Securing the future: the genetics of reintroductions
Dr Jennifer Pierson, Senior Ecologist
What do you think of when you hear the word biodiversity? For most of us, we see biological communities full of different plants and animals, areas teeming with life. But we often forget the building blocks of this view of biodiversity – the genes behind the scenes of life.
Genetic diversity is the foundation of all biodiversity. Evolution has led to the incredible diversity of species and communities we have here in Australia, many of which are not found anywhere else on the planet. Evolution is a genetic process, by which four main mechanisms determine the patterns of diversity:
1) Mutation – random errors that lead to new genes;
2) Drift – random changes in gene frequencies due to chance;
3) Migration – the movement of genes by dispersal followed by mating;
4) Selection – the differential survival and reproductive performance of individuals based on hereditary traits (i.e. genotypes or gene complexes).
AWC’s mission to reverse the decline of biodiversity in Australia includes actions to conserve and manage the precious genetic diversity that remains. Many endangered species of Australia, such as Bilby, Woylie and Mala once occupied large areas of the continent in considerable numbers. Large populations are reservoirs of genetic variation, and species whose ranges extend across varied environments have different gene frequencies. These differences are beneficial under a variety of conditions and increase the ability of a species to adapt to environmental changes.
Australia’s diminishing diversity
Massive declines in the number of populations, combined with the fragmentation of remaining habitats, have disrupted evolutionary processes such as migration and resulted in dramatic declines in the genetic diversity of many species.
Small populations continue to lose diversity much faster than large populations, due to the influence of genetic drift, where random changes in gene frequency occur due to chance. Small populations are also at greater risk for what is called inbreeding depression, or lower survival and reproduction rates due to the expression of rare deleterious alleles (genes). If genetic diversity is not managed in these small populations, even as they grow larger due to restoration efforts, the adaptive capacity, or the breeding capacity to cause genetic variation, is limited because selective forces do not. can act only on the genetic variation present.
Manage population genetics
AWC closely manages the genetic diversity of reintroduced populations. There are a number of actions AWC scientists take to give reintroduced species the best chance for recovery. First, when new populations are founded, we make sure that the number of individuals used to start the population is large enough to avoid negative outcomes such as inbreeding depression. The tricky part of genetic management is that not all founders have the chance to reproduce and without mating genes are not shared and passed on. So we need to make sure we have more founders than the minimum necessary to avoid inbreeding. The other aspect is to make sure that the individuals are not too genetically similar, because even a large number of genetically very similar individuals can have negative consequences on the physical condition.
Second, we aim to create a “genetic mix” of the remaining genetic diversity and maximize genetic variation in these newly established populations. This provides assurance for the conservation of the valuable diversity left behind in a species and provides the basis for populations to adapt to varying environmental conditions. Australia’s ecosystems are notorious for their extremes and climate change is likely to make conditions worse. As such, having the greatest possible diversity gives species a fighting chance to adapt to the uncertain future conditions they may face.
Achieve better results through collaboration
In order to achieve the best results, AWC has partnered with the Australasian Wildlife Genomics Group (AWGG) at the University of Sydney to obtain high quality genetic data using the latest sequencing technologies. For example, AWC scientists established a Red-tailed Phascogale captive breeding program to support our recent reintroduction to Newhaven and our planned reintroduction to the Mallee Cliffs. AWC worked closely with AWGG, with Alice Springs Desert Park and Zoos South Australia to optimize the genetic mix of founder populations. Wild populations were targeted to search for founder individuals and the field team were able to quickly obtain genetic data to determine if the captive population’s genetic mix was working and identify where to target in the second round of sampling for more founders. wild.
The Woylies provide another great example of the benefits of working closely with AWGG to achieve the best genetic results. When the Woylies were reintroduced to Mount Gibson, three different source populations were used in an attempt to obtain a good genetic mix representing the diversity of different regions. Recent genetic analysis has shown that Mount Gibson lacks genetic inbreeding and good levels of diversity. This meant that we could test how well a genetically mixed population could serve as a single source population. The Mount Gibson woylies were transferred to Newhaven in early August 2021 and small tissue samples were sent directly to AWC’s university partners for genetic analysis. The results will dictate whether the new Newhaven population will need to be supplemented or whether our “lucky drop” of Mount Gibson Woylies provided a sufficient amount of initial diversity. In truth, it’s not quite a lucky dive, as field crews spatially set traps to minimize the chances of catching related individuals.
These are just a few examples of AWC’s commitment to conserving and managing the genetic diversity of endangered Australian wildlife. In the end, everything is connected. Wherever an animal goes, it takes its genes with it …
Read and download the full issue of Wildlife Matters here.