Search results for "Polytomy"
showing 5 items of 5 documents
Simultaneous speciation in the European high mountain flowering plant genus Facchinia (Minuartia s.l., Caryophyllaceae) revealed by genotyping-by-seq…
2017
Understanding the relative importance of different mechanisms of speciation in a given lineage requires fully resolved interspecific relationships. Using Facchinia, a genus of seven species centred in the European Alps, we explore whether the polytomy found by Sanger sequencing analyses of standard nuclear (ITS) and plastid markers (trnQ-rps16) is a hard or soft polytomy by substantially increasing the amount of DNA sequence data, generated by genotyping-by-sequencing. In comparison to 142 phylogenetically informative sites in the Sanger sequences the GBS sequences yielded 3363 phylogenetically informative sites after exclusion of apparently oversaturated SNPs. Maximum parsimony, maximum li…
The tangled cases of Deinogalerix (Late Miocene endemic erinaceid of Gargano) and Galericini (Eulipotyphla, Erinaceidae): a cladistic perspective.
2018
The Late Miocene giant erinaceid Deinogalerix from Scontrone and Gargano (Italy) is associated with many other vertebrates in deposits of a past island, the “Abruzzo-Apulia Platform”. At Gargano, Deinogalerix is accompanied by the moderately endemized Galericini Apulogalerix. This first extensive cladistic analysis is aimed at defining the relationships of Deinogalerix with characteristic members of the tribe Galericini. The analysis was performed on a matrix of 30 characters and 19 taxa and identified some smaller clades, nested within three major ones. The latter include: (i) a pentatomy of Galerix species, (ii) a polytomy of “transitional” Galerix–Parasorex species and (iii) a large clad…
Identity of the Calcarata species complex in Viola sect. Melanium (Violaceae)
2020
The Calcarata species complex in Viola sect. Melanium (Violaceae) is a group of species from Italy and neighbouring islands. The complex is of considerable evolutionary interest because several hypotheses about hybrid speciation within the group have been previously proposed. Because the Calcarata complex is not well characterized morphologically, we used 142 samples representing 92 (of c. 120) species of V. sect. Melanium plus three outgroup species. Nuclear ITS and ETS and plastid trnS–trnG intergenic spacer sequences were analysed to test the monophyly of the Calcarata complex and to infer relationships among the constituent species. Both nuclear and plastid sequences resulted in very li…
Recent mathematical approaches to reconstruct phylogenies: A chemosystematist's and botanist's view
1989
Some basic problems of mathematical phylogenetics are discussed. While algorithms regularly depend on the principle of parsimony, some features of phylogenesis interfere with that principle. Nonrandomness of the distribution of mutations as well as the inconstancy of the molecular clock in time and within a given sequence can bias the calculated relationships of closely related taxa. True comparability of sequences is difficult to establish, since this requires defining of homology of positions and of functions of amino acids as well. Parallelism and convergence can give rise to errors in establishing homology. Furthermore, they are difficult to be integrated into a consistent mathematical …
Cracking the nut: Geographical adjacency of sister taxa supports vicariance in a polytomic salamander clade in the absence of node support
2008
The urodelan genus Lyciasalamandra, which inhabits a relatively small area along the southern Turkish coast and some Aegean islands, provides an outstanding example of a diverse but phylogenetically unresolved taxon. Molecular trees contain a single basal polytomy that could be either soft or hard. We here use the information of nuclear (allozymes) and mitochondrial (fractions of the 16S rRNA and ATPase genes) datasets in combination with area relationships of lineages to resolve the phylogenetic relationships among Lyciasalamandra species in the absence of sufficient node support. We can show that neither random processes nor introgressive hybridization can be invoked to explain that the m…