletic groups, each designated as a supergroup. This study uses 16S rRNA gene sequences to examine the genetic diversity of Wolbachia present in three species of Great Salt Lake brine flies, Cirrula hians, Ephydra gracilis, and Mosillus bidentatus. The brine fly Wolbachia sequences are highly similar, with an average nucleotide sequence divergence among the three species of 0.00174. The brine fly Wolbachia form a monophyletic group that is affiliated with a subset of supergroup B, indicating that this supergroup may be more diverse than previously thought. These findings expand the phylogenetic diversity of Wolbachia and extend their host range to taxa adapted to a hypersaline environment.  相似文献   

4.
Polyploid Prunus spinosa (2n = 4×) and P. insititia (2n = 6×) represent enormous genetic potential in Central Europe, which can be exploited in breeding programmes. In Hungary, 17 cultivar candidates were selected from wild-growing populations including 10 P. spinosa, 4 P. insititia and three P. spinosa × P. domestica hybrids (2n = 5×). Their taxonomic classification was based on their phenotypic characteristics. Six simple sequence repeats (SSRs) and the multiallelic S-locus genotyping were used to characterize genetic variability and reliable identification of the tested accessions. A total of 98 SSR alleles were identified, which presents 19.5 average allele number per locus, and each of the 17 genotypes could be discriminated based on unique SSR fingerprints. A total of 23 S-RNase alleles were identified. The complete and partial S-genotype was determined for 8 and 9 accessions, respectively. The identification of a cross-incompatible pair of cultivar candidates and several semi-compatible combinations help maximize fruit set in commercial orchards. Our results indicate that the S-allele pools of wild-growing P. spinosa and P. insititia are overlapping in Hungary. A phylogenetic and principal component analysis confirmed the high level of diversity and genetic differentiation present within the analysed genotypes and helped clarify doubtful taxonomic identities. Our data confirm that S-locus genotyping is suitable for diversity studies in polyploid Prunus species. The analysed accessions represent huge genetic potential that can be exploited in commercial cultivation.  相似文献   

5.
Members of the Diatrypaceae are predominantly saprotrophic on the decaying wood of angiosperms worldwide and the family has received little attention due to its difficult taxonomy. However, the recent detection of several pathogenic species, once considered saprotrophic, associated with the wood of diseased grapevines has increased interest in this family. The diversity of tropical species is less well known and more poorly sampled in phylogenetic studies than temperate species. In the present study, we investigated the diversity of diatrypaceous fungi from three areas in the Brazilian semi-arid region and performed phylogenetic analyses of the family based on the entire internal transcribed spacer (ITS) region and partial ß-tubulin gene. Twenty-eight new ITS and 19 new ß-tubulin sequences were generated, representing eight species distributed in five clades. Diatrypella atlantica, Eutypa guttulata, Eutypella cearensis, and Peroneutypa diminutispora are proposed here as new species, while Eutypella microtheca and P. curvispora are new records for Brazil. All eight species are described, illustrated, and discussed.  相似文献   

6.
Niche conservatism (NC) presence is a controversial question in evolutionary ecology. In Drosophila, little is known about which is the preponderant evolutionary pattern, since the adaptive radiation hypothesis first proposed by Throckmorton assumed niche divergence (ND) according to a niche occupancy scenario. Nevertheless, this hypothesis has not yet been straightforwardly tested. Our aim here was to test the role of NC patterns across evolution of American drosophilids belonging to the tripunctata and virilis-repleta lineages of the Drosophila subgenus, through measures of geographical, abiotic and biotic niche overlap and evaluations regarding the presence of phylogenetic signal or niche identity. We recovered phylogenetic signal attributable to phylogenetic niche conservatism when all species were analyzed together, but not in more restricted groups. Identity tests showed that niche equivalency was seldom rejected for the tripunctata lineage species. So, in general, neither the results for the Drosophila subgenus nor those for the tripunctata lineage support the hypothesis of an adaptive radiation. Notwithstanding, there were also several isolated cases supporting a scenario of ND, and ecological speciation was evident in some of the evaluated sister species pairs.  相似文献   

