Biogeography of Gibbons

I've been struggling on taxonomy of langurs and gibbons lately: langurs because I have an accepted paper "in press" that needs a little tweaking and the tweaks go back to early in the 19th Century; and because the gibbon monograph that I'm starting has taxonomic problems pre-dating Linnaeus 1771.

But the good news is that so many ancient manuscripts are finding their way on to the Internet that I can actually sit here in Coquitlam and read books from that era. And that they're often in French, Dutch, German or Latin doesn't matter so much, because the names of the authors and the journals are all the same, and the Latin names of the critters is still Latin. Takes time, though.

Last night I had an epiphany: I noticed that the 3 Indochinese species of gibbons are separated by big rivers: crested gibbons (Nomascus spp.) east of the Mekong, Lar-type gibbons (Hylobates spp.) between the Mekong and the Salween system, and Hoolock gibbons (Hoolock hoolock) west of there, between the Salween River and the Irrawaddy River. It's because gibbons can't swim, and these big rivers have been stable for long enough for these genera to evolve--that's back to the Pliocene, between 2 and 5 million years.

I'm not the first to notice that large rivers separate gibbon species, nor the first to notice that the biggest rivers separate the genera. But it was fun to figure it out for myself.