Data from: Looking into the black box: simulating the role of self-fertilization and mortality in the genetic structure of Macrocystis pyrifera

Patterns of spatial genetic structure (SGS), typically estimated by
genotyping adults, integrate migration over multiple generations and
measure the effective gene flow of populations. SGS results can be
compared with direct ecological studies of dispersal or mating system to
gain additional insights. When mismatches occur, simulations can be used
to illuminate the causes of these mismatches. Here we report a SGS and
simulation-based study of self-fertilization in Macrocystis pyrifera, the
giant kelp. We found that SGS is weaker than expected in M. pyrifera, and
used computer simulations to identify selfing and early mortality rates
for which the individual heterozygosity distribution fits that of the
observed data. Only one (of three) population showed both elevated kinship
in the smallest distance class and a significant negative slope between
kinship and geographic distance. All simulations had poor fit to the
observed data unless mortality due to inbreeding depression was imposed.
This mortality could only be imposed for selfing, as these were the only
simulations to show an excess of homozygous individuals relative to the
observed data. Thus, the expected data consistently achieved
non-significant differences from the observed data only under models of
selfing with mortality, with best fits between 32-42% selfing. Inbreeding
depression ranged from 0.70-0.73. The results suggest that
density-dependent mortality of early life stages is a significant force in
structuring Macrocystis populations, with few highly-homozygous
individuals surviving. The success of these results should help to
validate simulation approaches even in data-poor systems, as a means to
estimate otherwise difficult-to-measure life-cycle parameters.