DOI: 10.5061/dryad.pv910
title: Data from: Genetic Allee effects and their interaction with ecological Allee effects

description: 1. It is now widely accepted that genetic processes such as inbreeding
 depression and loss of genetic variation can increase the extinction risk
 of small populations. However, it is generally unclear whether extinction
 risk from genetic causes gradually increases with decreasing population
 size or whether there is a sharp transition around a specific threshold
 population size. In the ecological literature, such threshold phenomena
 are called “strong Allee effects” and they can arise for example from mate
 limitation in small populations. 2. In this study, we aim to a) develop a
 meaningful notion of a “strong genetic Allee effect”, b) explore whether
 and under what conditions such an effect can arise from inbreeding
 depression due to recessive deleterious mutations, and c) quantify the
 interaction of potential genetic Allee effects with the well-known
 mate-finding Allee effect. 3. We define a strong genetic Allee effect as a
 genetic process that causes a population's survival probability to be
 a sigmoid function of its initial size. The inflection point of this
 function defines the critical population size. To characterize
 survival-probability curves, we develop and analyze simple stochastic
 models for the ecology and genetics of small populations. 4. Our results
 indicate that inbreeding depression can indeed cause a strong genetic
 Allee effect, but only if individuals carry sufficiently many deleterious
 mutations (lethal equivalents). Populations suffering from a genetic Allee
 effect often first grow, then decline as inbreeding depression sets in,
 and then potentially recover as deleterious mutations are purged. Critical
 population sizes of ecological and genetic Allee effects appear to be
 often additive, but even superadditive interactions are possible. 5. Many
 published estimates for the number of lethal equivalents in birds and
 mammals fall in the parameter range where strong genetic Allee effects are
 expected. Unfortunately, extinction risk due to genetic Allee effects can
 easily be underestimated as populations with genetic problems often grow
 initially, but then crash later. Also interactions between ecological and
 genetic Allee effects can be strong and should not be neglected when
 assessing the viability of endangered or introduced populations.
description: Appendix S5 - Simulation
 source codeThis folder contains the
 C++ source code as well as pre-compiled programs for the simulation model
 presented in the manuscript "Genetic Allee effects and their
 interaction with ecological Allee effects" by Meike J. Wittmann,
 Hanna Stuis & Dirk Metzler in Journal of Animal Ecology. To
 re-compile, run "make". The simulation program operates on an
 input file. See Appendix S6 for the R scripts that we used to generate the
 input files for our simulations. Please note that the simulation program
 contains some options that are not used in this paper and that it was only
 run on Linux machines and has not been tested on other
 platforms.AppendixS5.zipAppendix S6 - R scripts to start and analyze simulationssee ReadMe fileAppendixS6.zip