The other day I was discussing with my friend Ramesh the isolated populations of Nilgiri tahr. Naturally the subject turned to inbreeding depression. Ramesh wanted to know whether anything could be done to overcome this problem. I drew his attention to a paper on big horn sheep that I had read sometime back.(2006) Here the researchers tried restoring gene flow to isolates.
Immigration was restored experimentally, beginning in 1985. The researchers detected marked improvements in reproduction, survival and five fitness-related traits among descendants of the 15 recent migrants. Trait values were increased by 23–257%
The researcher sign off saying that restoring gene flow deserve broader recognition as practical management tools with near-term consequences for large-mammal conservation.
As the paper referred to is an open access article I am pasting here the abstract which I had saved in my computer.
Abstract
Natural populations worldwide are increasingly fragmented by habitat loss. Isolation at small population size is thought to reduce individual and population fitness via inbreeding depression. However, little is known about the time-scale over which adverse genetic effects may develop in natural populations or the number and types of traits likely to be affected. The benefits of restoring gene flow to isolates are therefore also largely unknown. In contrast, the potential costs of migration (e.g. disease spread) are readily apparent. Management for ecological connectivity has therefore been controversial and sometimes avoided. Using pedigree and life-history data collected during 25 years of study, we evaluated genetic decline and rescue in a population of bighorn sheep founded by 12 individuals in 1922 and isolated at an average size of 42 animals for 10–12 generations. Immigration was restored experimentally, beginning in 1985. We detected marked improvements in reproduction, survival and five fitness-related traits among descendants of the 15 recent migrants. Trait values were increased by 23–257% in maximally outbred individuals. This is the first demonstration, to our knowledge, of increased male and female fitness attributable to outbreeding realized in a fully competitive natural setting. Our findings suggest that genetic principles deserve broader recognition as practical management tools with near-term consequences for large-mammal conservation.
Genetic rescue of an insular population of large mammals
Proceedings of the Royal Society B
June 2006 vol. 273 no. 15931491-1499
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