Gene flow in Plantago. II. Gene flow pattern and population structure. A simulation study

Abstract

The relative effects of the pattern of pollen flow, pattern of seed dispersal, presence or absence of a selfincompatibility system and annual versus perennial life cycle on hoiuozygosity and the evolution of population structure in a plant species were studied using computer simulation. Starting with a random distribution of genotypes at a diallelic marker locus in populations of 2500 individuals, simulations were run for the equivalent of 100 or 400 years. Sixteen different situations were investigated, one of which corresponded to a species like Plantago lanceolata: a perennial herb with restricted seed dispersal, a gametophytic self-incompatibility system and a protogyny-growth syndrome. Regression analysis of fixation index values (F) showed that the presence of the protogyny-growth syndrome or self-incompatibility lowered the increase of homozygosity, while restricted seed dispersal and perenniality promoted inbreeding. Analysis of population structure demonstrated that the "patchiness" of a population after 100 generations was higher in a perennial species than in an annual, while the pollen flow pattern caused by the presence of the protogyny syndrome reduced the development of population structure.It appears that genetic structure within populations of a species like P. lanceolata can still be explained by restricted gene flow, in spite of the presence of outcrossing mechanisms like self-incompatibility and protogyny.

Spatial autocorrelation of genotypes in populations of Impatiens pallida and Impatiens capensis

“…Such correlation suggests the past and continuing action of selection in creating and maintaining small-scale differentiation. On the other hand, Turner, Stephens, and Anderson (1982), Sokal and Wartenburg (1983), and Bos and van der Haring (1988) have deomonstrated that patch structure develops rapidly under isolation-by-distance models, and does not require spatiallyheterogeneous selection. After 50 generations, patch length approaches an equilibrium which is functionally related to Wright's neighbourhood size (Wright, 1969;Epperson and Clegg, 1986).…”

Effect of balancing selection on spatial genetic structure within populations: theoretical investigations on the self-incompatibility locus and empirical studies in Arabidopsis halleri

“…Influence of SI systems on SGS at unlinked neutral loci Self-incompatibility systems are mostly known as outcrossing devices in hermaphroditic plant populations, but it is also generally assumed that they contribute to a reduction in overall levels of biparental inbreeding within populations (Bos and van der Haring, 1988). This is because they cause a restriction in mating between close relatives sharing identical genotypes at the S-locus.…”

SPATIAL GENETIC STRUCTURE IN TWO TAMARACK [LARIX LARICINA(DU ROI) K. KOCH] POPULATIONS WITH DIFFERING ESTABLISHMENT HISTORIES

“…Models that have been developed to simulate the effects of evolutionary processes on spatial genetic structure of populations (Rohlf and Schnell, 1971;Sokal and Wartenberg, 1983;Bos and van der Haring, 1988;Sokal et al, 1989) may accurately describe the conditions for which they were intended. However, their direct application to the study offorest trees may be inappropriate.…”