J. Hattori Bot. Lab. No. 76: 207-219 (Oct. 1994)

SEXUAL REPRODUCTIVE CHARACTERS VS. MORPHOLOGICAL CHARACTERS IN LICHEN GENERA

E. I. KA.RNEFELT1 AND ARNE THELL2

ABSTRACT. The generic concept and its early historical development until today's more natural multi-character based concept is discussed. The modern generic concept for lichenized ascomy­ cetes has traditionally been slightly different concerning crustose groups on the one hand and foliose and fruticose groups on the other. More studies of sexual reproductive st ructures in the large groups of lichens should presumably be carried out since it has been demonstrated recently that a considerable variation actually occurs in both asci and pycnidia in the cetrarioid genera. Some examples of difficult cases of evaluation of structural characters in relation to characters in the sexual reproductive structures in cetrarioid genera and the Teloschistaceae are also discussed.

INTRODUCTION Almost two centuries ago during the classical period of botanical history, genera were basically described on simply recognized morphological characters or in a combination of the position of apothecia and pycnidia. Acharius ( 1803) in his Metho­ dus Lichenum separated 39 genera of which some are still valid, though in a different way, such as Alectoria, Cetraria, Evernia, Lecanora, Lecidea, Nephroma, Parmelia and Ramalina. Apothecial structures were also used later at the end of the classical period for the understanding of generic concepts. It was, however, not until in 1852 that spore characteristics were introduced by Massalongo for the recognition of genera. Massa­ longo even ranked characters in a certain order of importance, such as spores, asci, paraphyses, hypothecium, exciple and finally general thallus characters (Massalongo 1852). In all, Massalongo published more than a hundred lichen genera of which some are still recognized. His foremost opponent Nylander, however, ignored much of his work and instead emphasized the importance of anatomy and pycnidial characters. A large part of Nylander's impressive list of nearly 3000 newly described species and 83 genera is still valid. In some respects, the battle which was fought back in these days between Massalongo and Nylander and many others has continued to the present day, and no agreement has been reached regarding the most important characters for the separation of genera.

MODERN GENERIC CONCEPT In modern times, morphological characters have continued to be used at generic level especially in fruticose and foliose groups, but generally a combination of anatom-

2 ' · Department of Systematic Botany, University of Lund, OstraYallgatan 20, 223 61 Lund, Sweden. 208 J. Hattori Bot. Lab. No. 76 I 9 9 4 ical and or chemical characters have been more important. In crustose groups, characters in asci, spore development and paraphyse structure have traditionally been considered of greater importance than morphology. We cannot point to any good modern example where a crustose genus has been recognized on morphological characters of the thallus only. However, numerous new genera which were formerly included in the Lecanoraceae and Lecideaceae s. !at. have been recognized not only on ascomatal characters but basically on diverging characters in the asci and hamathecium (Hafellner 1984, Hertel 1984, 1987).

STRUCTURALLY-CHEMICALLY BASED GENERIC CONCEPT Chemical characters were already considered of major importance in the recogni­ tion of genera during the 1960s as in the case of the rather well-defined groups Cetrelia and Platismatia (Culberson & Culberson 1968). However, in other cetrarioid groups there is a relatively strong correlation between mainly morphologically based groups and secondary chemistry (Karnefelt & Thell 1993a, Karnefelt et al. 1992). In addition many recently recognized crustose genera such as Protoparmelia, Tephromela and Rhizop/aca were based on correlated chemical characters (Brodo 1986). Hale, who contributed considerably to the formation of a large number of genera in foliose groups was of the opinion that apothecial characters have far fewer or indeed no differences at all in larger groups. He was activelly searching therefore for new alternative characters which could support his systematic ideas. For instance, he emphasized the importance of thallus ornamentation such as the structure of rhizines and cilia (Hale 1974, Hale 1989, Hale & Fletcher 1990). Secondary chemistry of course became an important tool for supporting morphological characters (Elix 1993). Arcto­ parme/ia was recognized by a sparsely rhizinate under side in addition to the presence of alectoronic acid in the medulla (Hale 1986), Parme/ia was characterized by several combined medullary substances and effigurate pseudocyphellae (Hale 1987), Xanthom­ acu/ina by an umbilicate foliose thallus and strongly effigurate upper cortex (Hale 1985) andXanthoparmelia without atranorin in the upper cortex (Hale 1990). Many of these new or reevaluated names, which also include groups such as Pleurosticta characterized by the pored epicortex, cylindrical or sublageniform conidia and upper cortex HN03 negative (Lumbsch et al. 1988), however, have not been generally recognized for lack of strongly convincing correlated characters in the sexual reproduc­ tive structures (Eriksson & Hawks worth 1991).

