Empirical studies have documented both positive and negative density-dependent dispersal, yet most theoretical models predict positive density dependence as a mechanism to avoid competition. Several hypotheses have been proposed to explain the occurrence of negative density-dependent dispersal, but few of these have been formally modeled. Here, we developed an individual based model of the evolution of density-dependent dispersal. This model is novel in that it considers the effects of density on dispersal directly, and indirectly through effects on individual condition. Body condition is determined mechanistically, by having juveniles compete for resources in their natal patch. We found that the evolved dispersal strategy was a steep, increasing function of both density and condition. Interestingly, although populations evolved a positive density-dependent dispersal strategy, the simulated metapopulations exhibited negative density-dependent dispersal. This occurred because of the negative relationship between density and body condition: high density sites produced low condition individuals that lacked the resources required for dispersal. Our model therefore generates the novel hypothesis that observed negative density-dependent dispersal can occur when high density limits the ability of organisms to disperse. We suggest that future studies consider how phenotype is linked to the environment when investigating the evolution of dispersal.
These are output data from the model described in: Baines, Travis, McCauley & Bocedi. Negative density-dependent dispersal emerges from the joint evolution of density- and body condition-dependent dispersal strategies. Evolution. This is an individual-based model of the evolution of dispersal in a spatially structured metapopulation.
1) data output files ("output_dtX_dcX.txt"): Contain model output. Each file is the output of 20 replicates of each simulation with a given dispersal type and dispersal cost. Text after subscript indicates dispersal type and dispersal cost.
Notation description - dispersal_type:
dtBC = individual based dispersal decisions on body condition only
dtDENS = individuals based dispersal decisions on density only
dtNONE = individuals did not base dispersal decisions on body condition or density
dtBCDENS = individuals based dispersal decisions on both body condition and density
Notation description - dispersal cost, c:
dc0: c = 0
dc0.05: c = 0.05
dc0.1: c = 0.1
dc0.3: c = 0.3
2) "column headers.txt": provides definitions of column headers in data output files.
3) "Parameters.txt": provides model parameter values for all data output files.
This work is licensed under a CC0 1.0 Universal (CC0 1.0) Public Domain Dedication license.
- European Society for Evolutionary Biology
- Entomological Society of Canada
- Royal Society University Research Fellowship