Tina L. Graver - Investigation of plant functional traits in the Flint Hills, Kansas (Mentor: Kendra McLauchlin).  Plant functional traits give insight to strategies for competition in a given environment.  Land use practices such as burning and grazing are thought to have an impact on these functional traits. In addition, ecologists commonly use functional group characteristics (i.e., forb, grass, legume) to investigate prairie dynamics, such as dominance. I investigated whether functional groups, land management and dominance could be used to predict plant functional traits. I collected 135 plants from ten sites in the Flint Hills region of Kansas. For each plant, I measured leaf angle, thickness, area and mass. From these, I calculated leaf volume and density.  On average, grasses had a lower leaf thickness and density value than the forbs and legumes but had a higher leaf angle.  Differences in land management (burning and grazing) did not significantly affect plant traits in any functional group or dominance category.  These results indicate that ecological factors such as functional group and dominance are better factors for predicting functional traits than management techniques are.

Kelsey Hixson-Bowles - Generality of nematode bacterial defense pathways (Mentor: Michael Herman).  While the importance of environmental change has been established we have yet to understand organismal responses to change for many species in the soil environment. Even further, understanding the genetic responses to these changes will provide an explanation of the functionally important cellular responses that drive ecology. A number of important pathways have been discovered to regulate nematode responses to their bacterial prey and we seek to determine how general these pathways are to native nematodes feeding on soil bacteria? I exposed six C. elegans innate immunity pathway mutants (tol-1, dbl-1, pmk-1, sek-1, daf-2, and daf-16) to five bacteria isolated from native tallgrass soil (Variovorax varians, Gordonia rupripertincta, Arthrobacter luteolus, Arthrobacter gandavensis, and Burkholderia cepacia), using E. coli and wild type, C. elegans as controls. I observed the nematode worms daily in order to measure longevity which gives an indication of detrimental bacterial effects. I found that there was variation in the mutants’ responses to the bacteria suggesting that some of these C. elegans pathways are involved in defense against these bacteria while other defense pathways remain to be discovered.

Brian V. Kearns - Change in vocal culture of Spiza americana based on density, distance, and habitat (Mentor: Tim Parker).  The Dickcissel (Spiza americana) is a songbird that migrates between a breeding range in the central Great Plains of the United States and winter range in northern South America.  These birds sing a song which varies among individuals as a function of distance. Individuals close to each other tend to sound similar, and those far away from each other often sing very different song types. This makes them excellent for examination of the evolution of vocal culture in a spatial context.  We recorded songs of numerous Dickcissels on transects following rural roads in landscapes dominated by either row crops or prairie to seek to understand how Dickcissel songs vary in environments with different densities and distances between individuals.  We used Raven, a song analysis computer program developed by the Cornell Laboratory of Ornithology, to produce sound spectrograms to observe qualitative variations in song components and patterns.  This analysis led us to the conclusion that distance between individuals on a relatively small scale has a smaller effect on variation than does density.  Areas with higher densities of birds showed lower variation in song type along the length of the transect than did areas with low densities of Dickcissels. This suggests that close proximity between neighboring male Dickcissels facilitates song sharing.

Rose Keith - Development of simple sequence repeat loci in Helianthus maximilianii (Mentor: Mark Ungerer).  Simple sequence repeats (SSRs), also known as microsatellites, have proven to be extremely useful tools in the study of population genomics.  Short sections of the genome consisting of multiple repeats of a series of two or more nucleotides, microsatellites show among other characteristics an increased rate of mutation and polymorphisms, making them ideal for use in studies of closely-related populations.  One such population of interest is Helianthus maximilianii, a sunflower species which shows wide clinal variation across its latitudinal range in traits such as height, rate of growth, leaf area, age at flowering, and flower size.  The ongoing goal of this study is to compare and relate phenotypic differences across the latitudinal cline with genetic differences in and among geographically isolated populations within that range.  The necessary first step was the development of polymorphic microsatellite loci for use in measuring genetic diversity within those populations.  We designed primers using SSRs identifed within an EST library of Helianthus tuberosus, another perennial sunflower.  Amplification in H. maximilianii was tested with PCR and electrophoresis on an agarose gel with DNA samples from geographically diverse plants.  The primers that amplified well were run through an ABI capillary sequencer to determine the exact lengths and polymorphisms and heterozygosity within the samples.  Of the 60 primer pairs we tested, 40 amplified successfully and were run through the ABI sequencer.  Of those 40, 14 showed strong levels of polymorphism and heterozygosity and 12 more showed enough to also make them possible candidates for further use.  These primers will be used in a population genetics study of diverse H. maximilianii individuals and also tested for amplification in other diploid perennial Helianthus species.

