A Preliminary Survey of the Loculoascomycetes and Pyrenomycetes
of Saül, French Guiana

Abstract:  French Guiana was selected for a partial survey of the ascomycete mycota because of a rich assemblage of ascomycete specimens available from previous collectors and because this region has relatively undisturbed vegetation with a high level of species diversity. The focus of this work is a survey of the wood-inhabiting loculoascomycetes and pyrenomycetes of the Saül area based on two collecting trips, one by G.J. Samuels, the other by Huhndorf. One third of the ascomycete specimens collected by Samuels were in the Xylariaceae and one third in the Hypocreaceae.  On the Huhndorf trip, 18% of the ascomycetes collected were in the Xylariaceae and 8% in the Hypocreaceae. Twenty six percent and 68% of the Samuels and Huhndorf collections respectively were placed in 36 other families.  Species in five families were frequently encountered and some examples of the common wood-inhabiting species in these families of loculoascomycetes (Melanommataceae, Platystomaceae, Tubeufiaceae) and pyrenomycetes (Lasiosphaeriaceae, Nitschkiaceae) are discussed and illustrated.

Species in the family Melanommataceae were the most common wood-inhabiting loculoascomycetes found.  The most frequently encountered species were in Byssosphaeria. The genus is easily recognized by large ascomata often with bright-colored plane apices and usually with some surface vestiture. Two abundant species in Saül are B. schiedermayeriana with reddish-orange apices which is cosmopolitan in warmer regions (color plate 1) and B. jamaicana with a pallid or gray-colored pore area (color plate 2). Also common, the genus Mycopepon is distinctive and very easy to recognize macroscopically. It has the unusual habit of totally superficial, valsoid-like ascomata that have eccentric papillae that fuse into a common central ostiole (color plate 3) .  Ascomata of Ostropella albocincta, found on well rotted wood or bark, are large and usually have a conspicuous white covering around the apex (color plate 4). This character is variable however and cannot be used to verify species identification. A second species, O. striata known only from French Guiana was recently described (Huhndorf, 1998. Mycologia 90:527-530. (color plate 5). All four known species of Xenolophium occur here and X. applanatum can be easily recognized macroscopically by its distinctive ascomatal apex (color plate 6). The Platystomaceae was the second most frequently encountered family of loculoascomycetes in Saül. Trematosphaeria perrumpens occurs on hardened decorticated wood and is distinguished by large, dark brown, fusoid ascospores that may remain hyaline for some time (color plate 7).

The Lasiosphaeriaceae is the third most frequently encountered family of ascomycetes in Saül and in French Guiana overall according to information from Samuels collections and the second frequently encountered family according to information from Huhndorf collections. Most collections from French Guiana have not yet been identified to species because of the inadequacy of the keys in this group and the large numbers of species in some of the genera in the family.  Lasiosphaeriella noonae-daniae was collected in Saül, and is distinguished by ascospores that have a widely-reniform shape with a large gelatinous sheath and ascomata that are tuberculate with brown projections (color plate 8). A common wood-inhabiting species in the Nitschkiaceae found in Saül was Bertia moriformis var. latispora.  This variety is characterized by its wide, geniculate ascospores (color plate 9)  and ascomata that are coarsely tuberculate with a more-or-less sunken or collabent apex.

Preliminary collection data from the Samuels and Huhndorf collecting trips suggests there are some patterns of distribution of wood-inhabiting loculoascomycetes and pyrenomycetes within microhabitats.  Microhabitats in the valleys along streams that remain moist might have a greater diversity of pyrenomycetes than the upland ridge areas, where winds dry the forest in between rain showers. From the information for French Guiana, it is difficult to make generalizations about pyrenomycete diversity that can be compared with other tropical forests.  The Saül forest, which has a distinct dry season, may have a pyrenomycete and loculoascomycete composition that is different from tropical forests that have constant moisture throughout the year. Constant available moisture without inundation may be better that total rainfall in defining areas of high pyrenomycete diversity. Therefore forest areas with constant moisture available thoughout the year may have a greater diversity of pyrenomycetes.  Regardless, the information for one forest type in French Guiana serves as a baseline for future research. With detailed knowledge of specific study areas, such as the Saül area, we can begin to think in terms of the biogeography, endemism, species richness, and diversity of tropical ascomycetes.  Until this information is available for tropical areas, fungi will not be included in discussions on biodiversity, in spite of their extreme importance in the tropical forest ecosystem.

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