Gyalideopsis macarthurii
Gyalideopsis macarthurii is a species of corticolous crustose lichen in the family Gomphillaceae. The pale greenish-grey lichen forms thin, shiny crusts on bark and rotting logs in montane cloud forest environments, particularly in exposed areas along forest edges and pastures, and has been documented in Costa Rica, Florida, and Brazil. It is distinguished by its distinctive fruiting bodies with thin triangular lobes covering the margins, extremely small specialized reproductive structures called, and its habit of growing on bark rather than leaves, which separates it from its closest relative, Gyalideopsis lobulata.
Taxonomy
Gyalideopsis macarthurii was described in 2006 by the lichenologists Robert Lücking, Loengrin Umaña, and André Aptroot. The species epithet macarthurii honours the MacArthur Foundation, which has been a supporter of Instituto Nacional de Biodiversidad and conservation efforts in Costa Rica. The type specimen was collected in the province of Alajuela, within the Cordillera de Tilarán. It was found in Tenorio Volcano National Park, part of the Arenal-Tilarán-Tempisque Conservation Area, at the Pilón Biological Station. The collection took place at an elevation of in the lower montane cloud forest zone, where the species was found on wet, rotting logs in exposed areas, including trees and fence posts along pasture.This species belongs to the genus Gyalideopsis within the family Gomphillaceae, order Graphidales. It is distinguished from other species in the genus by its distinctive fruiting bodies with thin thalline lobules covering the margins, and by its extremely small reproductive structures called hyphophores. The only closely related species with similar characteristics is Gyalideopsis lobulata, which differs by growing on leaves rather than bark and having yellowish brown fruiting bodies without a powdery coating.
Description
Gyalideopsis macarthurii forms a thin, crustose thallus on bark. The thallus is continuous, measuring 5–10 mm across and only 10–20 μm thick, with a outer layer. Its surface is irregularly warty due to clusters of calcium oxalate crystals. The lichen is pale greenish-grey in colour and has a shiny appearance. The photosynthetic partner of the lichen consists of green algae with cells measuring 5–9 μm in diameter.The reproductive structures are distinctive for this species. They emerge from the surface, are round in outline, and measure 0.15–0.25 mm in diameter and 70–90 μm in height. The disc is flat and dark greyish brown with a coarse, white to pale grey powdery coating. The of the apothecia is inconspicuous and covered by 4–6 triangular, thin, pale grey, thalline lobules that lack algal cells.
The spore-producing layer is colourless and 50–60 μm high. The spore sacs are broadly club-shaped, measuring 45–55 by 20–25 μm. Each ascus produces a single, ellipsoid spore that is, with slight constrictions at the dividing walls. The spores measure 35–40 by 12–18 μm, are 2.5–3 times as long as broad, and are colourless.
The are distinctive, being shortly bristle-shaped with a pointed tip, measuring 0.04–0.06 mm high and 10–12 μm thick above the base. They are blackish brown with a pale base. The are branched throughout, shallowly, with segments broadly club-shaped or drop-shaped to ellipsoid, measuring 4–6 by 2–2.5 μm. Terminal segments are ellipsoid, often with one septum, and colourless.