PubMed Health⌕ Search

Biomedical subjects

R Tiedemann

Publications and source records attributed to R Tiedemann.

At least 19 recordsLinked to original sources
PubMed2007

Adaptive radiation in African weakly electric fish (Teleostei: Mormyridae: Campylomormyrus): a combined molecular and morphological approach.

We combined multiple molecular markers and geometric morphometrics to revise the current taxonomy and to build a phylogenetic hypothesis for the African weakly electric fish genus Campylomormyrus. Genetic data (2039 bp DNA sequence of mitochondrial cytochrome b and nuclear S7 genes) on 106 specimens support the existence of at least six species occurring in sympatry. We were able to further confirm these species by microsatellite analysis at 16 unlinked nuclear loci and landmark-based morphometrics. We assigned them to nominal taxa by comparisons to type specimens of all Campylomormyrus species recognized so far. Additionally, we showed that the shape of the elongated trunk-like snout is the major source of morphological differentiation among them. This finding suggests that the radiation of this speciose genus might have been driven by adaptation to different food sources.

Adaptation, Biological↗
PubMed2005

Electrophysiological and molecular genetic evidence for sympatrically occuring cryptic species in African weakly electric fishes (Teleostei: Mormyridae: Campylomormyrus).

For two sympatric species of African weakly electric fish, Campylomormyrus tamandua and Campylomormyrus numenius, we monitored ontogenetic differentiation in electric organ discharge (EOD) and established a molecular phylogeny, based on 2222bp from cytochrome b, the S7 ribosomal protein gene, and four flanking regions of unlinked microsatellite loci. In C. tamandua, there is one common EOD type, regardless of age and sex, whereas in C. numenius we were able to identify three different male adult EOD waveform types, which emerged from a single common EOD observed in juveniles. Two of these EOD types formed well supported clades in our phylogenetic analysis. In an independent line of evidence, we were able to affirm the classification into three groups by microsatellite data. The correct assignment and the high pairwise F(ST) values support our hypothesis that these groups are reproductively isolated. We propose that in C. numenius there are cryptic species, hidden behind similar and, at least as juveniles, identical morphs.

Africa↗
PubMed2004

Molecular and cytogenetic evidence for cryptic speciation within a rare endemic Malagasy lemur, the Northern Sportive Lemur (Lepilemur septentrionalis).

Evolutionary relationships of different populations of the threatened malagasy lemur Lepilemur septentrionalis were assessed by sequence analysis of mitochondrial DNA (D-loop region and partial Cyt b gene). One hundred and fifty nine samples were collected from five main different localities in the northern part of Madagascar. We applied the phylogenetic species concept based on fixed diagnostic differences to determine the status of different geographical populations. No nucleotide site diagnoses Ankarana from Andrafiamena or Analamera. However, numerous fixed differences separate Sahafary from all other populations. These results were corroborated by phylogenetic trees. As previous cytogenetic studies, our molecular data suggest that two cryptic species of Lepilemur occur in the extreme north of Madagascar. This speciation is probably caused by chromosomal rearrangements in at least one of the evolutionary lineages. Our study comprises another striking example of how molecular genetic assay can detect phylogenetic discontinuities that are not reflected in traditional morphologically based taxonomies. Our study indicates that the Sahafary population is a hitherto undescribed endangered endemic species which urgently needs conservation efforts.

Animals↗
PubMed2004

Mitochondrial DNA and microsatellite variation in the eider duck (Somateria mollissima) indicate stepwise postglacial colonization of Europe and limited current long-distance dispersal.

To unravel the postglacial colonization history and the current intercolony dispersal in the common eider, Somateria mollissima, we analysed genetic variation at a part of the mitochondrial control region and five unlinked autosomal microsatellite loci in 175 eiders from 11 breeding colonies, covering the entire European distribution range of this species. As a result of extreme female philopatry, mitochondrial DNA differentiation is substantial both among local colonies and among distant geographical regions. Our study further corroborates the previous hypothesis of a single Pleistocene refugium for European eiders. A nested clade analysis on mitochondrial haplotypes suggests that (i) the Baltic Sea eider population is genetically closest to a presumably ancestral population and that (ii) the postglacial recolonization progressed in a stepwise fashion via the North Sea region and the Faroe Islands to Iceland. Current long-distance dispersal is limited. Differentiation among colonies is much less pronounced at microsatellite loci. The geographical pattern of this nuclear genetic variation is to a large extent explained by isolation by distance. As female dispersal is very limited, the geographical pattern of nuclear variation is probably explained by male-mediated gene flow among breeding colonies. Our study provides genetic evidence for the assumed prominent postglacial colonization route shaping the present terrestrial fauna of the North Atlantic islands Iceland and the Faroes. It suggests that this colonization had been a stepwise process originating in continental Europe. It is the first molecular study on eider duck populations covering their entire European distribution range.

