Rain downpours affect survival and development of insect herbivores: the specter of climate change?
Chen et al., 2019.
Chen et al., 2019.
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.
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