College of Science and Engineering
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Item Genetic Variability in Palaemonetes pugio in Habitats Open and Closed to Migration(1977-12) Fuller, BelindaNine collections of the grass shrimp, Palaemonetes pugio, were made on Galveston Island to test the hypothesis that small populations show reduced genetic variability as a result of increased allele fixation due to random genetic drift. Four small ponds and five sites in or adjacent to the bay were sampled as representative of finite and infinite populations, respectively. Starch gel electrophoresis was used to analyze enzyme electromorphs encoded by seventeen loci. Four loci showed electromorph variation. Three measures of genetic variability were determined; percent polymorphism (P), the number of alleles per population for the polymorphic loci (n), and the average heterozygosity per locus (H). For all three measures, the four closed populations had values lower than or equal to the smallest value found among the open populations. These results are believed to support the hypothesis that population size can be an important determinant of genetic variability resulting in reduced variability in small populations.Item A General Hypothesis of Species Diversity(The American Society of Naturalists, 1979-01) Huston, Michael A.Many explanations for diversity patterns have been proposed, and there have been several recent reviews of the subject (Pianka 1966, 1974; Ricklefs 1973; Pielou 1975). High diversity has been attributed both to intense competition which forces niche restriction (Dobzhansky 1950; MacArthur and Wilson 1967)and reduced competition resulting from predation (Paine 1966; Harper 1969; Janzen 1970; Connell 1975). Diversity has been positively correlated with productivity (Connell and Orias 1964; Pianka 1966; MacArthur 1969) and negatively correlated with productivity (Yount 1956; Margalef 1969). The question is far from settled. This paper develops an approach to the problem of species diversity based on the nonequilibrium interactions of competing populations. Under nonequilibrium conditions, differences in diversity are strongly influenced by variations in the rates of competitive displacement between communities, and such factors as relative competitive abilities, niche partitioning, etc., may not be particularly important. This approach deals primarily with the maintenance of diversity, as opposed to the generation of diversity. While most of the current diversity hypotheses have some relation to the evolutionary origin of diversity, this will not be emphasized here.Item The Evolution of the Cuticle in Early Angiosperm Leaves from the Lower Cretaceous Potomac Group (Atlantic Coastal Plain, U.S.A.)(1981-01) Upchurch, Garland R.; Doyle, James A.; Beck, Charles B.; Fisher, Daniel A.; Wagner, Warren H.No abstract prepared.Item Computing History at Southwest Texas State University(1983-01) Early, Grady G.This dedication of MCS marks the latest step in Southwest Texas State University's 15-year progression from paper-and-pencil computing to state-of-the-art digital electronic computing. Originally published by Department of Mathematics and Computer Science, Southwest Texas State University, 1983.Item Cuticular Anatomy of Angiosperm Leaves from the Lower Cretaceous Potomac Group I. Zone I Leaves(Botanical Society of America, 1984-02) Upchurch, Garland R.Angiosperm leaf cuticles from the oldest part of the Potomac Group reinforce previous paleobotanical evidence for a Cretaceous flowering plant diversification. Dated palynologically as Zone I of Brenner (Aptian?), these remains show a low structural diversity compared to later Potomac Group and modem angiosperms. All cuticle types conform to a single plan of stomatal construction that is unusual in its extraordinary plasticity: both the number of subsidiary cells and their arrangement vary greatly on a single epidermis, such that the stomatamight be classified as paracytic, anomocytic, laterocytic, and intermediate. Such stomatal diversity is uncommon in extant angiosperms but is known from a few Magnoliidae. Many species possess secretory cells comparable to the oil cells of modem Magnoliidae, and a few show the bases of probable uniseriate hairs. None of the cuticle types can be assigned to a single modem family, but several show similarities with Chloranthaceae and Illiciales. These results support the concept that subclass Magnoliidae