Seeing Double

Day 125: Just to demonstrate how confusing lichen identification can be, here is another specimen of Ochrolechia laevigata with disks exhibiting the double-rim structure characteristic of closely related O. oregonensis. However, O. oregonensis occurs only on conifer bark, O. laevigata on deciduous species. The substrate here is vine maple (Acer circinatum), a species which frequently hosts this common lichen. It may also appear on alder and cottonwood. It's fortunate that I found this specimen on a living tree. If the bark had been detached, I might have drawn the wrong conclusion.

A Refuge For Ochrolechia Laevigata

Day 122: There I was, walking along the boardwalk at Billy Frank Jr. Nisqually National Wildlife Refuge, nudging the occasional foliose lichen and commenting aloud on their identities, but dismissing the common pale green crustose presence without truly getting in close. I had paused to sort out an Usnea on the wooden rail and was stepping away when little orange disks caught my eye. "Hang on a mo'," I said. "That's Ochrolechia!"

Now how could Crow have missed this, you wonder? Well, let me put it in perspective because I didn't think to drag out my penny. A standard pencil eraser is approximately 6 mm. The largest disk in this photo would measure out at roughly 2 mm or a little smaller. You could arrange six of the mid-sized ones on top of an eraser with space for imaginary grout between them.

Several Ochrolechias occur in the Pacific Northwest and can be separated from each other by identifying the substrate on which they are growing, or by performing chemical tests. Ochrolechia laevigata responds to the application of common chlorine bleach by turning red, a "C+" reaction.

Ochrolechia Laevigata, Smooth Saucer Lichen

Day 123: Superficially very similar to Multicolored Rim Lichen (Lecanora pacifica), Ochrolechia laevigata (Smooth Saucer Lichen) has an even closer look-alike in its cousin O. oregonensis (Double-rim Saucer). Two features distinguish them. The first is less obvious: Double-rim has a second narrow whitish-pink band just inside the outer rim, absent in O. laevigata. Much more telling is the fact that Double-rim grows almost exclusively on conifers, and Smooth Saucer will only be found on alder, vine maple and other deciduous species. The disks of Smooth Saucer seldom exceed 3 mm. Those of Double-rim may be up to 1 mm. larger. Both species respond positively to chemical testing with chlorine.