Abstract
Between 1975 to 2011, aphid Relative Growth Rates (RGR) were modelled as a function of mean outdoor temperature and host plant phenology. The model was applied to the grain aphid Sitobion avenae using data on aphid counts in winter wheat at two different climate regions in France (oceanic climate, Rennes (western France); continental climate, Paris). Mean observed aphid RGR was higher in Paris compared to the Rennes region. RGR increased with mean temperature, which is explained by aphid reproduction, growth and development being dependent on ambient temperature. From the stem extension to the heading stage in wheat, there was either a plateau in RGR values (Rennes) or an increase with a maximum at heading (Paris) due to high intrinsic rates of increase in aphids and also to aphid immigration. From the wheat flowering to the ripening stage, RGR decreased in both regions due to the low intrinsic rate of increase in aphids and high emigration rate linked to reduced nutrient quality in maturing wheat. The model validation process showed that the fitted models have more predictive power in the Paris region than in the Rennes region.
Highlights
In light of global climate change, more research is needed to study the effects of temperature trends and associated fluctuations on living organisms
To estimate the Relative Growth Rates (RGR) of aphids, we considered the logarithmic derivative of the smoothing curve, which directly gave an estimate of the instantaneous relative rate of increase
The minimal value of RGR is of the same order in both regions (20.5)
Summary
In light of global climate change, more research is needed to study the effects of temperature trends and associated fluctuations on living organisms. Changes in populations of indigenous or invasive insect pests are one of the most important challenges facing ecology and crop protection [2,3,4]. Modelling insect population dynamics requires the incorporation of various driving factors. Development of herbivorous insect species depends on biotic driving factors such as the phenology of the host plant. Other biotic factors act at higher trophic levels on insect development and include predators, parasitoids and entomopathogens, which in turn depend on herbivore population accumulation to survive. The insect food web is temperature dependent because all organisms involved are ectothermal. The combined response of insects to two or more driving factors is difficult to study experimentally because the interactions between these factors require a large experimental design and expensive testing chambers. In vitro results are often very different from what is observed in nature [5,6,7]
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