Mycologia, 93(4), 2001, pp. 720-731. ? 2001 by The Mycological Society of America, Lawrence, KS 66044-8897 Phylogenetic analyses of Aleurodiscus s.l. and allied genera Sheng-Hua Wu INTRODUCTION Department of Botany, National Museum of Natural AleurodiscusRabenh. exJ. Schrot. is a member of the Science, Taichung, Taiwan, ROC corticioid homobasidiomycetes. Seventy one species David S. Hibbett1 world-wide have been accepted in Aleurodiscus (Nu- Manfred Binder fiez and Ryvarden 1997). The limits of Aleurodiscus have been controversial. Lemke (1964) excluded Department of Biology, Clark University, taxa with inamyloid spores from Aleurodiscus sensu 950 Main Street, Worcester,MA 01610-1477 stricto. In contrast, Nunfiez and Ryvarden (1997) adopted a broad concept of Aleurodiscus. These two publications and the work of Boidin (1985) offer a Abstract: The limits and subdivision of possible comprehensive compilation of current taxonomy and Aleurodiscus s.I. into Acanthobasidium, Acanthofun- species concepts of this group. In this paper, Aleuro- gus, Acanthophysellum, Aleurobotrys, Aleurocystidiel- discus sensu lato is essentially equivalent to Aleurod- lum, Aleurodiscus s.s., and Gloeosoma were evaluated. iscus sensu Nfuniezand Ryvarden (1997). An overview Molecular characters were obtained from an approx- of character combinations used to discriminate Aleu- imately 980 base pair fragment at the 5' end of the rodiscus s.s. and segregate genera of Aleurodiscus s.l. nuclear large subunit ribosomal DNA, in 33 strains is provided in TABLEI. representing 23 species of Aleurodiscus s.l., Stereum, Mycologists recognize Aleurodiscus using either a Xylobolus, and Megalocystidium leucoxanthum. Pub- broad or a narrow generic concept (compare Boidin lished sequences of 20 additional species of the rus- et al 1985, and Nufiez and Ryvarden 1997). Several suloid clade were also included. Phylogenetic analy- narrowly defined genera have segregated from Aleu- ses suggest that Aleurodiscus s.l., Megalocystidium leu- rodiscus s.l., including Acanthobasidium Oberw., coxanthum, Stereum and Xylobolus form a monophy- Acanthofungus Sheng H. Wu et al, Acanthophysellum letic group, which may be classified as the family Parmasto, Aleurobotrys Boidin, Aleurocystidiellum P.A. Stereaceae. Corticium roseum, which is the type spe- Lemke, and Gloeosoma Bres. TABLE I summarizes cies of the Corticiaceae, is not in this group, thus characters used to separate these groups. Most spe- Stereaceae is not synonymous with Corticiaceae. Aleu- cies of Aleurodiscus s.l. have acanthophyses, whereas rocystidiellumis supported as a monophyletic group. Aleurodiscus s.s. and Aleurocystidiellum lack them. Spe- Acanthobasidium, which is characterized by pleuro- cies of Aleurodiscus s.s. have hyphidia, which may be basidia, is also monophyletic. Aleurodiscus s.s. is sup- occasionally branched. Dendrohyphidia, present in a ported as monophyletic, but Gloeosoma is not, and few species, could be considered as an intermediate the two are not congeneric. The importance of am- form between acanthophyses and occasionally yloid acanthophyses for recognizing Aleurobotrysis branched hyphidia. Most species of Aleurodiscus s.l. suspect, and its generic status should be further stud- are associated with a uniform white rot in wood, ied. Most of the smooth-spored species form a mono- whereas Acanthofungus and Xylobolus are associated phyletic group. Phylogenetic analyses suggest that with a white-pocket rot in wood. In Aleurodiscus s.l., there has been homoplasy in most of the characters the mycelia of uniform white rot-causing species usu- that have been used to subdivide Aleurodiscus s.l., in- ally show a positive phenoloxidase reaction, while this cluding spore ornamentation, hymenial color, hyphal reaction is usually negative for the white pocket rot- (S.-H. Wu, septation, clamp connections, acanthophyses, and causing species unpubl). were phenoloxidase reactions. Macroscopically, cupulate basidiocarps gen- as the but this char- Key Words: Basidiomycota, corticioid fungi, mo- erally recognized typical form, lecular systematics, russuloid clade acter varies among Aleurodiscus s.l., and effuse, ef- fused-reflexed, or pulvinate forms are present. A pinkish- or orange-tinted hymenial surfaces was re- Accepted for publication February 12 2001. garded as typical for Aleurodiscus, but white, gray, or 1 Corresponding author, E-mail: [email protected] cream-colored hymenial surfaces occur in many spe- 720 WU ET AL: PHYLOGENY OF ALEURODISCUSS.L. 721 TABLEI. Main charactersused for separatingsegregate genera in Aleurodiscuss.l., as Stereumand Xylobolusa Clamp Ornamented connections Phenoloxidase spores Acanthophyses in basidiocarps reaction Acanthobasidium + + + + Acanthofungus -+ + Acanthophysellum - + + + Aleurobotrys + + - + Aleurodiscus s.s. + - + + Aleurocystidiellum + -+ + Gloeosoma + + + + Stereum +- b + xylobolus - + - - a Data from Boidin et al 1985, Nfifunezand Ryvarden1997, and Wu et al 2000. b Some species of Stereumlack acanthophysesbut have acutophyses,which might be a reduced form of acanthophyses. cies. Boidin et al (1985) suggested that the pink or smooth spores, acanthophyses, and simple-septate hy- orange spore print is an important feature of Aleu- phae; A. moniliferMalencon has smooth spores, lacks rodiscus s.s. (including Gloeosoma),which differs from acanthophyses, and has nodose-septate hyphae; and the white spore print of other genera in Aleurodiscus A. limonisporus D.A. Reid has smooth spores, lacks s.l. This character may be important, but is not acanthophyses, and has simple-septate hyphae. These known for many species. three species cannot be placed in any of the segre- Microscopically, gloeocystidia and amyloid basid- gated genera of Aleurodiscus s.l. as currently circum- iospores are uniformly present in all species. Basidia scribed In fact, the known species in Aleurodiscus s.l. and basidiospores of many species are large, relative have satisfied all possible combinations for the three to other species of corticioid fungi. Acanthophyses important characters of spore surface (ornamented characterize the majority of the species in Aleurodis- or smooth), acanthophyses (present or not), and hy- cus s.l. Lemke (1964) regarded Aleurodiscusas having phal septation (nodose or simple-septate). Thus, a catahymenium, but Eriksson and Ryvarden (1973) some mycologists (Hjortstam 1997, Nunfiezand Ryvar- considered this character to be questionable, espe- den 1997) consider the subdivision of this group im- cially for the members in Acanthophysellum.The ca- possible. tahymenium is more typically present in Aleurodiscus The purpose of this study is to assess the limits of s.s. The distinction between a euhymenium and a ca- Aleurodiscus s.l. and the monophyly of its generic seg- tahymenium is hard to define, however. For instance, regates. The taxa chosen represent various segregate Lemke (1964) described all species in his concept of genera of Aleurodiscus s.l., plus the allied genera Ster- Aleurodiscus s.s. as having a catahymenium, but this eum and Xylobolus. Mycologists have traditionally re- is not correct. As a result, this character is not con- garded Aleurodiscus s.l. as a member of the Cortici- sidered in this study. Some other important charac- aceae Heter in the broad sense (Donk 1964, Parmas- ters vary among species of Aleurodiscus s.l. For in- to 1986). Parmasto's (1995) analysis based on mor- stance, basidiospores can be ornamented or smooth phological characters suggested that this group is in and the hyphae can be nodose or simple-septate. In the Corticiaceae s.s. Stereum and Xylobolus are gen- addition, nuclear behavior and mating systems vary erally placed in the Stereaceae Pilat (e.g., Ginns and among species of Aleurodiscus s.l. (Boidin and Lan- Lefebvre 1993). Stereaceae has been customarily quetin 1984b). used to accommodate genera with stereoid basidi- Aleurodiscus s.l. includes species with highly varied ocarps and dimitic hyphal systems (Donk 1964, Par- characters, which is why many mycologists are not masto 1986). Wu (1996) stressed the importance of willing to accept Aleurodiscus as a single genus. More- amyloid basidiospores and gloeoplerous hyphae and over, the characters used for separating different limited the Stereceae (in his concept of the subfamily groups in Aleurodiscus s.l. are not congruent. For ex- Stereoideae Ulbr.) to Stereumand Xylobolus, exclud- ample, some groups with ornamented spores have ing all other genera that lack these two characteris- acanthophyses whereas other do not, and some have tics. Stereumand Xylobolus share an important char- nodose hyphae whereas other have simple-septate hy- acter, the acanthophyses, with Aleurodiscus s.l., which phae. Further, some species still do not fit any genus suggests that they are closely related (Lemke 1964, as listed in TABLEI. For example, A. farlowii has Boidin et al 1979). This view has been upheld by 722 MYCOLOGIA molecular phylogenies (Hibbett et al 1997, Hibbett fungi/mycolab/primers.htm). Sequencing reactions were and Donoghue in press), which suggest that Aleuro- purified using Pellet Paint (Calbiochem, San Diego, Cali- discus botryosus, A. cerrusatus, Stereum hirsutum, S. fornia), and run on an Applied Biosystems 377XL auto- mated DNA with a 5% rugosum, Xylobolus frustulatus, and Megalocystidium sequencer Long Ranger acrylamide BioProducts). were edited and assem- leucoxanthumform a monophyletic group that is nest- gel (FMC Sequences bled using (GeneCodes Corp., Ann Arbor, ed in