Butterfly–host plant synchrony determines patterns of host use across years and regions

Abstract

Variation in the degree of synchrony among host plants and herbivores can disrupt or intensify species interactions, alter the strength of natural selection on traits associated with phenological timing, and drive novel host plant associations. We used field observations from three regions during four seasons to examine how timing of the butterfly herbivore Anthocharis cardamines relative to six host plant species (Arabis hirsuta, Cardamine pratensis, Arabis glabra, Arabidopsis thaliana, Thlaspi caerulescens and Capsella bursa‐pastoris) influenced host species use and the choice of host plant individuals within populations. Butterflies laid a larger fraction of their eggs on species that were closer to the butterfly's preferred stage of development than on other host species. Within host plant populations, butterflies showed a stronger preference for individuals with a late phenology when plants within the population were on average more developed at the time of butterfly flight. Our results suggest that changes in synchrony between herbivores and their host plants are associated with changes in both host species use and the choice of host plant individuals differing in phenology within populations. This is likely to be an important mechanism generating variation in interaction intensities and trait selection in the wild, and therefore also relevant for understanding how anthropogenic induced changes, such as global warming, will influence natural communities.

Plant–animal interactions mediate climatic effects on selection on flowering time

“…vernus development and thus to a later mean phenology, but have small effects on the beetles, which should therefore appear earlier relative to the mean flowering phenology, and preferentially attack earlier‐flowering individuals (Toftegaard et al. 2019). High April temperatures advance flowering of L .…”

“…In years with lower March and higher April temperatures, seed predation was higher in early-flowering plants, suggesting that the activity period of the seedpredator beetles overlapped more with individuals with an early phenology, and that the mean phenology of L. vernus was delayed with respect to the activity period of the seed-predator beetles. Lower March temperatures might lead to a later initiation of L. vernus development and thus to a later mean phenology, but have small effects on the beetles, which should therefore appear earlier relative to the mean flowering phenology, and preferentially attack earlier-flowering individuals (Toftegaard et al 2019). High April temperatures advance flowering of L. vernus (Ehrlén and Valdés 2020), and the fact that beetle activity seemed to overlap more with earlyflowering individuals in years with warm April temperatures suggests that beetle development responds more strongly to increased temperature than plant development during this period (Kharouba and Vellend 2015, Thackeray et al 2016, Toftegaard et al 2019.…”

Predictability of Biotic Stress Structures Plant Defence Evolution

“…Moreover, transition between ontogenetic or phenological stages of plants such as germination, leaf flushing, or flowering are often initiated by similar abiotic conditions that trigger the release from dormancy in insects or migration of vertebrate herbivores. Hence, phenologies of plants and their attackers may strongly correlate [29].…”

“…The adaptive value of ontogenetic changes in defence strategies match patterns that act on longer-term scales of development. Phenotypically, plants may use abiotic conditions to match seasonal variation in resistance to the likelihood of herbivore attack due to the correlation of seasonality and herbivore activity [29]. Over shorter timescales, plants may use reliable cues of presence of antagonists to anticipate actual attack by these antagonists.…”

Climate-driven variation in biotic interactions provides a narrow and variable window of opportunity for an insect herbivore at its ecological margin

“…The phenology of many consumers is closely synchronised with the development and availability of their resources, and their interactions occur within an often narrow 'window of opportunity' for the consumer defined by the phenology of both partners [10][11][12][13][14]. For herbivorous insects, the length of the phenological window of opportunity will be partly determined by the specificity of its interaction with the host, the host's growth form, and the broader environmental context.…”