Matt Nielsen - The genetics and evolution of cold tolerance within the Drosophila genus (Mentor: Ted Morgan).  The global distribution of the Drosophila genus means that its species are exposed to a wide range of temperature variation in their environment.  Because of this, cold tolerance is an important adaptation, which varies widely among both populations and species.  To identify genes contributing to cold tolerance/susceptibility, I identified 149 genes that are differentially expressed when a chill coma is induced by exposure to 0°C in the genetic model organism Drosophila melanogaster. To broaden this analysis to more of the Drosophila genus I quantified cold tolerance for 11 of the 12 Drosophila species with genomes sequenced by the Drosophila 12 Genomes Project.  As expected due to their variation in geographic ranges, there was remarkable variation in cold tolerance among these species with D. persimilis being the most resistant and D. ananassae the least. I then assessed the patterns of molecular evolution among these species for a set of genes with altered expression during a chill coma, all of which demonstrated purifying selection.  However, I found no clear patterns of interspecies evolution related to the cold associated genes.

Nathan Pavlovic - Nitrogen and phosphorus addition affect microbial polar lipid metabolism in a grassland ecosystem (Mentors: Richard Jeannotte and Ruth Welti).  Nutrient deposition in grassland systems has been studied extensively for its effects on aboveground processes, and important relationships with aboveground net primary production, plant species composition, and other variables have been identified.  However, relatively little is known about belowground microbial processes in response to fertilization regimes. The soil contains a wide diversity of microorganisms, including bacteria, fungi, and algae, and these microbes play important roles in nutrient cycling and soil aggregation.  In addition, they may be used as indicators of ecological change. Thus, the elucidation of microbial responses to changes in nutrient composition of the soil can provide insight into larger systemic processes. In specific settings, microbes have been shown to adapt to nutrient limitation by changing the composition of their membrane lipids.  However, such adaptations have yet to be investigated in terrestrial ecosystems. This study examines the resulting dynamics of microbial lipid metabolism in response to fertilization treatments in a grassland ecosystem.  Specifically, we studied the effects of nitrogen and phosphorus fertilization on the abundance of soil lipids in a native tallgrass prairie in the central United States. Soil samples were collected from control, nitrogen, phosphorus, and nitrogen and phosphorus fertilization treatments on annually burned, unmowed plots at the Konza Below Ground Plot experiment before and after the annual application of nutrients.  Using tandem mass spectrometry to quantify more than 400 lipid species from the soil, we investigate microbial response and adaptation to changing levels of nitrogen and phosphorus.  We find that microbial membrane metabolism in soil is largely stable across fertilization treatments, though small changes are apparent.  The shifts we observe in lipid composition suggest that, as has been observed in above-ground processes, nitrogen is the primary limiting nutrient in belowground processes.  However, we find that changes in phosphorus concentration can also significantly affect microbial lipid metabolism.  These results contribute to our emerging understanding of both belowground nutrient dynamics and microbial adaptations to nutrient limitations.

