What is it about?
In the North Pacific there are 3 types of killer whales that feed almost exclusively on salmon, marine mammals, and deep-water fish and sharks, respectively. They are often in the same waters, but don't mix or interbreed. Previous studies have concluded that they diverged from one another in sympatry (within the same area). We have re-analyzed genome-wide variation and determined that the data are not consistent the three types having diverged directly from a common ancestor, rather they most likely resulted from multiple colonization events from other oceans or regions, with some genetic mixing upon contact.
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Why is it important?
The process of speciation can be complex, especially for highly mobile marine mammals like killer whales, where cultural differences may drive divergence. This paper uses genomic methods to help describe the evolutionary path that has led to 3 types of killer whales in the North Pacific. The results support previous research indicating that there have been multiple colonization events from other oceanic regions, followed by limited genetic mixing, but cultural differences may have then reinforced divergence among ecotypes. This is in contrast the hypothesis that these 3 ecotypes diverged from each other within the North Pacific purely due to cultural differences among populations of related individuals. Regardless of the mechanisms, the 3 types are genetically isolated from one another, evolving independently and functioning as unique species. This has implications for independent management policies to protect them from human-caused impacts such as over-fishing, pollution, noise, and fishing gear entanglement.
Perspectives
Killer whales are unique in their culturally diverse populations, specialized for different ecological niche's within ecosystems. In the North Pacific there are 3 culturally distinct types, that differ in feeding habits, behavior, vocalization, and some physical characteristics. In the Antarctic and sub-antarctic, there are at least 6 ecologically and culturally divergent types, some of which are also physically very distinct. I'm interested in whether they are functionally different species, and what mechanisms have allowed for this relatively rapid diversification in the absence of apparent barriers to interbreeding. For conservation, it is important to know how species and populations are distributed in order to develop management policies that are most appropriate to maintain them as functioning parts of their respective ecosystems.
Dr Phillip A Morin
Southwest Fisheries Science Center
Read the Original
This page is a summary of: Genome-wide SNP data suggest complex ancestry of sympatric North Pacific killer whale ecotypes, Heredity, August 2016, Springer Science + Business Media,
DOI: 10.1038/hdy.2016.54.
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