Revision of Stigmatomycetinae

 

-Under Construction-

Of urgent concern as we begin this new millennium are monographic studies of the so-called “hyperdiverse but poorly known groups” (Hammond, 1990) such as bacteria, fungi, and invertebrates.  Mass collection protocols, combined with quantitative and molecular methods are improving specimen acquisition and the characterization of invertebrates and prokaryotic groups (Hammond, 1990; Hugenholtz, et al., 1998).  However, members of the Kingdom Fungi remain problematical. Fungi historically have been understudied because of the lack of trained researchers, problems in collection, culturing and isolation, and the general underestimation of their importance in ecosystem interactions. The lack of trained taxonomic specialists has become acute in North America and most parts of the world.  In tandem with this, it has been recognized that the potential magnitude of the global fungal resource has been grossly underestimated (Hawksworth, 1991) and that less than 5% of an estimated 1.5 million species have been described to date.  The above estimate, although since generally accepted by the mycological community, was considered by the author to be conservative, based partially on the knowledge that no special allowance had been made for the fungi associated with hyper-diverse hosts such as arthropods.  Despite recent analyses of the most diverse group of fungi associated with arthropods, the Laboulbeniales, in this case associated with a well-inventoried tropical beetle fauna (Weir and Hammond, 1997b), the likely magnitude of the global Laboulbeniales mycota and the way richness varies with latitude remain very imprecisely known. This project will build on previous work by the PI and consultant and will focus on the use of a monographic research component as an integral part of a broader training program in systematic biology. Laboulbeniales have already been promoted as a “model group” in the exploration of broader patterns of fungal (and parasite) species richness (Weir and Hammond, 1997a, b). Parasite systems are also recognized as excellent models for a variety of general evolutionary studies (Brooks and McLennan, 1993) with these assemblages offering exciting possibilities for the comparative study of rates of speciation and evolution in different organisms (Hafner and Nadler, 1990). Such studies rely upon phylogenetic analyses, utilizing detailed taxonomic monographs such as the one proposed here, as one source of potential characters.

 

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The primary objectives of the proposed project are to further develop a partnership between 2 of the remaining 3 specialists on Laboulbeniales systematics that will  (1) place a high priority on the training of several new Laboulbeniales systematists, (2) resolve some of the major questions pertaining to the systematics of this group using a combination of molecular and morphological approaches, (3) produce a comprehensive monograph of the subtribe Stigmatomycetinae (in both hard copy and as an on-line treatise), and (4) develop a web site that will provide information on the biology of the Laboulbeniales to the broader biological community and the general public.

 

We will center our attention in this training program on the order Laboulbeniales and specifically the subtribe Stigmatomycetinae sensu Tavares (1985) and the genus Stigmatomyces. Laboulbeniales are frequently overlooked by entomologists and ignored by mycologists. They comprise a distinctive and diverse group of ascomycetes that are exceptional in having reduced determinate thalli and arthropod-dependant life-histories. Most of the approximately 2000 described species exist as obligate external parasites of arthropods, primarily insects. Although representatives of ten orders of insects and both millipeds and mites are known as hosts, the vast majority of known parasite species both globally (79%) and in well-studied temperate mycobiotas (80%) have been recorded from beetles, with the contribution made by most other insect orders being very low (Weir and Hammond, 1997b). At first glance these organisms might seem a strange choice for modern monographic study; their bizarre morphologies and non-mycelial habit have deterred their study by all but a few mycologists worldwide, and even today many mycologists know these fungi solely from the literature, often from the exquisite drawings of  Roland Thaxter (Figs 1, 2) and more recently, R. K. Benjamin (Fig 3) and PI Weir. (Fig 4).

 
 

On the other hand there are a number of advantages which make the Laboulbeniales ideal for such monographic studies (Weir and Hammond, 1997b):

  1.   They are the only fungi known to exhibit any marked specificity that have been recorded from a wide range of and/or numerous arthropod hosts. As such they represent one of the major lacunae in attempts to refine current estimates of  fungal biodiversity.

  2. Although producing small fruit-bodies these are, for the most part, fairly easily seen on the integument of a given host, whether living, or a long-dead individual in a museum collection.

  3. There is no requirement to culture these fungi in order to identify them, or to assess patterns of species richness.   

  4. Large systematic collections of easily examined specimens of host groups are available for study in many of the major natural history museums of the world.

  5. Two competing morphology-based classifications exist which can now be tested using a recently developed DNA extraction and PCR amplification protocol developed by the PI (Weir and Blackwell, 2001a).