War in the world of lichens: parasitism and symbiosis as exemplified by lichens and lichenicolous fungi

Cyanolichens can have both cyanobacteria and green algae in a common layer as major contributors to photosynthesis

s of the XV International Botanical Congress , Yokohama, Japan. Ott, S. (1988) Photosymbiodemes and their development in Peltigera venosa , Lichenologist 20 , 361–368. Ott, S. (1987) Sexual reproduction and developmental adaptations in Xanthoria parietina , Nordic J. Bot. 7 , 219–228. Parks, C.R. and Wendel, J.F. (1990) Molecular divergence between Asian and North American species of Liriodendron ( Magnoliaceae ) with implications for interpretation of fossil floras, Amer. J. Bot. 77 , 1243–1256. Paulsrud, P. (2001) The Nostoc symbiont of lichens. Diversity, specificity and cellular modifications, Acta Universitatis Upsaliensis Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 662 , 1–55. Paulsrud, P. and Lindblad, P. (1998) Sequence variation of the tRNALeu intron as a marker for genetic diversity and specificity of symbiotic cyanobacteria in some lichens, Appl. Environ. Microbiol. 64 , 310–315. Paulsrud, P. Rikkinen, J. and Lindblad, P. (1998) Cyanobiont specificity in some

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Cyanolichens: an evolutionary overview

Three lichen species forming both a foliose chlorotype and a dendriscocauloid cyanotype are documented from western North America. Lobaria amplissima is reported from northern California and southeastern Alaska and is new to North America. Sticta oroborealis Goward & Tonsberg, sp. nov. is described from a small area in north coastal British Columbia. The cyanotype of Sticta wrightii, hitherto unknown, is reported from coastal southeastern Alaska. The cyanotypes of all these species occur primarily as epiphytes in old-growth forests supporting a high cyanolichen diversity. The occurrence of “Dendriscocaulon” intricatulum (Nyl.) Henssen in Pacific North America is questioned.

Sticta oroborealis sp. nov., and Other Pacific North American Lichens Forming Dendriscocauloid Cyanotypes

terricolous and saxicolous species of the genera Aspicilia A. Massal. and Circinaria Link (Megasporaceae, Pertusariales, lichenized Ascomycota), particularly those traditionally referred to as ‘manna lichens’. The group has previously been defined on the basis of relatively few morphological characters (mainly growth form), and the phylogeny of the group has not been previously studied. The phylogeny of the family Megasporaceae is inferred from the combined dataset of nuLSU and mtSSU sequences. Five genera i.e., Aspicilia, Circinaria, Lobothallia (Clauzade & Cl. Roux) Hafellner, Megaspora (Clauzade & Cl. Roux) Hafellner & V. Wirth, and Sagedia Ach. are recognized. Lobothallia is sister of the four other genera, while Aspicilia and Sagedia form the next clade. All these genera have small asci with eight spores. Circinaria is a sister genus of Megaspora, and these two have in common asci with (1–4) 6–8 large spores. In the resulting trees, Circinaria forms a monophyletic group and sphaerothallioid species form a monophyletic group within Circinaria. The presence of certain morphological characters such as pseudocyphellae, thickness of cortex and medulla layers, as well as ecological differences in sphaerothallioid species distinguish it from some other crustose species, especially those containing aspicilin and characterised by thin cortex and medulla layers, conidium length c. 6–12 μm and absence of pseudocyphellae. If sphaerothallioid species are accepted as a distinct genus, the rest of the Circinaria species would remain as a paraphyletic assemblage. The combined dataset of nrLSU and mtSSU did not fully resolve infrageneric relationships in Megasporaceae. Currently, the genus Circinaria includes all the sphaerothallioid species and its generic position is confirmed and accepted. Thus, it is proposed as a correct generic name also for the peculiar ‘manna lichens’ described originally in other genera. Phylogeny at the species level has been studied using nrITS sequence data. Traditionally, certain morphological characters (e.g., growth form, anatomy of apothecium, pycnidia and cortex layer) have been used for the recognition of species in Aspicilia s.lat. In order to find more reliable characters they were re-evaluated in the light of molecular data. Since characters such as vagrant, erratic and crustose growth forms proved to be misleading for the recognition of some species, a combination of several characters (including molecular data) is recommended for species recognition. Vagrant growth form seems to have evolved several times among the distantly related lineages and even within a single population, resulting in either crustose or erratic and vagrant growth forms. This pattern of crustose, erratic and vagrant growth forms distribution in the genus Circinaria may help us to interpret the morphological convergence and ecological adaptation through the evolutionary history. Despite these insights, the reasons behind the high plasticity in the external morphology of vagrant, erratic and crustose species in the sphaerothallioid Circinaria still remain unknown. Of the 15 species placed in the ‘manna lichens’ (except Circinaria tominii nom. provis.), 14 are included in the molecular study along with some additional species from closely related groups. Four new species of ‘manna lichens’ are recognized: Circinaria rogeri nom. provis., (syn. Aspicilia rogeri) from the U.S.A.; C. digitata nom. provis. (syn. Aspicilia digitata) from Kyrgyzstan; C. gyrosa nom. provis. from Armenia, Azerbaijan, Iran, Turkey, Turkmenistan and Spain, and C. rostamii nom. provis. from Azerbaijan, Iran and Turkey. Circinaria arida, described from the USA, contains aspicilin and lacks pseudocyphellae. Aspicilia tibetica, a terricolous species with small spore size (8–14 × 5–9 μm) and a 8-spored ascus, is described from China. Based on an analysis of nrITS dataset, three new erratic, vagrant and crustose species were also recognized, but these require additional study. The results also reveal that C. elmorei and C. hispida are not monophyletic as currently understood. In addition, 13 new combinations in the genus Circinaria are proposed.

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Taxonomy and phylogeny of the manna lichens and allied species (Megasporaceae)

Laundon (1995) has brought up for discussion the rather difficult situation arising from the fact that the same fungus, when associating with different photobionts, may form very different-looking lichens, previously named as separate species or even placed in different genera. While I agree that this problem needs to be clarified, I disagree with the solution suggested by Laundon: to classify correlated photobionts as forms of the same species. To me this is not a question of classification, only of nomenclature. It is quite clear that a lichen is classified according to its mycobiont. In mycology there is no tradition to classify, at a specified taxonomic rank, different-looking infections by the same fungus, e.g. different growth forms induced on different hosts. In parasitic fungi there has been a tradition to designate as formae speciales taxa which are characterized by their physiological adaptation to different hosts, being morphologically identical or nearly so, but this is an informal system without nomenclatural status (Code, Art. 4, Note 3). The situation for lichen phototypes is rather similar to and actually parallels that of fungi which show different morphological expressions during their life cycle, and accordingly have been given different names (Jorgensen, 1991), which are acceptable under the dual naming system provided for in Art. 59. Unfortunately the phototypes of lichens are not covered by that Article, not only because it excepts lichens, but because this kind of variation is not expression of a pleomorphic life cycle. I have previously (Jorgensen, 1991) argued that we need a similar system for phototypes, and Greuter (pers. comm.) has suggested that this would find its logical place among the exceptions mentioned in Art. 11.1, referring to names of form-taxa. A formal proposal for the emendation of that Article has not, however, been made, as opinions among lichenologists are rather divided in this respect, as recognized by Laundon (1994). The nomenclatural difficulties in handling this situation are clear from the examples chosen by Laundon (1995). I am sure that both Galloway (1988) and White & James (1988) felt a need to name the two phototypes of one species since they occur separately, having a different ecology and distribution, but they ran into nomenclatural difficulties which were not solved in a satisfactory way. Galloway

M. Roos

Papers

On the nomenclature of lichen phototypes