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Highlights
from 2007
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Pre-screening Review
Latino
Initiatives Fund
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NMNH Home | What's New ? | Calendar of Events | Information Desk | Search |
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Research
Abstracts |
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The
Role of Water in Oxidizing the Earth’s Mantle
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Rebecca Fischer Elizabeth Cottrell,
Ph.D.
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To constrain the relationship between the oxidation state and water content of the mantle below subduction zone volcanoes, we measured the water concentration and oxidation state of iron in volcanic melts. Our investigation included microanalysis of eighteen olivine-hosted melt inclusions, each approximately 100 microns in diameter, from a variety of subduction zones. Unlike lavas, which degas during volcanic eruptions, melt inclusions have the unique ability to preserve the water concentrations present during their formation. We measured the water contents of our samples using Fourier transform infrared (FTIR) spectroscopy, and determined their oxidation state using X-ray absorption near-edge structure (XANES) spectroscopy at a synchrotron radiation source. The high x-ray flux allowed us to measure the oxidation state of regions only nine microns across - orders of magnitude smaller than can be analyzed by the more traditional techniques of wet chemistry or Mössbauer spectroscopy. This is the first data set of its kind that we know of. We find a positive correlation between the melt inclusions' water contents and oxidation state, suggesting that water does act as an oxidizing agent in the Earth. There is significant debate over the oxidation state of the mantle over time and water's role in this process. Some recent research has indicated that the mantle beneath wet subduction zones is no more oxidized than the mantle beneath dry ridges; however, our data suggests that this is not the case. The relationship we found is consistent with water's oxidizing role in the mantle, supporting the idea that subduction zones are more oxidized than ridges due to their higher water content. We offer two possible mechanisms to explain our results: that the correlation we discovered is due to water oxidizing the oceanic lithosphere during its transit across the sea floor, or that water oxidizes the iron in the mantle during the melt generation process. This research was supported by grants and donations to the Research Training Program. |
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Morphology
and DNA Barcoding of the Ant Genus Pheidole: Are they congruent?
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Laura Florez Ted Schultz, Ph.D.
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Using specimens from an ant leaf-litter biodiversity survey from Guyana, the usefulness of DNA barcoding was tested for identifying Pheidole nominal species and morphospecies and for suggesting possible cryptic species. The results revealed correspondence between the morphologically identified species and the species suggested by DNA barcoding, and also proposed the existence of several distinct taxonomic units within the formerly identified Pheidole ruida specimens in our data set. In addition, DNA barcoding proved to be an efficient tool for associating major and minor castes within the same species, an important advance because the taxonomy of this genus is based largely on the major caste. A variety of protocol modifications were tested, providing useful improvements for dealing with massive sampling and low yields in DNA extraction from automated, high-throughput procedures. Applied to the genus Pheidole, DNA barcoding has shown consistency as a species identification method. However, it is important to keep in mind its purpose as a tool for species identification rather than description, and the need to integrate it with ecological, morphological and behavioral analyses in order to draw valid conclusions about taxonomy or evolution. This research was supported by grants and donations to the Research Training Program. View my powerpoint presentation |
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Reproductive
System Modification in Foam-Nesting Frogs
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Andrew Furness Roy McDiarmid, Ph.D.
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Leptodactylus is a South American genus of frogs made up of foam-nesting species. This genus is particularly interesting because the group contains a gradation of foam-nesting forms representing an adaptive trend towards a more terrestrial mode of reproduction (Heyer, 1969). In all foam-nesting species described in the literature, and those examined in this study, the posterior region of the oviduct shows a definite enlargement. This enlarged region is actually comprised of a series of oviducal folds that are compacted together into what has formerly been called a 'foam gland' (Coe, 1974; Kabisch et al., 1998). The secretion that is beaten into a foam nest by rhythmic leg movements is almost certainly produced in this enlarged region of the oviduct. Data were collected on the external morphology and histology of this 'structure' from representative species across the genus Leptodactylus and other closely related taxa. Even though all foam-nesters have an enlarged and compacted region of the posterior oviduct considerable variation exists in size and structure among species. This interspecific variation likely corresponds to the breeding behavior of the individual species and the size, type, and location of the foam nest. This research was supported by grants and donations to the Research Training Program. |
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A
Numerical Taxonomic Study of Muhlenbergia montana
and M. filiculmis (Poaceae: Chloridoideae) |
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Emma Harrower Paul Peterson, Ph.D.
