scholarly journals Nematodes as evolutionary commuters between marine, freshwater and terrestrial habitats

2019 ◽  
Vol 128 (3) ◽  
pp. 756-767 ◽  
Author(s):  
Martijn Holterman ◽  
Michaela Schratzberger ◽  
Johannes Helder
Keyword(s):  
Dna Sequences ◽  
Terrestrial Ecosystems ◽  
Small Subunit ◽  
Habitat Associations ◽  
Marine Systems ◽  
Rdna Sequences ◽  
Ecological Flexibility ◽  
Terrestrial Habitats ◽  
Nematode Cuticle ◽  
Small Subunit Ribosomal Dna

Abstract Nematodes are the only major metazoan group which is persistently abundant and diverse across marine, freshwater and terrestrial ecosystems. This could be the result of a few major habitat transitions followed by extensive diversification, or numerous habitat transitions followed by moderate diversification. To pinpoint habitat transitions, we superposed nematode habitat associations on an available phylum-wide phylogenetic tree based on small subunit ribosomal DNA sequences (≈2730 SSU rDNA sequences covering ≈1750 nematode taxa). Our analysis revealed at least 30 major habitat transitions within the phylum Nematoda. These transitions as well as their directionality were unevenly spread over the 12 major clades. Most transitions reside in Clades 1–6, and these transitions are bidirectional. Members of Clades 8–12 showed five full transitions, and these took place exclusively from terrestrial to marine systems. We relate our results to the distinct secretory–excretory systems in Clades 1–6 and Clades 8–12, as well as to differences in water permeability of the nematode cuticle. Hence, the phylum Nematoda is characterized by a relatively large number of habitat transitions followed by moderate diversification. The identification of multiple habitat transitions at a low taxonomic level will facilitate future investigations into the mechanisms underlying this unusual ecological flexibility.

A phylogenetic study of the Micarea prasina group shows that Micarea micrococca includes three distinct lineages

2009 ◽  
Vol 42 (1) ◽  
pp. 7-21 ◽  
Author(s):  
Paweł CZARNOTA ◽  
Beata GUZOW-KRZEMIŃSKA
Keyword(s):  
Maximum Likelihood ◽  
Ribosomal Dna ◽  
Dna Sequences ◽  
Maximum Parsimony ◽  
Small Subunit ◽  
Sister Species ◽  
Phylogenetic Study ◽  
Rdna Sequences ◽  
Small Subunit Ribosomal Dna

AbstractThe phylogeny of the Micarea prasina group was investigated using mitochondrial small subunit ribosomal DNA sequences from 14 taxa representing this group, four other members of the genus Micarea, and Psilolechia lucida as an outgroup. A total of 31 new mtSSU rDNA sequences were generated, including 10 from the M. micrococca complex. Bayesian, maximum parsimony (MP) and maximum likelihood (ML) methods were used to analyse the data. The results show that M. micrococca is not monophyletic and forms three strongly supported lineages: 1) M. micrococca s. str., 2) M. byssacea (Th. Fr.) Czarnota, Guzow-Krzemińska & Coppins comb. nov., and 3) a putative taxon that requires further studies. Micarea viridileprosa is a sister species to M. micrococca s. str. and the recently described M. nowakii is a sister species to M. prasina s. str. The placement of M. tomentosa within the M. prasina group is confirmed. Micarea hedlundii appears to be more closely related to the M. micrococca complex than M. prasina s. str. Descriptions, illustrations, taxonomic remarks, distribution and habitat data for M. micrococca s. str. and M. byssacea are provided. A lectotype for Biatora byssacea Hampe non Zwackh and a neotype for Catillaria prasina β [var.] byssacea are selected.