includes some of the most primitive living angiosperms.Item Cuticle Evolution in Early Cretaceous Angiosperms from the Potomac Group of Virginia and Maryland(Missouri Botanical Garden Press, 1984-11) Upchurch, Garland R.Studies of angiosperm leaf cuticles from the Lower Cretaceous Potomac Group reinforce previous evidence for a Cretaceous adaptive radiation of the flowering plants and suggest unsuspected trends in the evolution of stomata and trichomes. Early Potomac Group angiosperm leaf cuticles (Zone I of Brenner or Aptian?) show little interspecific structural diversity, particularly in stomatal organization. All species conform to the same highly plastic pattern of variation in subsidiary cell arrangement, in which the stomata on a single leaf conform to several types, including paracytic, hemiparacytic, anomocytic, laterocytic, and weakly cyclocytic. Several species resemble extant Chloranthaceae and Illiciales, but none represents a modem family. Later leaves (Subzone 11-B of Brenner, or Albian) exhibit greater interspecific structural diversity, particularly in stomatal organization. Three new patterns of variation in subsidiary cell arrangement are present in addition to the older one and each has a subset of the variation present in the older pattern. Cuticular anatomy is consistent with proposed leaf affinities to Platanaceae and Rosidae. The stratigraphic trend in cuticle types supports the concept that the subclass Magnoliidae includes the most primitive living angiosperms. However, it also suggests that the uniformly paracytic stomatal pattern characteristic of Magnoliales, generally considered primitive for the flowering plants, may actually be derived from the variable condition found in Zone I leaves.Item Plant Succession: Life History and Competition(The American Society of Naturalists, 1987-08) Huston, Michael A.; Smith, ThomasAn approach based on competition among individual plants is presented as an explanation for species replacements during plant succession. Inverse correlations among life history and physiological traits that confer competitive ability under different environmental conditions are sufficient to produce successional replacements but not sufficient for understanding the complex variety of successional patterns unless they are applied at the individual level rather than at the population level or higher. With models based on competition among individual plants, various combinations of life history and physiological traits can produce the great variety of population dynamics found in natural successions. The classic successional pattern of species replacement results from a particular structure of correlations among life history and physiological characteristics. Atypical patterns of succession result when this correlation structure is altered. Both primary and secondary succession are modeled as nonequilibrium processes, capable of interacting with disturbances to produce steady-state communities whose properties depend on abiotic conditions, such as temperature and resource levels, and on the type and frequency of disturbances to produce steady-state communities whose properties depend on abiotic conditions, such as temperature and resource levels, and on the type and frequency of disturbances.Item Leaf assemblages across the Cretaceous-Tertiary boundary in the Raton Basin, New Mexico and Colorado(National Academy of Sciences, 1987-08) Wolfe, Jack A.; Upchurch, Garland R.Analyses of leaf megafossil and dispersed leaf cuticle assemblages indicate that major ecologic disruption and high rates of extinction occurred in plant communities at the Cretaceous-Tertiary boundary in the Raton Basin. In diversity increase, the early Paleocene vegetational sequence mimics normal short-term etologic succession, but on a far longer time scale. No difference can be detected between latest Cretaceous and early Paleocene temperatures, but precipitation markedly increased at the boundary. Higher survival rate of deciduous versus evergreen taxa supports occurrence of a brief cold interval (‹1 year), as predicted in models of an "impact winter."Item Drewria potomacensis gen. et sp. nov., an Early Cretaceous Member of Gnetales from the Potomac Group of Virginia(Botanical Society of America, 1987-11) Crane, Peter R.; Upchurch, Garland R.Drewria potomacensis gen. et sp. nov. from the Lower Cretaceous Potomac Group of Virginia (Zone I, probably Aptian) provides the first definite Mesozoic