inbreeding depression - senecio7の日記

Willis JH 1999 The contribution of male-sterility mutations to inbreeding depression in Mimulus guttatus. Heredity 83:337-346.

recessive male-sterility alleles at individual loci are common in a primarily outcrossing population of the plant Mimulus guttatus
despite the high frequency of these major mutations, most of the inbreeding depression for male fertility and cumulative measures of lifetime fitness results from more mildly deleterious alleles
male-sterility alleles contribute to 31% of the inbreeding depression for the fraction of viable pollen grains, and to 26% of the inbreeding depression for total fitness
most of the inbreeding depression for male fertility in this population would not be purged, in the short term, with moderate inbreeding

a knowledge of the relative contribution of mutations of large effect to inbreeding depression is critical to several problems in evolution, conservation biology and agriculture
if inbreeding depression in an outcrossed population is primarily caused by recessive lethal or sterile mutations, then it is expected to be rapidly purged with even a small amount to inbreeding
the purging with inbreeding is much less effective if inbreeding depression is caused by many, partially recessive mutations of small effect on fitness
inbreeding depression resulting from mildly deleterious mutations may:
(i) be a more resilient barrier to the evolution of selfing than inbreeding depression of the same magnitude resulting from recessive lethal or sterility mutations;
(ii) hinder the production by plant and animal breeders of inbred agricultural varieties that are as productive as F₁ hybrids
(iii) increase the chances of extinction when a formerly abundant, outbred species is exposed to the inbreeding effects of small population size (Barrett & Charlesworth, 1991; Hedrick, 1994)

Templeton & Read (1983, 1984) argued that intentional inbreeding of historically outcrossed endangered species could rapidly reduce or eliminate inbreeding depression caused by deleterious mutations, thereby increasing the chances that the species could persist over the long-term
others have made similar recommendations (e.g. Fenster & Dudash, 1994)
the main problem with this idea is that if inbreeding depression is mainly caused by many mildly deleterious mutations, as suggested by this study, then such drastic inbreeding will fail to purge inbreeding depression, and will probably cause the species to go extinct (Hedrick, 1994)