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Inbreeding and endangered wild tigers

As habitat fragmentation increases globally, wildlife populations decline and become increasingly isolated, thus facing increased risk of inbreeding and extinction. It is not clear to what extent the viability of small isolated populations could be improved by purging deleterious alleles by natural selection. Anubhab Khan et al. analyzed the whole genome sequences of 57 wild Bengal tigers from a small isolated population or large connected populations in India. The results revealed evidence of partial purging of highly damaging variants across populations. However, the small isolated population showed genomic signs of greater inbreeding and a higher overall frequency of deleterious alleles, compared to two large populations. On average, pairs of individuals from the small isolated population shared about 40% of their genomes in regions at least 1 megabase long, while pairs from large, connected populations shared about 15 to 25% of their genomes. Taken together, the results suggest that purging may not eliminate all of the harmful alleles and the fitness costs associated with inbreeding in small isolated populations. According to the authors, the results highlight the need for genetic rescue strategies that improve the fitness of inbred populations by decreasing the frequency of harmful mutations and increasing genetic variation. – JW

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