Thursday, March 15, 2007

Speciation in the temperate zone?   posted by Razib @ 3/15/2007 10:29:00 PM

There's a new paper in Science which posits that speciation might be more common in the temperate zone than in the tropics. From a summary:
...For nearly a century, researchers have assumed that new species are constantly popping up here, while speciation is far more stagnant at Earth's relatively deserted poles. But a new study claims the opposite: Species evolve much more readily at higher latitudes. It's just that the new arrivals die off so fast that most of them never get counted.
The pair studied 309 pairs of bird and mammal sister species (the most closely related pair from a common ancestor) living from the tropics to the poles. DNA analysis revealed that, on average, birds and mammals near the equator diverged from a common ancestor 3.4 million years ago; in contrast, those near the poles diverged less than 1 million years ago....

One of the researchers, Dolph Schluter, has done work on sympatric speciation of 3-spined sticklebacks. It stands to reason that he would be interested in angles besides conventional allopatric speciation. The fact that temperate lineages have relatively shallow coalescence times due to extinction rates also suggests to me that their long term effective population will be smaller. For humans this is likely true, e.g., the withdrawal of Europeans into Ice Age "refugia" during the Last Glacial Maximum, while tropical populations would be less perturbed by the climatic change. The neurobiologist William Calvin had speculated in the 1980s about the role that the oscillating Ice Ages might have had in reshaping our hominid lineage, though the Out of Africa Hypotheses have shunted that idea aside.

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