Subpopulation n [A.sub.O] [H.sub.E] [H.sub.O] H-W P-value SE 84 8.7 0.689 0.659 0.26 SSW 14 4.8 0.631 0.488 <0.01 ** SW 14 5.8 0.694 0.650 0.41 N 22 5.7 0.651 0.629 0.58 NE 8 4.8 0.811 0.775 0.46 Subpopulation M-ratio SE 0.899 SSW 0.713 SW 0.800 N 0.849 NE 0.774 TABLE 2--Allele frequency-based correlation and variation ([F.sub.IS], Wright's inbreeding coefficient
) among individuals within each subpopulation of the star cactus Astrophytum asterias in Starr County, Texas.
Significant deviations from linearity in the relationship between quantitative fitness traits and Wright's inbreeding coefficient
can indicate selection against deleterious alleles or the presence of epistatic gene action (Dobzhansky 1970; Falconer 1981).
Frankel and Soule (1981) argue that there is a threshold level of inbreeding above which fitness "relentlessly declines." If increases in the level of inbreeding, as measured by Wright's inbreeding coefficient
f, exceed 1% per generation, then a population is at risk for serious inbreeding depression.
F: Wright's inbreeding coefficient
. F is the probability that the two alleles at the same locus in an individual are identical by descent.
Further, the sign and magnitude of Wright's inbreeding coefficient
varied in a similar manner across cohorts, ranging from large heterozygote deficiency (F = 0.123) to substantial TABULAR DATA OMITTED heterozygote excess (F = -0.185).
I was disappointed that Sewall Wright's inbreeding coefficients
, or F-statistics, were not given broader treatment in the theoretical chapters.