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2016 Research Showcase
EBAE Abstracts
Abstract Title : Spider Diversity at Scripps Coastal Reserve
Abstract : Adequate conservation requires a thorough understanding of the baseline ecosystem that is to be maintained. This includes the relationships between flora and fauna. As generalist predators, spiders are good overall indicators of ecosystem health. A better understanding of the distribution of foliage-inhabiting species will shed light on the potential effects of habitat disruption on spider diversity. Previous studies of spiders have categorized spiders into guilds based upon their hunting styles (Uetz 1991). Through the use of DNA barcoding, spiders collected at the Scripps Coastal Reserve were categorized into four guilds based on hunting behavior. Our research suggests that space web building spiders prefer California sagebrush, while orb weavers and stalking spiders prefer Coyote brush, and running spiders California buckwheat; Lemonade berry had the most diversity showing almost equal guild representation. This project allows future generations to continue to protect and maintain a diverse group of plant species and thus spiders as an indicator group for ecosystem health. ADDITIONAL PRESENTERS: Dustin James, Blaine Novak-Pilch
Abstract Title : Foraging preferences of the invasive Argentine ant, Linepithema humile
Abstract : The Argentine ant (Linepithema humile) disrupts native ant assemblages worldwide and displaces most native ants in the process. In invaded areas the Argentine ant dominates above-ground foraging, and its foraging preferences may affect arthropod food webs differently than the preferences of native ants. It remains unclear, however, whether the Argentine ant acts as a predator or a scavenger. To learn more about this issue, I presented free-living Argentine ant colonies with different species of live and dead arthropods to test the extent to which the Argentine ants feeds on carrion versus live prey. Using these paired comparisons, I hypothesized that recruitment and rate of consumption would depend on the species of the prey item and whether it was alive or dead. Understanding the Argentine ant's foraging preferences helps us to clarify the ecological function of this abundant invader and to predict how arthropod community structure changes in response to invasion.
Abstract Title : Compost tea as an organic fertilizer: Investigating the effect of compost tea on plant growth
Abstract : Compost tea (CT) is a water-based extract of compost gaining popularity among gardeners and organic crop-growers. CT is prepared by placing solid compost (SC) into water to allow soluble microbes and nutrients to transfer from solid into liquid. This study evaluated the effect of CT on lettuce (Lactuca sativa) growth compared to SC treatments and to a control of water alone. CT was prepared from three sources of SC: (i) cattle manure-based vermicompost, (ii) goat manure and carbon-based thermophilic compost, and (iii) human manure-based thermophilic compost. CT was brewed for 24 and 72 hours and applied every two days to potted lettuce plants (n=96). There was a significant effect of treatment type on leaf length and leaf width after 18 days of plant growth. Specifically, leaf length increase was significantly higher in plants with Goat CT (for both the 24-hour and 72-hour brew varieties) and in control plants, than for the Goat SC counterparts. With the exception of one treatment, all treatments of SC and CT experienced greater leaf width increase than control, although these results were not statistically significant. The components of the CT were different from the water used for control plants: Potassium and phosphorus levels increased or remained constant in all post-treatment 72-hour CT soils, whereas these nutrients declined in control soil. Additionally, the electrical conductivity and total dissolved solids of all CTs were significantly higher than that of water, indicating the presence of cations, microbes and other particles. The effect of treatments on plant growth was likely due to the repeated application of soil nutrients and beneficial microorganisms administered by CT.
