1,721,047 research outputs found
Diversità nei roditori delle savane dell’Africa orientale e del Corno d’Africa: meccanismi e modelli di evoluzione. Il caso di Tatera e Mastomys (Rodentia: Muridae)
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Morphometry and chromosomes of Tatera Lataste 1882 (Rodentia, Muridae, Gerbillinae) in West Africa
No full text5S 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
Evolutionary systematics in African gerbilline rodents of the genus Gerbilliscus: Inference from mitochondrial genes
No full textGerbilliscus has recently been proposed as an endemic African rodent genus distinct from the Asian Tatera. A molecular phylogeny of the genus, including nine species from southern, western and eastern Africa, is presented here based on the analysis of the cytochrome b and 16S mitochondrial genes. With an adequate taxonomic sampling over a wide geographic range, we here provide a clear picture of the phylogenetic relationships between species and species groups in this genus. Three distinct clades were resolved, corresponding to major geographical subdivisions: an eastern clade that possibly diverged first, then a southern and a western clades which appeared later. We suggest two possible hypotheses concerning the dispersal of the genus across Africa, considering also the patterns of karyotypic variation. Finally, we discuss the taxonomic status of G. gambianus and the relationships between Gerbillurus and Gerbilliscus, as previous studies have suggested that the former should be included in the latter. Our data seem to support the synonymy of the two taxa and suggest that Gerbillurus and Gerbilliscus lineages diverged from a common ancestor appeared in eastern Africa. (c) 2006 Elsevier Inc. All rights reserved
REDUCED GENE FLOW AT PERICENTROMERIC LOCI IN A HYBRID ZONE INVOLVING CHROMOSOMAL RACES OF THE HOUSE MOUSE MUS MUSCULUS DOMESTICUS
No full textThe West European house mouse, Mus musculus domesticus, is a particularly suitable model to investigate the role of chromosomal rearrangements in reproductive isolation. In fact, it exhibits a broad range of chromosomal polymorphism due to Robertsonian (Rb) fusions leading to various types of contact zones between different chromosomal races. In the present study, we analyzed a parapatric contact in central Italy between the Cittaducale chromosomal race (CD: 2n = 22) and the surrounding populations with standard karyotype (2n = 40) to understand if Rb fusions play a causative role in speciation. One hundred forty-seven mice from 17 localities were genotyped by means of 12 microsatellite loci. A telomeric and a pericentromeric locus situated on six chromosome arms (four Rbs and one telocentric) were selected to detect differences in the amount of gene flow for each locus in different chromosomal positions. The analyses performed on the two subsets of loci show differences in the level of gene flow, which is more restricted near the centromeres of Rb chromosomes. This effect is less pronounced in the homozygotes populations settled at the border of the hybrid zone. We discuss the possible cause of the differential porosity of gene flow in Rbs considering "hybrid dysfunctions" and "suppressed recombination" models
Multiple origins of the western European house mouse in the Aeolian Archipelago: clues from mtDNA and chromosomes
No full textThe expansion of Mus musculus domesticus from its origin has been studied in detail. The colonization routes and times depended on its commensal habits which favoured a rapid and recent dispersal, making it difficult to unravel the expansion pattern. The situation is still obscure in the central Mediterranean area. Mitochondrial D-loop was sequenced for 65 mice from the Aeolian Archipelago and the sixteen haplotypes identified were compared with the 528 available mouse haplotypes. The central Mediterranean phylogeography, the demographic history of the Aeolian mice and the relationships between mtDNA and karyotypes was investigate. Five lineages are present, belonging to five of the haplogroups previously described for the Mediterranean basin, and most individuals fall within the European haplogroups. The Archipelago was subjected to multiple colonizations and chromosomal and molecular data agree in indicating Sicily and Italy as possible sources of colonization in recent times. Nevertheless, the signatures of earlier colonizations might have been lost through extinction and admixing of mice due to human movements. Drastic events during the entire colonization process have led to the present-day random distribution of haplotypes. Furthermore, Salina emerges as an ancestral condition and no relation between karyotype composition and haplotype variability was highlighted
Comparative cytogenetic and genetic study of two Italian populations of the garden dormouse Eliomys quercinus L. (Sciuromorpha: Gliridae)
No full textThe garden dormouse Eliomys quercinus is a polytypic species that shows remarkable chromosomal variation (2n = 48, 50, 52, 54). Furthermore, among 2n = 48 populations of the species, distributed mainly in the circum-Mediterranean area, different populations may exhibit distinctive karyotypes. Here we analyse samples of E. quercinus from Sicily, the insular population so far barely studied, compared to the samples from the Central Apennines. The two populations show the same cytotype (2n = 48, NFa = 86), matching G- and C- chromosome banding patterns, and identical chromosome locations of major ribosomal genes (rDNA) and interstitial telomeric sequences (ITS). The samples from the two Italian populations show low genetic divergence (1.2%) based on mitochondrial cytochrome b gene sequence analysis, which suggests that both populations belong to the same taxon - E. quercinus pallidus. In addition, we compare the present results to karyological data reported in other 2n = 48 populations and identify possible chromosomal rearrangements
Morphometric 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
Pattern of shape variation in the eastern African gerbils of the genus Gerbilliscus (Rodentia, Muridae): Environmental correlations and implication for taxonomy and systematics
No full textGerbilliscus has been in recent years the subject of new molecular and karyological investigations that shed new light on the evolutionary processes of this taxon. However, the patterns of phenotypic diversification of Gerbilliscus remain poorly understood. Furthermore, the molecular phylogenetic analyses posed new questions concerning the systematics and taxonomy of the whole genus and revealed the possible occurrence of cryptic species and hence the need to carry out a taxonomic revision. We used geometric morphometrics to investigate the adaptive value of morphological changes and to elucidate the systematic relationships and taxonomic status of the Gerbilliscus species of east Africa. Our results show concordance between morphological and genetic species boundaries. However, the observed morphological differences appear not only related to hereditary characters. In fact, the correlation with the climatic variables suggests an adaptive value of shape changes related to different trophic resources availability. Finally, discriminant analysis of the eastern Africa Gerbilliscus species highlight the distinctiveness of G. vicinus, clearly separated from G. robustus and G. nigricaudus. (C) 2009 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved
The relevance of Italian museum collections for research and conservation: the case of mammals
No full textThe twentieth century saw the decline of interest toward museum collections and an increased support to 'experimental' and 'evolutionary' biology, implicitly recognising the opposite nature of the 'old' museum-based taxonomy. With few exceptions, such as those of Florence and Verona, Italian museums after World War II were pushed at the border of scientific activity by the academic world and had to fight for their survival. Examples from the USA and elsewhere show the increased relevance of modern mammal collections to several fields of research. Despite an increased and welcomed attention to the value of historical collections, there is still scarce awareness of the need and relevance of maintaining and implementing mammal collections in museums as a valuable, long-term, source of data in the field of conservation biology, faunistic, taxonomy, molecular biology and health monitoring. In the present paper we suggest to create a network between mammalogists and a number of mammal collections, with one museum serving as focal point for a national mammal collection. © 2014 Accademia Nazionale dei Lincei
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