DOI: 10.5061/dryad.mkkwh71bg
title: Game over: Conflict resolution through strategic growth in an invertebrate

description: In some multimember groups with unequal partitioning of reproduction and
 poor breeding opportunities outside the group, natural selection has
 favoured the evolution of adaptive mechanisms such as strategic growth
 modulation. Strategic growth is a form of body growth plasticity where
 individuals make growth adjustments calibrated to their closest
 competitor, establishing a size hierarchy that defines who has priority in
 reproduction. In this study we explored the occurrence of strategic growth
 in an invertebrate, the marine annelid worm Ophryotrocha puerilis, and
 investigated its underlying mechanisms via growth curve analysis.
 Size-matched juvenile worms exposed to different social environments
 established size hierarchies by following distinct developmental
 trajectories, with the intensity and duration of growth spurts correlated
 to the level of competition within their social environment. In monogamous
 environments, the onset of reproduction led to the weakening of the size
 hierarchy. Conversely, in reproductively competitive environments, the
 onset of reproduction led to the stabilisation of size differences,
 supporting the idea that individuals actively regulate their growth
 relative to rivals to mitigate reproductive conflict and size hierarchies
 emerge as a result of these strategic adjustments. This study provides the
 first evidence for strategic body growth in an invertebrate and explores
 both the establishment of the size hierarchy as well as its eventual
 dissolution upon conflict resolution.
description: # Game over: Conflict resolution through strategic growth in an
 invertebrate Dataset DOI:
 [10.5061/dryad.mkkwh71bg](https://doi.org/10.5061/dryad.mkkwh71bg) ##
 Description of the data and file structure This dataset contains data from
 a 60-day laboratory experiment designed to investigate strategic growth in
 the polychaete worm *Ophryotrocha puerilis* in response to the social
 environment. Age- and size-matched juveniles were randomly assigned to one
 of four social environments (Isolation, Pairs, Triplets, or Groups with
 adults). Individual body size (segment count) and the timing of sex change
 (male to female) were monitored every 2-5 days throughout the experiment.
 We then analysed growth curve parameters to quantify the individual growth
 trajectories and examine the underlying mechanisms of strategic growth. By
 fitting a logistic model, we derived parameters (Asymptotic Size, Growth
 Rate, and Age at Inflection) to correlate the intensity and duration of
 individual growth adjustments to the level of competition in the social
 environment. This analysis allowed us to explore how size hierarchies
 emerge and eventually dissolve upon conflict resolution (onset of
 reproduction). ### ### Files and variables #### File:
 Strategic_Growth_Data.xls **Description:** Longitudinal data tracking the
 body growth and timing of sex change for all experimental *Ophryotrocha
 puerilis* juveniles over 60 days. Each row represents a single measurement
 point for an individual worm on a specific day. ##### Variables * bowl.no
  \ Sequential, non-unique bowl identifier specific to each treatment
 group. This number identifies the replicate bowl within its specific
 treatment, not across the whole study (i.e., bowl numbers reset per
 treatment). Worms sharing a bowl (in Pairs and Triplets) share the same
 bowl.no value.\ *Ranges from 1 to a maximum of 30 (number of replicates
 per treatment).* - unique.ID\ The primary unique identifier for each
 individual worm that links it to its rank & its social environment.
