1,720,997 research outputs found
Mediterranean island biogeography: Oniscidean Isopods from the Pontine islands.
No full textIn this paper we report data on the oniscidean fauna from Pontine Islands, a volcanic archipelago located in the central Tyrrhenian Sea. We discuss the relationship between the faunistic diversity and the environmental het¬erogeneity. with a view to comparing the faunistic components of the Pontine Islands with the data from other islands of the Mediterranean area (Schmalfuss, 1979; Taiti & Ferrara, 1978; Caruso et al., 1987; Argano & Manicastri, 1996)..
Schmalfuss. H.. 1979. Revidierte Check-list der Landisopoden (Oniscoidea) Griechenlands. Taiti. S. & F. Ferrara. 1980. Redia. 63.
Caruso. D.. C. Baglieri. M. C. Di Maio & B. M. Lombardo. 1987. Anlmalia, 14.
Argano. R. & C. Manicastri, 1996. Biogeographia, 18
Island biogeography of the Mediterranean sea: the species-area relationship for terrestrial isopods
No full textAim We looked at the biogeographical patterns of Oniscidean fauna from the small islands of the Mediterranean Sea in order to investigate the species-area relationship and to test for area-range effects. Location The Mediterranean Sea. Methods We compiled from the literature a data set of 176 species of Oniscidea (terrestrial isopods) distributed over 124 Mediterranean islands. Jaccard's index was used as input for a UPGMA cluster analysis. The species-area relationship was investigated by applying linear, semi-logarithmic, logarithmic and sigmoid models. We also investigated a possible 'small island effect' (SIE) by performing breakpoint regression. We used a cumulative and a sliding-window approach to evaluate scale-dependent area-range effects on the log S/log A regression parameters. Results Based on similarity indexes, results indicated that small islands of the Mediterranean Sea can be divided into two major groups: eastern and western. In general, islands from eastern archipelagos were linked together at similarity values higher than those observed for western Mediterranean islands. This is consistent with a more even distribution of species in the eastern Mediterranean islands. Separate archipelagos in the western Mediterranean could be discriminated, with the exception of islets, which tended to group together at the lowest similarity values regardless of the archipelago to which they belong. Islets were characterized by a few common species with large ranges. The species-area logarithmic model did not always provide the best fit. Most continental archipelagos showed very similar intercepts, higher than the intercept for the Canary island oceanic archipelago. Sigmoid regression returned convex curves. Evidence for a SIE was found, whereas area-range effects that are dependent on larger scale analyses were not unambiguously supported<link rid="q2"></link>. Main conclusions The Oniscidea fauna from small islands of the Mediterranean Sea is highly structured, with major and minor geographical patterns being identifiable. Some but not all of the biogeographical complexity can be explained by interpreting the different shapes of species-area curves. Despite its flexibility, the sigmoid model tested did not always provide the best fit. Moreover, when the model did provide a good fit the curves looked convex, not sigmoid. We found evidence for a SIE, and minor support for scale-dependent area-range effects
Insights into the late-Sixties taxocenosis of Oniscidea from the Pontine islands (West Mediterranean) (Peracarida: Isopoda)
Full text linkWe report and discuss faunistic data of Oniscidea inhabiting the Pontine islands, a group of five small volcanic islands and several islets in the Tyrrhenian Sea, located about 60 km from the Italian mainland. Data here presented were primarily obtained from the examination of the material collected during a three-year (1965-1968) research program supported by the Italian National Council of Research and aimed at investigating Mediterranean small island faunas, including Oniscidea. Despite the sampling was not specifically directed at Oniscidea, these data may provide insights into the structure of the Oniscidean taxocenosis of the islands as it existed fifty years ago. Thirty-five species belonging to 11 families, 8 ecological and 7 biogeographical classes were found on these islands. Such number of species of Oniscidea is very high, if we consider the low number of islands and their small sizes. Changes in climate and environmental conditions occurred in the last fifty years would call for a new investigation
Evaluating the correlation between area, environmental heterogeneity, and species richness using terrestrial isopods (Oniscidea) from the Pontine Islands (West Mediterranean)
Full text linkArea and environmental heterogeneity influence species richness in islands. Whether area or environmental heterogeneity is more relevant in determining species richness is a central issue in island biogeography. Several models have been proposed, addressing the issue, and they can be reconducted to three main hypotheses developed to explain the species-area relationship: (1) the area-per se hypothesis (known also as the extinction-colonisation equilibrium), (2) the random placement (passive sampling), and the (3) environmental heterogeneity (habitat diversity). In this paper, considering also the possible influence of geographic distance on island species richness, we explore the correlation between area, environmental heterogeneity, and species richness by using faunistic data of Oniscidea inhabiting the Pontine Islands, a group of five small volcanic islands and several islets in the Tyrrhenian Sea, located about 60 km from the Italian mainland. We found that the colonisation of large Pontine Islands may occur via processes independent of geographic distance which could instead be an important factor at a much smaller scale. Such processes may be driven by a combination of anthropogenic influences and natural events. Even in very small-size island systems, environmental heterogeneity mostly contributes to species richness. Environmental heterogeneity could influence the taxocenosis structure and, ultimately, the number of species of Oniscidea via direct and indirect effects, these last mediated by area which may or may not have a direct effect on species richness
Le declin du phoque moine en Italie et sa survie dans un contexte mediterranean. Environmental Encouter
No full textSardinia, a hotspot of diversity for subterranean terrestrial isopods (Crustacea, Oniscidea)
No full textPhylogeography of Helleria brevicornis Ebner 1868 (Crustacea, Oniscidea): Old and recent differentiations of an ancient lineage
No full textThe phylogeography of Helleria brevicornis (Oniscidea, Tylidae) as revealed by mitochondrial DNA sequence data.
No full textHelleria brevicornis is with no doubt a very intriguing organism. lts peculiar morphological features clearly separate this species from the rest of Oniscidea. Even attempts at reconstructing its phylogenetic position by using mithochondrial DNA molecular data were largely unsuccessful, mainly because of some peculiarities of its mitochondrial genome (Michei-Salzat and Bouchon, 2000). The Tyrrenianan distribution of this species is an additional interesting issue. Distributed in two of the three major islands of the West Mediterranean Sea, Sardinia and Corsica, Helleria also occurs spottily in few continental areas of the Thyrrenian basin (France, ltaly), and some, but not all, islands of the Tuscanian Archipelago. The biogeography and the supposed ancient evolutionary history of this species provide ground for hypothesizing that the present geographic distribution could be a remnant of a once larger one, and that the paleogeographic events that led to the formation of the Sardinia-Corsica plate, datable back to the Oligocene, could be reflected in the present geographic distribution of this species. To address this issue, we investigated the phylogeography of Helleria brevicornis by sequencing approximately 1.4 Kb of the mtDNA (16S, 12S, and COI) in more than 50 individuals from 20 different populations. Taxonomic implications of the results obtained are also discussed
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