Analysis of Variance↗
PubMed2002

The genetic structure of natural and reintroduced roe deer (Capreolus capreolus) populations in the Alps and central Italy, with reference to the mitochondrial DNA phylogeography of Europe.

The first hypervariable fragment (HVI) of the mitochondrial DNA control region was sequenced in 90 individuals of the European roe deer (Capreolus capreolus) from the Alps, central Italy and Spain. Pooling these data with 70 published sequences from several European regions, we were able to identify patterns of divergence within the Italian peninsula, and in Europe in general. The results we obtained can be summarized as follows. First, the genetic structure of European roe deer populations is substantial (PhiST values around 0.6). Second, the divergence between some central Italian populations, the Alpine group (which is genetically close to the French, the Spanish and the Norwegian samples) and the Eastern European populations seems to reflect Upper Pleistocene subdivisions, possibly related to three southern European refugia. Third, a different group of central Italian individuals probably diverged more recently from the Alpine group, and their attribution to the subspecies C. c. italicus does not appear justified. Fourth, the analysis of mitochondrial DNA in the roe deer can be used to identify recently reintroduced animals in the western Alps which clearly cluster within the Eastern European group, thus providing an important tool for conservation and management strategies for this species.

Animals↗
PubMed2000

Myzostomida: a link between trochozoans and flatworms?

Myzostomids are obligate symbiotic invertebrates associated with echinoderms with a fossil record that extends to the Ordovician period. Due to their long history as host-specific symbionts, myzostomids have acquired a unique anatomy that obscures their phylogenetic affinities to other metazoans: they are incompletely segmented, parenchymous, acoelomate organisms with chaetae and a trochophore larva. Today, they are most often classified within annelids either as an aberrant family of polychaetes or as a separate class. We inferred the phylogenetic position of the Myzostomida by analysing the DNA sequences of two slowly evolving nuclear genes: the small subunit ribosomal RNA and elongation factor-1alpha. All our analyses congruently indicated that myzostomids are not annelids but suggested instead that they are more closely related to flatworms than to any trochozoan taxon. These results, together with recent analyses of the myzostomidan ultrastructure, have significant implications for understanding the evolution of metazoan body plans, as major characters (segmentation, coeloms, chaetae and trochophore larvae) might have been independently lost or gained in different animal phyla.

Animals↗
PubMed2000

Higher impact of female than male migration on population structure in large mammals.

We simulated large mammal populations using an individual-based stochastic model under various sex-specific migration schemes and life history parameters from the blue whale and the Asian elephant. Our model predicts that genetic structure at nuclear loci is significantly more influenced by female than by male migration. We identified requisite comigration of mother and offspring during gravidity and lactation as the primary cause of this phenomenon. In addition, our model predicts that the common assumption that geographical patterns of mitochondrial DNA (mtDNA) could be translated into female migration rates (Nmf) will cause biased estimates of maternal gene flow when extensive male migration occurs and male mtDNA haplotypes are included in the analysis.

Animals↗
PubMed1992

[Neurogenic tumors of the trachea].

To date, 20 cases of solitary neurilemmoma and neurofibroma of the trachea have been reported. We report the symptoms, diagnosis and treatment of a neurilemmoma of the upper trachea in an 8-year-old girl. The presenting symptom is usually progressive stridor. Radiography, without contrast medium, and tomography confirm the diagnosis. The latter should take into account the possible mediastinal involvement by dumb-bell tumours. The tumours appear in all sections of the trachea but usually lie on the back wall. Endoscopy is not always necessary because it carries risks. For most tumours a tracheotomy provides adequate access, if necessary combined with endoscopy. If the tumour lies distally in the trachea a thoracic approach may be necessary: in the case of mediastinal involvement, it is obligatory.

Child↗
PubMed1981

[The acute purulent and the secretory otitis media. Problems of definition (author's transl)].

Without change we know the typical manifestation of the purulent infection of the middle-ear with its complications. Certainly, however, opposite to these cardinal forms there are plenty of them with a mixed, falsified and levelled manifestation. Concerning the acute purulent otitis today Fleischer differentiates the "typical", the "light and abortive", the "latent" and the "protracted" form. Respecting the secretory otitis media however, there has been no change of shape - but only an evident increase of morbidity accounting to the acute purulent infection of the middle ear. Microscopical and electron microscopical as well as immunological researches have essentially cleared up the pathogeny of the secretory otitis media. The same is valid for the special form of the blue ear drum, the idiopathic hemotympanum.

Acute Disease↗
PubMed1975

[Surgical management of sudden deafness (author's transl)].

The conservative treatment of idiopathic sudden deafness generally shows good results. There are, however, some cases resistant to therapy which may be treated surgically by vestibulotomy. Reports are made on personal experiences as well as those of other authors. Vestibulotomy is recommended for those patients in whom the possibilities of conservative therapy have been exhausted and severe hearing loss has occurred.

Adult↗