DOI: 10.5061/dryad.wh70rxwt3
title: Data from: Evaluating the importance of individual heterogeneity in reproduction to Weddell seal population dynamics using integral projection models

description: Identifying and accounting for unobserved individual heterogeneity in
 vital rates in demographic models is important for estimating
 population-level vital rates and identifying diverse life-history
 strategies, but much less is known about how this individual heterogeneity
 influences population dynamics. We aimed to understand how the
 distribution of individual heterogeneity in reproductive and survival
 rates influenced population dynamics using vital rates from a Weddell seal
 population by altering the distribution of individual heterogeneity in
 reproduction, which also altered the distribution of individual survival
 rates through the incorporation of our estimate of the correlation between
 the two rates and assessing resulting changes in population growth. We
 constructed an integral projection model (IPM) structured by age and
 reproductive state using estimates of vital rates for a long-lived mammal
 that has recently been shown to exhibit large individual heterogeneity in
 reproduction. Using output from the IPM, we evaluated how population
 dynamics changed with different underlying distributions of unobserved
 individual heterogeneity in reproduction. Results indicate that the
 changes to the underlying distribution of individual heterogeneity in
 reproduction cause very small changes in the population growth rate and
 other population metrics. The largest difference in the estimated
 population growth rate resulting from changes to the underlying
 distribution of individual heterogeneity was less than 1%. Our work
 highlights the differing importance of individual heterogeneity at the
 population level compared to the individual level. Although individual
 heterogeneity in reproduction may result in large differences in the
 lifetime fitness of individuals, changing the proportion of above- or
 below-average breeders in the population results in much smaller
 differences in annual population growth rate. For a long-lived mammal with
 stable and high adult-survival that gives birth to a single offspring,
 individual heterogeneity in reproduction has a limited effect on
 population dynamics. We posit that the limited effect of individual
 heterogeneity on population dynamics may be due to canalization of
 life-history traits.
description: Individual Weddell seals are tagged at birth and resight surveys
 are conducted yearly to acquire the raw data used in this analysis. A
 multistate modeling approach in the Bayesian framework was used to
 estimate age-specific vital rates used in the integral projection model.
 The posterior estimates for calculating the age-specific vital rates of
 adults are contained in the file named
 "IPM_posterior_summary.rds".  The demographic functions are
 parameterized using point estimates from previous modeling efforts that
 are defined in the R code and the posterior estimates from the multistate
 modeling approach that are loaded into the IPM through the R
 script. 
description: The statistical computing program R will be required to run the
 integral projection model script. Additionally, the R packages
 <em>tidyverse</em> and <em>truncnorm</em> will be
 required to execute the integral projection model script.