7.
An important problem in phylogenetics is the construction of phylogenetic trees. One way to approach this problem, known as the supertree method, involves inferring a phylogenetic tree with leaves consisting of a set X of species from a collection of trees, each having leaf-set some subset of X. In the 1980s, Colonius and Schulze gave certain inference rules for deciding when a collection of 4-leaved trees, one for each 4-element subset of X, can be simultaneously displayed by a single supertree with leaf-set X. Recently, it has become of interest to extend this and related results to phylogenetic networks. These are a generalization of phylogenetic trees which can be used to represent reticulate evolution (where species can come together to form a new species). It has recently been shown that a certain type of phylogenetic network, called a (unrooted) level-1 network, can essentially be constructed from 4-leaved trees. However, the problem of providing appropriate inference rules for such networks remains unresolved. Here, we show that by considering 4-leaved networks, called quarnets, as opposed to 4-leaved trees, it is possible to provide such rules. In particular, we show that these rules can be used to characterize when a collection of quarnets, one for each 4-element subset of X, can all be simultaneously displayed by a level-1 network with leaf-set X. The rules are an intriguing mixture of tree inference rules, and an inference rule for building up a cyclic ordering of X from orderings on subsets of X of size 4. This opens up several new directions of research for inferring phylogenetic networks from smaller ones, which could yield new algorithms for solving the supernetwork problem in phylogenetics.  相似文献   

8.
We here present a molecular phylogenetic analysis of cultivated Zanthoxylum species which have a long history of cultivation both for economic and for chemical values in China. Three cpDNA markers, including matK, rbcL, and trnL-F, were sequenced, with the goals of untangling phylogenetic relationships and inferring biogeographic origin and patterns of distribution among Zanthoxylum species. Based on three cpDNA markers, 19 haplotypes with 64 polymorphic sites in Zanthoxylum provenances were identified in our study. A low genetic differentiation (G ST ?=?0.271, N ST ?=?0.373) was observed within Zanthoxylum provenances. Based on phylogenetic tree and haplotype network, all 19 haplotypes were grouped into six clusters. Our results also supported the hypothesis that the so-called “Green Huajiao” belongs to the species Zanthoxylum armatum rather than Zanthoxylum schinifolium. The results also revealed that haplotypes of two cultivated species, Zanthoxylum bungeanum and Z. armatum, most probably diverged during the Late Miocene. Ancestral area reconstruction indicated that cultivated Zanthoxylum species experienced multiple long-distance dispersal events and several vicariance events and the ancestors of Zanthoxylum first colonized Yunnan and Guizhou provinces (D). Accordingly, the current disjunct distribution of Z. bungeanum and Z. armatum may represent long-distance dispersal of ancestors popularly named “Dahongpao” and “Qinghuajiao,” respectively. It is concluded that cpDNA markers may provide a new conceptual and practical opportunity to evaluate genetic diversity and to identify local cultivars of Zanthoxylum, making it a valuable source to include into potential breeding programs.  相似文献   

9.
The results of analysis of the variability of body shape of different Daphnia galeata morphs from geographically distinct populations—Lake Glubokoe (Moscow oblast) and Lake Chany (Novosibirsk oblast) are given. The morphological analysis was combined with the analysis of the variability of fragments of the 16S and 12S genes of the mitochondrial DNA (mtDNA) and the internal transcribed spacer 2 (ITS2) of the nuclear DNA. A reconstruction of the phylogenetic relationships between species of the genus Daphnia has been performed using a combined fragment of the 16S and 12S genes of the mtDNA. An inconsistency in the distribution of the 12S- and ITS2-haplotypes for the species D. galeata has been revealed, which indicates the introgression of mtDNA in the Lake Chany population.  相似文献   

