排序方式: 共有38条查询结果,搜索用时 15 毫秒
1.
Acoel flatworms are small marine worms traditionally considered to belong to the phylum Platyhelminthes. However, molecular phylogenetic analyses suggest that acoels are not members of Platyhelminthes, but are rather extant members of the earliest diverging Bilateria. This result has been called into question, under suspicions of a long branch attraction (LBA) artefact. Here we re-examine this problem through a phylogenomic approach using 68 different protein-coding genes from the acoel Convoluta pulchra and 51 metazoan species belonging to 15 different phyla. We employ a mixture model, named CAT, previously found to overcome LBA artefacts where classical models fail. Our results unequivocally show that acoels are not part of the classically defined Platyhelminthes, making the latter polyphyletic. Moreover, they indicate a deuterostome affinity for acoels, potentially as a sister group to all deuterostomes, to Xenoturbellida, to Ambulacraria, or even to chordates. However, the weak support found for most deuterostome nodes, together with the very fast evolutionary rate of the acoel Convoluta pulchra, call for more data from slowly evolving acoels (or from its sister-group, the Nemertodermatida) to solve this challenging phylogenetic problem. 相似文献
2.
3.
4.
Eduard Solà Marta álvarez-Presas Cristina Frías-López D. Timothy J. Littlewood Julio Rozas Marta Riutort 《PloS one》2015,10(3)
Mitochondrial genomes (mitogenomes) are useful and relatively accessible sources of molecular data to explore and understand the evolutionary history and relationships of eukaryotic organisms across diverse taxonomic levels. The availability of complete mitogenomes from Platyhelminthes is limited; of the 40 or so published most are from parasitic flatworms (Neodermata). Here, we present the mitogenomes of two free-living flatworms (Tricladida): the complete genome of the freshwater species Crenobia alpina (Planariidae) and a nearly complete genome of the land planarian Obama sp. (Geoplanidae). Moreover, we have reanotated the published mitogenome of the species Dugesia japonica (Dugesiidae). This contribution almost doubles the total number of mtDNAs published for Tricladida, a species-rich group including model organisms and economically important invasive species. We took the opportunity to conduct comparative mitogenomic analyses between available free-living and selected parasitic flatworms in order to gain insights into the putative effect of life cycle on nucleotide composition through mutation and natural selection. Unexpectedly, we did not find any molecular hallmark of a selective relaxation in mitogenomes of parasitic flatworms; on the contrary, three out of the four studied free-living triclad mitogenomes exhibit higher A+T content and selective relaxation levels. Additionally, we provide new and valuable molecular data to develop markers for future phylogenetic studies on planariids and geoplanids. 相似文献
5.
The relative importance of the processes that generate and maintain biodiversity is a
major and controversial topic in evolutionary biology with large implications for
conservation management. The Atlantic Forest of Brazil, one of the world''s richest
biodiversity hot spots, is severely damaged by human activities. To formulate an efficient
conservation policy, a good understanding of spatial and temporal biodiversity patterns
and their underlying evolutionary mechanisms is required. With this aim, we performed a
comprehensive phylogeographic study using a low-dispersal organism, the land planarian
species Cephaloflexa bergi (Platyhelminthes, Tricladida). Analysing multi-locus
DNA sequence variation under the Approximate Bayesian Computation framework, we evaluated
two scenarios proposed to explain the diversity of Southern Atlantic Forest (SAF) region.
We found that most sampled localities harbour high levels of genetic diversity, with
lineages sharing common ancestors that predate the Pleistocene. Remarkably, we detected
the molecular hallmark of the isolation-by-distance effect and little evidence of a recent
colonization of SAF localities; nevertheless, some populations might result from very
recent secondary contacts. We conclude that extant SAF biodiversity originated and has
been shaped by complex interactions between ancient geological events and more recent
evolutionary processes, whereas Pleistocene climate changes had a minor influence in
generating present-day diversity. We also demonstrate that land planarians are an
advantageous biological model for making phylogeographic and, particularly, fine-scale
evolutionary inferences, and propose appropriate conservation policies. 相似文献
6.
Diversification and biogeographic history of the Western Palearctic freshwater flatworm genus Schmidtea (Tricladida: Dugesiidae), with a redescription of Schmidtea nova
下载免费PDF全文
![点击此处可从《Journal of Zoological Systematics and Evolutionary Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Laia Leria Ronald Sluys Marta Riutort 《Journal of Zoological Systematics and Evolutionary Research》2018,56(3):335-351
The freshwater flatworm genus Schmidtea is endemic in the Western Palearctic region, where it is represented by only four species, thus contrasting with the high species diversity of the closely related genus Dugesia within Europe. Although containing an important model species in developmental and regeneration research, viz. Schmidtea mediterranea, no evolutionary studies on the genus Schmidtea have been undertaken. For the first time, we present a well‐resolved molecular phylogenetic tree of the four species of the genus, inferred on the basis of two molecular markers, and provide also the first detailed morphological account of Schmidtea nova. The phylogenetic tree generated corroborates an earlier speciation hypothesis based on karyological data and points to chromosomal rearrangements as the main drivers of speciation in this genus. The high genetic divergence between the four species, in combination with previous dating studies and their current geographic distribution, suggests that Schmidtea could have originated in Laurasia but lost most of its diversity during the Oligocene. Thus, its present distribution pattern may be the result of the expansion of three of its four relictual species over Europe, probably after the Pleistocene glaciations. Our detailed morphological study of S. nova revealed that it shows a number of remarkable features: interconnected testis follicles, parovaria, an ejaculatory duct exiting into the primary as well as the secondary seminal vesicle by means of a nipple, and the wall of the distal section of the ejaculatory duct being sclerotic or chitinized. 相似文献
7.
