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Inclan D.J.,University of Padua | Cerretti P.,University of Rome La Sapienza | Cerretti P.,Centro Nazionale Biodiversita Forestale
Landscape Ecology | Year: 2014

Although many empirical and theoretical studies have elucidated the effects of habitat fragmentation on the third trophic level, little attention has been paid to the impacts of this driver on more generalist groups of non-hymenopteran parasitoids. Here, we used the highly-diverse group of tachinid flies as an alternative model to test the effects of landscape fragmentation on insect parasitoids. Our aims were: (i) to evaluate the relative importance of habitat area and connectivity losses and their potential interaction on tachinid diversity, (ii) to test whether the effects of habitat fragmentation changes seasonally, and (iii) to further assess the effect of habitat diversity on tachinid diversity and whether different parasitoid-host associations modify the species richness response to fragmentation. In 2012 a pan-trap sampling was conducted in 18 semi-natural grasslands embedded in intensive agricultural landscapes along statistically orthogonal gradients of habitat area, connectivity and habitat diversity. We found an interaction between habitat area and connectivity indicating that tachinid abundance and species richness were more negatively affected by habitat loss in landscapes with low rather than with relatively large habitat connectivity. Although tachinid communities exhibited large within-year species turnover, we found that the effects of landscape fragmentation did not change seasonally. Wefound that habitat diversity and host association did not affect tachinid species diversity. Our results have important implications for biodiversity conservation as any attempts to mitigate the negative effects of habitat loss need to take the general level of habitat connectivity in the landscape into account. © 2014 Springer Science+Business Media Dordrecht. Source


Inclan D.J.,University of Padua | Cerretti P.,University of Padua | Cerretti P.,University of Rome La Sapienza | Cerretti P.,Centro Nazionale Biodiversita Forestale | Marini L.,University of Padua
Landscape Ecology | Year: 2014

Although many empirical and theoretical studies have elucidated the effects of habitat fragmentation on the third trophic level, little attention has been paid to the impacts of this driver on more generalist groups of non-hymenopteran parasitoids. Here, we used the highly-diverse group of tachinid flies as an alternative model to test the effects of landscape fragmentation on insect parasitoids. Our aims were: (i) to evaluate the relative importance of habitat area and connectivity losses and their potential interaction on tachinid diversity, (ii) to test whether the effects of habitat fragmentation changes seasonally, and (iii) to further assess the effect of habitat diversity on tachinid diversity and whether different parasitoid-host associations modify the species richness response to fragmentation. In 2012 a pan-trap sampling was conducted in 18 semi-natural grasslands embedded in intensive agricultural landscapes along statistically orthogonal gradients of habitat area, connectivity and habitat diversity. We found an interaction between habitat area and connectivity indicating that tachinid abundance and species richness were more negatively affected by habitat loss in landscapes with low rather than with relatively large habitat connectivity. Although tachinid communities exhibited large within-year species turnover, we found that the effects of landscape fragmentation did not change seasonally. Wefound that habitat diversity and host association did not affect tachinid species diversity. Our results have important implications for biodiversity conservation as any attempts to mitigate the negative effects of habitat loss need to take the general level of habitat connectivity in the landscape into account. © 2014 Springer Science+Business Media Dordrecht. Source


Stireman III J.O.,Wright State University | Cerretti P.,University of Rome La Sapienza | Cerretti P.,Centro Nazionale Biodiversita Forestale | Whitmore D.,Centro Nazionale Biodiversita Forestale | And 2 more authors.
Insect Conservation and Diversity | Year: 2012

1.We analysed the canopy and understorey communities of flies in the family Tachinidae, the most diverse group of parasitoid Diptera, in a small and isolated temperate plain forest in northern Italy. Our objective was to assess whether and how these communities differ from one another, and how species distribution relates to forest structure, host distribution, mating sites, and season. 2.The study was carried out in 2008 with 14 Malaise traps installed between April and November in an equal number of sites randomly selected inside the forest, seven on the ground and seven in the tree canopy. 3.Overall species richness, abundance, and turnover were greater in the understorey traps, but most diversity metrics indicate greater overall diversity and evenness in the canopy traps. Community ordination and estimates of beta diversity indicate that the two habitat-associated communities are distinct and should both be considered in assessments of insect diversity and community structure. Indicator species values revealed the presence of a number of species that were effective indicators of canopy and understorey habitats. No strong male bias in canopy traps was observed across species; however, the only significant sex ratio biases in the canopy were towards males. Both male and female biases were observed in understorey traps, depending upon the species. © 2011 The Royal Entomological Society. Source


D'Amen M.,National Research Council Italy | D'Amen M.,Centro Nazionale Biodiversita Forestale | Birtele D.,National Research Council Italy | Birtele D.,Centro Nazionale Biodiversita Forestale | And 3 more authors.
European Journal of Entomology | Year: 2013

In this study we analyzed the inter-specific relationships in assemblages of syrphids at a site in northern Italy in order to determine whether there are patterns in diurnal co-occurrence. We adopted a null model approach and calculated two co-occurrence metrics, the C-score and variance ratio (V-ratio), both for the total catch and of the morning (8:00-13:00) and afternoon (13:00-18:00) catches separately, and for males and females. We recorded discordant species richness, abundance and co-occurrence patterns in the samples collected. Higher species richness and abundance were recorded in the morning, when the assemblage had an aggregated structure, which agrees with previous findings on communities of invertebrate primary consumers. A segregated pattern of co-occurrence was recorded in the afternoon, when fewer species and individuals were collected. The pattern recorded is likely to be caused by a number of factors, such as a greater availability of food in the morning, prevalence of hot and dry conditions in the early afternoon, which are unfavourable for hoverflies, and possibly competition with other pollinators. Our results indicate that restricting community studies to a particular time of day will result in certain species and/or species interactions not being recorded. Source

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