The high invasion success of fall armyworm is related to life-history strategies across a range of stressful temperatures.

Background: Insects living in unfavorably high or low temperatures are predicted to display a fast or slow life-history strategy. Here, we examined life histories of fall armyworm (FAW), a globally important invasive species with a broad ecological niche, at five constant temperatures of 13, 19, 25, 31 and 37°C, to study life-history responses to different temperatures.

Results: In our experiment, FAW had lower lifetime fecundity at unfavorable temperatures, a finding that is consistent with the idea that FAW can shift resources from reproduction to other functions under stressful conditions-such as heat or cold tolerance. Given the adverse effects of stressful temperatures, life-history strategies arise from individuals having limited remaining resources to allocate towards vital functions like survival or reproduction. Here we show plasticity in life-history strategies adopted at different temperatures. Rather than simply varying along a fast-slow continuum, FAW at unfavorably high temperatures exhibited lower daily fecundity and longer reproductive lifespans, and at unfavorably low temperatures showed a shorter peak in reproduction later in life, compared with FAW at 25°C. Such patterns, if adaptive, could suggest a strategy mitigating reproductive and mortality risk in unfavorable environments, however, this remains to be tested.

Conclusion: Our analysis suggests that the high invasion success of FAW may result from their ability to adjust life-history strategies, across a range of stressful temperatures, in a way that reduces not only mortality, but also fecundity loss. The adoption of such strategies may be instrumental for the global invasion success of FAW. © 2022 Society of Chemical Industry.