Friday, December 08, 2006

Lost species
Anyone who has been reading archy for a while knows I have a special fascination for Woolly Mammoths and other ice age megafauna. That interest springs in part from having lived in Alaska and come to love the local giant mammals. It also springs from that contrary streak that makes some of us seek out obscure areas of interest. If I have a side interest in paleontology, it won't be for dinosaurs, about which any twelve-year old knows more than me; it will be for obscure giant mammals of the recent past.

However, being an amateur means I'm not always up on the latest data. Once I was smug because I knew that Baluchitherium was the biggest land mammal of all time, but today I learned over at Carl Buell's Olduvai George that Baluchitherium is no longer a recognized species, it's been merged with several of its cousins into a single species, Paraceratherium. Mentioning a Baluchitherium in front of a knowledgeable naturalist would have been as embarrassing as saying Brontosaurus in front of the previously mentioned smart twelve-year old. At least I avoided that faux pas, but now I have to learn how to pronounce Paraceratherium.

This brings us to bears. Carl wrote to commiserate with me over lost species and mentioned that someone had once classified brown bears into over 90 species. Bears are getting back into a neighborhood where I'm comfortable. Today, there are maybe five species recognized in the genus Ursus (true bears). There are only about two-dozen recognized sub-species of bears in the world. The exact numbers constantly change.

After a little Googling I found that the mystery naturalist was Clinton Hart Merriam, the first chief of the USDA’s Division of Economic Ornithology and Mammalogy, an agency that preceded the National Wildlife Research Center, and one of the founders of the National Geographic Society. He was no wacky amateur; he was one of the leading authorities of his day whose works are still quoted. So how did he find so many species of bears? It seems that Merriam was an arch splitter.

It is common to divide paleontologists and naturalists into two camps--lumpers and splitters. Lumpers find a new specimen, whether a fossil or a living creature, and want to jam it into an existing species to keep the family tree as simple as possible. Splitters want to create a new species or even genus for every new sample. For living things, genetics have simplified this argument (but not ended it). Bears come in many sizes, colors, and even patterns of markings.
Merriam was the sort of scientist who had a color chart and set of calipers ready for all occasions. Whenever a hunter brought in a skull or pelt that showed a new combination of characteristics, Merriam was ready to declare a new species.

This is not a completely ridiculous approach. Species is a remarkably vague concept. In general it means a population capable of breeding and producing fertile offspring. Some related species can breed together and produce sterile hybrids (horses and donkeys produce sterile mules). Genetics isn't the only limit. Some species simply won't breed because of behavior or non-overlapping ranges. Many naturalists now divide African elephants into two species, forest and savannah elephants, who never mix even though they are nearly genetically identical.

Most bear species can interbreed, but don't. This creates some odd situations along the divides. Polar bears and brown bears are closer related to each other than either is to North American black bears, and hybrids do occasionally appear. One was killed in Canada last spring and is probably a result of the two bears' ranges changing due to global warming. While many of Merriam's species were likely just local populations or unusual individuals, some might have been interesting hybrids.

Now I'm hunting for a copy of Merriam's complete classification to see if I can figure out how many of his "species" are extinct.

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