Collection location: Dove Creek Hammock, south Key Largo, Monroe Co., Florida, USA [Click for map]
|I’d Call It That||3.0||6.42||1||(jason)|
sum(score * weight) /
(total weight + 1)
Mostly due to general lack of info on this species and the similar (at least on paper) P. poncinsii.
Having become better acquainted with Heterodermia albicans and Heterodermia in general, it is absolutely clear that the K+y to orange medullary reaction which I interpreted as weak norstictic acid does not signify. The upper cortex of Heterodermia is prosoplectencymatous (composed of elongated parallel hyphae) and has a distinctive “flowing” appearance. Physcia has paraplectenchymatous upper cortex (a palisade in mycological terms in this case), which has a uniform, spatially homogenous, dull appearance. Zeorin, it seems, when present in sufficient quantity, can result in a slow darkening of the K reaction (K+y initially due to atranorin in the medulla). (Upon subsequent examination of specimens I’ve already tested, the K+y test is observed to have turned finally dingy orange-red, not dingy brown-yellow as normal for material containing only atranorin.)
From More Florida Lichens: chemistry rules out P. crispa and P. americana; the pale underside rules out P. atrostriata and P. sorediosa. This leaves only P. poncinsii and P. undulata. Marginal soralia suggest P. undulata.
I have also discovered that tropical regions of northern Mexico (e.g. Sinaloa) have occasional records of many tropical Floridan species, and in this case, it has full desciptions of all of the species mentioned above except P. americana, P. atrostriata. Spore size is similar for all remaining species. However, chemistry and lower cortex color are confirmed. The distinction between P. poncinsii and P. undulata is blurred a little, however.
|P. poncinsii||P. undulata|
|lobe width||0.5-2 mm||to 2 mm|
|soralia|| usually laminal
eroded to capitate
|lower cortex||intermediate type||indistinct type|
19-24.5 × 8.5-10.5 µm
| intermediate type
18-27 × 8-11 µm
Moberg (in Sonoran Flora) emphasizes pruinose tips, undulate sorediate margins and pale lower side of P. undulata, and emphasizes capitate soralia and rock substrate of P. poncinsii (inferred from his comparison with P. caesia, another rock species from southwest with capitate laminal soralia).
Lastly, I believe P. poncinsii is likely to be more rare, as it was found only in one or two locations in Dade County as of the writing of More Florida Lichens, while P. undulata has been recorded many times for nearby Collier and Hillsborough Counties (but notice: not Monroe County for the Keys). The specimen in question is quite common throughout Key Largo, in most habitats I’ve studied: base of rough-barked hardwoods in shady hammocks, on coral blocks around canals, and most especially on buttonwood in bright open coastal scrub.
Created: 2011-01-21 19:29:12 PST (-0800)
Last modified: 2012-01-12 16:29:01 PST (-0800)
Viewed: 178 times, last viewed: 2018-03-12 17:58:34 PDT (-0700)