Variations in seasonal (not mean) temperatures drive rapid adaptations to novel environments at a continent scale

Abstract

The recent development of human societies has led to major, rapid, and often inexorable changes in the environment of most animal species. Over the last decades, a growing number of studies formulated predictions on the modalities of animal adaptation to novel or changing environments, questioning how and at what speed animals should adapt to such changes, discussing the levels of risks imposed by changes in the mean and/or variance of temperatures on animal performance, and exploring the underlying roles of phenotypic plasticity and genetic inheritance. These fundamental predictions, however, remain poorly tested using field data. Here, we tested these predictions using a unique continental‐scale data set in the European earwig Forficula auricularia L., a univoltine insect introduced in North America one century ago. We conducted a common garden experiment, in which we measured 13 life‐history traits in 4,158 field‐sampled earwigs originating from 19 populations across North America. Our results first demonstrate that 10 of the 13 measured life‐history traits are associated with two sets of variations in seasonal temperatures, that is, winter–summer and autumn–spring. We found, however, no association with the overall mean monthly temperatures of the invaded locations. Furthermore, our use of a common garden setup reveals that the observed patterns of variation in earwigs’ life‐history traits are not mere plastic responses to their current environment, but are either due to their genetic background and/or to the environmental conditions they experienced during early life development. Overall, these findings provide continent‐scale support to the claims that adaptation to thermal changes can occur quickly (in less than 100 generations), even in insects with long life cycles, and emphasize the importance of variation in seasonal temperature over mean population temperatures in climate adaptation.

Forficula auricularia (Dermaptera) in orchards: Monitoring seasonal activity, the effect of pesticides, and the perception of European fruit growers on its role as a predator or pest

“…Differences between our results and those of other authors are likely to be related to climatic changes, specific region, collection method, specificity of the year, orchard management, and perhaps many other factors. Variation of temperature has a significant effect on the life history traits of European earwigs 66 . Our results represent central European orchards with conditions characteristic of the Czech thermophyticum phytogeographic region 67…”

Friend or foe? The apparent benefits of gregarine (Apicomplexa: Sporozoa) infection in the European earwig

“…These nutritional benefits could be particularly important in the European earwig, as females experience long periods of food deprivation over winter (Gingras and Tourneur, 2001;Kölliker, 2007;Tourneur and Meunier, 2020) during which they also provide extensive and energetically costly forms of care to their eggs (Koch and Meunier, 2014;Diehl and Meunier, 2018;Van Meyel et al, 2019). Assuming that gregarines help to resist against starvation, having a large stock of gregarines in the gut before egg production (as we observed in September) might, therefore, ensure female survival over the coming periods of starvation and high energy demand.…”

“…This explanation is unlikely to apply to earwigs. Even if males exhibit a comparatively shorter lifespan (Tourneur and Meunier, 2020), they are known to exhibit higher levels of immune defence and could thus be more tolerant to infection compared with females (Rantala et al, 2007;Vogelweith et al, 2017a). Another potential explanation is that earwigs express sex-specific behaviours that increase (or decrease) the risk of gregarine infection.…”

“…During the subsequent weeks (i.e. all over winter), these mothers typically stop their foraging activities (Berleur et al, 2001;Kölliker, 2007;Tourneur and Meunier, 2020) to provide extensive forms of care to their eggs and then to their resulting juveniles (Gingras and Tourneur, 2001;Kölliker, 2007;Meunier et al, 2012;Boos et al, 2014;Thesing et al, 2015;Diehl and Meunier, 2018).…”

The first of five moults ofForficula auriculariaL. (Dermaptera: Forficulidae)

“…For example, number of moults is an important criterion in taxonomy (Chapman and Reynolds 2013), and these results call for future work to explore whether this new information could be used to discriminate amongst the sister species A and B currently included under the species name, F. auricularia (Wirth et al 1998). Similarly, natural variation in environmental constraints might affect the success, timing, and duration of this intermediate moult, as it does for any moulting event (Chapman 2013); our findings thus suggest investigations into the possible impacts of these constraints and of their potential stability in the invasion success of the European earwig worldwide (Quarrell et al 2018;Tourneur and Meunier 2020). Finally, maternal care towards the eggs is both extended and essential in this species (Boos et al 2014;Koch and Meunier 2014;Van Meyel et al 2019); our results prompt further tests to shed light on this behaviour's possible impact on the success of this first moulting event (e.g., Fig.…”