10.
The fungus Cenococcum geophilum Fr. (Dothideomycetes, Ascomycota) is one of the most common ectomycorrhizal fungi in boreal to temperate regions. A series of molecular studies has demonstrated that C. geophilum is monophyletic but a heterogeneous species or a species complex. Here, we revisit the phylogenetic diversity of C. geophilum sensu lato from a regional to intercontinental scale by using new data from Florida (USA) along with existing data in GenBank from Japan, Europe, and North America. The combination of internal transcribed spacer (ITS) ribosomal DNA and the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene resolved six well-supported lineages (87–100 % bootstrap values) that are closely related to each other and a seventh lineage that is phylogenetically distinct. A multi-locus analysis (small subunit (SSU), large subunit (LSU), translational elongation factor (TEF), and the largest and second-largest subunits of RNA polymerase II (RPB1 and RPB2)) revealed that the divergent lineage is the sister group to all other known Cenococcum isolates. Isolates of the divergent lineage grow fast on nutrient media and do not form ectomycorrhizas on seedlings of several pine and oak species. Our results indicate that C. geophilum sensu lato includes more phylogenetically distinct cryptic species than have previously been reported. Furthermore, the divergent lineage appears to be a non-mycorrhizal sister group. We discuss the phylogenetic diversity of C. geophilum sensu lato and argue in favor of species recognition based on phylogenetic and ecological information in addition to morphological characteristics. A new genus and species (Pseudocenococcum floridanum gen. et sp. nov.) is proposed to accommodate a divergent and putatively non-mycorrhizal lineage.  相似文献   

11.
The order Ceraceosorales (Ustilaginomycotina) currently includes the single genus Ceraceosorus, with one species, Ceraceosorus bombacis, parasitic on Bombax ceiba in India. The diversity, biogeography, evolution, and phylogenetic relationships of this order are still relatively unknown. Here, a second species of Ceraceosorus is described from West Africa as a novel species, Ceraceosorus africanus, infecting Bombax costatum in Benin, Ghana, and Togo. This species produces conspicuous fructifications, similar to corticioid basidiomata when mature, but sorus-like in early stages of ontogenetic development. The fructifications cover much of the leaf surface and resemble leaf blight. This contrasts with the inconspicuous fructifications of C. bombacis comprising small spots scattered over the lower leaf surface that resemble leaf spot. Both species of Ceraceosorus differ in several micromorphological traits, infect different host plant species in widely separated geographical areas, and are separated by a considerable genetic distance in 28S rDNA and RPB2 genes. The distinct corticioid fructification of C. africanus is a unique morphological trait within the Ustilaginomycotina. Molecular phylogenetic analyses of a single gene dataset (D1/D2 28S rDNA) supported the monophyly of the two Ceraceosorus species and the Ceraceosorales and their placement within the Ustilaginomycotina. Molecular phylogenetic analyses of a multigene dataset (18S/5.8S/28S rDNA/RPB2/TEF1) revealed Exobasidium rhododendri (Exobasidiales) as the closest relative of Ceraceosorus, both clustering together with Entyloma calendulae (Entylomatales), indicating affinities to the Exobasidiomycetes. This phylogenetic placement is in agreement with ultrastructural characteristics (presence of local interaction zone and interaction apparatus) reported for the Ceraceosorales, Entylomatales, and Exobasidiales.  相似文献   

12.
The plastid genome regions of two intergenic spacers, psbA–trnH and trnL–trnF, were sequenced to study the nucleotide diversity and phylogenetic relationships among Gladiolus cultivars. Nucleotide diversity of psbA–trnH region was higher than trnL–trnF region of chloroplast. We employed Bayesian, maximum parsimony (MP) and neighbour-joining (NJ) approaches for phylogenetic analysis of Gladiolus and related taxa using combined datasets from chloroplast genome. The psbA–trnH and trnL–trnF intergenic spacers of Gladiolus and related taxa-like Babiana, Chasmanthe, Crocus, Iris, Moraea, Sisyrinchium, Sparaxis and two out group species (Hymenocallis littoralis and Asphodeline lutea) were used in the present investigation. Results showed that subfamily Iridoideae have sister lineage with subfamily Ixioideae and Crocoideae. H. littoralis and A. lutea were separately attached at the base of tree as the diverging Iridaceae relative’s lineage. Present study revealed that psbA–trnH region are useful in addressing questions of phylogenetic relationships among the Gladiolus cultivars, as these intergenic spacers are more variable and have more phylogenetically informative sites than the trnL–trnF spacer, and therefore, are suitable for phylogenetic comparison on a lower taxonomic level. Gladiolus cultivars are extensively used as an ornamental crop and showed high potential in floriculture trade. Gladiolus cultivation still needs to generate new cultivars with stable phenotypes. Moreover, one of the most popular methods for generating new cultivars is hybridization. Hence, information on phylogenetic relationships among cultivars could be useful for hybridization programmes for further improvement of the crop.  相似文献   