Hidden diversity in forest soils: Characterization and comparison of terrestrial flatworm’s communities in two national parks in Spain
下载免费PDF全文
![点击此处可从《Ecology and evolution》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Terrestrial flatworms (Platyhelminthes, Tricladida, and Geoplanidae) belong to what is known as cryptic soil fauna of humid forests and are animals not easily found or captured in traps. Nonetheless, they have been demonstrated to be good indicators of the conservation status of their habitat as well as a good model to reconstruct the recent and old events affecting biodiversity. This is mainly due to their delicate constitution, their dependence on the integrity of their habitat, and their very low dispersal capacity. At present, little is known about their communities, except for some studies performed in Brazil. In this work, we analyze for the first time in Europe terrestrial flatworm communities. We have selected two protected areas belonging to the Red Española de Parques Nacionales. Our aims include performing a first study of the species richness and community structure for European terrestrial planarian species at regional and local scale. We evaluate the effect of type of forests in the community composition and flatworms’ abundance, but also have into account the phylogenetic framework (never considered in previous studies) analyzed based on molecular data. We find differences in the species composition among parks, with an astonishingly high diversity of endemic species in the Parque Nacional de Picos de Europa and an extremely low diversity of species in the Parque Nacional de Ordesa y Monte Perdido. These divergent patterns cannot be attributed to differences in physical variables, and in addition, the analyses of their phylogenetic relationships and, for a few species, their genetic structure, point to a more probable historical explanation. 相似文献
8.
Back in time: a new systematic proposal for the Bilateria 总被引:4,自引:0,他引:4
Baguñà J Martinez P Paps J Riutort M 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2008,363(1496):1481-1491
Conventional wisdom suggests that bilateral organisms arose from ancestors that were radially, rather than bilaterally, symmetrical and, therefore, had a single body axis and no mesoderm. The two main hypotheses on how this transformation took place consider either a simple organism akin to the planula larva of extant cnidarians or the acoel Platyhelminthes (planuloid-acoeloid theory), or a rather complex organism bearing several or most features of advanced coelomate bilaterians (archicoelomate theory). We report phylogenetic analyses of bilaterian metazoans using quantitative (ribosomal, nuclear and expressed sequence tag sequences) and qualitative (HOX cluster genes and microRNA sets) markers. The phylogenetic trees obtained corroborate the position of acoel and nemertodermatid flatworms as the earliest branching extant members of the Bilateria. Moreover, some acoelomate and pseudocoelomate clades appear as early branching lophotrochozoans and deuterostomes. These results strengthen the view that stem bilaterians were small, acoelomate/pseudocoelomate, benthic organisms derived from planuloid-like organisms. Because morphological and recent gene expression data suggest that cnidarians are actually bilateral, the origin of the last common bilaterian ancestor has to be put back in time earlier than the cnidarian-bilaterian split in the form of a planuloid animal. A new systematic scheme for the Bilateria that includes the Cnidaria is suggested and its main implications discussed. 相似文献
9.
Giribet G Rambla M Carranza S Baguñà J Riutort M Ribera C 《Molecular phylogenetics and evolution》1999,11(2):296-307
The phylogenetic relationships among the main evolutionary lines of the arachnid order Opiliones were investigated by means of molecular (complete 18S rDNA and the D3 region of the 28S rDNA genes) and morphological data sets. Equally and differentially weighted parsimony analyses of independent and combined data sets provide evidence for the monophyly of the Opiliones. In all the analyses, the internal relationships of the group coincide in the monophyly of the following main groups: Cyphophthalmi, Eupnoi Palpatores, Dyspnoi Palpatores, and Laniatores. The Cyphophthalmi are monophyletic and sister to a clade that includes all the remaining opilionid taxa (=Phalangida). Within the Phalangida the most supported hypothesis suggests that Palpatores are paraphyletic, as follows: (Eupnoi (Dyspnoi + Laniatores)), but the alternative hypothesis (Laniatores (Eupnoi + Dyspnoi)) is more parsimonious in some molecular data analyses. Relationships within the four main clades are also addressed. Evolution of some morphological characters is discussed, and plesiomorphic states of these characters are evaluated using molecular data outgroup polarization. Finally, Martens' hypothesis of opilionid evolution is assessed in relation to our results. 相似文献
10.
A molecular analysis of the phylogenetic position of the suborder Cavernicola within the Tricladida (Platyhelminthes), with the description of a new species of stygobiont flatworm from Benin
下载免费PDF全文
![点击此处可从《Zoological Journal of the Linnean Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Abdel Halim Harrath Lamjed Mansour Moïssou Lagnika Ronald Sluys Claude Boutin Saleh Alwasel Arnau Poch Marta Riutort 《Zoological Journal of the Linnean Society》2016,178(3):482-491
This paper presents a new species of cavernicolan planarian from the African continent, which enabled us to determine the position of the suborder Cavernicola within the order Tricladida on a molecular basis. A recent paper suggested a sister‐group relationship between Cavernicola and marine triclads. However, our work is the first molecular study to demonstrate unequivocally that the Cavernicola does not group with either the freshwater planarians or the land planarians, i.e. is not closely related to the suborder Continenticola, and corroborates the suggested sister‐group relationship with the marine triclads or Maricola. Two possible scenarios are proposed for the evolution of the Cavernicola from marine ancestors. The new species is assigned to the genus Novomitchellia and is characterized by the absence of eyes. Testicular follicles are numerous and only dorsal, extending from behind the ovaries to the posterior end of the body. The vasa deferentia separately penetrate the penis bulb and the seminal vesicle. The penis papilla is very short and blunt, and the penis bulb musculature is weak. A long and narrow copulatory bursa is situated behind the gonopore. The common oviduct is orientated perpendicularly to the short bursal canal. 相似文献