DOI: 10.5061/dryad.34tmpg4ks
title: Adult facilitation becomes competition as juvenile soapberry bugs age

description: Intraspecific interactions can change from facilitative to competitive
 depending on the organism’s ontogeny. In plant-feeding insects, host plant
 defenses can be strengthened or weakened by insect feeding, and can
 therefore be important for determining whether two insects feeding on the
 same plant help or harm each other’s fitness. Here I conducted two
 experiments looking at the direct effect of a physical seed defense and
 the role of intraspecific facilitation in reducing the effects of that
 defense for juveniles of the red-shouldered soapberry bug. I demonstrate
 that juveniles are severely inhibited by the tough seed coat of their host
 plant, leading to high mortality early in development. Adults, in
 contrast, can create holes through which younger individuals could
 potentially feed. I manipulated whether or not seeds were fed on by adults
 on two host plant species: a well-defended native host and a poorly
 defended introduced host. Survival in the first week of development was
 dramatically improved by prior adult feeding and this facilitation was
 stronger on the well-defended host plant. However, the benefits of prior
 adult feeding ceased after the first week of development and shifted to
 having a negative effect on survival, development time, and body size.
 These results indicate that ontogeny is a key factor determining the
 effects of plant defenses and the strength and direction of intraspecific
 interactions across multiple host plant species.
description: There are two datasets and processing scripts, organized into
 Experiment 1 and Experiment 2. Before running any of the scripts, ensure
 that 1) the data folders and scripts folders are all located in the same
 directory (e.g., put all folders on the Desktop) and 2) All references to
 setwd("~/Desktop/") in the script you are running have replaced
 "~/Desktop/" with the name of that directory (if it's the
 Desktop, you don't need to change these). Otherwise, attempts of
 stats or figure scripts to access data will fail. Statistics scripts will
 also source scripts from the general stats scripts folder, so make sure
 this folder is in the same directory. In Experiment 1,
 juvenile soapberry bugs were raised on seeds of three host plants
 (nathost=Cardiospermum corindum, Koelreuteria elegans, and Koelreuteria
 paniculata) that were either intact or had experienced prior feeding by
 adult soapberry bugs (Treatment: "Y"=prior feeding,
 "N"=intact). Before being given to juveniles, holes created by
 adults were counted for seeds in the prior feeding treatment. Once they
 reached adulthood, all bugs were measured for morphology.
 In Exp.1.data.survival.csv, the data is recorded as follows: ID
 (identifying number), Family (parent ID number), Population (collection
 location), pophost (host species from which the parents were collected),
 nathost (developmental host), Trmt (prior feeding or intact treatment),
 hatch.date (date the nymph hatched), S1.cones, S2.cones, and S3.cones
 (holes created by adults in seeds 1, 2, and 3), death.date (day the
 juvenile died, if it did not reach adulthood; otherwise NA), eclosion.date
 (date the juvenile reached adulthood; otherwise NA), sex (sex, if it
 reached adulthood), feeding1 (number of hours seed 1 was in the incubator;
 for prior feeding treatment, the number of hours it was exposed to adult
 feeding); lifespan (lifespan for bugs that died before reaching adulthood;
 otherwise #VALUE!), Dvpt.time (time from hatch to adulthood, for bugs that
 reached adulthood; otherwise #VALUE!). In
 Exp1.data.morphology.csv, morphological measures for the same experiments
 for individuals that reached adulthood. Columns are as follows: ID (same
 as in Exp.1.data.survival.csv), sex, thorax (width of pronotum at widest
 point), beak (length of rostrum), wing (length of forewing), and wmorph
 (wing morph, short or long). For all scripts, setwd()
 calls should be updated at the top of each section to the location of the
 unzipped dryad folder. Scripts call each other and data files using the
 organization of the whole file structure, so do not rearrange folders
 within these! Scripts analyzing these two Experiment 1 datasets are in the
 "Experiment 1 stats" folder, for comparing C. corindum and K.
 elegans. “1-load_survival” contains functions for loading and organizing
 the data files into a format that works for the analyses; these are loaded
 and called within the other scripts. “1a-facilitation.survival.R” analyzes
 survival in Experiment 1. “1b-facilitation.survival.by.holes” analyzes
 survival split in early and late, and as a function of the number of holes
 drilled in each seed within the prior feeding treatment alone.
 “1c-development.time.R” analyzes development time, both as a function of
 treatment and as a function of hole number within the prior feeding
 treatment. “1d-body size.R” analyzes thorax width, both as a function of
 treatment and as a function of hole number within the prior feeding
 treatment. Statistics scripts are in R and commented.
 Appendix A stats and Appendix B stats deal with cases including
 K. paniculata as a collection host and natal host, respectively.
 Statistics scripts are in R and commented to explain what's going on
 at each stage. In Experiment 2, juvenile soapberry bugs
 were raised on seeds of two host plant (C. corindum and K. elegans) that
 were either intact or cracked manually with pliers. Once they reached
 adulthood, morphology was measured for each individual.
 In Exp2.data.survival.csv, the data is recorded as follows:
 Number (identifying number), Parents (parent ID number), bugpop
 (collection location), natpop (collection location of rearing host seeds),
 hatch date (date the nymph hatched), eclosion date (date the juvenile
 reached adulthood; otherwise NA), death date (day the juvenile died, if it
 did not reach adulthood; otherwise NA), sex (sex, if it reached
 adulthood), cracked (seed treatment: n=intact, y=cracked), lifespan
 (lifespan for bugs that died before reaching adulthood; otherwise gigantic
 negative number), Dvpt.time (time from hatch to adulthood, for bugs that
 reached adulthood; otherwise #VALUE!), mathost (host the mother was reared
 on). In Exp2.data.morphology.csv, columns are as above,
 with the addition of beak (length of rostrum), thorax (width of the
 pronotum at the widest point), wing (length of forewing), and wing2 (wing
 morph, short or long) For all scripts, setwd() calls
 should be updated at the top of each section to the location of the
 unzipped dryad folder. Scripts call each other and data files using the
 organization of the whole file structure, so do not rearrange folders
 within these! Scripts analyzing these two Experiment 2 datasets are in the
 “Experiment 2 stats” folder. “2-load_survival.R” loads and organizes the
 Exp2.data.survival csv file into a format that works for the analyses.
 “2a-Cracked.vs.intact.survival.R” analyzes survival in Experiment 2.
 “2b-Crackedvsintact.survival.day7.R” analyzes survival split in early and
 late. “2c-Cracked.vs.intact.dvpt.time.R” analyzes development time.
 “2d-Crackedvsintact.body.size.R” analyzes thorax width. Statistics scripts
 are in R and commented. The “Figures” folder contains 3
 scripts. Figure code.R generates the figures from the body of the paper.
 FigsAA.R generates the figures from Appendix A. FigsAB.R generates the
 figures from Appendix B. The “general stats scripts”
 sub-folder contains scripts for running multiple model comparisons that
 are used for multiple analyses.