Article,
Fine-Scale Spatial Genetic Structure with Nonuniform Distribution of Individuals
148 (2): 905--919 (1998)
Abstract
This paper presents the first theoretical study of spatial genetic structure within nonuniformly distrib-
uted continuous plant populations. A novel individual-based model of isolation by distance was con-
structed to simulate genetic evolution within such populations. We found larger values of spatial genetic
autocorrelations in highly clumped populations than in uniformly distributed populations. Most of this dif-
ference was caused by differences in mean dispersal distances, but aggregation probably also produced a
slight increase in spatial genetic structure. Using an appropriate level of approximation of the continuous
distribution of individuals in space, we assessed the potential effects of density, seed and pollen dispersal,
generation overlapping, and overdominance selection at an independent locus, on fine-scale genetic struc-
ture, by varying them separately in a few particular cases with extreme clumping. When selfing was allowed,
all these input variables influenced both aggregation and spatial genetic structure. Most variations in spa-
tial genetic structure were closely linked to variations in clumping and/or local density. When selfing was
not allowed, spatial genetic structure was lower in most cases.
The model: Each simulated population consisted of
10,000 mature, hermaphroditic, diploid individuals. Individu-
als were located at the intersection points of a square grid of
size L 3 L , with L measured in grid units. There was at most
one individual at each intersection point. Thus the grid unit
was the minimum distance allowed between two individuals.
The grid size could be larger than the population size. There
was no density-dependent regulation, apart from the mini-
mum spacing of individuals due to their location on a grid.
