1,721,014 research outputs found
Cytotaxonomic considerations on the sex chromosome variation observed within Acomys ngurui Verheyen et al. 2011 (Rodentia Muridae)
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The phylogenetic position of Lygodactylus angularis and the utility of using the 16S rDNA gene for delimiting species in Lygodactylus (Squamata, Gekkonidae)
Full text linkThe African genus Lygodactylus Gray, is composed of roughly 60 species of diurnal geckos that inhabit tropical and temperate Africa, Madagascar, and South America. In this study, we assessed the phylogenetic position of L. angularis, for which molecular data were so far lacking, by means of sequence analysis of the mitochondrial 16S rDNA gene. We also compared intraspecific vs. interspecific genetic divergences using an extended data set (34 species, 153 sequences), to determine whether a fragment of this gene can be useful for species identification and to reveal the possible existence of new cryptic species in the genus. The analysis placed L. angularis in a monophyletic group together with members of "fischeri" and "picturatus" groups. Nevertheless, the independence of the "angularis" lineage is supported by the high genetic divergence. Comparison of intraspecific vs. interspecific genetic distances highlights that, assuming an equal molecular rate of evolution among the studied species for the used gene, the threshold value useful for recognising a candidate new species can be tentatively placed at 7%. We identified four species that showed an intraspecific divergence higher than, or close to, the 7% threshold: L. capensis (8.7%), L. gutturalis (9.3%), L. madagascariensis (6.5%) and L. picturatus (8.1%). Moreover, two species, L. mombasicus and L. verticillatus, are paraphyletic in terms of gene genealogy. Thus, the study shows that a short fragment of the 16S rDNA gene can be an informative tool for species-level taxonomy in the genus Lygodactylus
5S ribosomal RNA genes in six species of Mediterranean grey mullets: Genomic organization and phylogenetic inference
No full textThis paper describes a study of the 5S ribosomal RNA genes (5S rDNA) in a group of 6 species belonging to 4 genera of Mugilidae. In these 6 species, the relatively short 5S rDNA repeat units, generated by PCR and ranging in size from 219 to 257 bp, show a high level of intragenomic homogeneity of both coding and spacer regions (NTS-I). Phylogenetic reconstructions based on this data set highlight the greater phylogenetic and genetic diversity of Mugil cephalus and Oedalechilus labeo compared with the genera Liza and Chelon. Comparative sequence analysis revealed significant conservation of the short 5S rDNA repeat units across Chelon and Liza. Moreover, a second size class of 5S rDNA repeat units, ranging from roughly 800 to 1100 bp, was produced in the Liza and Chelon samples. Only short 5S rDNA repeat units were found in M. cephalus and O. labeo. The sequences of the long 5S rDNA repeat units, obtained in Chelon labrosus and Liza ramada, differ owing to the presence of 2 large insertion/deletions (indels) in the spacers (NTS-II) and show considerable sequence identity with NTS-I spacers. Interspecific sequence variation of NTS-II spacers, excluding the indels, is low. Southern-blot hybridization patterns suggest an intermixed arrangement of short and long repeat units within a single chromosome locus. © 2007 NRC
Molecular and karyological homogeneity in Trachylepis striata (Peters 1844) and Trachylepis wahlbergii (Peters 1869) (Scincidae Reptilia).
No full textGeographical pattern of genetic variation in the Robertsonian system of Mus musculus domesticus in central Italy.
No full textMorphometric and genetic divergence in island and mainland populations of Anolis nebulosus (Squamata: Polychrotidae) from Jalisco (Mexico): an instance of insular gigantism
No full textThe clouded anole Anolis nebulosus (Squamata: Polychrotidae) is widespread on the Pacific coast of Mexico. The species also inhabits Don Panchito, a small islet located near the coast of the Chamela-Cuixmala Biosphere Reserve in the state of Jalisco. We studied the extent of intraspecific differences in morphology (absolute size and body proportions) and in mtDNA sequences (16S and NDH2) between the population living on the islet (N = 18 for morphometry; N = 12 for mtDNA) and the one on the facing mainland (N = 38 for morphometry; N = 16 for mtDNA). The individuals on the islet are larger than those on the mainland with little overlap in size for either males (islet: 52.79 +/- 1.82 mm; mainland: 40.96 +/- 2.99 mm) or females (islet: 46.18 +/- 3.24 mm; mainland 37.14 +/- 2.13 mm). The presence of insular gigantism, as here found in A. nebulosus, seems uncommon in the genus and could be explained as a combination of low predation pressure and higher intraspecific competition on the island. Moreover, we found that sexual dimorphism (SD) is higher in the island population than in the mainland one. The molecular analysis shows the absence of shared haplotypes between the island and mainland populations. Ten mtDNA haplotypes belonged to the mainland population and three to the island population. The shape of the minimum spanning network and of the mismatch distribution indicates a single colonization event. These molecular data indicate a certain degree of isolation of the island population notwithstanding its proximity to the coast. The morphological characteristics of the anoles on Don Panchito match with the expectation of the so-called " reversed island syndrome" theory, which predicts an increased body size and sexual dimorphism in lizards living on very small islands characterized by unpredictable environmental conditions
Mitochondrial DNA reveals different phylogeographic structures in the water shrews Neomys anomalus and N. fodiens (Insectivora: Soricidae) in Europe
No full textWe studied the intraspecific genetic variation of 17 Neomys anomalus (Cabrera, 1907) (eight localities) and 24 Neomys fodiens (Pennant, 1771) (nine localities) in Europe. As molecular marker, we used the sequences of the mtDNA gene for cytochrome b (1140 bp from 24 specimens; 272 bp from 15 specimens). The phylogenetic analysis of N. fodiens shows slight divergence among haplotypes, with only one supported clade including two geographically distant haplotypes from Calabria (southern Italy) and Pyrenees (France); these haplotypes diverge from the others by 2.9% and 2.1%, respectively. In N. anomalus, one haplotype from Spain is very different, diverging from all others by 8-10% of the sequence. This level of divergence is similar to that found between N. anomalus and another species, Neomys teres. There are two other supported clades in N. anomalus, an Italian subclade and an eastern subclade comprising haplotypes from Turkey and Slovenia. Moreover, we found a different genetic structure between the two species with greater divergence in N. anomalus than in N. fodiens. The phylogeographic patterns are discussed in a temporal framework and considering the different ecological characteristics of these two species. © 2007 The Authors
The phylogeography of Crocidura suaveolens from southern Italy reveals the absence of an endemic lineage and supports a Trans-Adriatic connection with the Balkanic refugium
No full textA molecular phylogeographic study using a fragment of the mitochondrial gene for cytochrome b (cytb) was performed on the lesser white-toothed shrew, Crocidura suaveolens, from seven localities in central and southern Italy. Comparison with cytb European haplotypes revealed the absence of endemic lineages in the region, in contrast to what has been observed for many other Italian terrestrial vertebrates. Indeed all the Italian specimens results nested with Balkanic conspecific within an Italo-Balkan clade. Historical demography of this clade showed a scenario of expansion which preceded the LGM. This evidence of glacial persistence indicates a certain flexibility of the classic models of Pleistocene biogeography
Origin and evolution of Western European moles (genus Talpa, Insectivora): a multidisciplinary approach
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