The critically endangered vaquita is not doomed to extinction by inbreeding depression

Abstract

In cases of severe wildlife population decline, a key question is whether recovery efforts will be impeded by genetic factors, such as inbreeding depression. Decades of excess mortality from gillnet fishing have driven Mexico’s vaquita porpoise ( Phocoena sinus ) to ~10 remaining individuals. We analyzed whole-genome sequences from 20 vaquitas and integrated genomic and demographic information into stochastic, individual-based simulations to quantify the species’ recovery potential. Our analysis suggests that the vaquita’s historical rarity has resulted in a low burden of segregating deleterious variation, reducing the risk of inbreeding depression. Similarly, genome-informed simulations suggest that the vaquita can recover if bycatch mortality is immediately halted. This study provides hope for vaquitas and other naturally rare endangered species and highlights the utility of genomics in predicting extinction risk.

Population size and risk of extinction

The vaquita porpoise is one of the most endangered animals in the world, with only an estimated 10 individuals remaining. To determine the risk of extinction caused by inbreeding depression, Robinson et al . sequenced and examined 20 vaquita genomes to determine their heterozygosity and ancestral population size (see the Perspective by Grueber and Sunnucks). The authors determined that the long-term population size of vaquitas has been low for a marine mammal, with approximately 1000 years of stable genomic diversity. Genomic comparisons with other cetacean species and modeling indicated that vaquitas are unlikely to suffer from inbreeding depression. Therefore, if the risk of bycatch mortality caused by fishermen can be eliminated, then there is a chance that this species will not go extinct. —LMZ

Abstract

Genomic and population viability analyses suggest that the vaquita porpoise is not doomed to extinction.