Punctelia caseana Lendemer & Hodkinson sp. nov.

Recently, James Lendemer (of the New York Botanical Garden) and I put together a paper on the North American sorediate species in the genus Punctelia with lecanoric acid and a pale underside. In North America, these species have generally been called Punctelia subrudecta (a European name), but it was discovered more recently that the conidia do not match the European species. Incidentally, the European species P. perreticulata and P. jeckeri (syn. P. ulophylla) have been reported rarely in different parts of the North American continent. For reasons outlined in our recent paper (Lendemer & Hodkinson 2010; see the official website here), P. perreticulata became the accepted name for all three of these species in North America during the past few years. However, our observations in the field and lab told us that there was more than one entity here in North America. Therefore, we decided to generate rDNA internal transcribed spacer (ITS) sequence data from morphologically and geographically disparate populations to see if the observed morphotypes correlated with genetically-distinct entities.

In Eastern North America, we found that the species so long confused with Punctelia subrudecta actually seemed to be an undescribed species, which we named after my undergraduate advisor (Dr. Martha Case of the College of William & Mary):

Punctelia caseana Lendemer & Hodkinson sp. nov. A & B, thallus margin, ×0.5; A (top), morphotype 1; B (bottom), morphotype 2; C & D, soralia, ×1; C (top), morphotype 1; D (bottom), morphotype 2; E & F, epruinose lobe tips, ×3;E (top), morphotype 1; F (bottom), morphotype 2; G, geographic distribution based on herbarium material at CANL and NY; shaded region approximates to the eastern range mapped by Brodo et al. (2001)). Images of morphotype 1 are from Lendemer 12205 (NY) and morphotype 2 are from Harris 54826 (NY).

Punctelia caseana encompasses at least two morphotypes, illustrated in the figure above. However, one of the morphotypes is potentially paraphyletic based on our molecular phylogenetic analyses, leading us to recognize both morphotypes under a single name for the time being. Some additional photos of this species can be seen here (Sharnoff) and here (Mushroom Observer).

In western North America, we found that all of the lichens had a haze of pruina on at least some of the lobe tips, which is often difficult to discern, but immediately made me think of Punctelia jeckeri (syn. P. ulophylla). Of course, it seemed unlikely that the species dominating western North America was the same as the European P. jeckeri (especially given the mantra that pruinosity is not a good taxonomic character). However, we were quite excited to find that the ITS sequences of western North American material were indistinguishable from European P. jeckeri sequences! 

Punctelia jeckeri. (Lendemer 14695, NY). A & B, pruinose lobe tips with arrows highlighting position of the pruina, ×5; C, geographic distribution based on selected herbarium material at NY, shaded regions correspond to western populations mapped by Brodo et al. (2001); note that several populations in Canada are not mapped due to space constraints; D, thallus margin, ×0.5; E, soralia, ×1.

Even though the ITS sequences match up perfectly with European material, we refer to the western North American material as Punctelia jeckeri s. lat., since the conidia do not exactly match P. jeckeri as formally defined. However, we put forth the hypothesis that there may actually be two species in Europe with pruinose lobe tips, but different conidia. This hypothesis will need to be tested with rigorous sampling from throughout Europe.

The third species that we found in North America represented the 'real' Punctelia perreticulata as originally defined. P. perreticulata is the only species with a distinctly scrobiculate upper surface, and its distribution is centered in the Ozark Ecoregion.

Punctelia perreticulata. (Lendemer 7230, NY). A, soralia, ×1; B, thallus margin, ×0.5; C, pruinose lobe margin, ×4; D, geographic distribution based on herbarium material at CANL and NY.

Our paper also provides a key to the genus Punctelia in North America. Anyone who has tried to identify a species in this group should have a look. For those interested in the molecular data or the nitty-gritty of phylogenetic methods, links to the ITS sequences with full GenBank records can be found here and we have also posted the analyzed alignment file (NEXUS).

While there are surely further questions to be answered regarding the genus Punctelia, it is satisfying to have some degree of resolution in this often-misunderstood group of species!

-Brendan

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Works Cited:

Lendemer, J. C., and B. P. Hodkinson. 2010. A new perspective on Punctelia subrudecta in North America: previously-rejected morphological characters corroborate molecular phylogenetic evidence and provide insight into an old problem. Lichenologist 42(4): 405-421.
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