Symposium Abstracts 2011

Session 1:  Coastal Ecology and Biogeochemistry

  • Beach Biogeomorphology – Michele Tobias (Geography)
         Plants have been thought to build foredunes and dunes on beaches by stopping the landward movement of sand. These plants are adapted to thrive with repeated burial and effectively hold sand in place as they grow up through deeper deposits of sand. Measurements of the locations of plants and slopes on which plants grew were made at seventeen California beaches. A cluster analysis of typical beach plant species based on their distance from the high water line, slope on which the plants were found, and elevation reveals groups that can be attributed to the roles of plants in building beach topography, which are consistent with groups suggested by historic literature.
  • Predicting invasion potential for six marine and estuarine crab species – Raymond Crafton (Ecology)
         This study presents a simplified, holistic modeling approach, which includes biogeographic, climate change, and vector components, to identify coastal waters at risk of invasion by six marine and estuarine crab species. Long-term annual average sea surface temperature and salinity were considered as environmental parameters for the biogeographic model, using native and existing invasive ranges to determine tolerance limits. The results show that conditions are suitable for further expansion for all six species. Potential impacts of climate change were modeled using the thermal tolerances and a uniform 1 – 3 °C increase in sea surface temperature. The models illustrate the possibility for a pole-ward shift in potential distribution. More suitable conditions are predicted for the northern hemisphere due to the confluence of gained hospitable conditions and landmasses. The final component aimed to assess ballast water’s potential as a transpor t vector; global shipping patterns and data for ports in the United States were considered. Global patterns suggest that ports in Asia, especially China, are responsible for the largest volume of traffic. Regionally, traffic patterns in the United States show that vessels are more likely to originate from nearby countries resulting in disparities between the origins of vessels by coastal regions. (Work is from my Master’s thesis at the University of Manchester.)
  • Primate communities are structured more by dispersal limitation than by species sorting – Lydia Beaudrot (Ecology)
         A major goal in community ecology is to identify mechanisms that govern the assembly and maintenance of ecological communities. Current models of metacommunity dynamics differ chiefly in the relative emphasis placed on dispersal limitation and niche differentiation as causal mechanisms structuring ecological communities. Here we investigate the relative roles of these two mechanisms in structuring primate communities in Africa, South America, Madagascar and Borneo. We hypothesized that if dispersal limitation is important in structuring communities, then community similarity should depend on geographic proximity (controlling for ecological similarity). Conversely, if communities are assembled primarily through niche processes, then community similarity should be determined by ecological similarity (controlling for geographic proximity).  We performed Mantel and partial Mantel tests to investigate correlations between primate community similarity, ecological distance and geographic distance. Results showed significant and strongly negative relationships between diurnal primate community similarity and both ecological similarity and geographic distance in Madagascar, but significant and stronger negative relationships between community similarity and geographic distance in African, South American and Bornean metacommunities. We conclude that dispersal limitation is an important determinant of primate community structure and may play a stronger role in shaping the structure of some terrestrial vertebrate communities than niche differentiation.
  • The Effect of Litter Quality and Mineral Nitrogen on Microbial Functioning, Residue Decomposition and Soil Organic Matter Accumulation – Jennifer Denbow (Soils and Biogeochemistry)
         Can structural and physiological differences in microbial communities explain changes in residue decomposition and eventually soil organic matter (SOM) quantity? This study aims to elucidate the link between organic residue (OR) quality, N amendments, and the function of microbial communities in SOM stabilization. This was achieved in a medium-term incubation experiment through the integration of microbial methods designed to target different physiological aspects of the microbial community: growth yield efficiency, extracellular enzyme activity, respiration, PLFA and the measurement of SOM quantity at five time points along the decomposition continuum. Soils were collected in June 2009 from a long-term field site in Embu, Kenya. The following residue treatments, with and without the addition of mineral N (100 mg N kg-1 soil), were applied to 200g soil at a rate of 3.65 g C kg-1 soil and incubated at 25°C for 203 days: Tithonia diversifolia leaves, stems, leaves + stems, and Zea mays. Furthermore, a glucose treatment was added to the incubation to test the effect of a very labile C source. An increased understanding of the role that microorganisms play in OR decomposition and SOM stabilization will help improve predictive soil carbon models by considering microbial responses to agricultural management practices.

