Phenological synchrony between a plant and a specialised herbivore

Abstract

Global anthropogenic climate change is altering the phenology of many species, with implications for interacting species. If species use different cues or respond at different rates, this could result in asynchrony between hosts and herbivores. The larval stage of the endemic critically endangered Sinai Baton Blue butterfly (Pseudophilotes sinaicus) feeds exclusively on the buds and flowers of an endangered near-endemic plant, the Sinai Thyme (Thymus decussatus), with a narrow window in time when both larvae and flowers are present. We test for synchrony in time and space between the flowering phenology of the host plant and the associated timings and abundances of the Sinai Baton Blue. Together with significant spatial variation amongst patches, there were large inter-annual variations in flowering period, up to two weeks between years, indicating phenotypic plasticity in response to abiotic conditions. The butterfly flight period was approximately synchronised to the flowering of its host plant, but there was no evidence of any detailed spatial or temporal correlations in phenology. The dramatic annual population changes, possibly cycles, in the butterfly, may partly be driven by differences in the responses between plant and herbivore to climate that cause varying degrees of synchrony between years.