Evidence of trans-generational developmental modifications induced by simulated heat waves in an arthropod

Abstract

Heat waves are considered to pose a greater risk to arthropods with their limited thermoregulation abilities than the increase of mean temperatures. Theoretically, within- and trans-generational modifications may allow populations to keep pace with rapidly occurring heat waves. Here, we evaluated this assumption using individuals of predatory mite Amblydromalus limonicus from the F1 and F2 generation, which were exposed to summer or simulated heat wave conditions during juvenile development. Independent of generation, survival and male body size were insensitive to heat waves. Heat stress elongated juvenile development of F1 males and females, and lowered the F1 female size at maturity indicating non-adaptive within-generational effects. Trans-generational modifications speeded up the development of F2 males and females and resulted in larger body size of F2 females deriving from the heat wave-experienced F1 generation. Faster F2 development should be adaptive, because it reduces the exposure time to heat waves and promotes an early beginning of mating activities. Being large at extreme high temperatures maybe a benefit for the F2 females, because large individuals are less vulnerable to dehydration and overheating. Thus, the potential fitness loss from reduced F1 growth should be compensated by increased fitness in the F2 indicating adaptive trans-generational modifications.

RETRACTED ARTICLE: Artificial heat waves induce species-specific plastic responses on reproduction of two spider mite predators

“…However, the assessment of heat resistance at constant temperatures does not reflect heat wave conditions with short-term temperature peaks allowing a daily recovery at moderate temperatures. Thus, the survival probabilities of N. womersleyi are likely higher under heat waves than under constant high temperatures as it is also documented for aphids (Chen et al 2013), beetles (Chidawanyika et al 2017), caterpillars (Xing et al 2015), fruit flies (Petravy et al 2001) and predatory mites (Walzer et al 2020). (2) Predatory mite species with a high reproductive potential such as N. womersleyi and P. persimilis produce female-biased sex-ratios with 70% to 80% females under optimal conditions (Sabelis 1985), but the females are able to change the offspring sex-ratio under environmental stress resulting in a balanced sex-ratio (Sabelis 1985;.…”

“…However, thermal within-generational plastic modifications such as acclimation and hardening increased cold-tolerance, but had limited effects on heat-tolerance in ectotherms (Gunderson and Stillman 2015). Furthermore, heat-exposed parents may alter offspring traits and consequently their thermal performance via trans-generational plasticity, as it has been shown in fruit flies and predatory mites (Schiffer et al 2013;Walzer et al 2020). Finally, local adaptation to climatic conditions by genetic modifications is a further mechanism affecting heat resistance.…”

“…After 48 h, the females were removed and the progress of juvenile development was observed daily until the predatory mites reached adulthood. The young females of each species (8 to 10 days old) were placed singly in lockable cages (for detailed description of the cages see Schausberger 1997;Walzer et al 2020) and starved for 24 h. Only females, which were able to deposit eggs during this period, were used as study objects in the experiments. All rearing units and lockable cages were placed in a climate chamber under constant temperatures of 25 ± 2 °C, 60 ± 10% RH and 16:8 h L:D.…”

“…Thus, costs may arise for offspring of both species, if small egg size correlates with adult body size irrespective of offspring sex. Small females and males may suffer from dehydration and overheating at high temperatures (Kingsolver et al 2007;Gardner et al 2011;Walzer et al 2020). Inferiority in resource competition and reduced reproductive success are other potential disadvantages of small body size (Blanckenhorn 2000;Schausberger 2013, 2014).…”

“…To close this gap, we compared the reproductive output of P. persimilis and N. womersleyi exposed to short heat waves by evaluating the following assumptions: (1) mortality of both species is low and not affected by temperature so that all changes in predation, egg number and size are obviously plastic modifications (Walzer et al 2020); (2) N. womersleyi is less heat sensitive than P. persimilis, which is reflected in higher reproductive output under heat wave conditions.…”