“Of all the Islands in all the Seas in all the World…”

Ashley Jones wrote this post as a part of Dr. Stacy Krueger-Hadfield’s Scientific Communication course at the University of Alabama at Birmingham. She earned a B.S. in Animal Science from Auburn University where she also spent several years working at the Auburn University College of Veterinary Medicine. This past semester, she completed her M.S. in Biology at UAB with a focus on infectious diseases under the mentorship of Dr. Stephen Watts. Her graduate research project centered on the epidemiology of Lyme Disease in the United States. She is currently employed as a PCR technician in the virology laboratory at Takeda Pharmaceuticals where she is also enrolled in an MT certification program. In her free time, Ashley volunteers for local animal rescues and the Wildlife Resources and Education Network (WREN).

The study of genomic diversity lends itself to conservation efforts for threatened populations by providing information on which species may need intervention more urgently than others. For instance, when faced with a particularly harsh environment – such as in times of drought, famine, or disease – a population with high genetic diversity is more likely to have at least a few survivors due to their better-suited alleles. The survivors will then be able to pass along their “advantageous” alleles to future offspring. Et voilà!

Now, compare the previous example with a population that has very little genetic variation (i.e., those with inbred lines – often resulting from a lack of options for mating). If all members of a population have the same alleles, and all of these alleles are susceptible to a particular threat, then the population is doomed (Case in point: The Irish Potato Famine). As you might imagine, individuals living in island habitats are often predisposed to the latter scenario of low genetic variation – and its consequences – due to their environmental restrictions.

A recent article in Molecular Ecology (2019) applied these principles while studying genomic diversity on the Galapagos Islands (Brüniche-Olsen et al. 2019). This group of 13 islands in the Pacific Ocean is home to a large number of avian species, and for many years these islands have provided an excellent playing ground for evolutionary biologists. This study was no exception. 

In their study, the researchers were specifically interested in examining the ways in which island sizebody size, and historical populationdeclineseach affected the genomic diversity of various avian island species. They chose to study 180 birds from 27 populations. These included Darwin’s finches (comprised of 15 different finch species) in addition to two related tanager species, as they all varied in size, weight, beak-size, and niche preference. 

First, they found that as island size decreased, genomic diversity decreased. This finding indicated that the protection of habitats is a key-component of wildlife conservation. Larger habitats can generally support larger populations, which in turn provides more opportunities for finding un-related mates. 

Secondly, they found that as body size increased, genomic diversity decreased. Smaller-bodied species generally reach sexual maturity at a much younger age, have greater numbers of offspring, shorter gestational periods, and therefore a faster evolutionary rate of change as compared to their larger counterparts. 

Finally, they found that significant historical population-regressions were associated with significant declines in current genomic diversity. Huge population-size reductions can very quickly reduce the size of the available gene pool. After such a devastating event, it can take a very long time for a population to regain previous levels of genomic diversity (Brüniche-Olsen et al. 2019).

Interestingly, the researchers also found that the International Union for Conservation of Nature (IUCN) does not yet take genomic diversity into consideration when assigning conservation status. Currently, the IUCN uses predictive factors (such as “reduction in population size, geographic range, number of mature adults, etc.”) in order to determine which species are threatened and how imminent their individual threats are. 

However, the data collected in this study suggest that a more accurate method would also involve the incorporation of genetic information (Brüniche-Olsen et al. 2019). The incorporation of conservation genomics would be particularly useful in this instance because it accounts for the evolutionary potential of a population. Other similar research (Brüniche-Olsenet al. 2018Doyle et al. 2015) into IUCN-listed mammalian species also indicates that the inclusion of genetic diversity data could be very beneficial in the IUCN’s long-term conservation goals (Brüniche-Olsen et al. 2019). 

With a staggering 28,000+ threatened species currently on the IUCN Red List, it is crucial that proper prioritization be used. 

References

Brüniche-Olsen A, Kellner KF, Anderson CJ, DeWoody JA (2018) Runs of homozygosity have utility in mammalian conservation and evolutionary studies. Conservation Genetics 19, 1295-1307.

Brüniche‐Olsen, A., Kellner, K. F., & Dewoody, J. A. (2019). Island area, body size and demographic history shape genomic diversity in Darwins finches and related tanagers. Molecular Ecology 22: 4914-4925.

Doyle JM, Hacking CC, Willoughby JR, Sundaram M, DeWoody JA (2015) Mammalian genetic diversity as a function of habitat, body size, trophic class, and conservation status. Journal of Mammalogy 96, 564-572.

About Stacy Krueger-Hadfield

I am a marine evolutionary ecologist interested in the impacts of seascapes and complex life cycles on marine population dynamics. I use natural history, manipulative field experiments and population genetic and genomic approaches with algal and invertebrate models in temperate rocky shores,estuaries and the open ocean.
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