megafossil record of Gnetales. The stems are slender, display no evidence of secondary growth, and show axillary monopodial branching. Attached leaves are opposite and decussate, borne at swollen nodes, and have clasping sheathing bases. Each leaf is oblong, up to 20 mm long, and has a dense network of longitudinally aligned subepidermal fibers. Leaf venation consists of two, or possibly three pairs of longitudinal parallel veins that form a reticulum at the apex and higher-order crossveins that form apically oriented chevrons. Reproductive structures consist of short, loose spikes that are borne in dichasially arranged groups of three. The dichasia are either terminal or lateral in the axil of a leaf. Reproductive units of the lateral spikes in a dichasium contain seeds, each surrounded by at least one pair of opposite, broadly elliptical or ovate bracts. Characters of D. potomacensis that suggest a gnetalean relationship include the opposite bracts surrounding the seeds, the network of subepidermal foliar fibers, and the distinctive leaf venation, which is very similar to that seen in the cotyledons of extant Welwitschia. Other features consistent with a gnetalean relationship include opposite and decussate leaves, swollen nodes, and the dichasial arrangement of the reproductive spikes. Masses of polyplicate gnetalean pollen comparable to that of extant Welwitschia occur in the same bed as the megafossils. The morphology of D. potomacensis indicates that it was an herb or possibly a shrub. The growth habit of D. potomacensis and associated plants, combined with the sedimentary occurrence of the fossils, indicate that this species and perhaps related taxa were important components of early successional vegetation during the mid-Cretaceous.Item Dispersed Angiosperm Cuticles(1989-08) Upchurch, Garland R.Dispersed leaf cuticles are the second most abundant component of the angiosperm fossil record, but the study of dispersed angiosperm cuticles is still in its infancy. This paper reviews previous studies of dispersed angiosperm cuticles and discusses important features of cuticular anatomy and the occurrence of dispersed cuticles in the rock record. The stratigraphic density of dispersed cuticles is second only to that of pollen and spores, and dispersed cuticles more closely reflect local flora than palynomorphs. This means that dispersed cuticles are best suited to studies that require both greater facies resolution than what is obtainable for palynomorphs and greater sampling density than what is obtainable for megafossils. Reconstruction of paleocommunities/paleovegetation has been the most common use of dispersed cuticles, but other potentially productive uses include the reconstruction of paleofloras and analyses of angiosperm diversification and extinction.Item Latest Cretaceous and earliest Tertiary dispersed plant cuticles from Seymour Island(National Science Foundation, 1989-11) Upchurch, Garland R.; Askin, Rosemary A.No abstract prepared.Item Early Astronomy in Texas(Texas State Historical Association, 1990-01) Evans, David S.; Olson, Donald W.No abstract prepared.Item Cenomanian Angiosperm Leaf Megafossils, Dakota Formation, Rose Creek Locality, Jefferson County, Southeastern Nebraska(Dept. of the Interior, U.S. Geological Survey, 1990-01) Upchurch, Garland R.; Dilcher, David L.The leaves described in this report comprise the first assemblage of early flowering plant leaf megafossils to be accorded formal systematic treatment using modern methods of foliar architecture and cuticular anatomy. The 20 species of dicotyledonous leaves are described from a new locality in the Dakota Formation of Nebraska, near Rose Creek (Rose Creek locality). Seventy percent of the species represent either subclass Magnoliidae or forms with a similar grade of foliar architecture. Among Magnoliidae, species are assignable to the orders Magnoliales and Laurales, and one species shows resemblance to Illiciales. Although three species have strong similarities to one extant family (Lauraceae, or the laurel family), most species of Magnoliidae or magnoliid-grade foliage possess generalized features or combine the characteristics of two or more extant families. One species possesses unique features of foliar architecture that represent an unsuccessful 'experimental" design. Two species of Rosidae are present in the flora, and these combine features of foliar architecture that today are restricted to either