STRUCTURALLY-ANATOMICALLY BASED GENERIC CONCEPT In some genera, however, there is a clearer correlation between the general morphological characters and the anatomy of the cortex; for instance, genera such as Heppia and Peltu/a (Biidel 1987) and Psora and related genera (Timdal 1984) could partly be defined by their cortical structures. The genus Dege/ia was separated from Pannaria by the more periclinally arranged cortical hyphae (Arvidsson & Galloway 1981). Cortical structures have also been found to be of major importance in the definition of genera in the Physciaceae (Hale 1983). The larger forms of genera in the E. L. KARNEFELT & A. THELL: Sexual reproductive vs. morphological characters in lichen 209

1 2 3

' Figs. 1- 3. Schematic drawings of asci. Fig. l. The Cetraria type, Cetraria islandica. Fig. 2. The Lecanora type, Melanelia form, Melanelia slygia. Fig. 3. The Teloschistes type, Xanthoria parietina. ab = axial body, rs = ring structure, oc = ocular chamber, th = tholus. Bar in Figs. 1- 3 = LOµm.

Teloschistales, i.e. Caloplaca, Teloschistes and Xanthoria, can be defined on the com­ bined morphological anatomical character states, where the fruticose genus Teloschistes basically differs in its periclinally aranged cortical hyphae (Karnefelt 1989). Recently the genus Nimisia was mainly separated by unique characters in the cortical and medullary layers and well-separated from other possibly related groups (Karnefelt & Thell 1993b).

SEXUAL CHARACTER BASED GENERIC CONCEPT During our project on the evolution and phylogeny of the alectorioid and cetrari­ oid lichens, the importance of sexual reproductive characters over mainly morpholog­ ical characters arose several times (Karnefelt & Thell 1992, Karnefelt et al. 1992, 1993). We arrived at the conclusion that ascomycete characters like ascus and hama­ thecial structures were of major importance in the evaluation of higher taxonomic categories on family and on generic levels. Furthermore we also included conidia in the same category of sexual reproductive characters, since these structures must mainly have a function as spermatia (Honegger 1984, Poelt 1986). We also concluded that major differences such as morphology and anatomy in general thallus organization cannot be neglected entirely since there must be strong genetical differences behind distrinctive structural changes in various groups. A large variation was discovered in the structure of the asci in the species which had traditionally been treated in the genus Cetraria s. str. Correlated mainly with characters in the pycnidia, in addition to anatomical characters in the cortex and secondary chemistry, the genus Cetraria could be better divided into several new and natural genera. The genus Cetraria was defined in the first place for 15 species with 210 J. Hattori Bot. Lab. No. 76 I 9 9 4