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The grass (Poaceae) genus Muhlenbergia Schreb. is a large and widely variable group with 147 species found in the Western Hemisphere. Muhlenbergia montana (Nutt.) Hitchc. is an important range grass found in the southwestern United States, Mexico, and Guatemala. Muhlenberiga filiculmis Vasey has a restricted distribution and is found only in the southwestern United States. Both species are found on rocky slopes and dry meadows between 1400-3400 meters. To identify the characters best used to differentiate between these two species, 18 characters were measured on 114 specimens from the United States National Herbarium. Ninety-eight percent of all individuals were properly classified in the discriminant analysis, with only two specimens of M. filiculmis being misclassified. Principal components analysis also separated M. montana and M. filiculmis into two groups. Muhlenbergia filiculmis can be distinguished from M. montana by having shorter panicles, shorter and narrower leaf blades, shorter lemmatal awns, shorter leaf sheaths, and shorter culms. A key to the two species is given. This research was supported by grants and donations to the Research Training Program. View my powerpoint presentation |
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Investigating
Diversity of the Freshwater Medusa Craspedacusta sowerbii
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Santiago Herrera Steve Cairns, Ph.D. |
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Craspedacusta sowerbii named by Lankester in 1880 is by far the most common freshwater medusa jellyfish species in the world. It has a cosmopolitan distribution, been found in every continent but Antarctica, specially in sub-tropical and temperate zones. Even though the presence of jellyfishes in freshwater environments (such as: ponds, reservoirs, lakes, and rivers) is quite unfamiliar for most people, this animal is a regular inhabitant of those systems during the warm months of the summer. There are more than 1000 sights, in average, every summer in the United States alone (Peard T. personal communication). The species was described based solely in morphological characteristics. But, the molecular data (16S nuclear marker) generated in this research shows two well-differentiated clades, that might correspond to two different cryptic species under the same name of C. sowerbii. One of these clades groups only specimens from Europe and the other one from all around the world. Within the "Global" clade were found 5 different haplotypes, which give an account of the overall diversity that might be hidden under the same morphological features. Also a very unique sample from Arizona was identified as a specimen belonging to the Limnocnida sp. genus, which has only been reported to occur in Africa and India. This could constitute a evidence of a species introduction. This research was supported by grants and donations to the Research Training Program. |
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Three
New Species of Monotocheirodon (Teleostei: Characiformes)
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Addison Kemp Stanley Weitzman,
Ph.D.
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Three new species of the genus Monotocheirodon of the family Characidae are described. This genus was previously only known from the type species, Monotocheirodon pearsoni, briefly described in 1922 by Eigenmann from specimens collected in the rio Beni in Bolivia. The genus and M. pearsoni are herein redescribed from the syntype series as well as other specimens collected from a site near the type locality. The new species of Monotocheirodon were collected from the Madre de Dios drainage in Peru. Though all four species are inseminating, males of all three new species have a distinct intromittent organ absent in the males of M. pearsoni. This is the first occurrence of a true intromittent organ within the characid family. M. sp A males are easily distinguished from M. sp B and M. sp C males by short length of their organ. M. sp B and M. sp C males both possess long organs and modified pelvic fins, but can be distinguished from each other based on dentition and gonad structure. Comments on the implications of the morphology and histology of the reproductive characters of these fishes are also offered. This research was supported by grants and donations to the Research Training Program. View my powerpoint presentation |
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Phylogeny
Reconstruction and Trends of Floral Evolution
in Heliconia subgenus Heliconia (Heliconiaceae) |
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Laura Lagomarsino W. John Kress, Ph.D.
