Friday, July 18, 2008

Piney-Looking Trees Part 2: Douglas Fir is Named Wrong

The biggest foothills of the Wasatch are minor peaks like Grandeur Peak and Little Black Mountain. And as you climb these “Plus-Foothills”, the first Piney-Looking Trees (PLTs) you encounter are usually Douglas Fir, Pseudotsuga menziesii. Of the 3 common Wasatch PLTs, Douglas Fir does best in the hottest, driest, sunniest settings. Not nearly as well as any of the 3 Foothill Friends, but just a titch better than Fir or Spruce. It seems to do well seeding and growing up in the understory of sub-8,000 foot Aspen forests, another example of an ongoing succession battle between trees.

Part of Post Where I Whine About Bad Naming

Douglas Fir is named poorly. No reflection on David Douglas, the Scottish explorer-botanist (how do I get that job?) who discovered the species in California in 1831. But Douglas Fir is not a Fir. The cones are wrong, the needles are wrong, the ancestry is wrong.

It’s scientific name, Pseudotsuga, isn’t great either. The genus Tsuga is the Hemlocks, so Pseudotsuga literally means “False Hemlock”, and Douglas Firs are most certainly not Hemlocks, which don’t occur anywhere near Utah.

Worse yet, the generic name for other species in the genus is also “Douglas Fir”, so “Douglas Fir” can mean specifically Pseudotsuga menziesii, or just any species in the genus Pseudotsuga.

The problem with Douglas Fir from a Euro-centric naming perspective is that unlike Pines, Spruce, Firs, Larches and Hemlocks, they’re not native to Europe. So until Europeans encountered them in Western North America, there existed no “natural” name for them. Hence the goofy, awkward and unclear name.

There are only 7 species of Pseudotsuga in the world, all in North America or Asia. 3 of those are native to North America, and 2 of those native to the US (the other is in Mexico.) Besides Douglas Fir, the other Pseudotsuga is the equally poorly-named Big Cone Spruce, Pseudotsuga macrocarpa, which is emphatically not a Spruce, but does at least have large cones (compared to Dfir in pic, left), and this is the most notable visible difference between it and Douglas Fir. Big Cone Spruce is endemic to California, and specifically a few mountain ranges in Southern California.

Douglas Fir “proper” occurs in 2 varieties: Coastal Douglas Fir, Pseudotsuga menziesii menziesii, in the Pacific Northwest (range map left) and Rocky Mountain Douglas Fir, Pseduotsuga menziesii glauca, which occurs here in Utah (range map right). Coastal Douglas Fir is massive; after Redwoods they’re some of the tallest trees in the world. The can reach over 300 feet in height, and it’s thought that they may have grown as high as 400 feet in the recent past. They suffer easily from frost damage, and thrive in the moist and mild climate of the Pacific Northwest. Rocky Mountain Douglas Fir handles cold well, but lacks the stature of the coastal variety; in the Rockies it’s a decent-sized tree, but it would be a runt on Vancouver Island.

Tangent: This difference raises a nagging question about trees in North America. Why are all of the tallest trees- Redwood, Giant Sequoia, Douglas Fir, Sitka Spruce- in the West/Northwest? Why not in New Jersey, or North Carolina. And it’s not just because of settlement or logging; so far as we can tell, there were never 300-foot high trees in New Jersey or North Carolina...

Never Speak Ill of a Tree

Now, if it isn’t already clear from this blog, as a rule I try never to speak ill of any tree- or any plant for that matter- but to try and see some aspect of the Beauty of the World in every plant. And surely I’ve pointed out the wonderful and notable characteristics of many plants that are commonly maligned by others, including Box Elder, Scrub Oak, Cottonwoods, Dandelions and even Crabgrass. But it can’t be denied that the comparison between Coastal Rocky Mountain Fir and Rocky Mountain Douglas Fir is to the detriment of the Utah native. Nor does comparison of the 3 main Wasatch PLTs favor RM Douglas Fir; it’s foliage is the least attractive, its stands the least majestic, when compared with White Fir or Engelmann Spruce. Still, it’s often the first “real shade” one encounters on a Wasatch climb, and a welcome tree for it.

Tangent: Douglas Fir is one of many Pinaceae species grown commercially in plantations for Christmas trees. The tops are lopped off every 4-7 years or so for the actual Christmas “trees”. Its lackluster foliage generally distinguishes it as being the least expensive Christmas tree on the lot. Higher-end Christmas trees are usually Firs, often Silver Fir.

Although the 2 varieties of Douglas Fir can easily interbreed, they’re separated well enough by obstacles like the Great Basin that they generally don’t (Although up in British Columbia they do overlap and intergrade a fair bit.) But neither can interbreed with any other Pseudotsuga species, and the most likely reason for this sterility is chromosome count. Douglas Fir (both varieties) has 26 chromosomes, while all other Pseduotsuga species have 24.

There’s a real interesting analogous situation in Primates. Humans have 46 chromosomes. Other primates, including Chimpanzees, Bonobos, Gorillas and Orangutans, have 48. Apparently sometime in the last 5-7 million years, 2 small chromosomes fused into 1, reducing the hominid haploid count by 1 and the diploid count by 2. So far as is known, humans can’t interbreed with Chimpanzees. With Horses and donkeys however, the situation is more interesting. Both animals are member of the genus Equus, but Horses have 64 chromosomes, while donkeys have only 62. Horses and donkeys can and do interbreed, but the offspring- a mule- is a sterile aneuploid hybrid, with 63 chromosomes.

Coolest Thing About Evolution = When Things Stop Being the Same

This same fertility hybridization/mismatch/disconnect issue keeps popping up over and over again. And one of the things that has really surprised me in doing this blog is how many times, and in how many different stages we’ve seen it. We’ve seen it at the point where different varieties of a species are still able to interbreed as with Coast & Rocky Mountain Douglas Firs, Stellers & Blue Jays, Lazuli & Indigo Buntings, and the Black-headed and Rose-breasted Grosbeaks. We’ve seen species whose genetic histories seems to hint at a past hybridization event, like Cutleaf Balsamroot. We’ve seen species combinations that usually or always produce sterile hybrids, like Curlleaf & Alderleaf Mountain Mahogany (or like Donkeys and Horses.) And we’ve seen species that share a recent common ancestry, but have passed the genetic point of infertility-non-return, like Douglas Fir and Big Cone Spruce (or like humans and Chimpanzees.) And the thing is, this wasn’t something I was even thinking about when I started the blog. But it just keeps coming up, over and over again, how two offspring of the same parent can go on to produce lines off offspring that live and reproduce and change over and over until they’re not quite- or not at all- the same thing anymore.

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