Small-subunit rDNA sequences from representatives of selected families of the Gigartinales and Rhodymeniales (Rhodophyta). 3. Delineating the Gigartinales sensu stricto

2004 ◽  
Vol 82 (1) ◽  
pp. 43-74 ◽  
Author(s):  
Gary W Saunders ◽  
Anthony Chiovitti ◽  
Gerald T Kraft
Keyword(s):  
Ribosomal Dna ◽  
Dna Sequences ◽  
Family Relationships ◽  
Small Subunit ◽  
Sensu Stricto ◽  
Rdna Sequences ◽  
Small Subunit Rdna ◽  
First Time ◽  
Small Subunit Ribosomal Dna ◽  
Ordinal Level

Nuclear small-subunit ribosomal DNA sequences were determined for 65 members of the Gigartinales and related orders. With representatives of 15 families of the Gigartinales sensu Kraft and Robins included for the first time, our alignment now includes members of all but two of the ca. 40 families. Our data continue to support ordinal status for the Plocamiales, to which we provisionally transfer the Pseudoanemoniaceae and Sarcodiaceae. The Halymeniales is retained at the ordinal level and consists of the Halymeniaceae (including the Corynomorphaceae), Sebdeniaceae, and Tsengiaceae. In the Halymeniaceae, Grateloupia intestinalis is only distantly related to the type species, Grateloupia filicina, but is closely affiliated with the genus Polyopes. The Nemastomatales is composed of the Nemastomataceae and Schizymeniaceae. The Acrosymphytaceae (now including Schimmelmannia, formerly of the Gloiosiphoniaceae) and the Calosipho niaceae (represented by Schmitzia) have unresolved affinities and are considered as incertae sedis among lineage 4 orders. We consider the Gigartinales sensu stricto to include 29 families, although many contain only one or a few genera and mergers will probably result following further investigation. Although the small-subunit ribosomal DNA was generally too conservative to resolve family relationships within the Gigartinales sensu stricto, a few key conclusions are supported. The Hypneaceae, questionably distinct from the Cystocloniaceae on anatomical grounds, is now subsumed into the latter family. As recently suggested, the Wurdemanniaceae should be incorporated into the Solieriaceae, but the latter should not be merged with the Areschougiaceae. The Corynocystaceae Kraft, fam. nov., is described and added to the Gigartinales sensu stricto.Key words: Corynocystaceae, Cryptonemiales, Florideophyceae, Gigartinales, Rhodymeniales, systematics.

scholarly journals Sequences of psychrophilic fungi amplified from glacier-preserved ascolichens

2000 ◽  
Vol 78 (11) ◽  
pp. 1450-1459 ◽  
Author(s):  
Paula T DePriest ◽  
Natalia V Ivanova ◽  
Dianne Fahselt ◽  
Vagn Alstrup ◽  
Andrea Gargas
Keyword(s):  
Phylogenetic Analysis ◽  
Ribosomal Dna ◽  
Dna Sequences ◽  
Large Subunit ◽  
Ice Core ◽  
Small Subunit ◽  
Rdna Sequences ◽  
Three Samples ◽  
Tyrolean Iceman ◽  
Small Subunit Ribosomal Dna

Ribosomal DNA sequences were amplified from subfossils of the ascolichen Umbilicaria cylindrica (L.) Delise ex Duby collected at the ablating edges of Greenland glaciers. Surprisingly, phylogenetic analysis indicated that the amplified rDNA sequences were not closely related to those of the lichen-forming fungus but rather represented two groups of psychrophilic basidiomycetes (orders Cystofilobasidiales and Sporidiales) and one group of ascomycetes (order Leotiales). Two of these groups, the Sporidiales and the Leotiales, include other fungi previously detected in DNA extracted from the grass clothing of the Tyrolean Iceman desiccated and frozen for over 3000 years and also in 2000- and 4000-year-old ice core samples from northern Greenland. Large subunit ribosomal DNA sequences representing the group Cystofilobasidiales were nearly identical to those of the basidioyeast saprobe Mrakia frigida. The adjacent internal transcribed spacer sequence was more than 98% similar to those from three samples of U. cylindrica from different sites that had been subjected to ice burial for various lengths of time, suggesting they also were Mrakia sequences. Although ancient contamination of multiple U. cylindrica specimens with fungi such as Mrakia cannot be ruled out, it is more probable that saprobic colonization of the subfossil tissues by psychrophilic fungi proceeded during recent ice melt.Key words: ancient DNA, small subunit ribosomal DNA, 18S ribosomal DNA, phylogenetic analysis, psychrophilic fungi, lichen-forming fungi.