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Most of the 200 species of Heliconia (Heliconiaceae), an economically and ecologically important genus of tropical monocots, are native to the Neotropics. Heliconias are characterized by large banana-like leaves with peniparallel veination and colorful bracteate inflorescences. The nectar-rich flowers borne inside the bracts are pollinated by hummingbirds. Despite the fact that the ecology of heliconias is well studied, little is known about the evolutionary relationships among species. Five molecular loci representing two genomes (psbA-trnH [chloroplast], trnL-F [chloroplast], rpb2 [low-copy nuclear], ETS [nuclear ribosomal], and ITS [nuclear ribosomal]) were amplified and sequenced for use in the reconstruction of a phylogeny for Heliconia subgenus Heliconia. Phylogenetic relationships were hypothesized using principles of parsimony, maximum likelihood, and Bayesian inference and the results from the analyses were compared for topological similarity. The patterns of floral evolution within the subgenus were then studied using various phylogenetic comparative methods, including ancestral state reconstruction using squared change parsimony to determine direction in trait evolution and independent contrasts to examine correlation between traits. Quantitative traits, including corolla size, nectar chamber dimensions, and floral curvature were measured from spirit-fixed Heliconia flowers and qualitative color data were ascertained from photographs taken in the field. These results were used to make inferences about co-evolution between Heliconia subgenus Heliconia species and their hummingbird pollinators. This research was supported by grants and donations to the Research Training Program. View my powerpoint presentation |
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Ammonia
test morphology: a quantitative analysis of variation
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Benjamin Linzmeier Marty Buzas, Ph.D.
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Traditionally test morphology has been used to resolve species differentiation in foraminifera. In recent years molecular methods have come into vogue, but are not practical for comparison with fossil specimens. Test morphology isn't strictly dictated by genetics, but can be influenced by environmental factors experienced during ontogeny. Replicate samples of specimens were collected from the Indian River Lagoon's St. Lucie Inlet on the east coast of Florida. Water properties were recorded when samples were taken. Specimens living at the time of collection were sorted, imaged and measured. Thirty-two measurements were made of each specimen using Image pro plus ver. 5.0, by manual and automated techniques. Through multivariate analysis, this study will resolve differences between specimens and observe probable changes in morphology due to variations in salinity. This research was supported by grants and donations to the Research Training Program. |
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The
Source of Hopewell Extraterrestrial Metal and Its Anthropological Implications
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Amy Marquardt Tim McCoy, Ph.D.
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This study involves an investigation into the source and manufacturing techniques of Hopewell meteoritic iron necklace beads (2,336±250 BP) found in Havana, Illinois and implications for Hopewell trade routes. An examination of textural and geochemical data in the literature suggests the source of the Havana beads may be an iron meteorite found near Anoka, Minnesota. This work includes a comprehensive microscopy and microchemical study to more rigorously evaluate the Havana-Anoka provenance relationship. Electron and laser probe microchemical analyses were performed on the Havana bead and the Anoka iron to determine the source of the beads. Additionally, laboratory simulations were performed to discern manufacturing techniques. Results show significant microchemical similarities between the Havana bead and Anoka iron, suggesting Anoka is very likely the source material for the Havana artifacts. Microscopic examination of manufacturing simulations indicate the iron was cold-worked followed by heating at approximately 700°C, a temperature readily achievable in wood fires. The Anoka iron was likely traded by local people to a region knowledgeable in metal working technology where the iron was made into beads and finally traded to Havana as a finished good. This research was supported by grants and donations to the Research Training Program. View my powerpoint presentation |
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Quantifying
Diseases in Societies without Epidemiological Record
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Cecily Marroquin Alain Touwaide, Ph.D.
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Although the pioneers of modern medicine recorded the uses and medicinal benefits of therapeutics, there is little evidence of the ancient Mediterranean’s population health. In an attempt to recover the epidemiology, this study examines the relationship between the degree to which each disease pervades medicinal literature to the quantitative importance of the disease in society. Simply, the more prevalent a disease is, the more it will be discussed in the texts. To verify the hypothesis, pharmacological manuals from the 20th century were used to extract the amount of text dedicated to each disease as well as therapeutic agents listed. Morbidity rates throughout the century were also acquired and used to construct a correlation. By comparing the literary figures alongside the epidemiological statistics, preliminary results support the predictions made at the onset of the study. This research was supported by grants and donations to the Research Training Program. View my powerpoint presentation |
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Sheep
and Goat Domestication in the Eastern Fertile Crescent:
The Application of Dental Aging Techniques |
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Suzie Pilaar Melinda Zeder, Ph.D.
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The Zagros Mountains of Iraq and Iran are home to prime assemblages of sheep and goat remains which offer early evidence of the transition from hunting to herding and the beginnings of livestock domestication. This study focuses on applying techniques for determining age | |