compound-leaved or simple-leaved families. The leaves examined in this study show little evidence for fragmentation prior to burial and are preserved in a sequence of rooted mudstones containing brackishwater bivalves (including one specimen in life position); thus, the leaves represent predominantly local, brackish-water vegetation. This indicates that flowering plants evolved the ability to tolerate greater-than-freshwater salinities by the Cenomanian. The vegetation represented by the Rose Creek leaf remains shows few similarities to modern mangrove swamps but instead is most analogous to brackish-water swamps that occur inland from mangrove swamps.Item Lincoln and the Almanac Trial(Sky Publishing Corp., 1990-08) Doescher, Russell L.; Olson, Donald W.No abstract prepared.Item Paul Revere's Midnight Ride(Sky Publishing Corp., 1992-04) Olson, Donald W.; Doescher, Russell L.No abstract prepared.Item Automated Natural Language Evaluators - (ANLE)(1993-12) Kaikhah, KhosrowBy the turn of the century, it is expected that most computer applications will include a natural language processing component. Both developers and consumers of NLP systems have expressed a genuine need for standard natural language system evaluators. Automated natural language evaluators appear to be the only logical solution lo the overwhelming number of NLP systems that have been produced, are being produced, and will be produced. The system developed here is based on the Benchmark Evaluation Tool [7] and is the first attempt to fully automate the evaluation process. This effort was accomplished in two phases. In phase one, we identified a subset of the Benchmark Evaluation Tool for each class of NLP systems. And in phase two, we designed and implemented a natural language generation system to generate non-causal semantically meaningful test sentences. The generation system can be queued for each class of NLP systems. We followed an Object-Oriented Design (OOD) strategy. In this approach all concepts, including semantic and syntactic rules, are defined as objects. Each test sentence is generated as a chain of words satisfying a number of semantic, syntactic, pragmatic, and contextual constraints. The constraints imposed on the generation process increase dynamically while the sentence is being generated. This strategy guarantees semantic cohesiveness while maintaining syntactic integrity. In this approach, syntactic and semantic knowledge were utilized concurrently in word-objects. Each word-object is an independent knowledge source with local knowledge that can decide whether it can be a part of the sentence being generated, when called upon by the sentence-generator to join the chain.Item The Boston Tea Party(Sky Publishing Corp., 1993-12) Olson, Donald W.; Doescher, Russell L.No abstract prepared.Item The Megaflora from the Quantico Locality (Upper Albian), Lower Cretaceous Potomac Group of Virginia(Virginia Museum of Natural History, 1994-01) Upchurch, Garland R.; Crane, Peter R.; Drinnan, Andrew N.Item D-Day: June 6, 1944(Sky Publishing Corp., 1994-06) Olson, Donald W.; Doescher, Russell L.In this article Donald Olson and Russell Doescher explain why the advancing tide on D-day in 1944, rising as swiftly as a foot every 10 minutes, drove many Allied demolition teams toward the sea wall before they were able to clear gaps through German obstacles in Omaha Beach. As a result, the early assault waves had to slog forward through mined stakes, ramps, and "hedgehogs," as portrayed in this still photograph from 'The Longest Day,' the classic 1962 film about the Normandy invasion.Item Dating Ansel Adams's "Moon and Half Dome"(Sky Publishing Corp., 1994-12) Olson, Donald W.; Doescher, Russell L.; Burke, Amanda K.; Delgado, Mario E.; Douglas, Marillyn A.; Fields, Kevin L.; Fischer, Robert B.; Gardiner, Patricia D.; Huntley, Thomas W.; McCarthy, Kellie E.; Messenger, Amber G.ON A COLD and clear winter afternoon some three decades ago, Ansel Adams set up his tripod in Yosemite Valley and focused a Hasselblad camera on the distinctive profile of the mountain known as Half Dome. He waited as the Sun sank closer to the horizon and the long afternoon shadows extended across the granite cliffs. Adams had photographed Half Dome hundreds of times over the years, but on this day he captured an especially remarkable image that included a waxing gibbous Moon rising just north of the monolith. He discussed this photograph in his Autobiography.