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 15 毫秒
1.
The genus Pseudochlorodesmis (Bryopsidales) is composed of diminutive siphons of extreme morphological simplicity. The discovery of Pseudochlorodesmis‐like juveniles in more complex Bryopsidales (e.g., the Halimeda microthallus stage) jeopardized the recognition of this genus. Confronted with this uncertainty, taxonomists transferred many simple siphons into a new genus, Siphonogramen. In this study, we used a multimarker approach to clarify the phylogenetic and taxonomic affinities of the Pseudochlorodesmis‐Siphonogramen (PS) complex within the more morphologically complex bryopsidalean taxa. Our analyses reveal a new layer of diversity largely distinct from the lineages containing the structurally complex genera. The PS complex shows profound cryptic diversity exceeding the family level. We discuss a potential link between thallus complexity and the prevalence and profundity of cryptic diversity. For taxonomic simplicity and as a first step toward clarifying the taxonomy of these simple siphons, we propose to maintain Pseudochlorodesmis as a form genus and subsume Siphonogramen and Botryodesmis therein.  相似文献   

2.
Ranunculaceae are a nearly cosmopolitan plant family with the highest diversity in northern temperate regions and with relatively few representatives in the tropics. As a result of their position among the early diverging eudicots and their horticultural value, the family is of great phylogenetic and taxonomic interest. Despite this, many genera remain poorly sampled in phylogenetic studies and taxonomic problems persist. In this study, we aim to clarify the infrageneric relationships of Clematis by greatly improving taxon sampling and including most of the relevant subgeneric and sectional types in a simultaneous dynamic optimization of phenotypic and molecular data. We also investigate how well the available data support the hypothesis of phylogenetic relationships in the family. At the family level, all five currently accepted subfamilies are resolved as monophyletic. Our analyses strongly imply that Anemone s.l. is a grade with respect to the Anemoclema Clematis clade. This questions the recent sinking of well‐established genera, including Hepatica, Knowltonia and Pulsatilla, into Anemone. In Clematis, 12 clades conceptually matching the proposed sectional division of the genus were found. The taxonomic composition of these clades often disagrees with previous classifications. Phylogenetic relationships between the section‐level clades remain highly unstable and poorly supported and, although some patterns are emerging, none of the proposed subgenera is in evidence. The traditionally recognized and horticulturally significant section Viorna is both nomenclaturally invalid and phylogenetically unsupported. Several other commonly used sections are likewise unjustified. Our results provide a phylogenetic background for a natural section‐level classification of Clematis.  相似文献   

3.
Although Tropicoperdix has been considered to be either a full genus or a species complex within the Phasianid genus Arborophila (hill partridges), there is long‐standing uncertainty regarding the degree of difference that warrants generic separation, including reported anatomical cranial differences. In addition, the intra‐generic taxonomy remains under dispute. Most studies hypothesize that Tropicoperdix comprises three species, while others postulate from one to four species. However, no molecular study has been performed to clarify the systematic and taxonomic uncertainties surrounding Tropicoperdix. In the present study, we performed a series of molecular phylogenetic analyses of Tropicoperdix and Arborophila taxa based on two mitochondrial genes and five nuclear introns. All the results are consistent with the finding that Tropicoperdix and Arborophila are phylogenetically distinct and distant genera, although the precise phylogenetic position of Tropicoperdix remains undetermined. Retrospective examination of external characteristics also supports the generic separation, as well as providing evidence of remarkable multiple character convergence. We propose that Tropicoperdix comprises at least two full species based on mitochondrial data obtained from museum specimens by using a next‐generation sequencing method. © 2015 The Linnean Society of London  相似文献   

