What were the authors trying to test, and what predictions did they make?
Elk were introduced to Afognak Island, Alaska in 1929. Only 8 elk were introduced, but the population peaked at 1,400 in 2009. The authors studied specific loci in this unique population to examine founder effect and bottleneck effect. The purpose of the experiment was to determine the effects of translocation and demography on genetic variation. The isolated population was expected to vary significantly from their parent population due to the population experiencing a genetic bottleneck and founder effect. Therefore the population would suffer a significant loss in allelic diversity.
What, exactly, did the authors do?
The authors studied microsatellite loci in the Afognak population and compared them to the parent population. Microsatellites were used because they have a high degree of polymorphism. Tissue samples of elk from Afognak island and Olympic Peninsula were conducted. The Olympic Peninsula is where the elk that were introduced to Afognak island originated from. DNA extraction, amplification and genotyping took place, fifteen specific microsatellites were chosen to represent the elk genome.
What did the authors find (i.e, what were their data)?
The authors found that the two populations of Elk differed in both allele and genotype frequencies. Specifically 10 of 15 allele frequencies differed, and 11 of 15 genotype frequencies differed. One specific loci exhibited excess heterozygosity in Afognak. Another loci exhibited a deficit in heterozygosity in the Olympic population. The inbreeding coefficient for the Afognak population was 0.019, and -0.006 for the founder population. Surprisingly, a genetic bottleneck in the Afognak population was not found.“Despite the demographic bottleneck, no evidence of a genetic bottleneck in the Afognak population was detected using a test for heterozygosity excess or mode shift of allele frequencies.”
How did the authors interpret their findings?
The authors concluded that the combined founder and bottleneck effect resulted in a significant reduction in allelic diversity and heterozygosity. They were unable to reject the null hypothesis of no bottleneck and no inbreeding. One possible source of error is that the Olympic population, which yielded the Afognak founders, was not genetically identical 70 years later. This study demonstrated bottleneck detection, which can be a helpful tool for endangered species management.
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