By studying genomes of whales, scientists can trace the evolution of the largest aquatic mammal and four species of rorquals including the blue whale.
Scientists from the German Senckenberg Biodiversity and Climate Research Center have partnered with the Goethe University and the University of Lund in Sweden to analyze whale genomes and trace the evolution of its family trees.
The study, which was published in the journal Science Advances, showed that rorquals eventually grouped separately. The process is called sympatric speciation, which happens due to the absence of geographic barriers. Rorquals make up the largest species of baleen whales characterized by its slender body and elongated flippers.
Lead author Dr. Axel Janke, a professor and scientist at the center, reported that rorquals and blue whales mated with other species from different geographical locations. This is an extraordinary finding since sympatric speciation is rare and should not happen across species, he added.
"Speciation under gene flow is rare. Usually, species are assumed to be reproductively isolated because geographical or genetic barriers inhibit genetic exchange. Apparently, however, this does not apply to whales," said co-author Fritjof Lammers, also a scientist at the center.
Cross-Breeding
A genome analysis, conducted by sequencing whale chromosomes and differentiating one from the other, showed that migratory species, including the humpback, gray, and blue whale, inhabited distinct ecological niches but there were no genetic barriers. One evidence of this phenomenon is the hybrid offspring between fin whales and blue whales.
However, researchers were not able to find traces of recent interaction between the two whale species. They hypothesized that this could be because the available whale genome comes from only one or two animals.
These recent findings, according to Janke, deviates from the Darwinian Theory suggesting that species make up certain phylogenetic trees. Instead, species are interconnected in a single network but with their cloaked genetic signals, these associates remain undetected.
Outsiders
Surprisingly, Janke's team's study hinted that the rorqual species appear to be more complex than it was first believed to be. For example, the humpback whale is discovered to be an outsider to the rorqual species because its genome does not match the former's evolutionary trace. Gray whales are also believed to have come from a different species. However, genome analysis proves that gray whales simply belong to a new ecological niche of rorquals.
Janke said that their purpose is to "better understand biological processes and the fundamentals of biodiversity. It even reveals how population sizes of whales have changed during the last million years."
