DOI: 10.5061/dryad.bzkh1897w
title: Asymmetric regulation of caterpillar development by changes in photoperiod

description: Many insects possess the plastic ability to either develop directly to
 adulthood, or enter diapause and postpone reproduction until the next
 year, depending on environmental cues (primarily photoperiod) that signal
 the amount of time remaining until the end of the growth season. These two
 alternative pathways often differ in co-adapted life history traits, e.g.
 with slower development and larger size in individuals headed for
 diapause. The developmental timing of these differences may be of adaptive
 importance: if traits diverge early, the potential for phenotypic
 differences between the pathways is greater, whereas if traits diverge
 late, the risk may be lower of expressing a maladaptive phenotype if the
 selective environment changes during development. Here we explore the
 effects of changes in photoperiodic information during life on pupal
 diapause and associated life history traits in the butterfly Pararge
 aegeria. We find that both pupal diapause and larval development rate are
 asymmetrically regulated: while exposure to long days late in life
 (regardless of earlier experiences) was sufficient to produce non-diapause
 development and accelerate larval development accordingly, more prolonged
 exposure to short days was required to induce diapause and slow down
 pre-diapause larval development. While the two developmental pathways
 diverged early in development, development rates could be partially
 reversed by altered environmental cues. Meanwhile, pathway differences in
 body size were more inflexible, despite emerging late in development.
 These results show how several traits may be shaped by the same
 environmental cue (photoperiod), but along subtly different ontogenies,
 into an integrated phenotype.
description: Larvae of the speckled wood butterfly, <em>Pararge
 aegeria</em>, were subjected to six different photoperiod treatments
 from hatching to pupation (two static, and four incorporating a change in
 photoperiod during development). The primary data recorded was the time
 (resolution = 1 day) at which larvae molted from one instar to the next
 (or to the pupal stage), the weight at each molt, and whether or not the
 mature pupa entered diapause (dormancy). An R script is
 included that contains all the statistical analyses presented in the
 article to which this dataset belongs, including the generation of
 figures.
description: It is important to note that the dataset provided is
 post-mortality; it does not account for those individuals that died during
 the experiment (mortality rate not recorded, but is typically around
 10-15% in similar laboratory experiments with this species).
 Hatching weights and hatching dates are absent for one of the
 three populations used (Skåne), meaning that some analyses could not be
 carried out for this population. This should be apparent (when relevant)
 in the analysis script; otherwise, see article for details.
 Some individuals are missing weights or dates at certain time
 points. A ReadMe file is included with descriptions of
 the variables in the dataset.