Speciation and killer whales in the North Atlantic
Overview of
Speciation
A species is can be defined as a group of individuals that interbreed
in nature. Speciation is a lineage-splitting event that produces two or more
separate species. The cause of normal speciation can be related to geographic
isolation and a reduction in gene flow. Groups evolve with genetic differences (Berkley, n.d.). “These need
not be huge genetic differences. A small change in the timing, location, or
rituals of mating could be enough. But still, some difference is necessary.
This change might evolve by natural selection or genetic drift”(Morell, V., 2013).
Below are some of the different modes of
speciation.
Mode of speciation: new species formed from:
Allopatric geographically isolated populations
Peripatric small population isolated
At
edge of larger
Population
Parapatric continuously distributed
population
You may follow the link in the references for a more in
depth look at speciation.
Killer whales of the
North Atlantic
There is a debate among biologists as to whether it is
possible that a new species can arise in populations that have no geographic
barriers. This process is known as sympatric speciation. Killer whales have
multiple genetically distinct populations with different prey preferences in
the North Pacific and Antarctic, but they have not been formally described as
separate species.
This separation is due to prey preference. With enough time,
the two populations would become genetically distinct. Orca’s in the North
Atlantic have different hunting tactics and have been observed to be learned
behaviors. Cultural differences may contribute to driving the populations
apart.
At this time, researchers have not yet found any genetic
difference in the North Atlantic whales; however opinions tend to sway towards
these animals being at the beginning stages of speciation; which is a very long
process. The prey preference is not yet causing genetic change, but given time
it may lead to this.
References:
Berkley, Evolution 1010. Online. Available at: http://evolution.berkeley.edu/evosite/evo101/VADefiningSpecies.shtml
[Accessed on 09/05/2013].
Morell, V., 2013. Science Daily. North Atlantic Killer whales may be branching into two
species. Online. Available at: http://news.sciencemag.org/evolution/2013/08/north-atlantic-killer-whales-may-be-branching-two-species
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