Dumi Presuma – Variables affecting nitrogen uptake in prairie streams (Mentors: Alex Reisinger and Walter Dodds).  Streams provide many services including sources of drinking, irrigation, and cooling water; energy; transportation; recreation; and waste disposal.  Nutrient concentrations in stream water seem to be increasing dramatically which may be the cause of eutrophication in large bodies of water supported by streams.   Nutrient uptake in streams is the process in which available nutrients are taken up for assimilatory processes (such as growth and metabolism), or dissimilatory processes (e.g., electron acceptor in anaerobic respiration). The purpose of this study is to measure the rate of uptake in streams and to compare how canopied and non-canopied portions of the stream affect uptake. The nutrient addition technique is a commonly used approach, and is preferential when trying to determine variable solute-specific characteristics.  Using a previously determined in-stream ambient ammonium concentration as our base flow concentration we subsequently increased the nitrogen concentration 10, 20, and 35 fold by adding NH₄Cl. We chose these concentrations so as to have a detectable change in concentration as ammonium is assimilated; ammonium is preferred nitrogen species in streams it is readily taken up. We also performed a long term chamber (artificial stream) experiment to determine the effect highly preferred ammonium (NH₄Cl) uptake has on the nitrate (KNO₃) uptake. The conservative (non-reactive) solute is added to our solution for the purpose of detecting how far our solution travels and to observe how much dilution occurred to our addition.   We understand that algae are more abundant in areas where sunlight is more readily available, this led us to believe those larger populations in non-canopied regions are affecting the rate of up take more so then smaller populations under canopy. Canopy cover appears to affect ammonium uptake, but the factors that are affected by canopy cover are more intricate then originally anticipated. Our findings can be applied to various types in stream research so as to clarify which environments are better equipped for system-specific studies.

Zak Ratajczak - Positive micro-climate feedbacks lead to expansion of the shrub Cornus drummondii in tallgrass prairie: source water partitioning (d¹⁸O and dD), litter dynamics and leaf area index (Mentor: Jesse Nippert).  Conversion of tallgrass prairie to a mixed grass/shrubland is a marked trend in much of the Flint Hills Region, with associated decreases in plant diversity and changes in carbon cycling. Historic burn regimes are estimated to be every 3-6 years in the Flint Hills and woody vegetation was believed to be sparse. Curiously, there is expansion of Cornus drummondii in watersheds under four-year burn regimes at the Konza Prairie LTER Site, near Manhattan, KS. We investigated whether source water partitioning, shrub mediated changes in litter dynamics and changes in leaf area index (LAI) may be possible mechanisms of shrub expansion. To quantify source water partitioning, we measured the d¹⁸O and dD of soil, C. drummondii stem water and Andropogon gerardii rhizome water, along transects cutting through eight different patches of C. drummondii. Preliminary results suggest that C. drummondii access deeper water sources than the competing A. gerardii. This has important implications given current climate change predictions that there will be an increase in winter precipitation in the flint hills, which recharges deeper water sources. We found the amount of herbaceous littler at the edge of shrub islands decreases with age while woody litter increases. C. drummondii older than 7 years having an average of 14.20 g of herbaceous litter, compared to an average of 47.40 g in nearby A. gerardii dominated sites. This change in litter may decrease fire intensity around patches of C. drummondii while increasing soil water retention. Concurrent with past studies, we found that patches of C. drummondii achieved significantly higher LAI than nearby grassland sights, with a highest average of 6.16. Taken together, our results suggest that once established, rates of C. drummondii expansion may increase. Therefore, increasing our understanding of mechanisms that lead to C. drummondii establishment, such as changes in fire regime, seed disperser populations and habitat fragmentation may prove to be most effective means of preventing woody expansion.

Rebecca Spurr - Landscape-level variation in temperature sensitivity of soil carbon respiration (Mentor: Joseph Craine). Organic carbon sequestered in soil comprises a significant portion of the global carbon pool.  The decomposition of organic carbon in soil to CO₂ is a significant flux to the atmosphere. With global temperatures forecast to rise, warming will generally increase the rate at which SOM is converted to CO₂.  However, the degree to which warming will deplete SOM is poorly known due to our limited understanding of the patterns of temperature sensitivity of microbial decomposition of SOM across different soil types.  Q₁₀, the factor by which respiration rate increases for a given 10 °C increase in temperature, is a measure frequently used to compare temperature sensitivity in respiration rates across soils.  An analogous measurement to Q₁₀ is the activation energy of a reaction, E_a.  The relationship between E_a, temperature, and the reaction rate (k) is described by the Arrhenius equation: k=Ae^-Ea/RT wherein R is the gas constant and A is the reaction-specific frequency factor.  A higher E_a value implies higher temperature sensitivity.  To explore the variation in temperature sensitivity across soils, we collected 72 0-20 cm soil samples from varying landscape position across Konza Prairie.  Soil moisture was standardized at 35% water holding capacity and 20 g replicate soil samples were maintained at 22 °C. Periodically, soils were incubated for 48 h at range of temperatures (10, 15, 20, 25, and 30 °C) and respiration rates measured over this period using an infrared gas analyzer.  We hypothesized that soils with higher relative respiration rates, i.e. more labile carbon, should have a lower E_a than soils with lower relative respiration rates. As upland soils are generally considered to have more labile C than lowland soils, we expected higher E_a in the upland soils than the shoulder, lowland, and riparian areas.  Our data supported the prediction that soils with a higher relative respiration rate were less sensitive to increases in temperature. Additionally, upland soils had higher relative respiration rates and lower E_a than soils from other landscape positions. Interestingly, the soils taken from Konza displayed a level of variation in E_a comparable to those in similar continental-scale studies conducted by Fierer et al (2006) and Craine et al. unpublished.  This suggests that variation in temperature sensitivity among soils, although somewhat predictable with simple measurements, varies on multiple scales. Further study will be required to better understand and characterize the patterns if we are to better predict the impact of global warming on the carbon cycle.

