DOI: 10.5061/dryad.1ns1rn8xg
title: Plant phenology, aphid colony growth, and honeydew deposition data

description: 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.
description: In October of 2018, we marked eight, 16 m<sup>2</sup>
 plots of <em>L. porteri</em> in a subalpine meadow near RMBL
 with PVC poles. Each plot was randomly assigned to either the ambient or
 early snow melt treatment. In April of 2019, we then placed shade cloth
 (EasyShade 50% Black Bulk Shade Cloth UV Resistant) across plots assigned
 to the early snow melt treatment. We removed the shade cloth on May 16th,
 2019. Individual plants were marked with stake flags, and we tracked
 flowering phenology for all host plants with flowering stalks
 (<em>N</em>=81). On July 26<sup>th</sup>, 2019, we
 created experimental aphid colonies by adding 10 field-collected apterous
 (wingless) aphids to the terminal inflorescences of 6 plants in each plot
 (<em>n</em>=48). We did not include host plants whose
 flowering stalks were broken, spontaneously colonized by aphids, or
 senescent. During colony establishment, we excluded ants and flying
 predators by enclosing the aphids in a fine-mesh bag and creating a stem
 barrier below each colony (Tree Tanglefoot, Contech Enterprises,
 Marysville, OH). Half of the colonies in each plot (n=24)  were randomly
 assigned to experimental warming, and the colonies were surrounded by an
 open-top warming chamber that elevated temperatures by 1.3°C. We removed
 mesh bags on July 29<sup>th </sup>and counted the number of
 aphids and ants every two to three days until August
 5<sup>th</sup>, 2019. Another set of colonies remained bagged
 with ants excluded. On August 1<sup>st</sup>, we quantified
 honeydew production from six randomly selected aphid colonies in each
 treatment combination (<em>N</em>=24). We placed 100
 cm<sup>2</sup> squares of aluminum foil around the host plant
 stem of each colony. The foil squares remained in place for 24 hrs, during
 which time ants were excluded as described above for colony establishment.
 We counted the number of honeydew droplets from digital images of the foil
 squares using a dissection microscope.
description: Comma-separated data file (.csv) can be opened by Excel,
 OpenOffice Calc, or Google Sheets.