Evolution of the Largest Animal on Earth

Published 2018-04-17

A new study published in the journal Science Advances, reveals new information on the evolutionary history of the largest animal on earth, the blue whale. Researchers at the German Senckenberg Biodiversity and Climate Research Center, Geothe University, and the University of Lund in Sweden analyzed the genomes of three whale species: the blue whale, humpback whale, and gray whale.

Blue whales (Balaenoptera musculus) are currently listed as endangered on the ICUN Red List and populations are slowly increasing after heavy whaling in the 1900's. The whales can live to approximately 80-90 years old and mostly travel alone or in small pods of 2-3 individuals. However, little is known about their population connectivity, migration routes, or mating system. In addition, little is known about whales at the level of the genome. This new study offers new information on the relationships between large whale species and, specifically, information on the evolutionary history of the blue whale. Knowledge of evolutionary history and population dynamics of these large whales is important for basic biological understanding and conservation of endangered species.

Network analysis of genomes from blue, gray, and humpback whales suggest that rorqual species mated across emerging species boundaries resulting in speciation under gene flow. This type of speciation, referred to as sympatric speciation, is rare in nature. Speciation in animals is more often driven by separation as a result of a geographic or genetic barrier, which was not present in the case of the rorqual species as described in this study. The analysis also suggests that, contrary to their appearance, gray and humpback whales are not as evolutionarily distinct from other rorquals as previously thought. These results highlight the need for future genomic analyses to understand the complicated evolutionary relationships in whales.

Arnason, U. et. al. Whole genome sequencing of the blue whale and other rorquals find signatures for introgressive gene flow. Science Advances, 2018) DOI: 10.1126/sciadv.aap9873