Parmotrema and Allied Lichen Genera in Papua New Guinea

The layout of this work is that of a typical monograph, comprising an extensive introduction, which provides a mainly historical background to the lichenological knowledge of the area, the history of the genus Parmotrema and other related genera, intergeneric comparisons and a detailed analysis of species characters, with major emphasis on morphology, anatomy and chemistry, and a section on materials and methods. After the key to species, the genera Parmotrema, Canomaculina and Ricnelca are discussed in detail in that order, their species arranged alphabetically, being the larger section in the text and finishing with a list of references (just over five pages long), acknowledgements and the taxonomic index.

It is a pity that material from the Indonesian province of Irian Jaya, the west of the island of New Guinea, was not included in this study, since there is previous bibliographic information and a checklist for the whole of the island (see Streimann, 1986) and surely many of the species are to be found both sides of the political boundary. Yet the authors describe here no less than 50 species of Parmotrema, including six new to science and one new combination, three species of Rinzelia and one of Canomaculina.

It is perceived by colleagues abroad that in Britain we do not like to split Parmr.elia s. tat. into its many generic segregates; yet this might be so only for practical reasons, as most genera are now well-established. I was glad to see a section (Intergeneric Comparisons, pp. 12-14) on the differences and affinities, morphological as well as chemical, between Parmotrema and related genera, which was also complemented by a comparative table (Table 1, p. 13). From my own field work in SE Asia, although I found that I could distinguish the species of Parmotrema from other closely related genera such as Cetrelia and Canoparmelia without sophisticated chemical tests, my experience with the genera Rimelia and Rimeliella (now Canomaculina) was rather more problematic; the latter taxa all looked like Parmotrema to me. Now I know that we could have separated them from Parmotrema by the maculate, cracked upper cortex and also by the presence of rhizines near the edge of the lower surface of the thallus. This latter character should have been included in the table and within the dissertation on intergeneric comparisons, but was only mentioned in the keys to taxa. However, I still need further guidance on how to separate Rimelia from Canomaculina, and at present I remain unconvinced that they are different.

There is a good review of the value of morphological characters at species level. The authors conclude that, of these, the presence of vegetative propagules and ascospore and conidial variation, are the best to distinguish the taxa, in conjunction with medullary chemistry, whereas some thalline characters previously thought to be useful, such as colour of medulla, lower surface texture of thallus, presence of cilia and maculae, are really environmentally driven. There is also an interesting species pairs table (p. 18) and a worthwhile five-page account of chemical interspecific variation. Although I have not tested the key with individual specimens, it seems to work well (except for ascospore size discrepancies in couplets 7 and 8) and there has been, in general, a good attempt to correlate chemical differences with morphological features. I was also grateful for the inclusion of pictures of representative specimens, since from the descriptions of the taxa many seem to share multiple characters and it would appear that there is a great overlap between species. Thus, going back to the discrepancies in couplets 7 and 8 of the key, P. elacinulatum and P. pigmentosum could have been separated more easily by the presence of ciliate apothecia – at least as observed in the plates (figs 17 and 53). With regard to representativeness, I was a little surprised that very few types were seen for this study, so the users of the monograph will need to trust the second author's wider experience on these taxa.

In any case, I am sure that this work will be a 'must' for those studying parmotremas in SE Asia and the Indian subcontinent; it is certainly a much-needed monograph for this area."

- B. Aguirre-Hudson, Bibliography of Systematic Mycology (BSM) and Index of Fungi (IF)