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Usnea sphacelata R. Br.
Family: Parmeliaceae
[Neuropogon sphacelatus (R. Br.) D.J. Galloway,  more]
Usnea sphacelata image
Stephen Sharnoff  
Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus small, 2-3 cm (-4 cm), erect to subdecumbent, caespitose branched from a small basal holdfast, the base yellow, the upper parts blackened, somewhat soft; main branches terete, 0.5-1.3 mm diameter, smooth or minutely scabrid, rarely faintly scorbiculate, dull or sub-shining, often fracturing to expose the central strand, the outer parts black ringed, the terminal branches entirely black; soredia small and in small punctiform soralia, blackened; axis Vs to Vs the diameter of the branches; medulla white, thick, lax, rarely compact. Apothecia unknown.

Reactions: K— , P—; in a few Antarctic specimens K+ red, P+ yellow.

Contents: Usnic acid; in the Antarctic strain with the positive reactions there is a small amount of norstictic acid.

This species grows on granitic types of rocks, avoiding schists and calciferous types. It occurs from the coasts to considerable elevations, to 1700 msm in Greenland. Lynge (1941) speculates that it requires considerable atmospheric moisture.

The bipolar distribution of this lichen has caused considerable speculation. In the northern hemisphere it is on Greenland and Iceland and most of the arctic islands with the proper types of geology. In the southern hemisphere it occurs circumpolar on Antarctica and some adjacent islands. It also occurs on scattered high Andean stations in Equador, Peru, Bolivia, Chile, and Argentina. Discussions center about the possible relictual nature of these stations and also about possible connections with continental drift. However a simpler possibility exists. Dr. David Parmelee of the University of Minnesota has informed me that Skua gulls which were banded in Antarctica have been recovered three months later in Greenland. These birds also happen to nest in the Neuropogon colonies. What could seem simpler than that these birds with bipolar migration habits could carry the soredia of this lichen on their bodies to later shed them in the Arctic? Very germane is Lamb's comment that the Antarctic population of the Neuropogon exhibits a different spectrum of variability than the Arctic. This would suggest selection of only some of the available variations present in the south to be carried to the north, a logical possibility with the chances inherent in such long-distance dispersal. Certainly the center of development of the species of Neuropogon lies in the southern hemisphere. Whether the skua gulls also visit the high Andes is still open to investigation. But they do seem to be the only possible carriers with the bipolar migration patterns.