GYALECTIDIUM AURELII ( OSTROPALES : GOMPHILLACEAE ) , A NEW FOLIICOLOUS LICHEN FROM THE STATE OF MATO GROSSO , BRAZIL

(Gyalectidium aurelii (Ostropales: Gomphillaceae), a new foliicolous lichen from the State of Mato Grosso, Brazil). The new species Gyalectidium aurelii is described from leaves of Meliaceae collected in Chapada dos Guimarães, in the State of Mato Grosso, Brazil. The new taxon is characterized by very broad, marginal hyphophores with scales that project horizontally from the leaf margin and are closely appressed to the substrate. G. aurelii is distinguished from similar species, such as G. fantasticum and G. paolae, by its hyphophores being incurved (following the thallus outline) and having an entire margin, and further by its irregularly verrucose rather than areolate thallus. The genus Gyalectidium now comprises 37 species.


Introduction
The lichen genus Gyalectidium Müll.Arg.comprises mostly foliicolous species which are found in all tropical and subtropical rainforests throughout the world (Ferraro et al. 2001).Like other genera in the Gomphillaceae, Gyalectidium is characterized by hemiangiocarpous apothecia and non-amyloid hymenium, branched and anastomosing paraphyses, annelasceous asci, and conidiomata of the hyphophore type (Vezda 1979;Vezda & Poelt 1987;Lücking 1997;Ferraro et al. 2001).Gyalectidium can be recognized at the genus level by its immersed-erumpent apothecia (Fig. 1A), with zeorine margin (both true excipulum and thalline margin present) and its squamiform hyphophores (Fig. 1B-F), with the conidial hyphae (diahyphae) being produces at the base of variously shaped scales.Most other genera in the family have setiform hyphophores which produce the diahyphae at their tips.
For a long time, the genus was believed to be poor in species, but detailed studies revealed an unexpected diversity, with 29 species accepted in a recent world monograph (Ferraro et al. 2001).Soon after the monograph was published, no less than eight further new species were discovered in collections of foliicolous lichens from Mexico and Chile (Herrera-Campos & Lücking 2002;2003;in prep.;Lücking et al. 2003).

Gyalectidium aurelii
This new species is dedicated to Aurelio Schinini for his invaluable collections which add considerably to the knowledge of the lichen flora of northern Argentina and southern Brazil.
As stated in the introduction, the hyphophore scales in Gyalectidium are very variable and provide important characters to distinguish between species (Fig. 1B-F).While some taxa, such as the type species G. filicinum, have erect scales protruding from the thallus surface (Fig. 1B), in others the scales are adnate to the thallus (Fig. 1C) and often marginal (Fig. 1D-F).Mostly, the scales are unpigmented and whitish but might be darkened to pure black in a few taxa.Other specific characters are the presence of calcium oxalate crystals and their distribution in the thallus: they either form verrucae or large, sometimes completely confluent areoles.
Gyalectidium aurelii is characterized by adnate, marginal, dark hyphophore scales, in combination with a verrucose thallus (Fig. 1F).The species resembles two other species with broad, dark, marginal hyphophores with scales  2002).However, these two species have an areolate rather than verrucose thallus (Fig. 1D-E), and while the hyphophores of G. paolae are smaller and irregularly dissected, those of G. fantasticum are larger, usually recurved, and provided with two acute, lateral appendages.Another superficially similar species is G. imperfectum Vezda (Vezda 1994).It agrees with G. aurelii in the verrucose rather than areolate thallus (Fig. 1C), but its hyphophore scales are greatly reduced, leaving the diahyphal masses visible as dark, reniform spots on the thallus surface.