Graduate Student Theses
directed by Robert S. Egan
Derstine, K. S. 1978. Studies on the Lichen Genus Xanthoparmelia (Vainio) Hale in Texas. M. S. Thesis, Texas A&M University.
ABSTRACT. A study of Texas Xanthoparmelia (Vainio) Hale has been made from specimens collected throughout the state and from herbarium specimens available. Collecting sites were chosen in part by consulting earlier reports of collections of the genus but mostly wherever the plant was found on numerous forays. Locality data are listed for each site from which specimens were collected personally. Included is a key to the twenty known species of Xanthoparmelia in Texas. Xanthoparmelia arida Egan & Derstine is described as new and X. arseneana (Gyeln.) Hale, X. dissensa (Nash) Hale and X. joranadia (Nash Hale are reported for the first time from Texas. Xanthoparmelia lecanorica (Hale) Hale is removed from the North American lichen flora. Distribution maps are included for all species except Xanthoparmelia arseneana (Gyeln. ) Hale.
Cherney, T. 1985. Lichen Flora of the Eastern Nebraska Riparian and Adjacent Bluff Forests. M. A. Thesis, University of Nebraska at Omaha.
ABSTRACT. Seventy-one species in 31 genera were collected in 14 riparian and adjacent bluff forest sites in eastern Nebraska. Data were gathered on aspect, vertical zonation, substrate preference, and latitudinal differences with respect to species diversity. A majority of species were collected above one meter on wood substrates of northern aspect. Greatest number of lichen species were found in the central and southern counties of eastern Nebraska. Three genera are reported for the first time from Nebraska (Anisomeridium, Lepraria, and Thyrea), and 26 species collected were state records. Keys to the collected genera and species are provided with a brief discussion of each taxon.
Witt, R. 1996. The Effects of Selected Lichen Extracts and Purified Compounds on the Rat Heart. M.A. Thesis, University of Nebraska at Omaha.
ABSTRACT. Extracts of Letharia vulpina, Umbilicaria americana, Cladina subtenuis, Xanthoparmelia cumberlandia, Rimelia reticulata and Parmotrema austrosinense were used to study their electrophysical effects on the rat heart ventricular tissue. Additionally, solutions of four purified lichen metabolites--vulpinic acid, usnic acid, sticitc acid, and atranorin--were studied in the same manner. The action potential duration at 50% and 90% of repolarization was significantly reduced by two of the extracts and metabolites, those containing vulpinic acid and usnic acid and the purified forms of those compounds. A positive relationship between the effects of extracts and purified compounds was exhibited. These data suggest that the active metabolites may depress inward calcium current or enhance outward potassium currents. However, when single dissociated rat myocytes were exposed to vulpinic acid, activation of an ATP-sensitive potassium channel was observed, and this was blocked with glibenclamide, a specific blocker of that channel. This ATP-sensitive potassium channel created an overlapping current which made it appear that an inward calcium current or outward repolarizing currents were affected, when in fact they were not.
Morgan, S. 2001. The Lichen Flora of the Ponderosa Pine Forests of Nebraska. M. A. Thesis, University of Nebraska at Omaha.
ABSTRACT:Although generally thought of as a prairie state, Nebraska retains sizeable areas of both eastern deciduous and western pine forests. The state has five main western pine forest regions dominated by Pinus ponderosa. Three of these forests are naturally occurring-the northern Niobrara River Valley area of Brown and Cherry counties, the northwestern Pine Ridge region in Dawes, Sioux, and Sheridan counties, and the Wildcat Hills area of Scotts Bluff County. Samuel R. McKelvie National Forest in Cherry County and the Bessey Unit of the Nebraska National Forest in Thomas County were both planted in the early 1900's. From 541 identified lichens, I found 110 species within a total of 47 genera from these pine forest areas. Of these 110 taxa, 39 species and six genera are new state records. Four of the new species records for Nebraska represent significant extensions of their currently known ranges. The lichens of the planted pine forests are less diverse than the naturally-occurring pine forests, but a few lichen species are currently known only from these planted pine systems.
Reed, M. 2006. Influence of Feedlot Emissions on Lichen Distribution and Abundance in Eastern Nebraska. M. A. Thesis, University of Nebraska at Omaha.
ABSTRTACT: Environmental factors greatly influence what species of lichens may occur in a particular region. Among these factors is nitrogen deposition in the form of ammonia as a result feedlot operations, which may be manifested in increased bark pH. Lichens on trees located in close proximity to medium and large-scale feedlot operations in Eastern Nebraska were analyzed for species composition and abundance then compared to trees located at a greater distance from feedlot operation. Tree bark samples were collected and analyzed for pH increase in comparison to bark located at a greater distance. In order to determine lichen coverage in cm 2 , high-resolution digital images were acquired then evaluated employing ERDAS Imagine 8.6, geospatial imagery analysis software. To accurately identify lichen species, bark material was collected from within 30 cm x 30 cm quadrats after imagery data was collected. Five sites were selected based on the presence of trees, accessibility, and proximity to livestock operations. Ten trees from each site were chosen at each site based on uniform diameter at breast height (dbh) and proximity of feedlot operation. Analysis revealed that nitrophilous lichens species dominated all sites as well as a statistically significant increase in nitrophilous lichen coverage when comparing sites located near feedlot operations to those located at a greater distance from the feedlot operations.
Widhelm, T. 2008. Testing Species Delimitations in the Parmotrema Pperforatum Group (Parmeliaceae, Ascomycota) in Eastern North America. M. A. Thesis, University of Nebraska at Omaha.
ABSTRACT. The current taxonomy of the Parmotrema perforatum group of lichens recognizes six closely related species divided into three species pairs, a pair comprising one apotheciate and one sorediate species. Each pair is characterized by a distinct combination of lichen acids. W. L. Culberson hypothesized that the three apotheciate species are reproductively isolated sibling species, and that each sorediate species evolved once from the chemically identical apotheciate species. This species delimitation has been reexamined using 30 unique alleles of the glyceraldehyde-3-phosphate dehydrogenase ( GPD ) locus from 53 individual thalli from populations in Texas , Louisiana and North Carolina . Population aggregation analysis of eight Texas and Louisiana populations suggests that the Parmotrema perforatum group is instead two phylogenetic species due to the distributions of phenotypic characters (reproductive mode and chemistry) and GPD alleles among populations. One phylogenetic species is fixed for norstictic acid and polymorphic for stictic acid, and the other species is fixed for alectoronic acid. Both species are polymorphic for reproductive mode (apothecia or soredia), suggesting that sorediate thalli are part of the same sexually reproducing population as apotheciate thalli. There is also evidence suggesting that the norstictic acid-containing strain of P. subrigidum is a hybrid between the two recognized phylogenetic species.