Rain downpours affect survival and development of insect herbivores: the specter of climate change?

Abstract

Changes in the frequency, duration, and intensity of rainfall events are among the abiotic effects predicted under anthropogenic global warming. Heavy downpours may profoundly affect the development and survival of small organisms such as insects. Here, we examined direct (physically on the insects) and indirect (plant‐mediated) effects of simulated downpours on the performance of caterpillars of two lepidopteran herbivores (Plutella xylostella and Pieris brassicae) feeding on black mustard (Brassica nigra) plants. Host plants were exposed to different rainfall regimes both before and while caterpillars were feeding on the plants in an attempt to separate direct and indirect (plant‐mediated) effects of rainfall on insect survival and development. In two independent experiments, downpours were simulated as a single long (20 min) or as three short (5 min) daily events. Downpours had a strong negative direct effect on the survival of P. xylostella, but not on that of P. brassicae. Direct effects of downpours consistently increased development time of both herbivore species, whereas effects on body mass depended on herbivore species and downpour frequency. Caterpillar disturbance by rain and recorded microclimatic cooling by 5°C may explain extended immature development. Indirect, plant‐mediated effects of downpours on the herbivores were generally small, despite the fact that sugar concentrations were reduced and herbivore induction of secondary metabolites (glucosinolates) was enhanced in plants exposed to rain. Changes in the frequency of precipitation events due to climate change may impact the survival and development of insect herbivores differentially. Broader effects of downpours on insects and other arthropods up the food chain could seriously impair and disrupt trophic interactions, ultimately destabilizing communities.

The importance of extreme rainfall events and their timing in a semi‐arid grassland

“…Smith, 2011), is only beginning to emerge (e.g. Chen, Harvey, Biere, & Gols, 2019;Eekhout, Hunink, Terink, & Vente, 2018;Hammerl et al, 2019;Manea & Leishman, 2018;Zhang et al, 2019). While it is expected that changes in deluge frequency will impact most ecosystems to some degree (Jentsch & Beierkuhnlein, 2008;Knapp et al, 2008;Weltzin et al, 2003), it is likely that arid and semi-arid ecosystems will be disproportionately affected (Ahlstrom et al, 2015;Diffenbaugh, Giorgi, & Pal, 2008).…”

Spatiotemporal shifts in the role of floral traits in shaping tropical plant-pollinator interactions

“…For birds and bats it has been shown that rainfall increases the energy cost of flight (Aizen, 2003;Ortega-Jimenez & Dudley, 2012;Voigt, Schneeberger, Voigt-Heucke, & Lewanzik, 2011). This effect is even greater for smaller insect visitors whose activity can be partially reduced or even completely impeded, by directly damaging them and reducing their abundance (C. Chen, Harvey, Biere, & Gols, 2019;Kishimoto-Yamada & Itioka, 2015;Maicher et al, 2020Maicher et al, , 2018Struck, 1994). Similarly, the higher energetic requirements in upper elevations resulting from lower temperatures, is consistent with the increased nectar production per flower with elevation.…”

Effects of Longer Droughts on Holm Oak Quercus ilex L. Acorn Pests: Consequences for Infestation Rates, Seed Biomass and Embryo Survival

“…Rain hinders small insect flight [55] and reduces adult activity. In the case of eggs and first instar caterpillars, storms may provoke high mortality rates (see [56] and references therein). Cydia oviposition takes place mainly in September, and there is a period of two weeks in which eggs and L1 larvae are unprotected (on the oak shoots).…”