I’m rushing around frantically trying to get everything done before I leave for HiliLand on Saturday, so don’t expect much. Since people seemed to like the evolution post on ring species yesterday, I might do another tomorow on a new paper on the hooded crow/carrion crow hybrid zone (a famous area where two “species” meet and sometimes mate) in Europe. But for the nonce have a look at some animals: pronghorn antelopes sent by Stephen Barnard from Idaho (maybe I’ll just call him “SB” from now on, since everyone knows his photos), as well as a landscape taken from where he lives.
As I’ve explained before, pronghorn antelopes (Antilocapra americana) aren’t really antelopes: they’re the only species in the family Antilocapridae. Every other species in that family is extinct. Here’s a group photographed by Stephen (click all pictures to enlarge):
Wikipedia says this, though I haven’t verified it:
The pronghorn is the fastest land mammal in the Western Hemisphere, being built for maximum predator evasion through running. The top speed is very hard to measure accurately and varies between individuals; it can run 35 mph for 4 mi (56 km/h for 6 km), 42 mph for 1 mi (67 km/h for 1.6 km); and 55 mph for 0.5 mi (88.5 km/h for .8 km). It is often cited as the second-fastest land animal, second only to the cheetah. It can, however, sustain high speeds longer than cheetahs.
True antelopes are Old World creatures found in Africa and Eurasia (examples are the impala, the dik-dik, the sable antelope, the wildebeest, and the Thompson’s gazelle). I did a TimeTree search to find out the evolutionary relationship between the pronghorn and other deerlike mammals. (You should all know about the TimeTree site; put in any two species and you’ll find their divergence time and the scientific references for it. I’ll do a post someday on the weird counterintuitive relationships you can find using this site.)
Here’s the relationship between the pronghorn and a true antelope; their lineages diverged about 29 million years ago.
Here’s the divergence between pronghorns and giraffes. It’s not much different!
And the relationship between two “true” antelopes, whose ancestors diverged about half that long ago:
What this says is that the pronghorn is no more closely related to “true” antelopes than it is to the giraffe, which of course isn’t an “antelope” at all. The pronghorn, limited to North America, is a truly unusual species.
And now a landscape shot of where they live, also from SB: