Although outbreaks of rare species are unusual,several insect species have become emerging pests probably due to the ongoing environmental changes.Barbitistes vicetinus was first described in 1993 as an endemic bush-c...Although outbreaks of rare species are unusual,several insect species have become emerging pests probably due to the ongoing environmental changes.Barbitistes vicetinus was first described in 1993 as an endemic bush-cricket of north-east Italy and was considered rare until 2008,when it became an established pest,causing severe damages to forests and crops.The possible role of temperature in changing its life cycle has still to be fully understood.Here,we explored the effect of summer temperature on egg diapause and the effect of winter temperature on egg survival.Field observations showed that the proportion of embryos that can complete development at the end of summer ranged from zero to nearly 90% depending on summer temperatures.A substantial shift in the rate of development from 20% to nearly 80% occurred in a thermal range of about 1℃.On the contrary,overwinter egg survival was high and constant(90%)across a wide range of winter temperatures that go well beyond both the cold and warm thermal limits of the current species range.Overall,the results suggest a potential key role of summer temperature warming on the outbreak propensity of this species that is able to switch from a multiyear to an annual life cycle with just a 1-2℃ warming.展开更多
Parasitoid wasp communities of the canopy of temperate forests are still largely unexplored. Very little is known about the community composition ofparasitoids between canopy and understory and how much of this differ...Parasitoid wasp communities of the canopy of temperate forests are still largely unexplored. Very little is known about the community composition ofparasitoids between canopy and understory and how much of this difference is related to forest structure or parasitoid biological strategies. In this study we investigated upon the difference in the community composition of the parasitic wasps Ichneumonidae between canopy and understory in a lowland temperate forest in northern Italy. We used general linear models to test whether parasitic strategy modifies species vertical stratification and the effect of forest structure. We also tested differences in β-diversity between canopy and understory traps and over time within single forest layers. We found that stand basal area was positively related to species richness, suggesting that the presence of mature trees can influence local wasp diversity, providing a higher number of microhabitats and hosts. The ichneumonid community of the canopy was different from that of the understory, and theβ-diversity analysis showed higher values for the canopy, due to a higher degree of species turnover between traps. In our analyses, the vertical stratification was different between groups of ichneumonids sharing different parasitic strategies. Idiobiont parasitoids of weakly or deeply concealed hosts were more diverse in the understory than in the canopy while parasitoids of spiders were equally distributed between the two layers. Even though the ichneumonid community was not particularly species-rich in the canopy of the temperate forests, the extension of sampling to that habitat significantly increased the number of species recorded.展开更多
基金Funding provided by Universita degli Studi di Padova within the CRUI-CARE Agreement.
文摘Although outbreaks of rare species are unusual,several insect species have become emerging pests probably due to the ongoing environmental changes.Barbitistes vicetinus was first described in 1993 as an endemic bush-cricket of north-east Italy and was considered rare until 2008,when it became an established pest,causing severe damages to forests and crops.The possible role of temperature in changing its life cycle has still to be fully understood.Here,we explored the effect of summer temperature on egg diapause and the effect of winter temperature on egg survival.Field observations showed that the proportion of embryos that can complete development at the end of summer ranged from zero to nearly 90% depending on summer temperatures.A substantial shift in the rate of development from 20% to nearly 80% occurred in a thermal range of about 1℃.On the contrary,overwinter egg survival was high and constant(90%)across a wide range of winter temperatures that go well beyond both the cold and warm thermal limits of the current species range.Overall,the results suggest a potential key role of summer temperature warming on the outbreak propensity of this species that is able to switch from a multiyear to an annual life cycle with just a 1-2℃ warming.
文摘Parasitoid wasp communities of the canopy of temperate forests are still largely unexplored. Very little is known about the community composition ofparasitoids between canopy and understory and how much of this difference is related to forest structure or parasitoid biological strategies. In this study we investigated upon the difference in the community composition of the parasitic wasps Ichneumonidae between canopy and understory in a lowland temperate forest in northern Italy. We used general linear models to test whether parasitic strategy modifies species vertical stratification and the effect of forest structure. We also tested differences in β-diversity between canopy and understory traps and over time within single forest layers. We found that stand basal area was positively related to species richness, suggesting that the presence of mature trees can influence local wasp diversity, providing a higher number of microhabitats and hosts. The ichneumonid community of the canopy was different from that of the understory, and theβ-diversity analysis showed higher values for the canopy, due to a higher degree of species turnover between traps. In our analyses, the vertical stratification was different between groups of ichneumonids sharing different parasitic strategies. Idiobiont parasitoids of weakly or deeply concealed hosts were more diverse in the understory than in the canopy while parasitoids of spiders were equally distributed between the two layers. Even though the ichneumonid community was not particularly species-rich in the canopy of the temperate forests, the extension of sampling to that habitat significantly increased the number of species recorded.