13.
Members of the sea anemone genus Anthopleura are familiar constituents of rocky intertidal communities. Despite its familiarity and the number of studies that use its members to understand ecological or biological phenomena, the diversity and phylogeny of this group are poorly understood. Many of the taxonomic and phylogenetic problems stem from problems with the documentation and interpretation of acrorhagi and verrucae, the two features that are used to recognize members of Anthopleura. These anatomical features have a broad distribution within the superfamily Actinioidea, and their occurrence and exclusivity are not clear. We use DNA sequences from the nucleus and mitochondrion and cladistic analysis of verrucae and acrorhagi to test the monophyly of Anthopleura and to evaluate the pattern of distribution of acrorhagi and verrucae. We find that Anthopleura is paraphyletic: although species of the genus cluster together, some groups also include members of genera like Bunodosoma, Aulactinia, Oulactis, and Actinia. This paraphyly is explained in part by the discovery that acrorhagi and verrucae are pleisiomorphic for the subset of Actinioidea studied.  相似文献   

14.
Pinus massoniana is one of the important afforestation and pioneer tree species, which is widely distribute in southern China. Chloroplast simple sequence repeat markers (cpSSRs) have been widely used in studies of tree genetics, phylogenetic and breeding. We sequenced the whole chloroplast genome sequences of P. massoniana using PCR and Sanger sequencing. A total of 71 cpSSRs were identified, among which mononucleotide repeats were predominant (70.42%). Seventeen primer pairs were developed and amplification tests were conducted with 15 P. massoniana individuals. Also, cross-species amplification tests were conducted among 15 individuals per Pinus species, including P. elliottii, P. bungeana, P. armandii, P. caribaea, P. tabulaeformis, P. taiwanensis and P. yunnanensis which revealed polymorphic information content ranging from 0.2 to 0.8 and average of haploid diversity (h) ranging from 0.29 to 0.63. In addition, the polymorphic cpSSRs were useful in distinguishing the sampled pine species, and could be powerful tool in phylogenetic studies.  相似文献   

15.
As observed in other self-incompatible species in the Pyrinae subtribe, loquat (Eriobotrya japonica) demonstrates gametophytic self-incompatibility that is controlled by the S-locus, which encodes a polymorphic stylar ribonuclease (S-RNase). This allows the female reproductive organ (style) to recognize and reject the pollen from individuals with the same S-alleles, but allows the pollen from individuals with different S-alleles to effect fertilization. The S-genotype is therefore an important consideration in breeding strategies and orchard management. In an attempt to optimize the selection of parental lines in loquat production, the S-RNase alleles of 35 loquat cultivars and their 26 progeny, as well as five wild loquat species, were identified and characterized in this study. The best pollinizer cultivar combinations were also explored. A total of 28 S-alleles were detected, 21 of which constituted novel S-RNase alleles. The S-haplotypes S2 and S6 were the most frequent, followed by S 29 , S 31 , S 5 , S 24 , S 28 , S 33 , S 34 , S 32 , and S 15 , while the rare alleles S 1 , S 9 , S 14 , S 16 , S 17 , S 18 , S 19 , S 20 , S 21 , S 22 , S 23 , S 27 , and S 35 were only observed in one of the accessions tested. Moreover, the S-genotypes of five wild loquat species (E. prinoides, E. bengalensis, E. prinoides var. dadunensis, E. deflexa, and E. japonica) are reported here for the first time. The results will not only facilitate the selection of suitable pollinators for optimal orchard management, but could also encourage the crossbreeding of wild loquat species to enhance the genetic diversity of loquat cultivars.  相似文献   

