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Conventionally, small populations living on islands are expected to lose genetic variation by drift. Fluctuations in population size, combined with polygynous mating systems, are expected to contribute to the process by increasing sampling effects on genetic variation. However, in individually monitored populations of Red deer on Rum and Soay sheep on St. Kilda, which experience fluctuations in population size, two processes have been identified which mitigate loss of genetic variation. First, in a number of examples, population reductions are associated with selection. Selection may be in favour of heterozygotes, or, as we have documented in several cases, it may fluctuate in direction temporally. Second, in Soay sheep, in which mortality over population crashes is male-biased, ostensibly leading to low effective numbers of males, molecular studies show that there are systematic changes in the reproductive success of young males, and in variance in male success, that broaden genetic representation compared with expectation.

Original publication

DOI

10.1098/rstb.1996.0069

Type

Journal article

Journal

Philos Trans R Soc Lond B Biol Sci

Publication Date

29/06/1996

Volume

351

Pages

745 - 752

Keywords

Adenosine Deaminase, Animals, Deer, Demography, Female, Genetic Variation, Genetics, Population, Geography, Hebrides, Horns, Isocitrate Dehydrogenase, Male, Mammals, Mannose-6-Phosphate Isomerase, Polymorphism, Genetic, Sexual Behavior, Animal, Sheep