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POSTER #13:
Phenology of Milkweed and Monarch Butterflies with Climate Variation
Jessica Craft and Hannah Cha
Dr. Elsa Cleland
Monarch Caterpillars along with Milkweed were placed into five treatments with different temperatures. Each treatment was monitored to find out the average length of time spend in each life stage: larva and pupa. The plant's response to the temperature and Monarchs was also recorded. The milkweeds were eaten down while the Monarchs were in their larva and they regenerated during the pupa stage. Results showed a trend of decreased time spent in each life stage in the higher temperatures. The eating trials were carried out to determine the effects on temperature each catepillar's metabolism, the results confirmed that larger caterpillars consume more food than the smaller ones.
POSTER #14:
Swimming Ability of Sea Urchin Larvae in the Presence of Food and Turbulence
Taylor Debevec
Dr. Michael Latz
Many marine invertebrates begin their lives as a planktonic larva. Little is known about how environmental conditions affect the critical larval phase. Two important environmental factors are food availability and turbulence. Food is limited and patchy in the ocean, and patches are often formed by physical factors such as turbulence. Yet we do not know the ability of larvae to remain within a patch of food in the presence of turbulence. In this experiment we analyzed the swimming capabilities of larvae of the white sea urchin, Lytechinus pictus, while exposed to different shear forces and food conditions. L. pictus larvae were videotaped while exposed to different shear levels in the presence of either algal food or algal filtrate at two different larval stages. The film was then analyzed using a computer program, ImageJ, which provides the x and y coordinates of the trajectory paths of each larva. The x and y coordinates were used to calculate the Net to Gross Displacement Ratio (NGDR), which is a measure of how straight the trajectories are. One-way ANOVA was performed to test whether the differences were significant between the different treatments. Both the gastrula and 4 arm larvae had NGDRs that were significantly different and lower at the 1.2 s-1 shear level compared to the higher shear levels. This suggests that at 1.2 s-1 shear and below the larvae can control their swimming, but at higher levels they behave as passive particles. These results suggest that L. pictus larvae that encounter a food patch in the ocean will be able to actively swim and stay within the patch because shear levels are typically below 1.2s-1 in the ocean where food patches occur.
POSTER #15:
Comprehensive metagenomic characterization of salt-impacted microbial communities
Tobin Hammer
Dr. Eric Allen
The community genomics approach can provide insight into the ecological and evolutionary dynamics of microbes as they exist in nature. However, the high diversity of most microbial communities precludes genome assembly from all but the most “extreme” habitats. Aquatic environments with 20-30% salt are typically dominated by one or a few species of haloarchaea and provide a tractable system for metagenomic characterization. We analyzed more than 500,000 shotgun and fosmid end-sequences from spatiotemporally distinct sites in the hypersaline Lake Tyrrell system, aiming to reveal the ecological structure and functional potential of halophile communities and their response to salinity and seasonal changes. Bioinformatic binning of assembled fragments and unassembled reads indicated a replacement of haloarchaea by bacteria in lower-salinity samples, as well as a shift in taxonomic composition between winter and summer samples. A shotgun sequence assembler reconstructed the near-complete genomes of two novel, coexisting species of Haloquadratum, a globally distributed, square-shaped haloarchaeon. In addition to genome assembly, the deep level of metagenome sequencing enabled the analysis of patterns of genetic variation among individuals using alignment tools. The two Haloquadratum populations are relatively clonal and resistant to interspecific recombination, supporting previous assertions that the species is coherent. In contrast, other haloarchaeal populations are significantly more variable, containing a high abundance of single nucleotide polymorphisms and other forms of genetic heterogeneity. This variability most likely affected genome assembly for these groups, which was less successful despite a very large amount of available sequences. Using metagenomic data, we have reconstructed novel Haloquadratum genomes directly from the environment, and show that salt-impacted communities are dynamic consortia responsive to environmental fluctuations and composed of populations with distinct evolutionary signatures.
POSTER #16:
The Role of Carbon Amendments in Establishment of Artemesia californica Seedlings: An Experiment in Ecological Restoration
Francesca Henderson
Dr. Elsa Cleland
This experiment examines the competition between the native Artemesia californica costal sage plant and the extremely invasive Crystalline ice plant. The two species are competing for reign over the knoll at the Scripps Costal Reserve, in San Diego California. Native plants grow better in poor soil condition because that is what the natural terrain that they have adapted to live in is like. Most exotic species are the opposite so native species have a competitive advantage under low nutrient conditions. experiment hypothesizes that by adding carbon to the soil will favor the growth of the Artemesia californica. Carbon amendments such as rice straw, or woody mulch are frequently used in restoration and acts to reduce soil nutrients, by increasing soil microbial biomass. Also, activated carbon, or charcoal, is sometimes used to remove toxic compounds from soil, and can facilitate restoration of natives. The unique data and results from this experiment will be very helpful for determining future restoration practices in costal areas, many of which are faced with rapid native habitat destruction.
