Phylogeography, demographic history and hybridization in belugas Delphinapterus leucas

Research output: Book/ReportPh.D. thesis

The aim of the thesis is to further our understanding of the population structure and
demographic history of beluga whales in a range-wide context, using genomic data. The thesis
includes an introduction, and four chapters written as draft manuscripts; Chapter 1 is in revision
with Marine Fisheries Review, Chapter 2 has been published in Mitochondrial DNA Part B, Chapter 3
is a draft manuscript intended for Molecular Ecology and Chapter 4 is accepted for publication in
Scientific Reports and will be published June 22th 2019.
Chapter 1 Circumpolar mtDNA population structure and variation in belugas: a review. In this
manuscript we review the genetic studies of belugas published to date, and for the first time present
a range-wide analysis of levels of mtDNA diversity and differentiation in beluga populations. Our
analysis of 302 bp of overlapping mtDNA control region sequence includes 2,933 individuals
spanning all 21 recognized beluga stocks, and represents 71 haplotypes defined by 16 variable sites.
Results put the diversity and differentiation in a global perspective and highlights the limitations of
short mtDNA fragments in beluga phylogeography.
Chapter 2 Mitochondrial genome divergence between beluga whales in Baffin Bay and the
Sea of Okhotsk. This publication has the first comparison of two complete mitochondrial seque nces
from separate ends of the beluga range and their estimated divergence time. Despite the caveats of
small sample size and simplified methodology, we estimate that the divergence of beluga clades is in
the order of hundreds of thousands of years. The publication is available from:
(www.tandfonline.com/doi/full/10.1080/23802359.2017.1318686).
Chapter 3 Habitat fragmentation and secondary contact shape phylogeography and
demographic history of belugas. In this manuscript, we analyse 2 nuclear genomes and 202
mitogenomes from 23 localities covering the entire beluga distribution, applying population
genetics, bayesian phylogenetic and species distribution modeling analyses. Our results show that
the earliest split within belugas happened around 750 kya with four lineages established before the
start of the last glaciation, and that current population structure is largely a result of secondary
contact of these old lineages. Further, our results show that the effective population size of belugas
has increased six-fold since LGM and that the suitable habitat range has increased since LGM, with
the winter area increasing 3-4 fold.
Chapter 4 Hybridization between two high Arctic cetaceans confirmed by genomic analysis.
We present genome-wide DNA sequence data from a monodontid skull which from its intermediate
morphology was hypothesized to be a beluga/narwhal hybrid. Using DNA retrieved from the skull
and a reference genomic panel of each parental species, we show that the specimen is indeed a
first-generation hybrid. Our analyses reveal that it was a male, with a narwhal mother. We also present stable isotope analysis of the beluga/narwhal hybrid. The data suggest a unique diet of the
hybrid relative to either parental species. These results further our understanding of the interaction
between belugas and narwhals, and underscore the importance of natural history collections in
monitoring changes in biodiversity.
Original languageEnglish
PublisherDepartment of Biology, Faculty of Science, University of Copenhagen
Publication statusPublished - 2019

ID: 248938948