4.
卢永彬  黄俞淞  许为斌  黄洁  刘演  向春雷  张强 《广西植物》2017,37(10):1227-1239
石山苣苔属(苦苣苔科)约30种,主要分布于我国南部的石灰岩地区.目前该属已知物种数虽少但花形态极其多样,是该科中分类最为困难的类群之一.基于分子证据,其它8个属中花形态迥异的一些物种被并入石山苣苔属.然而,该属花形态的演化趋势缺乏系统性的研究,传统分类对属的界定与分子系统学研究结果相矛盾的原因,以及是否有形态特征支持新界定的石山苣苔属还不清楚.该研究中,总共编码了19种石山苣苔属植物和9种报春苣苔属植物的35个形态特征,其中包括26个花部形态特征,在分子系统树上追踪了它们的演化路径.结果表明:无论属内还是属间,多数花部形态特征,尤其以往属的分类界定特征,在演化过程中变化频繁且发生了高度同塑性演化,这是导致传统形态分类不自然的关键因素.此外,在观察研究的所有特征中,花丝和柱头的差异可能在石山苣苔属植物共同祖先中经历了演变,或可用于区分石山苣苔属与其姐妹报春苣苔属的大多数种类.因此,在苦苣苔科植物的分类学研究中应当慎用这些花部性状作为分类依据,而且应对形态特征进行广泛地观察研究,在密集的取样和分辨率更高、更可靠的系统树上追踪它们的演化规律.更为重要的是,需要进一步研究导致复杂形态性状演化的内在分子调控机理和外在的自然选择动力,最终更加深入地理解石山苣苔属等典型喀斯特植物的演化过程和机理.  相似文献   

5.
The globally distributed avian family Motacillidae consists of five to seven genera (Anthus, Dendronanthus, Tmetothylacus, Macronyx and Motacilla, and depending on the taxonomy followed, Amaurocichla and Madanga) and 66–68 recognized species, of which 32 species in four genera occur in sub‐Saharan Africa. The taxonomy of the Motacillidae has been contentious, with variable numbers of genera, species and subspecies proposed and some studies suggesting greater taxonomic diversity than currently recognized (five genera and 67 species). Using one nuclear (Mb) and two mitochondrial (cyt b and CO1) gene regions amplified from DNA extracted from contemporary and museum specimens, we investigated the taxonomic status of 56 of the currently recognized motacillid species and present the most taxonomically complete and expanded phylogeny of this family to date. Our results suggest that the family comprises six clades broadly reflecting continental distributions: sub‐Saharan Africa (two clades), the New World (one clade), Palaearctic (one clade), a widespread large‐bodied Anthus clade, and a sixth widespread genus, Motacilla. Within the Afrotropical region, our phylogeny further supports recognition of Wood Pipit Anthus nyassae as a valid species, and the treatment of Long‐tailed Pipit Anthus longicaudatus and Kimberley Pipit Anthus pseudosimilis as junior subjective synonyms of Buffy Pipit Anthus vaalensis and African Pipit Anthus cinnamomeus, respectively. As the disjunct populations of Long‐billed Pipit Anthus similis in southern and East Africa are genetically distinct and geographically separated, we propose a specific status for the southern African population under the earliest available name, Nicholson's Pipit Anthus nicholsoni. Further, as our analyses indicate that Yellow‐breasted Pipit Anthus chloris and Golden Pipit Tmetothylacus tenellus are both nested within the Macronyx longclaws, we propose transferring these species to the latter genus.  相似文献   

6.
Skeleton and musculature of valvae were examined in 19 species from the section Polyommatus (Lepidoptera, Lycaenidae) revised by Bálint and Johnson (1997). Functional organization of male genitalia in the section Polyommatus was shown to be relatively constant. Significant interspecific variation of the skeleton and muscles was found only in the structure of valvae. During their evolution, the valvae became elongated, the costal torsion and longitudinal medial fold appeared on their medial wall, the subcostal groove was formed, and the intravalval muscle differentiated into two muscles forming a chiasma. This muscular chiasma was formed at least twice in the evolution of the group, in Polyommatus Latreille, 1804 + Aricia [Reichenbach], 1819 and in Plebeius Kluk, 1802. The genus Chilades Moore, [1881] is the least advanced as concerns the functional organization of the valvae. The genera Polyommatus and Aricia are the most advanced and constitute a sister pair. The intermediate position is occupied by Plebeius Kluk, 1802 and probably Madeleinea Bálint, 1993. The genus Albulina Tutt, 1809 is a compound taxon, its species occupying an intermediate position between Polyommatus and Aricia on the one hand, and Plebeius on the other hand. With a sole exception, they are characterized by a plesiomorphic state of the valval musculature that does not allow their mutual phylogenetic relations to be evaluated consistently. The only examined species of the genus Agriades Hübner, [1819], A. glandon (De Prunner, 1798), also possesses undifferentiated musculature, but according to the characters of the vaginal area, its females are close to the branch Polyommatus + Aricia.  相似文献   