Systematic status of Campydora Cobb, 1920 (Nematoda: Campydorina)

Nematology ◽  
2003 ◽  
Vol 5 (5) ◽  
pp. 699-711 ◽  
Author(s):  
Peter Mullin ◽  
Timothy Harris ◽  
Thomas Powers
Keyword(s):  
Maximum Likelihood ◽  
Ribosomal Dna ◽  
Dna Sequences ◽  
Maximum Parsimony ◽  
Phylogenetic Analyses ◽  
Small Subunit ◽  
Systematic Position ◽  
Nominal Species ◽  
Competing Hypotheses ◽  
Small Subunit Ribosomal Dna

AbstractThe systematic position of Campydora Cobb, 1920, which possesses many unique morphological features, especially in pharyngeal structure and stomatal armature, has long been a matter of uncertainty with the 'position of the Campydorinae' (containing only Campydora) being questionable. A review of the morphology of C. demonstrans, the only nominal species of Campydora concluded that the species warranted placement as the sole member of a monotypic suborder, Campydorina, in the order Dorylaimida. Others placed Campydorina in the order Enoplida. We conducted phylogenetic analyses, using 18s small subunit ribosomal DNA sequences generated from a number of taxa in the subclasses Enoplia and Dorylaimia, to evaluate these competing hypotheses. Although precise taxonomic placement of the genus Campydora and the identity of its closest living relatives is in need of further investigation, our analyses, under maximum parsimony, distance, and maximum likelihood criteria, unambiguously indicate that Campydora shares a common, more recent, ancestry with genera such as Alaimus, Pontonema, Tripyla and Ironus (Enoplida), rather than with any members of Dorylaimida, Mononchida or Triplonchida.

On the phylogeny of Ophiostoma, Ceratocystis s.s., and Microascus, and relationships within Ophiostoma based on partial ribosomal DNA sequences

1993 ◽  
Vol 71 (9) ◽  
pp. 1249-1265 ◽  
Author(s):  
G. Hausner ◽  
J. Reid ◽  
G. R. Klassen
Keyword(s):  
Dna Sequences ◽  
Sequence Data ◽  
Large Subunit ◽  
Small Subunit ◽  
Data Set ◽  
Rdna Sequences ◽  
Morphological Criteria ◽  
Small Subunit Rdna ◽  
Rdna Sequence Data ◽  
Large Subunit Rdna

Phylogenetic analysis of partial rDNA sequences suggests that Ophiostoma should remain the sole genus of the Ophiostomataceae, and this should be the sole family within the Ophiostomatales, whereas Ceratocystis s.s. would be best disposed within the Microascales. Although morphological criteria suggest that the genus Ophiostoma is heterogeneous, analysis of partial small subunit rDNA sequence data shows that Ophiostoma (excluding O. roraimense) represents a monophyletic taxon. Analysis of a partial large subunit rDNA data set, which included sequences from 55 species assignable to Ophiostoma, failed to support the strict subdivision of the genus based on either ascospore characters or the nature of the anamorph. Key words: Ceratocystis, Microascus, Ophiostoma, partial rDNA sequences, phylogeny.

Phylogeny of the Micareaceae inferred from nrSSU DNA sequences

2004 ◽  
Vol 36 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Heidi L. ANDERSEN ◽  
Stefan EKMAN
Keyword(s):  
Bayesian Inference ◽  
Maximum Likelihood ◽  
Dna Sequences ◽  
Phylogenetic Analyses ◽  
Sister Group ◽  
Small Subunit ◽  
Sensu Stricto ◽  
Confidence Set ◽  
Tree Topologies ◽  
Small Subunit Ribosomal Dna

The phylogeny of the Micareaceae and the genus Micarea Fr. was studied using 39 nuclear small subunit ribosomal DNA sequences. Phylogenetic analyses were carried out using maximum parsimony, maximum likelihood, and Bayesian inference. A confidence set of trees was estimated using expected likelihood weights to investigate a series of hypotheses of monophyly. Tree topologies were very similar between methods and differed only in the placement of a few poorly supported branches. The results indicate that the Micareaceae in its current circumscription belongs in the Lecanorales, but that it is not monophyletic. Psilolechia, Micarea with a ‘non-micareoid’ photobiont, Micarea sensu stricto and Byssoloma form a paraphyletic grade in this study. Micarea sensu stricto and Byssoloma (Pilocarpaceae) form a strongly supported monophyletic group, which constitutes the sister group to the Bacidiaceae. Scoliciosporum A. Massal has sometimes been considered close to Micarea, but no support was found for that hypothesis.

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