16.
17.
Species in Plectosphaerella are well known as pathogens of several plant species causing fruit, root and collar rot and collapse. In an investigation of endophytic fungi associated with cucurbit plants in China, we isolated 77 strains belonging to the genus Plectosphaerella. To identify the isolated strains, we collected the type or reference strains of all currently accepted species in Plectosphaerella except P. oratosquillae and conducted a phylogenetic analysis. Phylogenetic analysis of the partial 28S rDNA sequences showed that all species in Plectosphaerella were located in one clade of Plectosphaerellaceae. Based on multi-locus phylogenetic analysis of the ITS, CaM, EF1, TUB and morphological characteristics, all species in Plectosphaerella were well separated. Three endophytic strains from stems of Cucurbita moschata, Citrullus lanatus and Cucumis melo from North China were assigned to a new species described as P. sinensis in this paper. The new species differs morphologically from other Plectosphaerella species by irregular chlamydospores, and the dimensions of phialides and conidia. The other endophytic strains from several cucurbit plants were identified as P. cucumerina.  相似文献   

18.
19.
Limonium vulgare and related species form a complex group, but until now cytological and genetic studies have been based on single species and specific geographical areas. We investigated genome size, karyological and genetic diversity in samples from Western Mediterranean and evaluated the phylogenetic relationships among the species of this complex. Genome size was assessed using flow cytometry on samples from natural populations of L. vulgare, L. maritimum and L. narbonense. Chromosome counts were conducted in plants obtained from seeds collected in the field. The internal transcribed spacer ITS1 of the nuclear rDNAs was used to assess ITS polymorphisms as well as the phylogenetic relationships within the L. vulgare complex. Our analyses showed that all species were tetraploid, with the chromosome number of L. maritimum being presented here for the first time. Significant differences were observed in genome size, with L. narbonense having lower genome sizes than the other two species, and possible aneuploids being detected. Ten new ITS sequences from L. vulgare, L. narbonense and L. maritimum were provided. Most species’ populations showed unique ribotypes, and L. narbonense has the highest ribotype diversity. One of the L. maritimum populations presented a closer genetic relationship with L. vulgare, whereas the other two seemed to be more related with L. narbonense. Phylogenetic analyses confirmed that L. vulgare and L. narbonense form a monophyletic group, sister to the remaining Limonium species. Our results put into evidence that the studied species may represent a relatively early stage of divergence.  相似文献   

20.
The campo rupestre sensu lato is among the most species-rich vegetation in the world, harbouring a high proportion of endemic species. We aimed to identify the processes that could generate a high level of phylogenetic diversity (PD) in campo rupestre for woody species and point out biodiversity hotspot areas which may provide additional information for conservation planning. We compiled a database of 2049 woody species from 185 community inventories. We calculated the evolutionary history using species richness (SR), PD, mean pairwise phylogenetic distance between species (MPD), the mean nearest taxon distance (MNTD) and their equivalents standardised (ses.PDss, ses.MPD, ses.MNTD), evolutionary distinctiveness (ED), and biogeographically weighted evolutionary distinctiveness (BED). Cloud dwarf-forests had the highest SR, PD, MPD and ses.MPD and lowest MNTD, while rupestrian cerrado presented the highest ses.PD and ses.MNTD. All areas are important for conservation, but the intersections between the hotspots should receive special attention in future conservation actions. The grids identified as hotspots by three or more metrics were localized mainly in Espinhaço Range in Minas Gerais State and a further expansion of protected areas is required. Moreover, the intersections between the hotspots obtained by mean ED and ses.PD are concentrated in the rocky dwarf forest and rupestrian cerrado, with considerable conservation gaps. The degree of protection of campo rupestre was low with unprotected areas comprising 56% of the species. Our results show an urgent need for increasing protected areas of campo rupestre in order to avoid the loss of valuable, endemic species with unique evolutionary history.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号