 *Composite of the bowl, worm designation (see Note), and treatment.\ e.g.,
 1G_L1 Groups (Worm L1 in Bowl 1, Groups treatment).* **Note : **Worm
 Designation L1 L2 L3 : Component of unique.ID\ This label (L1, L2, L3) was
 assigned to simplify initial tracking based on the worm's starting
 size relative to others in the bowl. \ L1: The smallest/only juvenile in
 the bowl. \ L2: The larger juvenile in Pairs or the intermediate juvenile
 in Triplets. \ L3: The largest juvenile in Triplets. - worm.id\ The unique
 numerical identifier assigned sequentially to each individual experimental
 worm. This column links data across the main longitudinal data file
 (Strategic_Growth_Data.xls) and the derived growth parameters file
 (growth.parameters.xls). \ *Ranges from 1 to 270 (total sample size).* -
 bowl.id \ A unique, study-wide identifier for the housing bowl. All
 individuals that were housed together (e.g., in Pairs and Triplets) share
 the same ID. This links the bowl across both data files.\ *Format:* *[Bowl
 Number][Treatment First Letter].* \ *e.g., 2T (Bowl 2 in Triplets
 treatment).* - replicate \ The name of the researcher who took the
 measurements.\ *e.g., Pooja or Noé* - treatment\ One of four social
 environments the individual worm was randomly assigned to at the start of
 the experiment. \ *Isolated, Pair, Triplets, Groups* - exp.day\ The total
 number of days elapsed since the start of the experiment (Day 0). This
 variable marks the time point for each measurement (body size, time of sex
 change). \ *0 to 60 days* - rank\ Hierarchical rank of the individual worm
 (based on size on day 5 of the experiment) within its bowl. This is used
 for comparative analysis in Pairs and Triplets.\ *Rank 1 (Largest), Rank 2
 (Second Largest/Intermediate), Rank 3 (Smallest).* \ *NA = Not Applicable
 (used for Isolated and Groups treatments). - body.size\ The number of
 chaetigerous body segments counted for every individual worm at each
 measurement point (exp.day). This is the primary metric used to track
 individual growth. \ *Unit : Integer (number of chaetigerous segments)* -
 presence.of.eggs \ Indicates whether the individual had visible oocytes
 (eggs) on the measurement day, indicating transition to the female sex. \
 *Column Values: yes (visible yellow oocytes) or no (no oocytes
 observed).*\ \ **Note on Visibility:** Oocytes are visible due to the
 worms' transparent bodies and the yellow coloration derived from
 their spinach diet. - moment.sex.change\ Indicates the specific
 experimental day (exp.day) when the sex change to female was first
 observed (i.e., the exp.day that presence.of.eggs changed from
 'no' to 'yes'). \ *Column Values: 1 (day of sex
 change), 0 (no sex change observed on this day)* **Note:** Each individual
 worm has only one instance of moment.sex.change = 1 across the entire time
 series, reflecting the first day of their male-to-female sex change. If no
 sex change occurred, the value remains 0 for all recorded days. #### File:
 growth.parameters.xls **Description:** Derived data containing the fitted
 growth curve parameters for each juvenile, based on the body size
 measurements in the *Strategic_Growth_Data.xls* file. These parameters
 were derived by fitting a logistic growth model to the body growth data
 for each individual to quantify individual growth trajectories #####
 Variables * worm.id\ The unique numerical identifier assigned sequentially
 to each individual experimental worm. This column links data across the
 main longitudinal data file (Strategic_Growth_Data.xls) and the derived
 growth parameters file (growth.parameters.xls). \ *Ranges from 1 to 271
 (total sample size).* * C\ Age at Inflection (t0): The age (in days) at
 which the maximum growth rate (growth spurt) begins to slow down.\
 *Numerical, age at which growth spurt ended.* * B\ Slope (r): The maximum
 growth rate (steepness of the curve). \ *Numerical, maximum growth rate
 per day* * A\ Asymptotic Body Size (K): The estimated maximum body size
 (in segments) that the juvenile is expected to reach based on the model
 fit. \ *Integer, number of chaetigerous segments* * treatment\ One of four
 social environments the individual worm was randomly assigned to at the
 start of the experiment. \ *Isolated, Pair, Triplets, Groups* * bowl.id \
 A unique, study-wide identifier for the housing bowl. All individuals that
 were housed together (e.g., in Pairs and Triplets) share the same ID. This
 links the bowl across both data files.\ *Format: [Bowl Number][Treatment
 First Letter]. \ e.g., 2T (Bowl 2 in Triplets treatment).* * Worm
 Designation \ This label (L1, L2, L3) was assigned to simplify initial
 tracking based on the worm's starting size relative to others in the
 bowl. L1: The smallest/only juvenile in the bowl.  L2: The larger juvenile
 in Pairs or the intermediate juvenile in Triplets. L3: The largest
 juvenile in Triplets. #### ## Code/software Statistical analyses were
 performed in R (version 4.3.1). Required R Packages: lme4 (Bates et al.,
 2015) - Used for Generalized Linear Mixed-effects Models (GLMMs) and
 Linear Mixed-effects Models (LMMs). drc (Ritz et al., 2015) - Used for
 fitting non-linear Logistic growth models to individual growth data. zoo
 (Zeileis et al., 2020) - Used for interpolation of missing values.