Figs. 4- 8. Asci in some cetrarioid lichens. Fig. 4. Asci of Arctocetraria nigricascens, characterized by a tholus (th) with a clearly broader axial body (ab) than in Cetraria, Russia, Jenisejsk 1876, Brenner 1827c (S). Fig. 5. Cetraria aculeata , ascus. Note the well developed apical ring structure. Sweden, Blekinge, 1871 , Swanlund (LD). Fig. 6. Ascus of Melanelia form with its typically, large axial body, here represented by Cetraria weberi, U.S.A., Arizona, 20. 05. 1987, Nash 22, 647 (LD). Fig. 7. Esslingeriana idahoensis, ascus of Tuckermannopsis form, U.S. A., Idaho, 1987, Anderegg 10 489 (LD). Fig. 8. Asci of Flavocetraria cucullata also with distinct ring structures (rs), Sweden, Oland, Andersson 1914 (LD). Bar in Figs. 4- 8 = lOµm. E. L. KXRNEFELT & A. THELL: Sexual reproductive vs. morphological characters in lichen 211 narrowly clavate asci with a ring structure in the tholus, oblong citriform conidia and a 2-layered cortical layer (Fig. S) (Karnefelt et al. 1993). Three morphologically similar groups were recently separated from Cetraria on anatomical and chemical grounds. The genus Arctocetraria, comprising two species, differs in a larger axial body in the tholus, paraphyses with very wide basal parts, bifusiform conidia and a 1-layered cortex (Figs. 4, 9). There are also chemical differences, since these species contain rangiformic and norrangiformic acid instead of the frequently occurring substances lichesterinic and protoloichesterinic acid in Cetra­ ria. The genus Cetrariella, comprising two species, is quite different, with broadly clavate asci without a ring structure, a rather large axial body, sublageniform conidia, and a thin I-layered cortical layer. The secondary chemistry is quite different charact­ erized by presence of hiascinic and gyrophoric acid (Karnefelt et al. 1993). The genus Flavocetraria, also comprising two species is characterized by a similar type of ascus as in Cetraria, but has bifusiform conidia, a special type of cortical layer and presence of usnic acid in the cortex (Karnefelt et al. 1994).

MORPHOLOGICALLY BASED GENERIC CONCEPT As a consequence of the new taxonomy, a few rather well-known species treated in the genus Coelocaulon had to be replaced in Cetraria, since the species included here basically differed in only one simple character, i.e. the more radially built lobes (Fig. 10). This morphological variation observed in the cetrarioid groups caused us some­ thing of a philosophical dilemma. How should we evaluate differences in external morphology when anatomical and characters in the asci, and pycnidia are similar (Karnefelt et al. 1993). There were no basic differences in characters in the asci between these two former recognized genera, i.e. the narrowly clavate ascus has a distinctive ring structure in the tholus. In addition, several other important characters in common, i.e. the typically double structured cortical layer, the position of the pycnidia on short projections, the oblong citriform shape of the pycnoconidia, the secondary chemistry in addition to habitat ecology and distribution. The only difference then remaining is the more radially built structure of lobes in the species previously referred to the genus Coelocaulon. How should we actually interpret the importance of external morphology in these groups? Another case of morphologically based generic concept became obvious in the delimitation of the genera Cetrariopsis and Nephromopsis. Both the genera Cetrariopsis and Nephromopsis belong to a group of large, foliose, cetrarioid lichens abundant in mountainous regions in South-East Asia. The two species included in Cetrariopsis, C. pallevcens and C. laii are, however, only separated from Nephromopsis on the laminal position of the apothecia (Kurokawa 1980, Lai 1980). In most cases this character also seems to be significant. But since we also occasionally found truely lamina! apothecia Nephromopsis it is difficult to support Cetrariopsis as a separate genus (Randlane et al. 1994). 212 J. Hattori Bot. Lab. No. 76 I 9 9 4

Figs. 9-11. Anatomy and morphology in cetrarioid lichens. Fig. 9. Cross section through apothecium of Arctocetraria andrejevii, showing the very broad paraphyse bases (pb), Canada, Manitoba, Miller 1969 (LD). Fig. 10. Morphology of Cetraria aculeata, Sweden, Blekinge, 1871, Swanlund (LD). Fig. 11. Cetraria arenaria, U.S.A., Michigan, lmshaug 20321 (WIS). Bars in Fig. 9= 10µm, in Figs. 10-ll = lcm. E. L. KARNEFEL T & A. THELL: Sexual reproductive vs. morphological characters in lichen 213