Abstract Title : A Longitudinal Study of the Biodiversity of the Soil Microbiomes of California Sagebrush Versus Crystalline Iceplant
Abstract : Microbiomes are closely tied to the plants with which they coexist. In a symbiotic relationship, plants provide resources to microbes in soil, while microbes synthesize natural products necessary for plants. Introduction of invasive plant species can disrupt this relationship. An examination of soil microbiomes may yield insights on ecological competitions between native and invasive plants. This study aims to compare functional and genetic biodiversity of microbiomes associated with California sagebrush (Artemisia californica, native species) and crystalline iceplant (Mesembryanthemum crystallinum, invasive species) over a longitudinal timescale. We hypothesize that the two plant species are associated with different soil microbiomes. Soil samples were collected every three months from September 2014 to January 2016 at the Scripps Coastal Reserve, a part of the University of California Natural Reserve System. Our current results indicate that crystalline iceplant soil is consistently about 1 pH unit more basic than California sagebrush soil across seasons (p<0.05). Functional biodiversity was compared by measuring carbon source utilization, and we found no statistical differences between the soil samples. Genetic biodiversity was compared through targeted metagenomics of 16S rDNA sequencing, and soil microbiomes associated with California sagebrush have a higher species evenness, based on Shannon Evenness Index. ADDITIONAL PRESENTER: Kenneth Collado
Abstract Title : Passive acoustic monitoring of Cuvier's beaked whale density in the Southern California Bight
Abstract : Cuvier's beaked whales (Ziphius cavirostris) are deep-diving cetaceans found in offshore tropical to temperate waters globally. They are notoriously difficult to observe visually due to their prolonged dives. Passive acoustic monitoring provides a unique opportunity to observe Cuvier's beaked whales in their environment. Our study used a combined total of nineteen years of continuous passive acoustic data recorded at six sites within the Southern California Bight to document presence of Cuvier's beaked whales in this region. Echolocation frequency-modulated pulses were automatically detected and manually verified, and then two different counting methods for estimating animal density were applied. These counts were then used to determine animal density and spatiotemporal trends. Cuvier's beaked whales were more abundant towards the southern and western parts of the Southern California Bight with a seasonal pattern of lower presence during the late summer, early fall months. These findings will improve our knowledge of beaked whale habitat and behavior and help inform conservation efforts.
Advisor : DR. JAMES NIEH
Abstract Title : Behavioral Responses of Honey Bees to Waggle and Tremble Dancing
Abstract : Both waggle and tremble dances are vibratory signals known to elicit following behavior in neighboring bees. However, it is not known how tremble dances attract receivers. We trained honey bees (Apis mellifera) to a feeder where half were artificially attacked to elicit tremble dancing. They were then tracked back to the hive and filmed along with neighboring bees to capture both dancer and follower behavior. We found that waggle dancers attracted followers from a greater distance than tremble dancers, indicating waggle dancing to be more attractive than tremble dancing. We also found that, once near the dancer, a tremble follower would prefer to be oriented with her head facing the dancer's head while a waggle follower would prefer to be oriented with her head perpendicular to the dancer's abdomen. We are continuing to analyze our data, but these results provide the first insights into how tremble dancers broadcast their dance information.
Advisor : DR. ERIC E. ALLEN
Abstract Title : The Persistence of Community: A Comparison of Microbial Community Composition to Elucidate Stability of Dysideidae Sponge Holobionts
Abstract : Marine sponges are well known to contain a diverse community of microorganisms within their tissues. Recent efforts to understand the relationship of sponge animals and their microbiomes have used the term 'holobiont' to refer to the sponge and all of its microbial endosymbionts as one functional and evolutionary unit. While these host-microbe assemblages may contain hundreds to thousands of different members, advances in high-throughput sequencing have made it possible to examine the validity of the holobiont concept. The work presented here focuses on a family of Dysideidae sponges known to harbor endosymbiotic cyanobacteria, Oscillatoria spongeliae, that produce potentially toxic and bioaccumulating polybrominated diphenyl ethers (PBDEs). Past work has shown that phylogenetically distinct Dysideidae sponges harbor unique O. spongeliae strains and contain a distinct PBDE chemical profile. The stable correlation of host, cyano-symbiont and chemotype suggests a stable holobiont, which we further examined by characterizing the whole bacterial community of two different Dysideidae sponges. Using 16S rRNA high-throughput data, we compared the variability of the bacterial community composition in these Dysideidae hosts across time and space. Additionally, we explore the contribution of O. spongeliae abundance to the species-specificity and stability of the microbiome. In addition to describing the dynamics of the animal-microbial relationship in these holobionts, the findings presented here further our understanding of the total microbial complement that may contribute to the production and modification of bioactive compounds in these sponges.