POSTER #17:
Effects on Primary Production from Nutrient Limitations in Semi-arid Grasslands
Frances Ho and Leah Murphy
Dr. Elsa Cleland
We will be analyzing the effects on primary production from different nutrient limitations in semi-arid grasslands. The nutrient types will be potassium, nitrogen, and phosphorus and there will be varying levels of each nutrient in each plot of grass. The biomass from each plot of grass will be cut and sorted into forbs, grasses, legumes, and litter and weighed separately to see the effects the nutrient limitations have on biomass variability as well as differences in types of primary production according to the nutrient limitations.
POSTER #18:
Chlorophyll fluoresence as a measure of photosynthetic capacity for Encelia farinosa along gradients of soil nitrogen and water availability
Rachel Jao
Dr. Elsa Cleland
We are looking at the success of plants given different amounts of water and nitrogen. Our hypothesis is that the plants will have greatest photosynthetic capacity with the highest levels of both nitrogen and water available. We tested this by examining three replicates of Encilia farinosa planted in 8x8 water/nitrogen gradient plots and measuring the effects of various amounts of water and nitrogen on the plant using a fluorometer. We were able to gather this data and present it in a graph which shows us where the greatest and least success lies.
POSTER #19:
Plant productivity patterns in a greenhouse experiment varying soil water and nitrogen availability
Christina Lee
Dr. Elsa Cleland
A look at specific Californian plants in a controlled greenhouse environment, analyzing the different effects as a result of varying amounts of water given as well as varying levels of soil nitrogen. We examined the biomass of each sample in a given plot, and compared it to the amount of water and nitrogen availability in the soil.
POSTER #20:
Above and Below Ground Growth Allocation of 'Encelia californica' Through Varying Nitrogen and Water Levels
Lauren Oquita
Dr. Elsa Cleland
This greenhouse controlled study examined the above and below ground growth responses of native Californian shrubs exposed to various levels of nitrogen and water. 'Encelia californica' seedlings were exposed to eight concentrations of nitrogen added directly to the soil during initial set up. Each level of nitrogen addition was subjected to eight levels of water. Comparisons were then made between the allocation of above ground growth to the below ground growth. The ratio of nitrogen to water was analyzed in conjunction with the sprout and root growth to determine which levels produced the largest biomass. Low water levels consistently produced the lowest growth. Nitrogen levels had a similar growth pattern at low levels. Preliminary observations seemed to favor soil with a medium level of nitrogen and water mixture.
POSTER #21:
Using Ion Exchange Menbranes to Measure Soil Nitrate and Ammonium Availability
Christoff Saaiman
Dr. Elsa Cleland
More nitrogen is fixed annually by human activity than by all combined natural pathways. I evaluated soil nitrate and ammonium availability by burying ion exchange membranes attached to plastic spikes in two different soil compositions. One block consisted of the plant Encelia, and the other block had Encelia and the invasive grass Avena growing together. It was expected to see a higher degree of nitrate uptake by the roots of the Encelia and Avena species together than with only the Encelia. As part of a correlative study, it is hoped that the exchange membrane technique can be a helpful tool for measuring soil nutrient availability.
POSTER #22:
Influence of soil nutrient availability and herbivore exclusion on plant community composition and diversity
Claire Wainwright
Dr. Elsa Cleland
Across terrestrial ecosystems, the effects of top-down versus bottom-up activities have been shown to play a significant role in determining the configuration of plant communities. Primary production is known to be nutrient-limited, with the addition of various nutrient combinations often having drastic results on the relative proportions of various species and functional groups within these vegetative assemblages. In addition, the presence of herbivorous consumers can exert control over plant community structure and abundance. This primary trophic level of terrestrial ecosystems is rarely controlled solely by either top-down or bottom-up effects; rather, the two effects may interact to determine the make-up of plant communities. Our study system was at the UC Elliot Chaparral Reserve, focusing on an herbaceous-dominated community containing a variety of native shrubs and perennial grasses intermixed with exotic annual grasses and shrubs. Various manipulations of soil nutrients were implemented, along with instances of herbivore exclusion in order to illuminate the effects of both resources and consumers on the composition and diversity of this plant community.
POSTER #23:
Predation or scavenging? Thoracic muscle pH and rate of water loss reveal arthropod cause of death
Christine Young
Dr. David Holway
Little is known about the relative contributions of scavenged carrion and prey in a generalist predator’s diet. This is largely due to the inability to determine how a diet item was obtained. Distinguishing between prey and scavenged items in arthropod diets is essential for gaining a better understanding of the ecological interactions between organisms. Such relationships can form intricate food webs, where generalist predators may be subsidized by carrion in addition to consuming prey. Without a method of distinguishing between scavenged and prey items, diet analyses may overestimate the predatory impacts on a species. This is the first study to develop a method that differentiates prey from scavenged diet items by utilizing quantitative physiological properties of thoracic muscle in Hymenoptera (e.g. rate of water loss, thoracic muscle pH and muscle coloration). We used the western yellowjacket, Vespula pensylvanica, as our model predator. This generalist predator actively preys upon and scavenges bees and yellowjackets. We therefore analyzed the post-mortem physiological responses to predation stress on bees (Apis mellifera and Bombus impatiens) and yellowjackets (V. Pensylvanica). Time since death can be estimated from water loss rates and cause of death can be determined from the acidity of thoracic muscle pH. The ability to successfully differentiate carrion from prey is critical for determining what ecological mechanisms drive population-level dynamics and for formulating accurate food webs.