PARALLEL CASES IN THE TELOSCHISTALES Since one of the authors has been working in the lichen family Teloschistaceae we saw a possibility of drawing attention to a number of parallel difficult systematic cases especially related to the value of morphology in the delimitation of genera (Kiirnefelt 1989, Kiirnefelt 1991). We know that in this family sexual reproductive characters have no real systematic value. Characters in the asci and pycnida are more or less identical in all groups. The asci are elongate clavate and characterized by a well-developed amyloid cap, discharged by a longitudinal crack (Fig. 14-15) (Kiirnefelt 1989). The pycnoconidia are generally small and staff shaped. This organization is basically the same in all 10 genera included in the family. Are such characters of less value here than in other groups where a large variation can be demonstrated? Only a few cases are included here as they display a direct parallel to the situation with Cetraria and Coelocaulon, namely the differences between the genera Xanthodactylon and Xanthoria in one case, and Caloplaca and Xanthoria as another well-known example. The genus Xanthodactylon, with its only species X. jiammeum restricted to the southwesternmost part of Africa, is above all characterized by its radially built and hollow lobes (Fig. 12) (Kiirnefelt 1989). This thallus organization is to some extent reminiscent of the organization in the genus Dactylina in the Parmeliaceae: there is only a thin layer of paraplectenchymatic cortical layer followed by denser peripheral medullary layer. A local endemic species within Xanthoria, X. turbinata, has similarly radially built lobe portions but otherwise the lobes on this species are dorsiventral with upper and lower cortical layers (Fig. 13). The situation is basically the same between the radially built Coelcoaulon and dorisventrally built Cetraria with both upper and lower cortical layers similar to the case in Xanthoria. Xanthodactylon in fact only differs from Xanthoria in the radially built hollow lobes. The distinctiveness of the genera Caloplaca versus Xanthoria has been discussed many times (Kiirnefelt 1989, Poelt & Hafellner 1980). The simplest way of referring to these forms of genera in the original way is to classify them as crustose and foliose groups respectively. However, even with the knowledge of the extensive variation we have of these taxa today it is nevertheless still not possible to arrange them in an alternative way. The supergenus Caloplaca, comprising a wide range of structural groups including altogether some 500 species, cannot be defined in this simple way (Kiirnefelt 1989). In the group of species which has been referred to as Gasparriniae, i.e. the species which in appearance approach certain species of Xanthoria, we even find a few taxa with tendencies towards a development of a lower cortical layer. The structure of the cortical layer in the Gasparriniae is also of a similar type of paraplect­ enchyma to that which we can see in most species within Xanthoria. In addition, in Xanthoria we have species which approach the Gasparrinae in many ways and the borders are not clear. Nevertheless it is still possible to sort out species referred to as Xanthoria in most cases. So for merely practical reasons the two form genera could at least be kept as they are until we have presented new facts for a better understanding of natural genera. 214 J. Hattori Bot. Lab. No. 76 I 9 9 4

Figs. 12- p. Morphology m Teloschistaceae. Fig. 12. Xanthodactylon fiammeum, South Africa, Cape Province, Kinges 1950, PRE 3884 (LD). Fig. 13. Xanthoria turbinata, thallus, South West Africa, Rostock District, 1986 01 07, Karnefelt 7603-12 (LD). Bar in Figs. 12- 13 = I cm. E. L. KXRNEFELT & A. THELL: Sexual reproductive vs. morphological characters in lichen 215

CONCLUSIONS It is more or less generally accepted that lichen genera should be recognized on true ascomycete characters, i.e. characters in the ascomata and in the pycnidia. These characters, such as the formation of asci, including production of ascospores and production of pycnoconida are certainly not influenced by environmental factors to the same degree as is the case with structural characters. It is therefore more logical to assign those characters directly associated with sexual reproduction a larger value, especially in the recognition of higher taxonomic categories. Other characters which are indirectly associated with sexual reproduction, such as the structure of excipulum hyphae and paraphyses, are also presumably less influenced and variable by changes in the environmental situation. The structural characters, however, such as in the external morphology of the thallus, various extensive organs and the hyphal anatomy of cortical and medullary layers show a broad variation which can be caused in part by a variety of environmental factors (Jahns et al. 1981, Jahns 1984, Poelt 1974, 1986). A large number of mainly foliose and fruticose genera recognized during recent decades were basically separated on structural characters or from a combination of caracters in their secondary chemistry, and in only a few cases were characters in the asci actually considered.

