[__ Science __ ] The Great Species Mix-Up

[AIG.com]

The wild and woolly world of hybrids is setting evolutionary ideas back on their heels.

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[Barbarian]

They must be running out of news. This stuff wasn't new when I was an undergraduate in the 1960s. Long time ago, there was a zoo that had to do some work on the grizzly bear habitat. Someone mentioned that they could be kept with polar bears; "they seem to get along just fine."

They got along extremely well. Yes, "grolar bears." Or "pizzly bears." It's not surprising. They diverged only at the last glaciation, and are genetically very close. With the warming of the Earth and loss of Arctic Sea ice, the polar bears have been coming ashore, looking for food. And they meet with grizzly bears, sometimes mating with them. And now we see their hybrids occasionally in the wild. If the warming continues, polar bears might mate themselves out of existence.

And biologists are coming back to Darwin's view that hydridization is a normal phenomenon and sometimes the source of new species:

Philos Trans R Soc Lond B Biol Sci. 2008 Sep 27; 363(1506): 2971–2986

Hybridization, ecological races and the nature of species: empirical evidence for the ease of speciation​

Here, I show how recent genetic studies of supposedly well-behaved animals, such as insects and vertebrates, including our own species, have supported the existence of the Darwinian continuum between varieties and species. Below the level of species, there are well-defined ecological races, while above the level of species, hybridization still occurs, and may often lead to introgression and, sometimes, hybrid speciation.