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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.
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