62,956 research outputs found
POPULATION GENETIC STRUCTURING IN ISOPODS: HISTORICAL AND ECOLOGICAL DETERMINANTS
No full textIsopods are crustaceans that show a wide adaptive radiation. They inhabit benthic marine and freshwater envi-ronments, are parasites of crustaceans and fishes, and have colonized terrestrial habitats. Isopods show an extraor¬dinary diversification in adaptations, coinciding with an equally diverse array of different degrees of stenoecy, char¬acterizing individual species. Among terrestrial isopods, trichoniscids show a very limited dispersal ability. This is mainly due to physiological constraints that necessitate them to inhabit humid edafic environments, and subterranean habitats. Results from genetic surveys have revealed that genetic variability in trichoniscids ranges in a wide spec¬trum, and a high degree of specific structure is often detectable (Gentile & Sbordoni, 1998; Gentile et al. 1998; Gentile & Allegrucci, submitted; Cobolli Sbordoni et al., 1997). Thus, trichoniscids are a valuable tool to study the inter- intrapopulation components of genetic variation, often allowing the researcher to detect the action of the different evolutionary factors as genetic drift, selection, and gene flow, separately. In this communication we discuss some case studies in which it has been possible to relate the genetic structure observed to historical and ecological factors.
Centile. C. & V. Sbordoni. 1998. Evolution 52: in press.
Gentile, G.. S. Sarbu, M. Menichetti 4 S. Galdenzi. 1998. In: H. Wilkens (ed.). Ecosystems of the World. In press.
Cobolli Sbordoni, M.. V. Ketmaier. E. De Matthaeis & S. Taiti. 1997. Heredity. 79: 463-472
Towards a georeferenced checklist of the butterflies of Bhutan: a preliminary account (Insecta: Lepidoptera)
No full textThis paper presents the first attempt to build a georeferenced dataset of the butterflies of Bhutan. The huge range of habitats in Bhutan, from subtropical in the south to alpine in the north, presents a wide assemblage of habitat niches for butterflies. The digitized data was collected by four of the authors (Bozano, Wangdi, Sherub and Sbordoni) during recent trips from 2008 to 2013, as well as data obtained from a few recently published papers, where recording localities were presented with an acceptable degree of accuracy.
At this time the dataset consists of more than 3000 records and includes observations and collection data for 533 butterfly species. Data came from 300 sampling sites throughout the whole of Bhutan, with a fairly good geographical coverage of the country, from tropical Dooars up to the alpine zone at 5000 m. Like other Himalayan countries, Bhutan lies in the Sino-Himalayan transition zone at the boundary between the Palaearctic and Oriental Region. From the checklist it was shown that the species can be sorted into four biogeographic classes. As expected, species attributed to Oriental fauna are by far the most abundant (63%) followed by Sino-Himalayan species (28%), only a few species were ascribed to Palaearctic (5%) and Widespread (4%) species
Molecular phylogeny and biogeography of the Satyrid genus Callerebia and allied taxa: an attempt to trace the origin of the Himalayan faunal elements
No full textPleistocene evolutionary history of the Clouded Apollo (Parnassius mnemosyne): genetic signatures of climate cycles and a 'time-dependent' mitochondrial substitution rate
No full textGenetic data are currently providing a large amount of new information on past distribution of species and are contributing to a new vision of Pleistocene ice ages. Nonetheless, an increasing number of studies on the 'time dependency' of mutation rates suggest that date assessments for evolutionary events of the Pleistocene might be overestimated. We analysed mitochondrial (mt) DNA (COI) sequence variation in 225 Parnassius mnemosyne individuals sampled across central and eastern Europe in order to assess (i) the existence of genetic signatures of Pleistocene climate shifts; and (ii) the timescale of demographic and evolutionary events. Our analyses reveal a phylogeographical pattern markedly influenced by the Pleistocene/Holocene climate shifts. Eastern Alpine and Balkan populations display comparatively high mtDNA diversity, suggesting multiple glacial refugia. On the other hand, three widely distributed and spatially segregated lineages occupy most of northern and eastern Europe, indicating postglacial recolonization from different refugial areas. We show that a conventional 'phylogenetic' substitution rate cannot account for the present distribution of genetic variation in this species, and we combine phylogeographical pattern and palaeoecological information in order to determine a suitable intraspecific rate through a Bayesian coalescent approach. We argue that our calibrated 'time-dependent' rate (0.096 substitutions/million years), offers the most convincing time frame for the evolutionary events inferred from sequence data. When scaled by the new rate, estimates of divergence between Balkan and Alpine lineages point to c. 19 000 years before present (last glacial maximum), and parameters of demographic expansion for northern lineages are consistent with postglacial warming (5-11 000 years before present)
Patterns of genetic variability and differentiation in mediterranean populations of Penaeus kerathurus (Crustacea, Decapoda).
No full textStudio sistematico su Meligethes exilis Sturm, in base a dati elettroforetici, morfo-ecologici e biogeografici (Coleoptera, Nitidulidae).
No full textGenetic changes in seven generations of hatchery stocks of the kuruma prawn, Penaeus japonicus (Crustacea, Decapoda).
No full textAsymmetrical responses of forest and “beyond edge” arthropod communities across a forest–grassland ecotone
No full textHistorically, where forest habitats are deemed as the pristine landscape state, anthropogenic habitats such as managed grasslands or open spaces are often perceived to be antagonistic and of secondary conservation priority. Traditionally, studies on biodiversity responses to ecological variation, i.e. edge effect, have mostly focused on forest habitats. Yet recently there has been increased attention on communities beyond the forest edge in an effort to better understand how interactions between forests and adjacent habitats may potentially affect regional biodiversity. However, in Europe and the Mediterranean basin (a biodiversity hotspot), areas with high landscape heterogeneity and high edge density, there is a paucity of studies analysing the community responses across forest and “beyond edge” habitats across ecotones. In a protected area of central Italy, we investigated the responses of ground-dwelling arthropods [Araneae (spiders), Chilopoda (centipedes) and Carabidae (ground beetles)], which were differentiated into habitat-specific guilds (forest, edge and grassland species) across a forest–grassland ecotone. We investigated the extent to which a habitat edge influenced communities of arthropods associated with either the forest or grassland, and how far from the edge this effect penetrated into each habitat. Twelve 150 m-transects perpendicular to a forest–grassland edge were established and arthropods were sampled at nine progressive distances across the ecotone. An indicator species analysis was used to detect species significantly associated with forest, edge-belt or grassland habitats, which were assumed representative of the respective communities. Logistic models of indicator species richness and abundances were used to describe responses of grassland and forest communities across the ecological boundaries. We found that grassland and edge habitats had habitat specialists and higher species richness compared to the forest habitat. Moreover, the occurrence of grassland-specific species was influenced by the presence of an edge up to 15 m from the habitat border. In contrast forest-associated indicator species were not affected by proximity to the habitat edge, rather individuals typical of forest habitats tended to “spill over” into grassland habitats. These findings support the hypothesis that in a forest–grassland mosaic, forest species are less sensitive to an edge and influence the community beyond the forest edge and into the grassland more than the reverse, i.e. the effect was asymmetric. From these data, we estimated that a minimum grassland habitat width of 600 m is necessary for grassland species to maintain a core area that is relatively unaffected by the spillover of species from adjacent forest habitats. Incorporating the directional influences of adjacent communities on each other allows for an empirical assessment of habitat vulnerability that doesn’t a priori value the conservation of one habitat over another
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