Is Evolutionary Biology Essential for Conservation of Biodiversity?

Is evolutionary biology essential for conservation of biodiversity? originally appeared on Quora - the knowledge sharing network where compelling questions are answered by people with unique insights.

Answer by Jesse Gray, PhD student in community ecology and population genetics, on Quora.

It is important to have a grasp of evolutionary biology when undertaking conservation efforts. To do otherwise could easily do more harm than good. In order for conservation work to be successful, you have to know the reason why a population or a species is doing poorly. Misidentifying the reason, and then acting on that misconception can result in a lack of response from the population you are trying to help, and that comes with losses of resources, time, and effort. Worse yet, certain types of conservation efforts can actually result in a population that may be temporarily bigger, but less fit than it was before the conservation work was done, leaving it vulnerable to complete collapse.

For example, suppose a population is doing very poorly, not because its habitat has been degraded, but because the population is very small and lacks genetic diversity, but we don't know this about them. We could try to remedy the problem by working very hard to improve their ecosystem, investing huge amounts of money and manpower in the process, but we would still see a decline in the species. This might be due to what is called an extinction vortex. When there is low genetic diversity, recessive genetic mutations are more often expressed because they are more often found in homozygous form. This decreases the average fitness of the population as a whole. This in turn should result in strong selecting against those mutations (also known as genetic purging) but if there aren't enough healthy alleles available in the population, then selection still might not be strong enough to eliminate those deleterious mutations, and the population will get smaller and smaller, less and less fit with each generation. In such a scenario, we will have invested so much effort only to see the population continue to spiral towards extinction.

On the other hand, if the conservation team includes a population biologist, this might be avoided. They can fairly easily assess the genetic diversity within the population and determine if low genetic diversity is a more likely cause of the decline. Assuming they do find that this is the case, then efforts to inject genetic diversity into the population would be considered a better option than habitat restoration. However, here again lies another pitfall associated with ignorance of evolutionary biology. Genetic diversity is in general a good thing to have, and bringing in new individuals from outside the population is a good way to restore genetic diversity, but ignoring the genetically-determined characteristics of those new individuals can also be hazardous to the ailing population.

Evolutionary biologists know that there are genetic differences between populations of the same species. Many of these differences are inconsequential, having nothing to do with natural selection. Other differences, however, are a result of natural selection acting in different ways in different habitats. If we were considering a short plant species, and one of its populations was found in a forest habitat, we might find that it has evolved to be more shade-tolerant than other populations of the same species that are found out in the open, away from the shade of trees. If that forest population was declining, and we found that it had low levels of genetic diversity, our immediate response might be to pollinate it with pollen from one of those other populations. However, while pollination might be successful, once the offspring have germinated, their shade-tolerance might be significantly less than that of the parent plants. This would result in a severe reduction in the average fitness of the population, and may result in a complete collapse.

In essence, there are a lot of factors involved in conservation, and while it is a noble and needed effort, it should not be undertaken without understanding and careful consideration of multiple factors, including evolutionary biology.

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