Emeritus Professor of Plant Biology
655 Morrill MC-116
Ph.D., 1971, University of Maryland
In freshwater habitats, leaves and branches of riparian vegetation are important as a food resource for stream heterotrophs. Fungi serve as intermediaries in making this resource more palatable and nutritious for aquatic invertebrates. We are interested in finding out why certain fungal species are more successful in colonizing resources initially, why other species are able to displace initial colonists over time, and how environmental factors influence colonization and decomposition processes. Field and laboratory studies are used to determine the relative importance of intrinsic characteristics of species that comprise their overall ability to colonize and decompose resources. These characteristics include: spore germination and germ tube elongation rates, growth rates, enzymatic capabilities, and ability to produce and resist antibiotics. Interspecific interactions among fungal species and between fungi and other organisms, such as grazing invertebrates, are also important determinants of species success in resource colonization. Field and laboratory experiments in which the interacting species are manipulated are used to determine the effects of species interactions on colonization processes.
Systematic studies in my laboratory deal with two general areas: fungal geography and biodiversity and phylogenetic relationships in Ascomycetes. The number of fungal species has been conservatively estimated at 1.5 million but only about 69,000 species actually have been collected and described. The freshwater ascomycetes, a group that has only recently been studied, are very poorly known. As part of the effort to determine fungal biodiversity as it relates to latitude, we are collecting fresh-water ascomycetes and their asexual states along latitudinal gradients through North America, which encompass arctic through tropical biomes. Species are collected, identified, described if new or rare, isolated in pure culture, and tested for the production of bioactive compounds.
Phylogenetic relationships among ascomycete taxa are poorly understood. This is especially true for aquatic and marine species which have undergone convergent evolution in response to habitat. We use cladistic analyses of morphological and molecular sequence data to resolve relationships among morphologically similar freshwater, marine and terrestrial species.
Zelski S.E., Raja H.A., Miller A.N., and Shearer C.A. 2011. Longicollum biappendiculatum gen. et sp. nov., a new freshwater ascomycete from the Neotropics. Mycosphere 2:539–545.
Zelski S.E., Raja H.A., Miller A.N., Barbosa F.R., Gusmão L.F.P., and Shearer CA. 2011. Chaetorostrum quincemilensis, gen. et sp. nov., a new freshwater ascomycete and its Taeniolella-like anamorph from Perú. Mycosphere 2: 593-600 Doi 10.5943/mycosphere/2/5/9.
Zelski S.E. and Shearer, C.A. 2013. Humedales de Madre de Dios, Perú: Impactos y amenazas en aguajales y cochas. Chapter 5.4. Hongos Acuáticos pp. 81-83.
Zelski S.E., H.A. Raja, A.N. Miller, C.A. Shearer. 2014. Conioscypha peruviana sp. nov., its phylogenetic placement based on 28S rRNA gene, and a report of Conioscypha gracilis comb. nov. from Peru. Mycoscience pp. 1-7.
Zelski S.E., J.A. Balto, C. Do, H.A. Raja, A.N. Miller, and C.A. Shearer. 2014. Phylogeny and morphology of dematiaceous freshwater microfungi from Peru. IMA Fungus 5: 425-438.
Shearer, C.A., K-L Pang, S. Suetrong and H.A. Raja. 2014. Phylogeny of the Dothideomycetes and other classes of freshwater fissitunicate Ascomycota. Pp 25-45 In Freshwater Fungi and fungal-like organisms. Eds. E.B.G. Jones, K.D.
Hyde, and Ka-Lai Pang, De Gruyter, 496 pp.
Fournier, J., H.A. Raja, C. A. Shearer. 2015. Freshwater Ascomycetes: Jahnula purpurea (Jahnulales, Dothideomycetes), a new species on submerged wood from Marinique Island, Lesser Antilles. MycoKeys: In press.