Plant phenology, aphid colony growth, and honeydew deposition data

Changing phenological cues can lead to trophic mismatch for plants and
herbivores, and this often shifts herbivore feeding to plant stages of
lower quality. Temperature can also mediate how herbivores respond to
plant quality, leading to temperature-by-phenology interactions. We
examined how both temperature and host plant phenology impact aphid
abundance and their mutualism with ants. Our study system was composed of
aphids (Aphis asclepiadis) that colonize flowering stalks of the host
plant, Ligusticum porteri. Abundance of this aphid species is dependent on
mutualism with several ant species. To understand how host plant phenology
and temperature affect aphid abundance, we experimentally accelerated snow
melt date by two weeks, which correspondingly advanced flowering
phenology. Then, we factorially combined this phenology treatment with
open top warming chambers surrounding aphid colonies. We tracked aphid
colony growth and interactions with ants, and results showed the greatest
colony growth at cooler, ambient temperatures on host plants without
accelerated phenology. These colonies also showed the highest levels of
honeydew deposition relative to their overall size. Our findings show that
trophic mismatch decreases aphid abundance, and changes to the ant-aphid
mutualism exacerbate this effect.