Moving Towards an Epigenetic Understanding of Inbreeding Depression in Mirounga angustirostris

• Main Author: Weng, Watson
• Other Authors: vonHoldt, Bridgett
• Format: Bachelor Thesis
• Language: English
• Published: 2020
• Subjects: Nes; Nes’; Elephant Seal
• Online Access: http://arks.princeton.edu/ark:/88435/dsp01nv9355828

At the turn of the 19th century, the northern elephant seal Mirounga angustirostris was erroneously declared to be extinct due to human overhunting, though today the population appears to have recovered substantially. However, following the severe genetic bottleneck, it would have been expected for M. angustirostris to demonstrate inbreeding depression, and so it becomes especially intriguing when there exists no body of evidence for this in the NES. Therefore, this investigation was focused on determining whether classical thought being focused solely on the level of genetic diversity while skirting the potential for diversity to exist on the level of the cytosine methylation, is inherently flawed. That is, in populations that lack genetic diversity, what explains the persistence of extant populations? Eight blood samples of M. angustirostris were used to determine their relatedness and to discover whether there exists differential methylation between individuals, first by examining runs of homozygosity, which are enriched in deleterious variants and whose mediation by methylation would prevent that, and then more broadly on the level of the entire genome. The investigation was able to determine that there were indeed differences between the mean levels and ranks of methylation as calculated by the ANOVA and Kruskal-Wallis statistical tests on the genome-level, though we were unable to find evidence for methylation data overlapping runs of homozygosity, precluding analysis on how differential methylation could impact phenotypic values of inbreeding at those sites. Thus, these results advocate for the relevance of diversity in an epigenetic rather than genetic context.