7.
Species in the genus Bothrops s. l. are extraordinarily variable in ecology and geography, compared with other genera in the subfamily Crotalinae. In contrast to the trend of splitting large and variable groups into smaller, more ecologically and phenotypically cohesive genera, the genus Bothrops has remained speciose. In addition, previous phylogenetic analyses have found Bothrops to be paraphyletic with respect to the genus Bothriopsis. Taxonomic arguments exist for synonymizing Bothriopsis with Bothrops, and for splitting Bothrops into smaller genera, but the greatest hindrance to taxonomic revision has been incomplete phylogenetic information. We present a phylogeny of Bothrops, Bothriopsis, and Bothrocophias based on 85 characters of morphology and 2343 bp of four mitochondrial gene regions, and with significantly greater taxonomic coverage than previous studies. The combined data provide improved support over independent datasets, and support the existence of discrete species groups within Bothrops. The monophyly and distinctness of these groups warrant recognition at the generic level, and we propose a new taxonomic arrangement to reflect these findings. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 617–640.  相似文献   

8.
Ivanova  E. P.  Mikhailov  V. V. 《Microbiology》2001,70(1):10-17
The taxonomic positions of the marine genera Alteromonas, Pseudoalteromonas, Idiomarina, and Colwellia within the gamma subclass of the class Proteobacteria were specified on the basis of their phenotypic, genotypic, and phylogenetic characteristics. Gram-negative aerobic bacteria of the genera Alteromonas, Pseudoalteromonas, and Idiomarina and facultatively anaerobic bacteria of the genus Colwellia were found to form a phylogenetic cluster with a 16S rRNA sequence homology of 90% or higher. The characteristics of these genera presented in this paper allow their reliable taxonomic identification. Based on the analysis of our experimental data and analyses available in the literature, we propose to combine the genera Alteromonas, Pseudoalteromonas, Idiomarina, and Colwellia into a new family, Alteromonadaceae fam. nov., with the type genus Alteromonas.  相似文献   

9.
The genera Elliptochloris and Pseudochlorella were erected for Chlorella‐like green algae producing two types of autospores and cell packages, respectively. Both genera are widely distributed in different soil habitats, either as free living or as photobionts of lichens. The species of these genera are often difficult to identify because of the high phenotypic plasticity and occasional lack of characteristic features. The taxonomic and nomenclatural status of these species, therefore, remains unclear. In this study, 34 strains were investigated using an integrative approach. Phylogenetic analyses demonstrated that the isolates belong to two independent lineages of the Trebouxiophyceae (Elliptochloris and Prasiola clades) and confirmed that the genera are not closely related. The comparison of morphology, molecular phylogeny, and analyses of secondary structures of SSU and ITS rDNA sequences revealed that all of the strains belong to three genera: Elliptochloris, Pseudochlorella, and Edaphochlorella. As a consequence of the taxonomic revisions, we propose two new combinations (Elliptochloris antarctica and Pseudochlorella signiensis) and validate Elliptochloris reniformis, which is invalidly described according to the International Code for Nomenclature (ICN), by designating a holotype. To reflect the high phenotypic plasticity of P. signiensis, two new varieties were described: P. signiensis var. magna and P. signiensis var. communis. Chlorella mirabilis was not closely related to any of these genera and was, therefore, transferred to the new genus Edaphochlorella. All of the taxonomic changes were highly supported by all phylogenetic analyses and were confirmed by the ITS‐2 Barcodes using the ITS‐2/CBC approach.  相似文献   

