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Prato allo Stelvio - Prad am Stilfser Joch, Italy

Dapporto L.,Istituto Comprensivo Materna Elementere Media Convenevole da Prato | Dennis R.L.H.,Oxford Brookes University | Dennis R.L.H.,Staffordshire University
Biological Conservation | Year: 2013

Recognizing how different species react to environmental changes provides fundamental information for conservation biology. Population and distribution trends in changing environments have been hypothesized to be highly dependent on the degree of generalism and dispersal capacity. However, different outcomes are expected for different situations. Assessing these is complicated by the paucity of reliable data over time and by the lack of continuous variables measuring the degree of species' generalism and dispersal capability. We demonstrate the value of applying two newly constructed indices, that measure the degree of species' generalism and dispersal ability, to recently published reliable data on distribution and population trends for British butterflies. We tested linear and non-linear relationships between distribution trends and species' characteristics and found that distribution cover (number of occupied squares) is highly, positively correlated with degree of generalism and dispersal ability. However, we found that distribution trends (fraction of area gained or lost over the last 10. years) has a non-linear, 'U' shaped, relationship with generalism and no relationship with dispersal ability. The non-linear relationship revealed that specialists have the highest positive trends and mid generalists the most negative trends. In accordance with a recent review, we concluded that specialists can monopolize restricted resources on fragmented habitats as long as these are large, and profit from local conservation measures, while extreme generalists can profit from any resource and can move easily among suitable patches. Intermediate species cannot competitively engage either of these alternative strategies and are thus most seriously affected by the recent environmental changes. © 2012 Elsevier Ltd.

Dapporto L.,Istituto Comprensivo Materna Elementere Media Convenevole da Prato
Journal of Insect Conservation | Year: 2011

In this paper a conservation biogeography approach has been applied to predict distribution and conservation priorities in West Mediterranean Zygaena moths. The presence/absence matrix data for mainland region and for the three largest islands (Sardinia, Corsica and Sicily) has been analyzed. The analyses have been performed on individual species and revealed that species distribution in the Mediterranean mainland can be largely predicted. However, Sardinia and Corsica islands showed highly impoverished faunas while Sicily did not revealed a lower richness than predicted. Logistic regressions at individual species level showed that several taxa, predicted to be present in Sardinia and Corsica are actually absent. For Sicily the opposite trend was obtained and several unpredicted species actually occur on this island. Conversely to butterflies, ecological traits did not differ between predicted and unpredicted Sicilian species, suggesting that ancient and stochastic colonisations are responsible for the occurrence of several species. Due to the very low probabilities that relict populations could re-colonize islands following possible extinctions, they are suggested to deserve particular conservation efforts. In particular, Z. orana from Sardinia, Z. corsica from Corsica and Z. trifolii, Z. purpuralis and Z. carniolica from Sicily showed distinctive biogeographic patterns and/or particular rarity. © 2010 Springer Science+Business Media B.V.

Dapporto L.,Istituto Comprensivo Materna Elementere Media Convenevole da Prato
Biological Journal of the Linnean Society | Year: 2010

The Mediterranean islands of Sardinia and Corsica are known for their multitude of endemics. Butterflies in particular have received much attention. However, no comprehensive studies aiming to compare populations of butterflies from Sardinia and Corsica with those from the neighbouring mainland and Sicily have been carried out. In the present study, the eleven Satyrinae species inhabiting Sardinia and Corsica islands were examined and compared with continental and Sicilian populations by means of geometric morphometrics of male genitalia. Relative warp computation, discriminant analyses, hierarchical clustering, and cross-validation tests were used to identify coherent distributional patterns including both islands and mainland populations. The eleven species showed multifaceted distributional patterns, although three main conclusions can be drawn: (1) populations from North Africa and Spain are generally different from those belonging to the Italian Peninsula; (2) populations from Sardinia and Sicily often resemble the North Africa/Spain ones; Corsica shows transitional populations similar to those from France; and (3) sea barriers represent filters to dispersal, although their efficacy appears to be unrelated to their extension. Indeed, the short sea straits between Sardinia and Corsica and between Sicily and the Italian Peninsula revealed a strong effectiveness with respect to preventing faunal exchanges; populations giving onto sea channels between Corsica and Northern Italy and between Sicily and Tunisia showed a higher similarity. A comparison of island and mainland distributions of the eleven taxa have helped to unravel the complex co-occurrence of historical factors, refugial dynamics, and recent (post-glacial) dispersal with respect to shaping the populations of Mediterranean island butterflies. © 2010 The Linnean Society of London.

