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Visitors : Robert Luecking and Marcela Caceres

Summer-Fall 1999

Dr. Robert Luecking
Department of Plant Systematics,
University of Bayreuth,
D-95447 Bayreuth, Germany
and
Marcela Caceres
M.Sc.
Department of Mycology,Centre of Biological Sciences,
Federal University of Pernambuco,


During their two-month stay at the Field Museum, Robert Luecking and Marcela Caceres collaborated with Franšois Lutzoni to gather molecular data for the large subunit ribosomal DNA (LSU) to better understand the phylogeny of the lichen family Gomphillaceae. This family is composed of 150-200 mainly tropical species which mostly grow on the surface of living leaves, but can also be found on bryophytes, bark and rocks, usually under humid or semi-aquatic conditions.

The Gomphillaceae as a whole are well-distinguished and easily recognized by a combination of morphological and anatomical features: hemiangiocarpous apothecia, non-amyloid asci with apical tholus and ring-structure, richly branched and anastomosing paraphyses, and highly specialized conidiomata, the so-called hyphophores. Unfortunately, the type genus, Gomphillus (with two species), appears to be isolated from the rest of the family, and hence, the nomenclatural typification of the group is linked to a taxon with unsettled affinities, which causes trouble when talking about the family as a whole ("Are you referring to Gomphillus or to the rest of the family?").

Another problem is the high plasticity of the apothecia (biatorine or zeorine, applanate or vertically elongated, with pale or carbonaceous margin), ascospores (transversely 1-septate to muriform), and hyphophores (setose to scale-like). These characters have so far been used to delimit genera, but recently it became obvious that similar apothecial or hyphophore types (not to mention the ascospores) may have evolved several times independently, so that hitherto defined genera may be polyphyletic. Based on the molecular data, it is hoped not only to produce a reliable backbone phylogeny of the family which can help to establish sound generic limits, but also to ascertain the position of Gomphillus and the placement of the whole family in the fungal system.

A second project dealt with a particular type of disc-shaped isidia which are abundant on leaves and traditionally referred to an imperfect lichen genus, Phyllophiale. Since these isidia are occasionally found on thalli of other lichens, it has been suggested that they form the vegetative propagules of these lichens. Indeed, the three distinct forms of isidia that are known occur specifically on three different species of the lichen genus Porina. To test this hypothesis, molecular data from the ITS-region was gathered.


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