10.
Modern multilocus molecular techniques are a powerful tool in the detection and analysis of cryptic taxa. However, its shortcoming is that with allopatric populations it reveals phylogenetic lineages, not biological species. The increasing power of coalescent multilocus analysis leads to the situation in which nearly every geographically isolated or semi‐isolated population can be identified as a lineage and therefore raised to species rank. It leads to artificial taxonomic inflation and as a consequence creates an unnecessary burden on the conservation of biodiversity. To solve this problem, we suggest combining modern lineage delimitation techniques with the biological species concept. We discuss several explicit principles on how genetic markers can be used to detect cryptic entities that have properties of biological species (i.e. of actually or potentially reproductively isolated taxa). Using these principles we rearranged the taxonomy of the butterfly species close to Polyommatus (Agrodiaetus) ripartii. The subgenus Agrodiaetus is a model system in evolutionary research, but its taxonomy is poorly elaborated because, as a rule, most of its species are morphologically poorly differentiated. The taxon P. (A.) valiabadi has been supposed to be one of the few exceptions from this rule due to its accurately distinguishable wing pattern. We discovered that in fact traditionally recognized P. valiabadi is a triplet of cryptic species, strongly differentiated by their karyotypes and mitochondrial haplotypes.  相似文献   

11.
12.
Nuclear‐encoded small subunit rDNA, 1506 group I intron, and internal transcribed spacer sequences were obtained from 39 strains representing five core desmid genera, Staurastrum, Staurodesmus Teil., Cosmarium Corda ex Ralfs, Xanthidium Ehr. ex Ralfs, and Euastrum Ehr. ex Ralfs (Desmidiaceae, Zygnematophyceae), and used individually and concatenated to assess phylogenetic relationships between putatively allied members of the family. To identify positional homology between divergent noncoding sequences, secondary structure models were generated and their reliability assessed by screening the alignment for compensating base changes. The phylogeny based on coding and noncoding sequence comparisons confidently resolved a monophyletic core of the genus Staurastrum but also revealed the artificial nature of the traditional genus. Twenty distinct species representing a wide range of morphotypes of Staurastrum formed a strongly supported generic clade that was further split into three well‐resolved lineages. The phylogenetic relationships revealed within Staurastrum were in conflict with all previous formal or informal classifications of the genus. The genera Staurodesmus and Cosmarium were shown to be highly polyphyletic, and some morphologically similar taxa displayed high sequence divergence that exceeded generic boundaries. Apparently, the taxonomic significance of some morphological characters in Staurastrum and other desmid genera has been greatly overestimated.  相似文献   

13.
14.
The unpredictable and low cross-amplification success of microsatellite loci tested for congeneric amphibian species has mainly been explained by the size and complexity of amphibian genomes, but also by taxonomy that is inconsistent with phylogenetic relationships among taxa. Here, we tested whether the cross-amplification success of nine new and 11 published microsatellite loci cloned for an amphibian source species, the fire salamander (Salamandra salamandra), correlated with the genetic distance across all members of True Salamanders (genera Chioglossa, Lyciasalamandra, Mertensiella and Salamandra that form a monophyletic clade within the family of Salamandridae) serving as target species. Cross-amplification success varied strongly among the species and showed a highly significant negative relationship with genetic distance and amplification success. Even though lineages of S. salamandra and Lyciasalamndra have separated more than 30 Ma, a within genus amplification success rate of 65% was achieved for species of Lyciasalamandra thus demonstrating that an efficient cross-species amplification of microsatellite loci in amphibians is feasible even across large evolutionary distances. A decrease in genome size, on the other hand, paralleled also a decrease in amplified loci and therefore contradicted previous results and expectations that amplification success should increase with a decrease in genome size. However, in line with other studies, our comprehensive dataset clearly shows that cross-amplification success of microsatellite loci is well explained by phylogenetic divergence between species. As taxonomic classifications on the species and genus level do not necessarily mirror phylogenetic divergence between species, the pure belonging of species to the same taxonomic units (i.e. species or genus) might be less useful to predict cross-amplification success of microsatellite loci between such species.  相似文献   