Dennis R.L.H.,Oxford Brookes University | Dennis R.L.H.,Staffordshire University | Dapporto L.,Istituto Comprensivo Materna Elementere Media Convenevole da Prato | Fattorini S.,University of Milan Bicocca | And 2 more authors.
Biological Journal of the Linnean Society | Year: 2011

Specialisms on resources and for niches, leading to specialization, have been construed to be tantamount to speciation and vice versa, while the occurrence of true generalism in nature has also been questioned. We argue that generalism in resource use, biotope occupancy, and niche breadth not only exists, but also forms a crucial part in the evolution of specialists, representing a vital force in speciation and a more effective insurance against extinction. We model the part played by generalism and specialism in speciation and illustrate how a balance may be maintained between the number of specialists and generalists within taxa. The balance occurs as an ongoing cycle arising from turnover in the production of specialists and generalists, speciation, and species extinction. The nature of the balance depends on the type of resources exploited, biotopes, and niche space occupied. These vary between different regions and create taxonomic biases towards generalists or specialists. We envisage that the process may be sympatric/parapatric, although it is more likely initiated by allopatry driven by abiotic forces. © 2011 The Linnean Society of London.

Dennis R.L.H.,Oxford Brookes University | Dennis R.L.H.,Staffordshire University | Hardy P.B.,81 Winstanley Road | Dapporto L.,Istituto Comprensivo Materna Elementere Media Convenevole da Prato
Journal of Biogeography | Year: 2012

Aim To relate variation in the migration capacity and colonization ability of island communities to island geography and species island occupancy. Location Islands off mainland Britain and Ireland. Methods Mean migration (transfer) capacity and colonization (establishment) ability (ecological indices), indexed from 12 ecological variables for 56 butterfly species living on 103 islands, were related to species nestedness, island and mainland source geography and indices using linear regression models, RLQ analysis and fourth-corner analysis. Random creation of faunas from source species, rank correlation and rank regression were used to examine differences between island and source ecological indices, and relationships to island geography. Results Island butterfly faunas are highly nested. The two ecological indices related closely to island occupancy, nestedness rank of species, island richness and geography. The key variables related to migration capacity were island area and isolation; for colonization ability they were area, isolation and longitude. Compared with colonization ability, migration capacity was found to correlate more strongly with island species occupancy and species richness. For island faunas, the means for both ecological indices decreased, and variation increased, with increasing island species richness. Mean colonization ability and migration capacity values were significantly higher for island faunas than for mainland source faunas, but these differences decreased with island latitude. Main conclusions The nested pattern of butterfly species on islands off mainland Britain and Ireland relates strongly to colonization ability but especially to migration capacity. Differences in colonization ability among species are most obvious for large, topographically varied islands. Generalists with abundant multiple resources and greater migration capacity are found on all islands, whereas specialists are restricted to large islands with varied and long-lived biotopes, and islands close to shore. The inference is that source-sink dynamics dominate butterfly distributions on British and Irish islands; species are capable of dispersing to new areas, but, with the exception of large and northern islands, facilities (resources) for permanent colonization are limited. The pattern of colonization ability and migration capacity is likely to be repeated for mainland areas, where such indices should provide useful independent measures for assessing the conservation status of faunas within spatial units. © 2012 Blackwell Publishing Ltd.

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