Observation 79074: Xanthoparmelia (Vain.) Hale

When: 2011-09-25

Collection location: Serra de São Mamede, Portugal [Click for map]

Who: zaca

No specimen available



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Believe me, I know what you mean!
By: Jason Hollinger (jason)
2011-10-10 00:48:24 IST (+0530)

I’ve spent years trying to make sense of this stuff! :)

All this material
By: zaca
2011-10-09 23:59:11 IST (+0530)

is new to me and, thus, I´m very grateful to you in giving me some details about this group of species and their relations. That kind of information is very difficult or even pratically impossible to find. Thanks, Jason.

X. digitiformis is really distinctive
By: Jason Hollinger (jason)
2011-10-09 23:08:51 IST (+0530)

… I think! I’ve really been paying attention to this group of non-isidiate Xanthoparmelia with salazinic acid. X. lineola, X. somloensis, X. coloradoensis, and X. digitiformis are the ones that occur in southwestern North America… maybe anywhere in North America.

Almost everything I’ve seen are slight variations on what your specimen looks like. But one time I found this extremely lobulate thing in New Mexico that formed a thick mat of overlapping minute finger-like lobules. I concluded that it was safe to call that thing X. digitiformis and all the rest must fall into the other three species, all of which are very common.

The material in BC, Canada has “normal” peripheral lobes but has a tangle of variably-sized overlapping lobes in the interior and has relatively few apothecia. Apparently this is called X. coloradoensis, the most common species up there.

The other two apparently differ only in whether the tips have a white mottled pattern (maculae). I’m still sampling the variation, so I can’t recommend any advice for distinguishing X. lineola from X. somloensis.

To complicate matters, X. somloensis has been synonymized with X. stenophylla, at least for North American material. And genetic evidence suggests that the whole group is totally messed up. In ten years none of these species concepts will be of any use, I bet.

It’s also worth noting that X. cumberlandia essentially differs from the above group only in chemistry: stictic acid and variable amounts of norstictic acid and satellites. I’ve seen specimens which react strongly K+ yellow to red and others which remain K+ yellow. A rule of thumb that seems to work in Xanthoparmelia is norstictic acid results in “bright” red often with orange and/or yellow outline; salazinic acid results in dark “blood” red with no outline. But note that while X. cumberlandia contains no trace of salazinic acid, the other three can contain traces of norstictic acid. In principle, norstictic acid can be distinguished from salazinic acid under the microscope: place bit of thallus on slide, introduce KOH, after about one minute norstictic acid will produce a “snow” of needle-shaped red-orange crystals visible even at 400x; salazinic acid produces no crystals. This is remarkably sensitive, but is especially easy to see when concentrations are high. But do keep in mind that salazinic specimens may also contain some norstictic acid! Arg!

Created: 2011-10-09 17:21:40 IST (+0530)
Last modified: 2011-10-11 02:40:11 IST (+0530)
Viewed: 39 times, last viewed: 2017-06-10 10:25:43 IST (+0530)
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