Placopsis Let's-Call-It Lambii

Day 155: There is a good bit of debate over whether this particular Placopsis lichen should be P. gelida or P. lambii. Some sources claim that P. gelida has not been found in Washington, and that herbarium records labelled as such are actually misidentifications of P. lambii. Others will tell you that P. gelida is the most common species of Bull's-eye Lichen from Alaska to California. Who do you believe? And why can't they nail it down? The simple answer (and trust me, the alternative is much more complex) is that sufficient genetic analysis of the samples has not been done. Gene sequencing is a fairly new tool for the lichenologist's toy box, and obviously, there's a substantial backlog of research to be done. As lichen DNA is examined, we are having to split genera, create new taxonomy, and to reevaluate what we thought we knew. Science is not a static field (no pun intended, but I'll leave it there for your enjoyment). It is always changing, always evolving as technology progresses and allows us to take a closer look.

Placopsis Gelida

Day 261: Bullseye! It's easy to see how Placopsis gelida got its common name "Bullseye Lichen," although the cephalodium is not always as perfectly oriented as it is in this specimen. It is this nitrogen-rich feature of lichen anatomy which makes it possible for Placopsis to colonize the seemingly bare surface of recently broken rock. When wet, this lichen may exhibit a greenish-blue tint. Placopsis is a "pioneer" species, i.e., one of the first to establish itself on freshly exposed surfaces. It contributes to the breakdown of rock and in decay, supplies both the matter and nutrients in which vascular plants can establish themselves. The next time you see a rock cliff dappled with wildflowers, thank the lichens which made it possible for them to thrive.

Placopsis Gelida, Bullseye!

Day 177: Many crustose lichens are easy to overlook. At a glance, they might appear to be an inclusion in a rock face or a mineral deposit on the surface. For example, this specimen of Placopsis gelida (a "bullseye" lichen, ref. Vitt et al) could have been mistaken for a discoloured bit of quartz in a darker matrix when seen from a distance. Up close, the lichen reveals its complex form, brown cephalodia (wart-like structures) dotting the pale green thallus and darker lobes extending like fingers along its margins. Crustose lichens adhere tightly to their substrate material; it would be difficult to lift one of those tiny projections even with a pocket knife.