Gabriella Sterne - Dickcissel site fidelity and local vocal culture (Mentor: Tim Parker).  Vocalizations of male dickcissel (Spiza americana) tend to be more similar between neighbors than between males with distant and disjunct territories (Schook et al. in 2008 Auk).  This effect seems to be the outcome of learning song from neighbors, as is common in male oscine songbirds.  However, the spatiotemporal factors affecting the extent to which songbirds share songs within a site have yet to be investigated.  This study was undertaken in the interest of building increased understanding of whether site fidelity of individual birds influences the homogeneity of the song culture within a site.  REU students banded and monitored male dickcissels at five sites near Manhattan, Kansas during the summers of 2008 and 2009.  Of these five sites, two were on row-crop agricultural lands owned by the Kansas State University and three were grassland sites within the Konza Prairie Research Natural Area.  We made four visits to each site each year. I then performed statistical mark-recapture analysis to find the model that best predicted the observed pattern of re-sighting of birds.  The best model contained higher apparent survival probabilities (probability of neither dying nor emigrating) for birds living in cropland versus those in grassland, but held constant the probability of re-sighting birds in each habitat type.  These results support the hypothesis that dickcissels residing in agricultural sites have lower site fidelity than those residing in grassland sites. Additionally, based on preliminary qualitative analysis of songs recorded from banded birds, lower site fidelity for cropland birds may lead to less homogenous vocal cultures within agricultural sites.   Further quantitative analysis of the recorded dickcissel songs will be required to more thoroughly assess the link between site fidelity and local vocal culture homogeneity.

Maya Wilson - Ecology of the Texas horned lizard (Phrynosoma cornutum) in the Flint Hills of Kansas (Mentor: Eva Horne).  The Texas horned lizard is found throughout Northern Mexico and the south-central plains of the United States. While a considerable amount of research has been done on the Texas horned lizard in Texas, where it is considered threatened, not much is known about horned lizard ecology in other parts of its range, and additional research might prove useful in future conservation efforts.  Konza Prairie Biological Station is located in the northwestern Flint Hills of Kansas, and is near the northern border of this lizard’s range. We searched various habitats on Konza Prairie to measure and observe horned lizards. The areas where we found lizards all had ground cover estimates of less than fifty percent vegetation and were all in annually burned, ungrazed watersheds. Through much of the lizard’s range, harvester ants of the genus Pogonomyrmex make up a majority of its diet. However, harvester ants are not present in this region of Kansas. In an attempt to identify the ants that were being consumed in place of harvester ants, we collected ants from areas where lizards had been sited. We determined that ants of the genus Crematogaster are commonly present in the all the areas where ants were collected. Crematogaster lineolata is the most common ant species of this genus in Kansas, and are considerably smaller than harvester ants. If they are a primary food source, they may contribute to smaller body size in the horned lizards at Konza Prairie relative to those in southern regions of the range. Further field observations of feeding behavior are needed to confirm these ants as a food source. We observed one female in a recently excavated nest, and the site will be monitored until the eggs hatch. We will then be able to determine clutch and hatchling size for comparison to data in other areas of the range.