Introduction to Hypoxylon



Hypoxylon as delimited by Ju & Rogers (1996) encompasses xylariaceous fungi sharing the four following main features: Nodulisporium-like anamorphs, stromata unipartite, never erect, with a solid and homogenous basal tissue below the perithecial layer. Moreover stromata are very frequently waxy with coloured granules yielding pigments in 10% KOH, ascospores often have a dehiscent perispore and usually have the germ slit on the more convex side, and ascal apical rings are discoid or flattened. Ju & Rogers (1996) recognized two sections in Hypoxylon, section Hypoxylon and section Annulata. The members of the latter section differ in having papillate ostioles usually encircled with an annulate disc, usually black and carbonaceous stromata, and ascopores with a perispore featuring a thickened area on the more convex side. Unfortunately, the most common European taxa which belong to this section on account of the presence of the two latter characters lack the distinctive ostiolar discs. Therefore, this separation into two sections, which is very efficient and convenient with extra-European taxa, was not adopted for the following presentation of Hypoxylon in France.

Besides this approach based on morphology of teleomorphs and anamorphs, and stromatal pigments yielded in KOH, the genus Hypoxylon was recently investigated by means of DNA sequencingin studies including other xylariaceous genera (Granmo et al., 1999; Sánchez-Ballesteros et al., 2000; Mazzaglia et al., 2001; Triebel et al., 2005), and by means of HPLC (High Performance Liquid Chromatography) applied to secondary metabolites present in stromata or in cultures (Mühlbauer et al., 2002; Quang et al.,2003 b, 2004; Stadler et al., 2001a, 2001b, 2004b; Hellwig et al., 2005). For a more detailed account of the outcomes of the latter method, see the chapter Chemotaxonomy of Hypoxylon hereafter. The results of both approaches largely confirmed the taxonomic concepts of Ju & Rogers (1996) and Ju et al. (2004).

Hypoxylon is a very well represented genus in southwestern France, since we were able to collect 24 different species or varieties among the 30 European taxa, of which H. carneum**, H. crocopeplum**, H. julianii*, H. laschii*, H. macrosporum* H. porphyreum* and H. submonticulosum** are newly recorded from France* or from Europe**. Only one taxon illustrated in this study, H. michelianum, was collected in western Spain, and its occurrence in southern France remains possible.

Among the European Hypoxylon taxa dealt with by Ju & Rogers (1996), two rare species, H. commutatum and H. ferrugineum were not recorded during this study and therefore are not illustrated. Hypoxylon fuscopurpureum, a North American species recently reported from Europe by Mühlbauer et al. (2002) is likewise lacking illustrations, awaiting collections from France. For a description of these taxa the reader is referred to Ju & Rogers (1996).

Three additional species, not dealt with by Ju & Rogers (1996), H. liviae, H. porphyreum and H. salicicola were recently described from Norway by Granmo (Granmo, 1999, 2001). These three species are included in a survey of recently described species of Hypoxylon by Ju et al. (2004). H. liviae and H. salicicola are so far unknown from southern Europe, but we give descriptions and illustrations of these taxa from material kindly sent by Dr. Granmo. H. porphyreum was recently (2003) discovered in Ariège and therefore is newly added to the present study.

We do hope that our contribution to the knowledge of this genus in Europe will lead to new collections of these rare species and, possibly, to collections of species new to science.

Nomenclature used in this study follows Ju & Rogers (1996), who give synonyms of taxa treated herein.