Advisor : DR. JAMES NIEH
Abstract Title : Immune Priming of adult Apis mellifera against Nosemaceranae
Abstract : Apis mellifera, the Western honey bee, is anessential pollinator in a multitude of worldwide ecosystems, and thereforeoccupies a prominent niche in the agricultural industry. Preserving colonyhealth is important. In particular, the microsporidian pathogen, Nosemaceranae, is a major contributor to poor colony health. One potentialsolution is to activate natural honey bee immunity. We therefore tested immunepriming by inoculating day-old A.mellifera adults with heat-killed N. ceranae spores and countedspore levels (infection levels) in bees at different ages and upon adult death. Bees that havebeen immune primed (IP) upon adult emergence and subsequently challenged withlive N. ceranae spores had 75% lower infection levels thannon-primed and challenged bees. Control bees were uninfected. Interestingly, IP reduced longevity, even in bees not exposed to livepathogen. This demonstrates a potential trade off between immune activation andlongevity. Priorresearch (including studies in the Nieh lab) demonstrated that the Toll pathwayprovides a major defense against Nosema infection. We will test theactivation of Toll genes in future trials and will continue to investigate the effects of IP on adult longevity.
Abstract Title : Effects of Restoration on Arthropod Diversity
Abstract : Deforestation and land use change continues to be a global issue. Fortunately, there are available methods for reversing this process, including reforestation and regeneration, and available techniques for measuring the progress of this restoration. One such technique is the measurement of arthropod diversity and abundance in sites undergoing restoration. This study examined arthropod diversity as well as trophic level diversity in five sites at La Calandria in Los Llanos, Monteverde, Costa Rica. These sites included active sugarcane cultivation left growing for 16 years, coffee cultivation left to regenerate for 16 years, pasture left to regenerate for 16 years, pasture reforested 15 years ago, and secondary forest. Each plot was approximately 1 hectare. My prediction was that the secondary forest sites would have the most diversity, and sugarcane would have the greatest abundance. Using pitfall traps, ground-dwelling arthropods were captured and identified to the Order and Family. Once identified, the typical diet of each taxon was used to sort each arthropod into a trophic level (predator, omnivore, herbivore, or detritivore). Chi-square analysis was used to determine the presence of significant differences in diversity between plots, and the Shannon Diversity Index was used to determine which plot was the most trophically diverse. Data showed that that there was no significant difference in Order or Family diversity between plots, only between abundance of arthropods. In addition, reforested pasture proved to be the most trophically diverse according to the Shannon Diversity Index. Perhaps identification to the morpho-species level would prove more insightful in measuring diversity.
Abstract Title : Effect of Stable and Fluctuating Low pH on Growth and Feeding Behavior in Tectura paleacea
Abstract : It is common for marine invertebrates to experience altered metabolism and growth under experimental ocean acidification (OA) conditions. For the diverse animals living in nearshore surfgrass (Phyllospadix spp) habitats, however, reductions in local pH due to OA may be buffered by surfgrass photosynthesis, thereby causing inhabitants to experience daily fluctuations in pH that are not typically accounted for in OA experiments. We therefore exposed surfgrass limpets (Tectura paleacea) to both stable (without surfgrass) and fluctuating (with surfgrass) ambient and reduced pH treatments to determine the potential impact of realistic OA conditions on animal feeding behavior and growth. It is hypothesized that reduced pH will negatively impact animal growth and feeding, but to a lesser extent in fluctuating conditions. Results from this study will highlight the importance of considering local habitat dynamics when trying to determine the realistic impacts of future ocean conditions on marine organisms.