http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-05-22T03:53:37Z http://hdl.handle.net/2067/1799 Title: Genetic diversity of the killifish Aphanius fasciatus paralleling the environmental changes of Tarquinia salterns habit Authors: Angeletti, Dario; Cimmaruta, Roberta; Nascetti, Giuseppe Abstract: The habitat in the Natural Reserve of the Tarquinia salterns, located on the Tyrrhenian coast of central Italy, has undergone dramatic alterations over the last 10 years. After salt production was terminated in 1997 the site was abandoned until 2002, with consequent degradation of habitat quality and stiffening of the environmental conditions. From 2003 to 2006 ecological rehabilitation of the site was carried out, restoring water circulation to its previous equilibrium. The genetic variation in the killifish Aphanius fasciatus inhabiting the salterns was monitored using allozymes from 1998. The results showed that the genetic variability of the killifish strongly reduced through time: a high number of rare alleles were lost and both heterozygosity and allele richness were significantly decreased. The most recent samples, taken after the ecological restoration, showed that to date the genetic erosion of A. fasciatus gene pool has slowed down, since no significant differences have been detected for any genetic variability parameter. Concerning the mechanisms leading to the impoverishment of the genetic variability, the strong loss of rare alleles suggests a role of genetic drift, which accords with the fluctuation of the effective population size recorded over the period of study and with the low gene flow typical of this species. The low levels of gene flow reported for this species imply that once lost, the genetic variability can rarely be restored through immigration from highly variable populations. Description: L'articolo è disponibile sul sito dell'editore http://www.springerlink.com 2009-12-31T23:00:00Z http://hdl.handle.net/2067/1800 Title: Genetic structure and temporal stability in the horse mackerel (Trachurus trachurus) Authors: Cimmaruta, Roberta; Bondanelli, Paola; Ruggi, Alessandra; Nascetti, Giuseppe Abstract: This study aimed at assessing the temporal and spatial genetic structure of the horse mackerel (Trachurus trachurus) using allozymes, within the frame of a multidisciplinary research project directed at the stock assessment of this species. To this end, 19 samples were taken from a large part of the geographical range of the species, providing more than 2200 specimens analysed. Samples from 14 localities were caught twice in different years, so that the temporal stability of their genetic structure could be investigated. The genotypes and the allele frequencies obtained at different times from the same locality were statistically consistent, suggesting that the genetic structure of horse mackerel populations is stable overtime. Allozyme analysis showed that all the horse mackerel populations studied, although geographically separated, were genetically homogeneous and connected by high levels of gene flow. Attempts to highlight subtle genetic structure only revealed a slight differentiation between eastern Mediterranean samples (Ionian and Aegean Seas) versus the western Mediterranean and Atlantic ones, in agreement with the horse mackerel’s migration routes so far identified and with the results obtained using different approaches (parasites as biological tags, otoliths). A further objective of the research was to assess the level of genetic variability in this species. We found very high variability in all the studied samples, among the highest recorded in the literature for many pelagic and demersal fishes. Since the levels of genetic variability are increasingly used as indicators of the state of exploited and human-impacted populations, the results obtained suggested that the biomass depletion suffered by the horse mackerel has not impoverished its genetic resources yet. However, it is worth noting that the significantly lowest values were recorded for the samples from the so-called north-western stock, where the catches are rapidly decreasing since 1996. Description: L'articolo è disponibile sul sito dell'editore http://www.sciencedirect.com 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1766 Title: Population genetic structure and diversity of the Apennine endemic stream frog, Rana italica – insights on the Pleistocene evolutionary history of the Italian peninsular biota Authors: Canestrelli, Daniele; Cimmaruta, Roberta; Nascetti, Giuseppe Abstract: For most species in the Western Palaearctic region, southern Mediterranean peninsulas have been identified as major Quaternary refugia and hotspots of intraspecific diversity, and thus, as areas of particular relevance for the conservation of the evolutionary potential. We analysed the patterns of geographical variation among 26 populations of the Italian stream frog, using both nuclear (allozymes) and mitochondrial (partial cytochrome b sequences) markers. Phylogenetic, phylogeographical and population genetic analyses suggested that the species survived the last glacial–interglacial cycles in two distinct refugia, one restricted to the tip of the Calabrian peninsula, at the extreme south of the species’ range, the other spanning from central Calabria to central Apennines and showing evidences for further population subdivision therein. Historical demographic tests suggested a significant population expansion from the latter, which most likely began around the last pleniglacial. This expansion would have led to the rapid colonization of the northern Apennines to the north, and to a secondary contact and population admixture with the population from the southern refugium in southern central Calabria. A comparison of the evolutionary history inferred for the Italian stream frog with the data emerging for other codistributed species suggests: (i) the generality of a multiple-refugia scenario for the Italian peninsula, (ii) the possible occurrence of at least one suture zone in southern Italy, and (iii) that for most species, this Pleistocene refugium is not only a hotspot, but also a melting pot of intraspecific genetic diversity. Finally, the conservation implications of these results are also briefly highlighted. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com 2007-12-31T23:00:00Z http://hdl.handle.net/2067/1767 Title: Phylogeography and historical demography of the Italian treefrog, Hyla intermedia, reveals multiple refugia, population expansions and secondary contacts within peninsular Italy Authors: Canestrelli, Daniele; Cimmaruta, Roberta; Nascetti, Giuseppe Abstract: We investigated the geographical patterns of genetic diversity in the Italian treefrog through sequence analysis of a mitochondrial cytochrome b gene fragment. Three main mitochondrial lineages were identified, distributed in northern, central and southern Italy, respectively. Their divergence appears indicative of a split time largely predating Late Pleistocene climatic oscillations, and syntopy between them was only observed in the geographically intermediate populations. The historical demographic reconstructions suggest that in both northern and central Italy, an expansion occurred during the last major glacial phase, when a vast widening of the lowland habitats followed the glaciation-induced fall of the sea level. Instead, in southern Italy an expansion event likely followed the end of the last glaciation, although the inference of expansion appears less reliable for the southern clade than for the others. Within this geographical area, a sharp phylogeographic discontinuity separated peninsular from Sicilian populations, and the overall pattern of diversity suggests that the latter derived from a recent colonization of the island, probably through a Late Pleistocene land bridge. Phylogenetic, phylogeographic and historical demographic analyses thus concur in delineating a scenario of multiple refugia, with four groups of populations which survived the last glacial–interglacial cycles in at least three distinct refugia arranged along peninsular Italy, and have recently come into contact following range expansions. Therefore, these results support the hypothesis that a plethora of microevolutionary processes, rather than the prolonged stability of populations, were mainly responsible for shaping the patterns of diversity within this major biodiversity hotspot. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com 2006-12-31T23:00:00Z