Genetic Jinx
Once a population becomes extinct in the wild, conservationists use captive in-breeding to maintain the species' survival. However, increased homozygosity causes recessive deleterious genotypes. Common characteristics include depression and mutations that are dysfunctional for re-wilding. Whilst the goal is to prevent the species from becoming extinct, the damage to the life quality of offspring and the populations' reproductive fitness is crippling.
This is true for domesticated and wild species: I present Siberian and Iberian.
Domesticated: White but not right
Have you ever wondered why white tigers are a rarity? Truth be told, there are ~200 remaining in captivity, a result of 9 generations of inbreeding. These tigers carry an autosomal recessive trait that causes their whiteness. This mutation is often coupled with scoliosis, cleft palates, immune deficiency, mental impairments, cross-eyes and shorter life expectancy. Such a phenomenon of captive breeding is much against what conservationists stand for. White tigers are not Siberian, they are inbred. As an anti-zoo advocate, I urge you to boycott the business of viewing the exoticized.
Curious to read more? Click here.
Wild: A fragile felid
Loss of genetic diversity can also happen in the wild. Restricted to the Mediterranean Iberian Peninsula, the Iberian lynx are a small range species. In the 20th century, a series of population bottlenecks caused drastic population declines. This caused inevitable inbreeding, producing lynxes that suffered from depression and reduced fitness levels.
Conservation efforts over the past two decades have recovered the population from less than 100 to over 300 in 2012. Once critically endangered, the IUCN have shifted their status to endangered. A rare case of positive demoting!
The modest recovery owes much to rescuing genetic variation by promoting admixture of different populations. Unlike the Siberian tiger, captive breeding was used for genetic management. Re-introducing genetic diversity enabled healthier offspring that were fit for re-wilding.
However, genetic rescue has not restored the original diversity. The long term survival of the population and how they respond to environmental change is yet to be seen.
Declines in genetic diversity foreshadow declines in population, this further reduces the gene pool, creating a negative feedback loop.
Takeaway message: A toolkit for the future health of a population - a diverse gene pool.
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