A Synopsis of the Genera Skyttea, Llimoniella and - Lichens of ...

460 THE LICHENOLOGIST Vol. 32
Careful studies of numerous lichenicolous leotialean species have led us to
conclude that Skyttea cruciata is congeneric with Geltingia stereocaulorum,
Llimoniella fuscoatrae, L. neglecta, L. pubescens and several undescribed taxa.
They all share the following characters: ascomata blackish, initially partly
immersed, often urceolate, exciple often covering the disc when young,
epihymenium with a green, K+ olivaceous pigment (in some species also
present in the upper exciple), exciple with a brownish, K — pigment, ascus
wall apically not thickened, no reactions with iodine (all parts I — and KI — ),
paraphyses easily separating in KOH with pressure, ascospores O(-l)-septate,
hyaline, smooth, ellipsoid to fusiform. The exciple is composed of ± isodiametric
cells below, but of narrow, elongate, sometimes almost filiform cells
above; these elongate cells are either embedded in a gel and are thus part of the
exciple s. str., or they are free and form excipular hairs. We initially hesitated
to include species with and without excipular hairs in the same genus, but as
both situations have been observed in R. pertusariae, described below, in the
same specimen and on the same host thallus, it is clear that this character is of
a minor taxonomic importance in this group of fungi.
These species differ from Skyttea by the apically non-thickened ascus wall,
the completely different excipular margin (see Figs 1A, 13) and hairs, the
hymenium with paraphyses easily separating in KOH with pressure, the
intensively green epihymenium and the different ascomatal opening.
They are very distinct from the known lichenicolous leotialean fungi with
excipular hairs, Echinodiscus lesdainii (Etayo & Diederich 2000), Polydesmia
lichenis Huhtinen & R. Sant. (Hyaloscyphaceae; Huhtinen & Santesson 1997)
and Unguiculariopsis spp. {Hyaloscyphaceae [H.-O. Baral pers. comm.]; e.g.
Rambold & Triebel 1990; Zhuang 1988; see also below). We initially
wondered if these species belong to Llimoniella, in which two of them were
described, and two more have been combined later. The type species of
Llimoniella and all other species included by us in the same genus, have no
excipular hairs, and present a different, reddish, K+ purplish violet excipular
pigment, the green, K+ olivaceous epihymenial pigment being absent;
the exciple, which is more strongly developed at the base of the ascomata, is
entirely composed of ± isodiametric cells and does not or only hardly
covers the ascomatal disc. As some of these differences, such as the
different pigmentation, might just be important at specific and not at
generic level, we hesitated for a long time in separating the 'Skyttea
cruciata-group' from Llimoniella. We believe now that there is a strong case
in favour of this separation. The technique required consists of examining
apothecial sections in C (commercial bleach), which lets the dark excipular
pigments disappear completely, allowing an accurate study of the excipular
structure. A detailed study of most species involved confirmed that the
excipular structure is clearly different in these two groups of fungi (see Figs
7, 8). The outer excipular cells in Llimoniella are ± isodiametric, often
± swollen, whilst those in the l S. cruciata-group' are narrowly elongate.
These ± linear outer excipular cells in the latter group may well be
interpreted as excipular hairs, which in some species are free and visible,
whilst in others they are embedded in an excipular gel, the exciple thus
appearing as devoid of hairs.