Keystone species:
As you can see if you look at the Vancouver poster, it appears that it is impossible to have a population of indefinite size that survives for an indefinite time because of speciation effects. Without some sort of check the population will die out. Since there are still people and animals on the earth it must be that evolution has developed a fix for the problem. Population size is strictly limited. Thus indefinite survival is possible and, indeed, can seen to be the case in many species.
It would probably take about two thousand generations for the axe to fall from speciation effects. But that is a long time. Over such a period of time it is highly probably that there will be drift between local populations of the species. Some intrepid mouse will scale a mountain range; some baffled salmon will swim up the wrong creek; some storm driven marmot will wind up on the wrong side of a valley. In that case it would not only be the local population that would die out but the whole species. Evolution cannot rest on such a threat and so the limitation is imposed much faster.
“And,” I would say cheerfully to any whom I could beg or hornswoggle into listening to my presentation, “If it is a keystone species you could lose the whole ecosystem.”
In the event nobody challenged me on the point, which was a lucky good thing because I didn’t know what I was talking about. I couldn’t really have named such a species.
After the fact, science has come through with an example. It is mammoths. (Michael J. Benton The Biosphere Rebooted NATURE vol. 471 no. 7228 March 17, 2011 page 303 reviewing Here on Earth by Allen Lane/ Atlantic Monthly Press 2011) The article points out that the book points out that when folks went into the Siberian tundra and killed all the mammoths (Sure, sure. Blame the Neanderthals.) the productivity of the entire region fell. Apparently the mammoths were rummaging around munching on the vegetation and stirring up and fertilizing the ground and in their absence, assuming people were not willing to plow on that scale, the ecosystem fell apart.
Please ignore those stories about mammoths found frozen in ice with unwilted flowers in their stomachs. Mammoths are believed to have digested their vegetables in the lower GI tract, not high up like cows. So it would have taken days, not minutes for those flowers to wilt. Now I know that there are Philistines out there who will point out that minutes or days makes little difference if those mammoths remained frozen until recent times. They were grazing. Whoosh. An ice age descended and is only now going quite away. The ice age might have reduced the number of mammoths and lowered the productivity at the same time.
All right. I don’t know. I wasn’t there. I never found a frozen mammoth. I haven’t even been to Grasshopper Glacier where the same thing happened.
The important thing is that somebody else thinks that there is such a thing as a keystone species. That makes it respectable, which is all I need.
The article goes on to announce that overpopulation is the biggest problem in the world.
I can sure give you good news on that one.
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