1,721,094 research outputs found
Isolation by distance, gene flow and phylogeography in the Proasellus coxalis-group (Crustacea, Isopoda) in Central Italy: Allozyme data
Full text linkFifteen populations belonging to the Proasellus coxalis-group were surveyed for genetic variation at 19 enzymatic loci in order to clarify the degree of genetic structuring of this species at the scale of Central Italy. With Neighbour-Joining analysis, it was possible to identify two main clusters, the first grouping populations sampled in coastal areas of Central Italy, the second comprising several populations from inland areas of the Apennines. In the first group, genetic relationships follow a geographic scheme, with populations arranged according to the proximity of the collecting sites. The inland populations have less clear geographic relationships and a higher degree of genetic differentiation. In view of the paleogeography of the study areas, I hypothesise a more recent penetration of this taxon into the Central Italian alluvial coastal plains (subjected to cyclical marine ingressions during the Quaternary) from sources of colonisation in the inland areas. The higher genetic differentiation of the inland populations presumably reflects a longer evolutionary history and could be explained by the periodic fragmentation of river catchments during Pleistocene climatic fluctuations. Such an evolutionary scenario is supported by F-statistics analyses. Effective dispersal of individuals between populations can be hypothesised for the coastal populations but not for the inland ones. On the whole, there is a pattern of isolation by distance, but a large amount of gene flow seems to reflect historical rather than ongoing gene exchange
Anthropogenic changes in the freshwater fish fauna of Italy, with reference to the central region and Barbus graellsii, a newly established alien species of Iberian origin
Full text linkIn a survey of the west-central Italian rivers Ombrone, Fiora, Albegna and Bruna, among established exotic species, the Iberian barbel Barbus graellsii was recorded in Italian fresh waters for the first time. Morphological identification was supported by comparison of cytochrome b sequences with those from related barbel species. Other exotics of particular note were Barbus barbus. Pseudorasbora parva and Leuciscus cephalus, together with the Padano-Venetian Chondrostoma genei and Padogobius bonelli. Native species still present included Leuciscus lucumonis, Telestes muticellus, Rutilus rubilio and Padogobius nigricans, but were now more restricted to upper reaches and smaller watercourses. The deleterious effect of alien species on native forms is discussed with particular reference to probable competition between C. genei and L. lucumonis, and between the two gobies. The checklist of species introduced to the fresh waters of Italy is now, updated to 34. For the Italian freshwater fish fauna in general, the conservation status of three native species (Acipenser naccari, Salmo marmoratus and Knipowitschia punctatissima) has been improved but five species are believed to he at risk (Salmo carpio, L lucumonis, Scardinius scardafa, Gobio benacensis and P. nigricans) and four anadromous species (Petromyzon murinus, Lampetra fluviatilis, Acipenser sturio and Huso huso) no longer breed in Italian fresh waters. The processes of change in the composition of the Italian freshwater fish fauna as a whole may be summarized as successively 'padanization', 'danubization' and now 'globalization'. (C) 2001 The Fisheries Society of the British Isles
Will the Italian endemic gudgeon, Gobio benacensis, survive the interaction with the invasive introduced Gobio gobio?
Full text linkThe genus Gobio in Italy was represented by the endemic species G. benacensis. The original distribution of this species was the Padano-Venetian district, but since a long time it was introduced in central Italy. Introductions of alien species to Italy during the last 10 years brought the sudden introduction of the Danubian G. gobio. Genetic and morphological analyses revealed the extensive presence of G. gobio, which rapidly colonised several rivers in Italy causing the progressive decline of G. benacensis, which now should be considered as an endangered species. Among examined populations those found in the Tagliamento River and transplanted in the Ombrone River represent genetic reservoirs of this species which will probably disappear in northern Italy
Isolation and characterization of five microsatellite loci in Dolichopoda cave crickets (Orthoptera Rhaphidophoridae)
Full text linkFive microsatellite loci are described for the cave cricket genus Dolichopoda. Preliminary data on allelic variation of these loci are presented for one population of D. schiavazzii and one population of D. laetitiae to test their usefulness in fine-scale studies of the genetic aspect of cave colonization. Cross-species amplifications were carried out in four other Dolichopoda species and in two species belonging to another cave cricket genus (Troglo-philus) to test the potential use of these microsatellite markers in studies of both congeneric species and species belonging to the same family
ALLOZYMES AND mtDNA REVEAL TWO DIVERGENT LINEAGES IN ORCHESTIA CAVIMANA (AMPHIPODA: TALITRIDAE)
No full textWe report on allozyme and mitochondrial DNA variation in 13 populations of the supralittoral amphipod Orchestia cavimana. The species colonizes fresh and brackish shores of Northern Africa, Near East and throughout Europe. Populations were sampled across a large part of the species range (Cyprus, Turkey, northern and southern Italy, United Kingdom and Germany), including the type locality (Cyprus). Both sets of molecular markers agree in identifying two divergent lineages. A first lineage includes populations from Cyprus and Turkey. A second genetically homogeneous lineage groups Italian, English and German populations. Genetic divergence between the two lineages is high (D-Nei = 0.720 +/- 0.06 for allozymes and K2P = 0.191 +/- 0.001 for mitochondrial DNA) and comparable to that among morphologically distinct congeneric species reported for the same set of molecular markers
Patterns of genetic structuring and levels of differentiation in supralittoral talitrid amphipods: an overview
No full textTalitrids are the only family within the order Amphipoda to have colonised supralittoral and terrestrial environments. They live in a variety of settings, from sandy to rocky and pebble beaches, to river and lake banks, and to leaf litter and caves. A common feature is the absence of a planktonic larval stage to facilitate passive dispersal over long-distances. However, some species have broad distributions. Genetic studies over the past 25 years have tried to explain this apparent contradiction by assessing patterns of species genetic structuring on different geographical scales. Here, we review the molecular studies available to date and focus on the population genetics of talitrids. Most of these studies considered populations in the Mediterranean area, but also along the Atlantic coast and in Canary Island caves. From this review, the group emerges as a potential model to understand processes of dispersal and divergence in non-highly-vagile supralittoral organisms. At the same time, studies on these issues are still too restricted geographically: a worldwide scale including different regions would provide us with a better perspective on these problems
Twenty Years of Molecular Biogeography in the West Mediterranean Islands of Corsica and Sardinia: Lessons Learnt and Future Prospects
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Pattern of gene flow and genetic divergence in the three Italian species of the cave cricket genus Troglophilus (Orthoptera, Rhaphidophoridae): allozyme data
No full textIn this paper, we report data on the levels of genetic differentiation among and gene flow within each of the three species of the cave cricket genus Troglophilus living in Italy. We analyzed genetic variation at 18 enzymatic loci in 12 populations of T. cavicola, 6 populations of T. neglectus and 3 populations of T. andreinii. In particular, populations of T. cavicola and T. neglectus were sampled in overlapping geographical areas, from North-Eastern Italy to Slovenia and Croatia. We found a significant isolation by distance pattern for T. cavicola, indicating that the spatial distribution of genetic heterogeneity is best described by a stepping-stone model. The same does not hold for T. neglectus. Within the three species, the pattern of genetic structuring was mainly related to the limestone structure of the area rather than the availability of epigean routes for dispersal. A calibration for gene flow estimates in cave crickets is provided to discriminate between and current gene flow. This supports previous cave cricket data suggesting that detected gene flow is due to historical rather than current connections among populations
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