Moelleriella, and Samuelsia - CBS

Ch av e r r i e t a l.Morphological analyses and geographicaldistributionMoelleriella, Samuelsia, and Hypocrella/AschersoniaThe distributions of the species presented here are generally poorlyknown. Based on the specimens collected for this study, Moelleriellais most diverse and common in the Neotropics (22 known species),followed by Hypocrella (5 known species), and Samuelsia (5known species). Moelleriella and Hypocrella species are alsomore abundant that Samuelsia. Field collections and additionalspecimens from collaborators and herbaria yielded hundredsof specimens of Moelleriella and Hypocrella from many differentcountries. On the other hand, Samuelsia species are only knownfrom one collection each. Samuelsia rufobrunnea, S. chalalensis,and S. geonomis are known from Bolivia and Peru; S. sheikhii fromHonduras; and S. intermedia from Chile.Examination of multiple morphological characters showsthat segmentation of ascospores and conidial size and shapeare the main characters that distinguish Moelleriella, Samuelsia,and Hypocrella. All known species of Moelleriella have filiformmultiseptate ascospores that disarticulate at maturity inside theascus and fusiform conidia < 15 µm long. Hypocrella specieshave filiform to long-fusiform multiseptate ascospores that do notdisarticulate and fusiform conidia > 15 µm long. Samuelsia specieshave long-fusiform, non-disarticulating ascospores and smallallantoid conidia < 10 µm long. Another character common to mostspecies of Hypocrella and Samuelsia is a reddish colour reaction ofthe stroma when 3 % KOH is applied. However, H. citrina does notchange colour. All studied species of Moelleriella lack a reaction to 3% KOH. Moelleriella gaertneriana and M. cornuta release brownishpigments when 3 % KOH is added, but the tissue of the stromatadoes not change colour. Stromal anatomy is somewhat conservedin Hypocrella. The Hypocrella species examined have pulvinatestromata, with or without hypothalli. On the other hand, stromata inMoelleriella are highly variable: from flat or effuse with loose hyphaltissue (e.g. M. libera), to somewhat pulvinate (e.g. M. madidiensis)or knob-shaped (e.g. M. phyllogena, M. basicystis, M. umbospora,M. disjuncta), to large, globose and hard stromatal tissue (e.g. M.macrostroma, M. gaertneriana).Characters of the anamorph are somewhat useful indistinguishing between Hypocrella, Samuelsia, and Moelleriella.The three genera have pycnidial-acervular conidiomata, slenderflask-shaped to cylindrical phialides arranged in a compacthymenium, with or without paraphyses, brightly coloured and slimyconidial masses, and fusoid, unicellular conidia. Only conidialshape and size are useful characters.Moelleriella morphologyThe stromatal size of Moelleriella species treated in this studyranges from 0.5–30 mm diam. Moelleriella macrostroma, M.gaertneriana, and M. cornuta have large stromata that range from2–30 mm diam. The smallest stromata are those of M. umbospora,M. basicystis, M. turbinata, M. castanea, and M. colliculosa, whichrange between 0.5 and ca. 2 mm in diam. The size of the stromais generally correlated with the number of perithecia or pycnidiaper stroma. The colours of the stromata of the species studiedare in shades of white, yellow, orange, brown, or black. Whiteand orange are the most common colours. A few species, i.e. M.cornuta, M. turbinata, M. palmae, M. guaranitica, M. globosa, andM. castanea, have brown to almost black stromata; these speciesare phylogenetically related in the Globose clade (Figs 1–2).Most of the examined species in the Effuse clade have stromatain shades of white or orange. The shapes of the stromata arehighly variable. They can range from effuse or flat, to somewhatpulvinate, globose, cerebriform, tubular, conical, or knob-like.Moelleriella libera, M. ochracea, M. sloaneae, and M. evansii haveeffuse or thin, pulvinate stromata. Moelleriella zhongdongii, M.madidiensis, M. rhombispora, M. guaranitica, M. castanea, andM. epiphylla, have pulvinate to convex stromata. The surface ofthe stroma can be shiny or dull/matt, opaque, glabrous or scurfy,and tomentose or roughened. Most species of Moelleriella have astromatal surface that is opaque and pruinose; however, there aremany exceptions. Moelleriella libera, M. evansii, M. zhongdongii,M. madidiensis, M. ochracea, M. rhombispora, M. sloaneae, andsome forms of M. basicystis, M. disjuncta, M. phyllogena, and M.umbospora, have tomentose stroma surfaces. Teleomorph stromataof M. basicystis, M. disjuncta, M. phyllogena, and M. umbospora,and stromata of M. macrostroma, M. gaertneriana, M. boliviensis,M. turbinata, M. epiphylla, M. cornuta, M. palmae, M. globosa, M.guaranitica, M. castanea, and M. colliculosa have almost glabroussurfaces. Stromata of M. macrostroma, M. gaertneriana, and M.cornuta, have somewhat shiny stromata. Hypothalli are presentin some species, except M. epiphylla, M. turbinata, M. boliviensis,M. macrostroma, and M. gaertneriana, M. castanea, M. colliculosa,M. globosa, and M. guaranitica. There is no reaction to 3 % KOHon the tissue of the stromata; only M. gaertneriana and M. cornutarelease brownish pigments when KOH is added. The tissuestructure of the stroma surface is highly conserved among theexamined species. All species studied have the tissue type referredto as textura intricata or epidermoidea. Some differences are foundin the thickness of the cell walls. Darkly pigmented hard stromataare composed of hyphae with thick cell walls (ca. 2–6 µm). Lightlypigmented stromata with loose hyphal tissues have thin-walledhyphae (ca. 1 µm). The inner tissue below the outermost layerof the stroma is generally of textura oblita, intricata, epidermoideaor a condition intergrading between these tissue types.Perithecia in some species of Moelleriella can be formed inwell-separated or gregarious tubercles, or they can be completelyembedded in the stroma. Moelleriella libera, M. ochracea, M.rhombispora, M. zhongdongii, M. evansii, and M. sloaneaeform perithecial tubercles. When the stroma contains peritheciaand pycnidia, the perithecia are either towards the edges of thestroma or scattered, with pycnidia either clustered in the centre orinterspersed among the perithecia, respectively. The ostioles canrange in colour from yellow to orange yellow, to reddish brown orbrownish yellow. In longitudinal section, perithecia are generallyelongated to subglobose, sometimes globose, with walls composedof 3–4 layers of highly compacted, thin-walled cells.The asci are cylindrical and sometimes swollen in the middlewhen ascospores have disarticulated and accumulated towardsthe middle. Generally the ascus cap is thickened (ca. 2–5 µm)and capitate. Moelleriella boliviensis, M. epiphylla, M. globosa,M. guaranitica, M. colliculosa, and M. castanea have thin ascustips (< ca. 1.5 µm). Because the multiseptate filiform ascosporesdisarticulate at the septum inside the ascus upon mounting, itis difficult to know exactly the length of intact ascospores. Thepart-ascospores are always hyaline and smooth. They canvary in shape, from cylindrical, to fusoid, ventricose, or almostovoid. Moelleriella basicystis, M. phyllogena, M. umbospora,and M. disjuncta have a swollen protuberance on one side ofthe part-spore. In M. rhombispora, the part-spores have similarprotuberances in the middle (i.e. ventricose shape). For themost part, the species studied have part-spores ca. 9–14 µm16