Landscape effects on the thermotolerance of carabid beetles and the role of behavioral thermoregulation

Physiological thermotolerance and behavioral thermoregulation are central to seasonal cold adaptation in ectothermic organisms.For species with enhanced mobility,behavioral responses may be of greater importance in the cold stress response.Employing the carabid beetles as a study organism,the current study compared physiological thermotolerance and behavioral thermoregulation in carabid species inhabiting cereal fields in different landscape contexts,from fine grain heterogeneous“complex”landscapes to homogenous“simple”landscapes.Physiological thermotolerance was determined via measurement of the CTmin and chill coma temperature.Behavioral responses to cold temperature exposure were determined employing a purpose built arena,and thoracic temperature measured to estimate the efficacy of the behavior as a form of behavioral thermoregulation.Results revealed an influence of landscape composition on the cold tolerance of carabid beetles,although species differed in their sensitivity to landscape intensification.A reduced effect of landscape on the thermotolerance of larger carabid beetles was observed,thought to be the consequence of greater mobility preventing local acclimation to microclimatic variation along the landscape intensification gradient.Investigation into behavioral thermoregulation of the 3 largest species revealed burrowing behavior to be the main behavioral response to cold stress,acting to significantly raise carabid body temperature.This finding highlights the importance of behavioral thermoregulation as a strategy to evade cold stress.The use of behavioral thermoregulation may negate the need to invest in physiological thermotolerance,further offering explanation for the lack of landscape effect on the physiological thermotolerance of larger carabids.

Climatic niche shift of an invasive shrub (Ulex europaeus): a global scale comparison in native and introduced regions

Aims Invasive species,which recently expanded,may help understand how climatic niche can shift at the time scale of the current global change.Here,we address the climatic niche shift of an invasive shrub(common gorse,Ulex europaeus)at the world and regional scales to assess how it could contribute to increasing invasibility.Methods Based on a 28187 occurrences database,we used a combination of 9 species distribution models(SDM)to assess regional climatic niche from both the native range(Western Europe)and the introduced range in different parts of the world(North-West America,South America,North Europe,Australia and New Zealand).Important Findings Despite being restricted to annual mean temperature between 4℃ and 22℃,as well as annual precipitation higher than 300 mm/year,the range of bioclimatic conditions suitable for gorse was very large.Based on a native versus introduced SDM comparison,we highlighted a niche expansion in North-West America,South America and to a lesser degree in Australia,while a niche displacement was assessed in North Europe.These niche changes induced an increase in potential occupied areas by gorse by 49,111,202 and 283%in Australia,North Europe,North-West America and South America,respectively.On the contrary,we found no evidence of niche change in New Zealand,which presents similar climatic condition to the native environment(Western Europe).This study highlights how niche expansion and displacement of gorse might increase invasibility at regional scale.The change in gorse niche toward new climatic conditions may result from adaptive plasticity or genetic evolution and may explain why it has such a high level of invasibility.Taking into account the possibility of a niche shift is crucial to improve invasive plants management and control.

Evaluation of soil erosion risk and identification of soil cover and management factor (C) for RUSLE in European vineyards with different soil management

Vineyards show some of the largest erosion rates reported in agricultural areas in Europe.Reported rates vary considerably under the same land use,since erosion processes are highly affected by climate,soil,topography and by the adopted soil management practices.Literature also shows differences in the effect of same conservation practices on reducing soil erosion from conventional,bare soil based,management.The Revised Universal Soil Loss Equation(RUSLE)is commonly adopted to estimate rates of water erosion on cropland under different forms of land use and management,but it requires proper value of soil cover and management(C)factors in order to obtain a reliable evaluation of local soil erosion rates.In this study the ORUSCAL(Orchard RUSle CALibration)is used to identify the best calibration strategy against long-term experimental data.Afterwards,ORUSCAL is used in order to apply the RUSLE technology from farm based information across different European wine-growing regions.The results suggest that the best strategy for calibration should incorporate the soil moisture sub-factor(Sm)to provide better soil loss predictions.The C factor,whose average values ranged from 0.012 to 0.597.presented a large spatial variability due to coupling with local climate and specific local management.The comparison across the five wine-growing regions indicates that for the soil protection management,permanent cover crop is the best measure for accomplishing sustainable erosion rates across the studied areas.Alternate and temporary cover crops,that are used in areas of limited water resources to prevent competition with vines,failed to achieve sustainable erosion rates,that still need to be addressed.This raises the need for a careful use of C values developed under different environmental conditions.

The effect of landscape complexity and microclimate on the thermal tolerance of a pest insect

Landscape changes are known to exacerbate the impacts of climate change. As such, understanding the combined effect of climate and landscape on agroecosystems is vital if we are to maintain the fimction of agroecosystems. This study aimed to elucidate the effects of agricultural landscape complexity on the microclimate and thermal tolerance of an aphid pest to better understand how landscape and climate may interact to affect the thermal tolerance of pest species within the context of global climate change. Meteo- rological data were measured at the landscape level, and cereal aphids （Sitobion avenae, Metopolophium dirhodum and Rhopalosiphum padi） sampled, from contrasting landscapes （simple and complex） in winter 2013/2014 and spring 2014 in cereal fields of Brittany, France. Aphids were returned to the laboratory and the effect of landscape of origin on aphid cold tolerance （as determined by CTmin） was investigated. Results revealed that local landscape complexity significantly affected microclimate, with simple homogenous landscapes being on average warmer, but with greater temperature variation. Landscape complexity was shown to impact aphid cold tolerance, with aphids from complex land- scapes being more cold tolerant than those from simple landscapes in both winter and spring, but with differences among species. This study highlights that future changes to land use could have implications for the thermal tolerance and adaptability of insects. Fur- thermore, not all insect species respond in a similar way to microhabitat and microclimate, which could disrupt important predator-prey relationships and the ecosystem service they provide.

Response of life-history traits to artificial and natural selection for virulence and nonvirulence in a Drosophila parastitoid, Asobara tabida

Co-evolution of host-parasitoid interactions is determined by the costs of host resistance, which received empirical evidence, and the costs ofparasitoid virulence, which have been mostly hypothesized. Asobara tabida is a parasitoid, which mainly parasitizes Drosophila melanogaster and D. subobscura, the first species being able to resist to the parasitoid development while the second species is not. To parasitize resistant hosts, including D. melanogaster, A. tabida develops sticky eggs, which prevent encapsulation, but this virulence mechanism may be costly. Interindividual and interpopulation variation in the proportion of sticky eggs respectively allowed us to （i） artificially select and compare life-history traits of a virulent and a nonvirulent laboratory strain, and （ii） compare a virulent and a nonvirulent field strain, to investigate the hypothetical costs of virulence. We observed strong differences between the 2 laboratory strains. The nonvirulent strain invested fewer resources in reproduction and walked less than the virulent one but lived longer. Concerning the field strains, we observed that the nonvirulent strain had larger wings while the virulent one walked more and faster. All together, our results suggest that virulence may not always be costly, but rather that different life histories associated with different levels of virulence may coexist at both intra- and interDoDulation levels.