15.
Some of the morphological characters used in Porifera taxonomy have often been shown to be inconsistent. In the present study, we tested the phylogenetic coherence of currently used taxonomic characters of the calcarean genus Clathrina. For this, 20 species of Clathrina and three other calcinean genera (Ascandra, Guancha, and Leucetta) were sequenced for the ITS and D2 region of the 28S ribosomal DNA. Maximum‐likelihood and maximum‐parsimony algorithms were used to reconstruct phylogenetic trees. Deep divergences were observed in our tree and Clathrina was shown to be paraphyletic. The major split in our topology showed a clear‐cut distinction between sponges with and without tetractine spicules. Moreover, a group of yellow‐coloured Clathrina was clearly separated from the remaining white‐coloured species. Our results show that the presence of diactines, water‐collecting tubes, the degree of cormus anastomosis, and actine shapes do not correlate with the major clades of the calcinean phylogeny. On the other hand, the presence of tripods, the absence of tetractines, and the presence of spines in the apical actine of tetractines seem to be good synapomorphies for clades in our tree. Our results demonstrate that skeleton characters can be reliably used in higher level taxonomy in Clathrinida. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 1026–1034.  相似文献   

16.
17.
The lizard genus Liolaemus and different clades within it have been the focus of several recent phylogenetic studies mainly based on morphology and mtDNA. Although there is general consensus for recognizing two clades (subgenera) within the genus, [Liolaemus (sensu stricto) and Eulaemus], phylogenetic relationships within each subgenus remain difficult to elucidate, given incomplete taxonomic sampling and large discordance between published studies. Here, new phylogenetic relationships for the Eulaemus subgenus are proposed based on the largest molecular data set ever used for this clade, which includes 188 individuals and 14 loci representing different parts of the genome (mtDNA, anonymous nuclear loci and nuclear protein‐coding loci). This data set was analysed using two species tree approaches (*beast and MDC). Levels of discordance among methods were found, and with previously published studies, but results are robust enough to propose new phylogenetic hypotheses for the Eulaemus clade. Specifically well‐resolved and well‐supported novel hypotheses are provided within the lineomaculatus section, and we formally recognize the zullyae clade, the sarmientoi clade and the hatcheri group. We also resolve species relationships within the montanus section, and particularly within the melanops series. We found discordance between mitochondrial and nuclear trees and discussed alternative hypotheses for the lineomaculatus and montanus sections, as well as the challenge in resolving phylogenetic relationships for large clades in general.  相似文献   

18.
19.
Arisaema has a long and complicated taxonomic history regarding its infrageneric classification. In the latest system, 14 sections were recognized, based on an unpublished, tentative phylogenetic analysis; in addition the type species and nomenclatural priority for each section were confirmed. Here, we present an updated, genus‐wide phylogenetic analysis, based on four plastid non‐coding regions (3′trnLtrnF, rpl20–5′rps12, psbBpsbH and rpoC2rps2) for > 150 accessions. The maximum parsimony and maximum likelihood phylogenetic analyses identified eight major clades and one branch with unique sequence variation, although the relationships were unclear due to a polytomy and weak support. In the phylogenetic trees, most of the sections proposed in the latest system were distinct and corresponded to the major clades, but some sections are not monophyletic. On the basis of the phylogenetic relationship: (1) A. schimperianum is treated as a member of section Arisaema, rather than section Tenuipistillata or section Sinarisaema; and (2) section Fimbriata, which was synonymised into section Attenuata in the latest system but is morphologically distinct from the other species, is redefined as a monotypic section. In conclusion, we recognize 15 sections of Arisaema and species‐level classifications are discussed in a phylogenetic context.  相似文献   

20.
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