According to recent reports red squirrels in Britain are facing extinction. There may be only 30,000 left in England, 10,000 in Wales, 10,000 in Northern Ireland, and 121,000 in Scotland [Red Squirrel Facts]. The European Red squirrels (Sciurus vulgaris) are being out-competed by American or Eastern gray squirrels (Sciurus carolinensis) introduced into Great Britain in 1876.Human Brits are banding together to help the red squirrels fight off the foreign invasion [Friends of the Red Squirrel] but the prospects are dim. It looks like curtains for the reds.
This clearly has something to do with evolution. When one species out competes another and drives it to extinction we think of this as part of the process of evolution. But which process is it? It doesn't really count as natural selection, strictly defined, since that process involves differential success of individuals within a population. What do we call it when two species go head-to-head and only one survives?
12 comments :
It is very similar to the situation when the Fundies and the Darwimps square off as they so obviously do on internet blogs. It is a great spectator sport especially for someone like myself who is convinced both factions are bananas.
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
We call it "macroevolution" in my opinion.
Nick
John A. Davidson says,
It is very similar to the situation when the Fundies and the Darwimps square off as they so obviously do on internet blogs. It is a great spectator sport especially for someone like myself who is convinced both factions are bananas.
Be patient. It will all be over in a few years. The first group to go extinct will be the fence-sitters like yourself, followed shortly thereafter by the other IDiots.
"What do we call it ...?"
Payback for the starling?
Larry
It is Davison as in John Davison Rockefeller not Davidson.
I am hardly a fence sitter as I have rejected both factions in favor of the Prescribed Evolutionary Hypothesis. I have no more respect for Dilliam Wembski than I do for Dichard Rawkins. They are both lightweight egomanical losers as apparently so are you.
I love it so!
"A past evolution is undeniable, a present evolution undemonstrable."
John A. Davison
"both factions are bananas."
Of course, argumentum ad bananas. It fits because it is artificially selected, creotin. ;-)
What do we call it...?
Competitive exclusion, I believe. But note that Darwin himself thought this was a kind of selection.
Isn't it interesting that we don't have a handy term to describe this kind of evolution?
It's very common whenever two previously isolated groups come into contact. The classic example is the competition between North American animals and South American animals when the isthmus of Panama was formed.
Another, ongoing, example is the destruction of Australians by superior beings from other continents. :-)
This clearly has something to do with evolution. When one species out competes another and drives it to extinction we think of this as part of the process of evolution. But which process is it? It doesn't really count as natural selection, strictly defined, since that process involves differential success of individuals within a population. What do we call it when two species go head-to-head and only one survives?
As stated above, it's the competitive exclusion principle at work - according to this principle, red squirrels will either adapt or die out. Not even drift can save them!
Grey squirrels have a competitive advantage in mixed/deciduous woodland since they can handle the phytotoxins present in immature seeds such as acorns, whilst the reds cannot. Reds fare better in coniferous forests (like those in Scotland), apparently because they're better at moving around in the canopy. Greys also raid reds food caches (lowering red females fecundity) and are vectors of squirrel poxvirus which is lethal to reds but not to greys.
This type of interaction is known as exploitation competition and is an integral part of natural selection.
But we don't need a special term for "this kind of evolution." It's regular old natural selection, with each competitor a new feature of the biotic environment of the other.
Sven DiMilo says,
But we don't need a special term for "this kind of evolution." It's regular old natural selection, with each competitor a new feature of the biotic environment of the other.
Really? Can you find me an evolution textbook that defines natural selection in terms of one newly introduced species driving an endogenous one to extinction? Which species is undergoing adaptation? In which species are there beneficial alleles being selected?
Right, well, I see your point. I was perhaps too hasty. The introduced-competitor-drives-native-
population-extinct scenario is one possibility of several:
If a new competitor is introduced or migrates into the habitat of species B, then:
a. they can subdivide the niche via coevolution; this could theoretically result from one or the other species evolving, but many cases of ecological release suggest that, most often, both species adapt to the presence of the other.
b. the introduced or new species goes locally extinct and thus fails to establish itself
or
c. the native species goes extinct and is replaced by the new competitor.
Scenarios b and c could result either from a lack of sufficient adaptation on the part of the "loser" and/or from the evolution of superior competitive ability on the part of the "winner."
But either way, it's the same three possible results of any environmental change: 1) no big deal; no adaptation and no need for it; 2) adaptation by natural selection to the changed environment, or 3) failure to adapt to a changing environment and consequent extinction.
Evolutionary ecology has had this stuff down for decades; it doesn;t need to be identified as a special kind of evolution with its own special name.
IMO.
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