Genomic study reveals impact of near extinction and hunting in Swedish moose

In the new study, the researchers analysed 87 genomes from the 1840s to 2019 from all across Sweden.
Photo: Flora M.C/Mostphotos

Moose is one of the most abundant cervid species in Scandinavia and in Sweden alone, about 320,000 individuals exists and about 60 000 of the population is harvested annually. However, from the 15th century onwards through the intensification of hunting during the 18th and 19th centuries, the species went nearly extinct and may have numbered in the low thousands at the time.

Now, the first large-scale genomic study of moose in Scandinavia reveals the effect of this near-extinction event. In spite of the severe decline, inbreeding does not seem to have increased and the species seems to have maintained most of its historical genetic diversity. The analyses, conducted by researchers from Stockholm University and Swedish University of Agricultural Sciences in collaboration with the Swedish Environmental Protection Agency and their national environmental monitoring program, are reported in the journal Communications Biology.

Nicolas Dussex
Photo: Private

“In spite of the near extinction event, moose do not show strong evidence for a loss in genetic diversity,” says Nicolas Dussex, researcher who led the work at Stockholm University.

“Maintenance of genetic diversity is essential for the survival of species,” adds professor Linda Laikre at Stockholm University. “Importantly, genetic indicators like the ones we estimated here are not only applicable to moose but are an important part of monitoring programmes advocated by Convention on Biological Diversity and currently employed by Swedish Agencies.”

In the new study, the researchers analysed 87 genomes from the 1840s to 2019 from all across Sweden, including Öland.

When populations decline, inbreeding may increase rapidly and thus harmful genetic mutations can be easily expressed, reducing the health of the population as a whole. In the new study, the researchers find overall limited indication of increased inbreeding and thus it is less likely that the population will suffer from genetic defects, unlike critically endangered species that number a few hundreds of individuals.

Regional differences in inbreeding

However, the researcher also found that not all populations are equal from a genetic standpoint.
“We also found that there were regional differences in inbreeding and the amount of harmful mutations as well as suggestion of a risk of future reduction in genetic diversity and gene flow. Particularly in the southern parts of Sweden including Öland. Therefore, there could be a risk of reduction in genetic health if dispersal is reduced among subpopulations, particularly in the south of the range,” adds Dussex.

Most importantly, the researchers found that over the past decades some genetic changes occurred involving a number of genes important for individual health (e.g., fertility, insulin and fat metabolism, body weight).

“We found that over a relatively short period of time of 40 years, some genes may have been impacted, possibly as a result of population fluctuations and/or through the effects of the harvesting strategy such as trophy hunting. This suggests that the harvesting strategy may not only impacts population sizes but also the genetic viability of the population as whole,” says Dussex.

Linda Laikre
Photo: Sören Andersson

The findings in moose also have implications for the management of other harvested cervids.
“Our results show that not only past declines but also current management can impact the health of wild populations over a relatively short period of time and that genetic considerations and indicators for genetic diversity should be incorporated into management plans of wildlife”, says Linda Laikre.

The work was supported by the Swedish Environmental Protection Agency within the framework of their environmental monitoring program that includes a new section for monitoring of genetic diversity.

Read the article i Communications Biology