Euopsis and Harpidium, Genera of the Lichinaceae (Lichenes) with Rostrate Asci*

Abstract

Based on corresponding ascocarp ontogeny and thallus structure, the genera Euopsis and Harpidium are included in the family Lichinaceae. In the two species of Euopsis, E. granatina and E. pulvinata, the apothecia develop from ascogonia in generative tissue, while in H. rutilans they are pycnoascocarps. In thallus anatomy, the species of Euopsis resemble Pyrenopsis haematopsis and allied species, while H. rutilans corresponds in structure and development of the thallus and apothecia to Pyrenopsis haemaleella (syn. P. sphinctotricha). H. rutilans is the first member of Lichinaceae known to have only a green algal symbiont. In E. granatina, two phycobionts are always present, a species of Gloeocapsa and a chlorococcalean alga. In Euopsis and Harpidium, the ascus wall is composed of an outer, non‐expansible and an inner, expansible layer; the latter surrounds the protoplast as an amyloid collar, which expands during spore release into a long, tapering rostrum. In Euopsis, the outer wall layer is strongly amyloid and the upper part separated from the expanded amyloid rostrum by a non‐amyloid zone, appearing like a slit in LM studies. The ultrastructure and function of the ascus in E. granatina has been studied in TEM and is interpreted as functionally unitunicate‐rostrate. Unitunicate asci with short rostrum are described for P. haemaleella and P. haematopsis.

Origin and Evolution of the Lichenized Ascomycete Order Lichinales: Monophyly and Systematic Relationships Inferred from Ascus, Fruiting Body and SSU rDNA Evolution

“…The lecanoralean ascus type would be a synapomorphy of the Lecanorales and the Lichinales since such asci are also present in the Lichinales (Peltula, Pyrenopsis, Euopsis, Harpidium). The evolution of the prototunicate ascus type by reduction, as hypothesized by Henssen et al (1987 [12] ), is not in conflict with this interpretation. The starting point for a reduction could be the rostrate, lecanoralean ascus present in the common ancestor of the Lichinales.…”

“…The lack of an apical pore apparatus in the ascus tip and passive spore discharge, as present in the Lichinales, Caliciales and Mycocaliciales, were considered ancestral. In contrary, Henssen (1994 [9] ) and Henssen et al (1987 [12] ) hypothesized that the prototunicate ascus of the Lichinaceae and Heppiaceae evolved by reduction from a more complex ascus with an apical pore apparatus. Therefore, the Lichinales appear to form a heterogenic assemblage since the genus Peltula of the Peltulaceae has structurally two-layered asci with active spore discharge whereas the Lichinaceae have structurally singlelayered asci with passive spore discharge.…”

Ascomycete Systematics

“…5). A corresponding development of pseudoparaphyses was observed in the ascostromata of Lichenothelia species (Henssen, 1987).…”

“…Pseudoparaphyses are the interascal filaments of the uniloculate Dothideales that are attached by both ends in the cavity of the fruit-body. They arise from rows of short cells of reticulately branched hyphae (Luttrell, 1965;Henssen and Jahns, 1973;Henssen 1976Henssen , 1987. Paraphysoids develop from the generative tissue, and later mainly at the margin of the hymeniun.…”

“…During comparative studies in many lecanoralean genera, a high degree of congruence regarding hymenial characters between Euopsis and Harpidium has been noted . Henssen et al (1987), however, included both these genera in Lichinaceae, pointing to similarities in thallus structure and ascocarp development between some species of Pyrenopsis and the mentioned genera (Le. Euopsis and Harpidium), thus allowing a great variety of ascus types in one family.…”