Yellow Flowers are Complicated

Tangent: Can I begin a post with a tangent? Anywho, it’s June already. Spring is racing by, and there’s so much I’ve wanted to blog about in the last few weeks that I haven’t been able to- birds, flowers, leaves, weather, mammals. So much happens this time of year in such a short time. Already the foothills below 6,000 feet around the valley are starting to turn brown; the blast of green is just so short. But higher up- around Big Mountain Pass and Kimball Junction and Pinebrook, the green blast is just beginning and the trails are opening up…

Update/Correction: One last note before leaving May behind: I was way wrong, way wrong about the extent of Dyers Woad in the foothills. It’s all over the place, especially behind the U. Hospital, along Shoreline trail, and in the lower part of Emigration Canyon.

The Arrowleaf Balsamroot (pic left)is peaking in the foothills. Big yellow flowers are covering the hillsides between 5,000 and 7,000 feet. But not all of these are Arrowleaf Balsamroot.

Today my friend Cory and I biked out to Morgan and back, 40 miles each way. We noticed that East of Little Mountain Pass, the Balsamroot flowers looks the same, but the leaves are different. Instead of each leaf-stalk ending in a single large, arrowhead-shaped leaf. Each leaf stalk has a dozen-plus pointy leaves jutting out perpendicular to the stalks. This plant is Cutleaf Balsamroot, Balsamorhiza macrophylla (pic right). East of Little Mountain Pass, and again after Big Mountain Pass, clear out to Morgan, Cutleaf Balsamroot dominates. Yesterday I mtn biked up around the Glenwild trails North of Kimball junction, and Cutleaf and Arrowleaf were both plentiful, side-by-side.

There are 10 species of Balsamorhiza in the Western US, 2 of which extend in Southern Canada and 1 of which reaches down into Northern Mexico. All have the same big sunflowerish heads, but the leaves are quite different. Different Balsamorhiza species hybridize easily. 3 of the 10 species occur here in Utah: Arrowleaf, Cutleaf, and (the as-of-yet-not-spotted-by-me) Hooker Balsamroot, Balsamorhiza hookeri.

In my poking around the foothills over the last several days, it seems that Arrowleaf dominates in the driest, sunniest, most exposed sites, and that Cutleaf (closeup pic right) does a little better higher up, where it’s just a touch cooler and wetter

But there’s something else interesting about Cutleaf, besides being just-another-Balsamroot. Within the Baslamorhiza genus, it appears to be somewhat of an anomaly in two ways. First is structure. Balsamroots are divided by botanists into 2 sections: 6 of the 10 species have “pinnately divided”, or feather-like leaves and a slender, un-branched taproot. 3 of the remaining species have “simple” leaves, and a thicker taproot that branches into multiple crowns above. (This second section includes Arrowleaf Balsamroot.) But Cutleaf has the pinnately-divided leaves of the first section, with the thick branching taproot of the second section.

The second difference is even more interesting: All 9 other Balsamroots are chromosomally diploid, with 38 chromosomes. But Cutleaf is polyploid, with between 98 and 102 chromosomes. Many botanists believe that Cutleaf Balsamroot is the result of an ancient hybridization between 2 species of Balsamroot (1 species from each of the 2 sections described above) or that even more tantalizingly- is a hybrid between a species of Balsamorhiza and a species of Wyethia.

There are seven species of Wyethia, all native to Western North America. The common Wyethia in Northern Utah is Mule’s Ear, Wyethia amplexicaulis, (pic left) which I described when introducing Arrowleaf Balsamroot as the flower most often mistaken for it. It’s now beginning to bloom in force, and on the map below I’ve marked a couple of spots along the Shoreline trail where it dominates over Arrowleaf Balsamroot.

Tangent: Back when I first described Mule’s Ear, I highlighted the smooth leaves as the easiest way to distinguish it from Arrowleaf Balsamroot. Though this distinction is valid in Utah, it breaks down further afield. Arizona Mule’s Ear, Wyethia arizonica, for example has very hairy leaves and stems. Where W. amplexicaulis and W. arizonica meet (Southwestern Colorado for example) they frequently hybridize. The hybrid is known as Wyethia x magna, and W. x magna can have very hairy, slightly hairy, or completely smooth leaves. Net-net: Mule’s Ear identification is easy up around Salt Lake, but gets hairy (pun intended) down South.

Nested Tangent: W. x magna occurs clear down in Arizona, even though W. amplexicaulis hasn’t grown in Arizona since the Pleistocene (>10,000 years ago.) in this sense, W. x magna in Arizona is a living relic of past flora. We’ll see this kind of living relic again soon when we look at hybrid Oaks here in Northern Utah.

Mule’s Ear (closeup pic right) seems to do better with a little more shade and water than Balsamroot, and it grows best in clay soils. Though they look similar, Arrowleaf Balsamroot is a favored food of domestic sheep, Bighorn Sheep and Mule Deer, but all of these animals avoid Mule’s Ear. As a result, Mule’s Ear often thrives, and out-competes other native ground cover, in areas that are heavily grazed or foraged (pic left). Like Balsamroot, Mule’s Ear is pollinated primarily by Osmia bees (who I suspect like many of us can’t tell the flowers apart!)

Wyethia and Balsamorhiza are closely related (both pictured side-by-side, right). Both are distinguished within their larger tribe, Heliantheae, within the Sunflower family, (a "tribe" is basically a grouping within a biological family that includes multiple genera...) by having pistillate ray flowers, which means that the ray flowers of each are sexually functional. All other genera within Heliantheae have sterile ray flowers (but sexually functional disk flowers.) (See this earlier post for a brief review of composite flower structure, and the definition of ray and disk flowers.) Like 9 out of 10 Balsamorhiza species, all Wyethia species are diploids with 38 chromosomes.

Recent genetic analysis shows that Balsamorhiza is monophyletic, meaning that they form a group descended from a common ancestor which includes all descendants of that ancestor. Example: You, your siblings, and your sibling’s children/grandchildren form a monophyletic group. A monophyletic grouping forms a clade. Wyethia however is paraphyletic, meaning that they form a group descended from a common ancestor, but that group does not include all of the descendants of that common ancestor.

For example, my Dad has 2 brothers: John and Peter. If we got together for a barbecue that included Uncle John, his kids and grandkids, together with my Dad, his kids and grandkids, but left out Uncle Peter and his clan, our grouping would be paraphyletic. For our barbecue to be monophyletic, we’d have to invite Uncle Peter and his descendants along as well.

For Wyethia to be monophyletic, it would have to include Balsamorhiza. And this highlights one of the big problems of traditional biological taxonomy: as modern DNA analysis reveals the ancestry of and relationships between living things, the traditional taxonomies- in this case genera- don’t always hold up. From time-to-time botanists address this problem by reclassifying a plant or group of plants (a recent example was moving Yuccas out of the Lily family and into the Asparagus family) but this results in various sources (textbooks, etc.) with conflicting information.

Bottom line: those simple, uniform-looking yellow flowers you see all over the place right now are pretty darn complicated, and they have some interesting stories to tell.