Warming counteracts defoliation‐induced mismatch by increasing herbivore‐plant phenological synchrony

Abstract

Climate change is altering phenology; however, the magnitude of this change varies among taxa. Compared with phenological mismatch between plants and herbivores, synchronization due to climate has been less explored, despite its potential implications for trophic interactions. The earlier budburst induced by defoliation is a phenological strategy for plants against herbivores. Here, we tested whether warming can counteract defoliation‐induced mismatch by increasing herbivore‐plant phenological synchrony. We compared the larval phenology of spruce budworm and budburst in balsam fir, black spruce, and white spruce saplings subjected to defoliation in a controlled environment at temperatures of 12, 17, and 22°C. Budburst in defoliated saplings occurred 6–24 days earlier than in the controls, thus mismatching needle development from larval feeding. This mismatch decreased to only 3–7 days, however, when temperatures warmed by 5 and 10°C, leading to a resynchronization of the host with spruce budworm larvae. The increasing synchrony under warming counteracts the defoliation‐induced mismatch, disrupting trophic interactions and energy flow between forest ecosystem and insect populations. Our results suggest that the predicted warming may improve food quality and provide better growth conditions for larval development, thus promoting longer or more intense insect outbreaks in the future.

Dynamic effects of insect herbivory and climate on tundra shrub growth: Roles of browsing and ramet age

“…temperatures, especially at high latitudes (Bale et al, 2002;Barrio et al, 2017;Kozlov et al, 2015;Lehmann et al, 2020;Ren et al, 2020;Wagner & Doak, 2018). It is also compatible with find- in their 2-year experiment.…”

Climate change alters plant–herbivore interactions

“…In general, arthropod herbivores are advancing their phenology faster than plants, as they are more sensitive to temperature, while plants often have specific photoperiod thresholds (Visser & Christiaan, 2005; Menéndez, 2007; Körner & Basler, 2010; but see Forrest & Thomson, 2011). Asynchronous phenological shifts may generate temporal mismatches, which could amplify or dampen herbivore damage (Dewar & Watt, 1992; Diamond et al ., 2011; DeLucia et al ., 2012; Abarca & Lill, 2015; Ren et al ., 2020). Warm springs in temperate regions often induce earlier insect emergence and activity, especially for insects that overwinter as adults (Diamond et al ., 2011; Bell et al ., 2015).…”

Improved performance of the eastern spruce budworm on black spruce as warming temperatures disrupt phenological defences

“…Previous work showed that synchrony between black spruce budburst and budworm emergence improves with higher temperature in both the field (Pureswaran et al, 2019) and the greenhouse (Ren et al, 2020). In naturally occurring microclimates in the forest, Pureswaran et al (2019) demonstrated that budburst in black spruce advanced by up to 3 days per degree increase in temperature.…”

“…Recent work suggests that improved phenological synchrony between black spruce budburst and budworm emergence from diapause in the spring allows the budworm to overcome black spruce defences and makes black spruce a very suitable host (Fuentealba et al, 2017). Subsequent work showed that higher temperatures increase phenological synchrony between black spruce and the budworm (Neau, 2014; Pureswaran et al, 2019; Ren et al, 2020). This suggests that under a warming climate, black spruce is becoming more susceptible to defoliation by the eastern spruce budworm, thus increasing acceptability of black spruce to the budworm and putting the vast boreal ecosystem in peril of budworm defoliation under a warmer climate (Pureswaran et al, 2015).…”