DOI: 10.5061/dryad.d2547d84j
title: Climate-driven thermal opportunities and risks for leaf miners in aspen canopies

description: In tree canopies, incoming solar radiation interacts with leaves and
 branches to generate temperature differences within and among leaves,
 presenting thermal opportunities and risks for leaf-dwelling ectotherms.
 Although leaf biophysics and insect thermal ecology are well understood,
 few studies have examined them together in single systems. We examined
 temperature variability in aspen canopies, Populus tremuloides, and its
 consequences for a common herbivore, the leaf-mining caterpillar
 Phyllocnistis populiella. We shaded leaves in the field and measured
 effects on leaf temperature and larval growth and survival. We also
 estimated larval thermal performance curves for feeding and growth and
 measured upper lethal temperatures. Sunlit leaves directly facing the
 incoming rays reached the highest temperatures, typically 3 – 8 °C above
 ambient air temperature. Irradiance driven increases in temperatures,
 however, were transient enough that they did not alter observed growth
 rates of leaf miners. Incubator and ramping experiments suggested that
 larval performance peaks between 25 and 32 °C and declines to zero between
 35 and 40 °C, depending on duration of temperature exposure. Upper lethal
 temperatures during one-hour heat shocks were 42 – 43 °C. When larvae were
 active in early spring, temperatures generally were low enough to depress
 rates of feeding and growth below their maxima, and only rarely did
 estimated mine temperatures rise beyond optimal temperatures. Observed
 leaf or mine temperatures never approached larval upper lethal
 temperatures. At this site during our experiments, larvae thus appeared to
 have a significant thermal safety margin; the more pressing problem was
 inadequate heat. Detailed information on mine temperatures and larval
 performance curves, however, allowed us to leverage long-term data sets on
 air temperature to estimate potential future shifts in performance and
 longer-term risks to larvae from lethally high temperatures. This analysis
 suggests that, in the past 20 years, larval performance has often been
 limited by cold and that the risk of heat stress has been low. Future
 warming will raise mean rates of feeding and growth but also the risk of
 exposure to injuriously or lethally high temperatures.
description: These data were collected primarily at the MPG North Ranch, as
 detailed in the associated paper. The data are derived from weather
 stations, local measurements of leaf temperatures using thermocouples and
 infrared cameras, measurements of feeding, growth, and survival of larvae
 of the aspen leaf miner (Phyllocnistis populiella) as functions of
 temperature. Some growth data were obtained at the University of
 Montana.
description: Scripts and data files are arranged by the figures in which they
 occur (Figures 3 - 12 in the main paper). Each R script reads in the
 necessary data from associated .csv or .txt files. One figure (Figure 3)
 also requires reading in a set of raw files from data loggers, which are
 provided in two zip files. The script provides a call to unzip those files
 locally.