The Curatorial Voice: U.S. Institutions Exhibit the Ancient Andes

Two new exhibits on ancient Andean civilizations are open in the United States. Machu Picchu: Unveiling the Mystery of the Incas is a large traveling exhibition and Tiwanaku: Ancestors of the Inca is a smaller temporary exhibition that is not traveling. Both introduce North American audiences to objects and information that have never been exhibited in the United States and each includes some extraordinary artifacts. The two exhibits differ in many ways: Machu Picchu emphasizes information, archaeological science, and cultural history, whereas Tiwanaku focuses on art style and objects. The curatorial voice and point of view are strong in each exhibit, as is the institutional perspective of its originiating museum. In this respect these exhibits differ significantly from contemporary ones on ancient North America, which generally include the voices and points of view of descendant communities and others.     

The Effects of Ultraviolet Radiation on the Biology of Amphibians

SYNOPSIS. Potential causes for the global decline of amphibiansinclude habitat loss, disease, environmental contaminants andclimate changes. The diminishing ozone layer and consequentincrease of ultraviolet-B radiation reaching the earth's surfacehas been hypothesized to be a mortality factor, especially inhabitats otherwise undisturbed. We discuss the fundamental physicsof UV and types of biological damage after exposure. A deleteriouschange in DNA, especially the production of pyrimidine dimers,is a main effect of UVB exposure. Damaged DNA can be repairedby enzymes such as photolyase when organisms are irradiatedwith UVA or visible light. We review studies including laboratoryand field approaches on damage to amphibians from UVB exposure.Field studies in which embryos were exposed to natural sunlightor sunlight with UVB removed have shown conflicting results:some show increased embryonic mortality after UVB exposure,whereas others show that current levels of UVB are not detrimentalto amphibian embryos. The abiotic factors such as water depth,water color, and dissolved organic content of aquatic ovipositionsites effectively reduces UVB penetration through water andreduces exposure to UVB of all life history stages. Biotic factorssuch as jelly capsules around eggs, melanin pigmentation ofeggs, and color of larvae and metamorphosed forms further reduceeffectiveness of UVB penetration. We suggest areas of futureresearch to test the hypothesis of the causal connection betweencurrent UVB levels and amphibian decline.     

Autochthonous leaf assemblages as records of deciduous forest communities: an actualistic study

How well do autochthonous leaf assemblages reflect live plant communities? How do leaf assemblages accumulating over different time scales compare in paleoecologic information content? Forest-floor leaf assemblages accumulating over ten-day intervals (referred to here as short-term assemblages) and over a five-month season of leaf abscission (referred to here as a long-term assemblage) were compared with the surrounding community in a modern temperate deciduous forest in northern Ohio. Leaf number in the long-term leaf assemblage is strongly correlated with the abundance of taxa (stem number) around the accumulation site and weakly correlated with both average taxon size (stem circumference) and average taxon distance from the accumulation site. Of the variance in leaf number, 45% is explained solely by stem number and 67% by stem number and average distance together. Average size explains an insignificant amount of the variance in leaf number. Like the long-term assemblage, leaf number in the short-term leaf assemblages is usually strongly correlated with stem number and usually weakly correlated with average taxon size and average taxon distance. However, these patterns are not consistent, and the correlations are highly variable. Similarly, there is high variability in the degree to which stem number, average taxon size and average taxon distance account for variance in leaf number. Short-term leaf assemblages are characterized by great fluctuations in taxonomic relative abundance, caused by seasonal variation in the timing and rate of leaf abscission among taxa. While autochthonous leaf assemblages accumulating over several months can reflect the surrounding community with fair accuracy, leaf assemblages accumulating over shorter time spans are inconsistent records of the surrounding community. The depositional circumstances producing short-term assemblages (i.e. event burial) may result in well-preserved specimens, but community data from such assemblages should be treated with caution and, if possible, compared with data from contemporaneous long-term assemblages.Paleobotany, taphonomy, actualism, paleocommunity reconstruction, time-averaging. Keith H. Meldahl, Damon Scott and Karen Carney, Department of Geology, Oberlin College, Oberlin, Ohio, 44074, USA; 6th June, 1994; revised 8th February, 1995.     

State Bias and Women's Status

There is another bias beside male bias present in interpretive works about women. I call it state bias to refer to a hierarchical way of conceptualizing characteristic of state societies. As regards women, it assumes that sexual equality can come in only one form: androgyny. But recent ethnographic studies and reexaminations of data suggest that for nonstates, equality may take various forms from both the perspectives of outside observers and members of the society as well.     

Nucleosome Phasing in Tetrahymena Macronuclei1

Core-protected DNA can drive only 60% of the Tetrahymena thermophila macronuclear genome into duplexes in hybridization experiments. This core-protected DNA therefore contains only a subset of the genome complexity. We interpret this to mean that a large fraction, if not all, of the genome is phased with respect to nucleosome placement. Among the sequences present in total DNA and absent from core-protected DNA are most of the sequences containing N⁶-methyladenine (MeAde) residues, consistent with our previous demonstration that most of these residues lie in linker DNA. We show that these results are not due to artifacts resulting from the small size of the DNA driver, nor are they due to any sequence preferences exhibited by staphylococcal (staph) nuclease. This is the first evidence that nucleosome phasing may be a bulk genome characteristic.     

Reduced N cycling in response to elevated CO2, warming,and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

Field‐scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a seminatural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO₂), warming, and extended summer drought in all combinations. Here, we report on the short‐term responses of the nitrogen (N) cycle after 2 years of treatments. Elevated CO₂ significantly affected aboveground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co‐dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Belowground, elevated CO₂ had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH₄⁺ consumption, gross mineralization, potential nitrification, denitrification and N₂O emissions. Drought reduced belowground gross N mineralization and decreased fauna N mass and fauna N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue in response to elevated CO₂, as well as drought‐induced decreases in litter N production and fauna N mineralization prevailed in the full treatment combination. Overall, the simulated future climate scenario therefore lead to reduced N turnover, which could act to reduce the potential growth response of plants to elevated atmospheric CO₂ concentration.