Responses of insect herbivores and their food plants to wind exposure and the importance of predation risk

Abstract

Abstract1. Wind is an important abiotic factor that influences an array of biological processes, but it is rarely considered in studies on plant-herbivore interactions.2. Here, we tested whether wind exposure could directly or indirectly affect the performance of two insect herbivores, Plutella xylostella and Pieris brassicae, feeding on Brassica nigra plants.3. In a greenhouse study using a factorial design, B. nigra plants were exposed to different wind regimes generated by fans before and after caterpillars were introduced on plants in an attempt to separate the effects of direct and indirect wind exposure on herbivores.4. Wind exposure delayed flowering, decreased plant height and increased leaf concentrations of amino acids and glucosinolates.5. Plant-mediated effects of wind on herbivores, that is effects of exposure of plants to wind prior to herbivore feeding, were generally small. However, development time of both herbivores was extended and adult body mass of P. xylostella was reduced when they were directly exposed to wind. By contrast, wind-exposed adult P. brassicae butterflies were significantly larger, revealing a trade-off between development time and adult size.6. Based on these results, we conducted a behavioural experiment to study preference by an avian predator, the great tit (Parus major) for last instar P. brassicae caterpillars on plants that were exposed to either control (no wind) or wind (fan-exposed) treatments.Tits captured significantly more caterpillars on still than on wind-exposed plants.7. Our results suggest that P. brassicae caterpillars are able to perceive the abiotic environment and to trade off the costs of extended development time against the benefits of increased size depending on the perceived risk of predation mediated by wind exposure. Such adaptive phenotypic plasticity in insects has not yet been described in response to wind exposure. K E Y W O R D Sabiotic factors, Brassica nigra, development, Parus major, Pieris brassicae, plant-herbivore interactions, Plutella xylostella, predatorThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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

“…In a previous study (Chen et al. ), P. brassicae exposed to wind developed slower but attained more biomass. Predation of caterpillars by birds (Great Tits) was considerably reduced when reared on plants exposed to wind.…”

“…In a previous study, we reported that caterpillars of P. xylostella are also more strongly disturbed by wind than the caterpillars of P. brassicae (Chen et al 2018). The higher mortality of P. xylostella in response to rainfall, especially when occurring at higher frequencies (80% reduction), is even stronger than mortality caused by wind exposure (10%; this study, Chen et al 2018). Eggs and (early) first-instar larvae of Lepidoptera are the most vulnerable life stages and mortality during each of these stages can be significant (>40%; Zalucki et al 2002).…”

“…In a previous study, we reported that caterpillars of P. xylostella are also more strongly disturbed by wind than the caterpillars of P. brassicae (Chen et al. ). The higher mortality of P. xylostella in response to rainfall, especially when occurring at higher frequencies (80% reduction), is even stronger than mortality caused by wind exposure (10%; this study, Chen et al.…”

“…Therefore, it is important to determine the relative importance of abiotic and biotic factors when studying plant-herbivore (multitrophic) interactions. In a previous study (Chen et al 2018), we showed that wind exposure can extend larval development time of two lepidopteran herbivores, Plutella xylostella (L.) (Plutellidae) and Pieris brassicae (L.) (Pieridae), respectively. Interestingly, wind exposure also reduced adult biomass of P. xylostella, whereas butterflies of P. brassicae were heavier on wind-exposed plants.…”

“…Interestingly, wind exposure also reduced adult biomass of P. xylostella, whereas butterflies of P. brassicae were heavier on wind-exposed plants. Plant-mediated effects were relatively small (Chen et al 2018).…”