Genetic diversity and indicators
Genetic diversity is variation at the DNA level, and includes differences among individuals within populations of species, as well as differences between populations of species.
Within populations: The diversity within populations of a species helps a population adapt quickly to changing conditions, avoid inbreeding problems, and persist when environmental disturbances happen. Small populations lose genetic diversity quickly.
Between populations: The diversity between populations of a species is critical for ensuring the adaptive potential of that species (e.g. to a range of environmental conditions). Loss of any unique, genetically distinct population can compromise a species’ ability to adapt to change (both anthropogenic or environmental).
It is therefore imperative that all populations be maintained, and that populations are sufficiently large to maintain genetic health. Based on these fundamental premises, we can assess and monitor genetic diversity not only using genetic data, but also by assessing loss of populations and population sizes relative to Ne 500 - in other words, by monitoring the process that affects genetic diversity. The genetic diversity indicators adopted at COP15 by the Global Biodiversity Framework are based on these processes.
Figure Visualization of two genetic diversity indicators in the Global Biodiversity Framework. The complementary, Populations Maintained (PM) indicator (left) estimates genetic diversity among populations of a species. Different populations may have different adaptive traits or properties (denoted by the different colours) that enable them to survive in their current situation, and helps the species persist in the face of environmental change. The loss of one population can therefore reduce the adaptive potential of a species. The headline indicator, Ne 500 indicator (right), estimates diversity within populations to ascertain their ability to survive in the long-term. Populations with an effective population size (Ne) less than 500 lose genetic diversity more rapidly, making them less resilient to environmental changes and more susceptible to inbreeding when compared to populations with Ne greater than 500, which are considered healthy and stable.
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Although there are no global, standardized databases for reporting the number of species’ population and their census sizes, this information is available for many species in various other sources (e.g., reports, national databases, scientific literature, government gazettes, consulting experts and knowledge holders, community science, etc.). This guidance document will help you gather and use the necessary data, from diverse sources, in a standardized way (see Data Collection).