Study Challenges Theories On Species
Cooler climates may produce more species than warmer ones
http://www.msnbc.msn.com/id/17630802/
More species develop in warm, tropical climates or cooler, temperate areas? It turns out the longtime answer — the tropics — may be wrong.
True, more different types of animals exist there than in places farther from the equator.
New research suggests that is because tropical species do not die out as readily. Cooler regions have a higher turnover rate, with more species developing but also more becoming extinct.
By analyzing the DNA of 618 mammal and bird species that lived in the past several million years, they were able to determine that new species develop more readily farther away from the tropics.
“It would take one species in the tropics 3 to 4 million years to evolve into two distinct species, whereas at 60 degrees latitude (two-thirds of the way toward either pole), it could take as little as 1 million years,” Weir said.
“In other words, there’s a higher turnover of species in places like Canada, making it a hotbed of speciation, not the Amazon,” said Schluter.
That, however, is balanced by a higher extinction rate in colder climates, so the tropics still have more diversity.
It also raises the question of whether a more variable climate causes more rapid evolution.
“That’s our belief, but we can’t prove it yet,” Weir said.
The upshot seems to be the obvious, that cold climates impose far greater selection pressure than warm ones. I rely mostly on the Web for my evolutionary and genetic news so this is a first for me. Until now I had no concrete evidence for the commonsense idea that Europids and NE Asians developed higher IQ because they evolved in more selective environments.
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There’s also the fact that with lower population densities, gene flow costs more, so you tend to get more inbreeding. That increases the rate at which the effects of recessives—typically deactivating mutations—express. This means the greater selective pressure is applied to a higher rate of expressed mutation.
There I go being “Nordicist” again…
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