"Should we save small endangered species?"


6 November 2017

Biodiversity isn’t just for nature geeks. Understanding the genetic mechanisms behind the adaptability of populations is an absolute necessity if we are to have any hope of preserving this diversity, writes Jacob Höglund, Professor of Animal Conservation Biology.

In 2000, Nobel Laureate Paul Crutzen introduced the concept of the Anthropocene. The idea behind the term is that human impact on the Earth's environment has now become so significant that it justifies the introduction of a new geological epoch.

Jacob Höglund, Professor

One consequence of human environmental impact is the impoverishment of biodiversity at all levels, a process that has ultimately led to the beginning of the so-called "sixth mass extinction.” This means that our planet is now losing more types of species per unit of time than the number of new ones it is possible to form. Geologists have ascertained that at least five such mass extinctions have occurred in the course of Earth’s history. In the past, they have been associated with climate changes due to geophysical events such as enormous volcanic eruptions or collisions with larger celestial bodies.

These mass extinctions delineate the geological eras; in other words, in the distant future intelligent beings would be able to observe the geological evidence of Earth’s current, ongoing mass extinction. The big difference is that today's ongoing mass extinction cannot be attributed to any geophysical event. Rather, it is the direct result of the influence of one of Earth’s species: Homo sapiens.

Biodiversity can be studied at many different levels: one may examine ecosystems, species, or populations; it is even possible to investigate biodiversity at the genetic level. In order to adapt to a changing environment, the organisms within a species must accommodate genetic variation. There can be no evolution (and thus no adaptation) without variation. In such cases, the only possible outcome is extinction. Extinction occurs when environmental conditions are so greatly altered that a population of a species can no longer compensate for the increased mortality rate of new births.

In my research group, we focus on genetic variation in natural populations, and examine how populations can adapt to local changes. We use the latest genetic methods to studying variation in different species’ genomes, and to examine how variation is affected by natural selection, seasonal fluctuations (quantity changes) and the populations’ genetic structures. Above all, we focus on understanding what occurs in the cases of rare and endangered species.

The population size of these species is crucially important for understanding what influences their genetic diversity. It has long been known that adaptability is greatest in individual-rich populations. Under such conditions, the best adapted individuals contribute more descendants to future generations, and their genetic properties are thus preserved within the population. However, small populations are primarily controlled by random genetic changes. This evolutionary mechanism is known as genetic drift.

Put simply, the smaller and more fragmented the species, the less adaptable it will be. When small populations can no longer adapt, they lose even more genetic variation. This in turn leads to yet more exposure to random factors, which results in an even greater loss of variation. This process is often referred to as “the extinction vortex.” Our research aims to understand how species end up in this downward spiral, to propose measures to prevent this from happening, and to examine what can be done to pull a species out of the extinction vortex.

It goes without saying that scientists must gain an understanding of the processes that affect small and isolated populations of natural organisms, and must succeed in halting the ongoing mass extinction. I may be biased, but I find it difficult to think of a more important area of research. Biodiversity isn’t just for nature geeks. Understanding the genetic mechanisms behind the adaptability of populations is an absolute necessity if we are to have any hope of preserving this diversity.

Jacob Höglund
Professor of Animal Conservation Biology
Department of Ecology and Genetics, Animal Ecology
Uppsala University

Last modified: 2021-02-14