Loss of Species, Loss of Genetic Variation, and the Future of Earth’s Biota

We are experiencing an accelerated rate of loss of species due to human activities. This anthropogenic phenomenon extends beyond extinction. It encompasses an expanded loss of biodiversity as the genetic diversity of species diminish, reducing gene pools to “gene puddles.” One-third of all species analyzed by the International Union for the Conservation of Nature (IUCN), are estimated to be undergoing population declines. Twenty-eight percent of 134,425 species assessed by IUCN are categorized as threatened or endangered.

We know details of species extinctions events from the fossil record, historical record, and from ancient DNA studies, and that historical processes shape extinction risk. Genome sequencing of extinct species reveals in many cases trajectories of population decline and accumulation of deleterious mutations. Habitat loss and changing eco-environmental conditions, competition, and other factors produce genomic impacts, influencing extinction risk.

The legacy of past events impacts resiliency of species in the current environment in interpretable ways. Demographic trajectories reveal vulnerability to extinction. This has been accepted for recent declines, e.g., population bottlenecks, but declining effective population size is associated with risk of endangerment over many thousands of years, as revealed by new data from analyses of aligned whole genome sequences of mammals. Some species with small populations have purged deleterious mutations, portions of their “genetic load,” as assessed through genomic analyses that can serve to identify species’ extinction risk.

Although we are but in the initial phase of exploring genomic correlates with past and pending extinctions, comparative and population genomics analyses can provide for knowledge-based management and serve to set priorities for protections and interventions.

Remarkable advances in genomics technologies portend a deeper understanding of the evolution of life and the vulnerability of extant species to changes now taking place through human agency. The loss of genetic diversity is associated with historical and ancient extinction events. Cryopreserved cell cultures and gametes can contribute to population sustainability and mitigate extinction risk, the full extent of which is yet to be realized, but which will depend exquisitely on expansion of current efforts in conservation biobanking.