Figs. 14-15. Asci in Teloschistaceae. Fig. 14. Ascus of Ca/oplaca chalybaea, Poland, Pieniny, 14. 9. 1957, Tobolewski (LD). Fig. 15. Exactly the same type of ascus is present in Xanthoria turbinata, South West Africa, Rostock District, 1986 01 07, Karnefelt 8603-12 (LD). Bar in Figs. 14- 15 = IOµm. 216 J. Hattori Bot. Lab. No. 76 I 9 9 4

A majority of the generic groups separated in the Parmeliaceae have asci which show very little variation. The most frequent ascus type has been recognized as the Melanelia-form (Thell et al. 1994). It is a type of broadly clavate ascus, c. 30-50µm high, with a small tholus and a broad axial body (Fig. 6). To this type belong genera such asArctoparmelia, Bulbothrix, Canomaculina, Flavoparmelia, Karoowia, Namakwa, Neofuscelia, Pleurosticta, Punctelia, Relicina and Xanthoparmelia. Common to these groups, including many others not listed here, is that they are generally not accepted as representing distinctive genera since they were based mainly on structural and chemical characters (Eriksson & Hawksworth 1991). Nevertheless those generally not accepted as forming genera altogether represent a considerable morphological and chemical variation. The structural characters, including in many cases the distinctive secondary compounds, must be the result of a long evolutionary history resulting from natural selection and isolation of populations. In our opinion it is therefore incorrect to lump them all into one paraphyletic group mainly because some people assume that they were based upon variable character states. At least we should try to present some better reasons why structural and or chemical characters should be of less systematic value in foliose and fruticose lichens. In some other groups, however, such as the Cladoniaceae, Ramalinaceae, Umbil­ icariaceae and Verrucariaceae, structural characters often combined with secondary chemistry have traditionally been of significant value in the generic systematics. Nevertheless it is obvious that new or reestablished genera which were mainly separated on these character states have been far from fully accepted. For instance, the separation of the structurally rather well-defined genus Cladina has never been fully recognized ( Ahti 1984, Eriksson & Hawksworth 1991). Most of the genera separated in the Ramalinaceae, i.e. Desmazieria, Fistulariella, Niebla and Trichoramalina have only been acknowledged locally. The generaActinogyra,Agyrophora, Gyrophora and Ompha­ lodiscus, which Llano (1950) tried to reestablish based mainly on the development of the apothecial disc have never been generally accepted. Recently Harada ( 1993) separated three new genera related to Dermatocarpon in the Verrucariaceae i.e. Derma­ tocarpella, Neocatapyrenium and Scleropyrenium which were all defined on structural characters in the excipulum and cortex. It is too early to judge upon their general recognition but as seen from other examples mentioned, these entities will presumably be considered as belonging within the variation of Dermatocarpon. In the other cases we referred to the Teloschistaceae where the genera obviously represent more or less well-defined forms of genera, the problem of acceptance mainly based upon a traditional view rather than bringing up the same arguments as in the Parmeliaceae. Since these species or form genera now only differ in such a low and weak number of main organizational characters only should we go ahead and unite these groups, such as in the case of Cetraria vs. Coelocaulon? It is a difficult question. Following the discussion we had on the importance of ascus structures in the cetrarioid genera we were, however, forced to drop the genus Coelocaulon. At the same time, we must conclude that characters in the sexual reproductive structure is of less value in the Teloschistales. Could this group then be considered as representing a phylogenetically E. L. KARNEFELT & A. THE LL: Sexual reproductive vs. morphological characters in lichen 217 relatively younger group than the Lecanorales where we have wider range of types of asci now interpretated as representing a large number of families and genera (Hafellner 1984, 1988). In the Teloschistales the evolution of structural forms adapted to new environments is still very difficult to understand and demonstrate. We can only see the realitively large number of groups which obviously are still not possible to define as representing distinctive genera (Kiirnefelt 1991). Future research with molecular data might provide us with some evidence for understanding their structural evolution better than we do today. Until then we might just as well leave things as they are at present such as is the case in the Teloschistaceae. As Mason Hale once said "the most productive and exciting period in the history of lichenology still lies ahead of us".

ACKNOWLEDGMENTS We are grateful to the Swedish Natural Science Research Council for support with a travelling grant to Japan to one of the authors. Dr. Hiroshi Harada is thanked for his good company during fieldwork in Nagano prefecture and Dr. Hirojuki Kashiwadani for valuable comments on the manuscript.

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