Session 2:  Conservation and Management

  • Using Social Network Analysis for Monitoring and Evaluation in Natural Resource Management – Meredith Niles (Ecology)
         Social network analysis is a tool that can be used to analyze social structures, networks and relationships. As such, it can evaluate the strength and capacity of different networks to achieve potential outcomes. Social network analysis has been historically used in sociology and other social science networks, and has increasingly grown with the popular use of the internet. Social network analysis also has the capacity to function as a tool for effective monitoring and evaluation of projects and goals by measuring network collaboration, trust and cooperation over time. More recently, social network analysis has been used in ecology and conservation to trace network structures for achieving natural resource management. This presentation will detail the process of attaining social network data through participatory stakeholder engagement and the analysis of results. Research is based on ongoing work with USAID projects in Nicaragua, Uganda and the Dominican Republic. The three cases all aim to achieve some type of natural resource conservation and yet present different network structures which may present unique challenges to achieving conservation goals. Understanding network structures can provide insight into effective ways to create and achieve project indicators, monitoring and evaluation goals.
  • Evaluating synergies and tradeoffs between conservation and production goals in an agricultural ecosystem – Kelly Garbach (Ecology)
          Agricultural lands are increasingly important targets of conservation initiatives, being called upon not only to minimize their negative environmental impacts, but also to support habitat for biodiversity and sustain multiple ecosystem services. Reintroducing woody species in hedgerows or live fence plantings is a common strategy to enhance habitat and services. However, concerns about decreases in agricultural productivity have prevented their widespread adoption. This study investigated synergies and tradeoffs between supporting bird diversity and pasture productivity in a cattle ranching system in central Costa Rica. We explored: 1) the extent to which live fences supported bird species assemblages and influenced pasture productivity and microclimate regulation; 2) how live fence management (e.g., pruning) influenced the spatial distribution of these services.
          We found that live fences that incorporated un-pruned trees (e.g., full canopy size) hosted twice the number of bird species as fences that were regularly pruned and surrounding pastures. Pasture productivity, measured as grass dry weight biomass, was reduced by up to 60% in the zone directly beneath the tree canopy of un-pruned live fences, however this reduction was limited to a narrow zone, ≤5m wide. In contrast, pruned live fences did not reduce pasture productivity, nor did they foster bird diversity.
  • Applications of participatory GIS for improved planning and evaluation of natural resource management – Matt Hamilton (International Ag & Development)
          Efforts to manage natural resources, conserve biodiversity, and protect threatened ecosystem services depend upon a sophisticated empirically based understanding of local conditions. Yet collecting data can be difficult and costly, particularly in developing regions such as Central America. On the other hand, without access to comprehensive, accurate and local-level data, conservation efforts run the risk of poor decision-making, ineffective implementation, and failure to achieve long-term, meaningful progress. In my study, I collaborated with NGO staff affiliated with a water resource management project to identify three “space-based” methodologies for gathering data needed for monitoring progress, as well as planning and decision-making. In the first, NGO staff gathered data using GPS units; in the second, NGO staff worked with local community members to gather data using hand-drawn maps; in the third, NGO staff again worked with local community members, but this time using a satellite photo printout of the community to help guide the mapping exercise. We tested these methods in twelve communities throughout Central America. Our results suggest that by using the satellite photo method to gather local level data, natural resource managers can avoid the tradeoff of comprehensiveness versus accuracy, and thereby potentially increase the effectiveness of environmental programs through improved decision-making.
  • Reaching Zero Waste by 2020 – Veronica Pardo (Community Development)
          The University of California has declared the intention of reaching zero waste by 2020.  What does zero waste actually mean and how do we reach our goal?  Veronica Pardo will explore the current opportunities available for waste reduction on our UCD campus. She will identify areas of improvement and suggestions to achieve zero waste. 

Session 3:  Spatial Dynamics and Forecasting

  • Retention of oak gall communities on urban trees – Ian Pearse (Entomology)
         Urban areas are an increasingly prevalent feature in modern landscapes. We often plant or maintain native plants in urban settings in order to maintain historical ecological interactions (such as herbivory, bird roosting sites, or pollination), but aspects of the urban environment other than the plant alone may influence those interactions. In this study, we surveyed gall wasp communities on valley oak trees in 10 cities and paired natural areas throughout California’s Central Valley. We found that gall diversity was greater in natural areas than urban areas, but the community composition of gall communities did not differ between natural and urban areas. Instead community composition varied between geographic regions. We found that aspects of the immediate environment around oak trees (such as litter cover and the presence of irrigation) correlated with higher gall diversity of galls on urban oaks. We also found that dispersal-limiting features (such as the number of neighboring oaks) predicted gall diversity on urban oaks. Cities are valuable habitats for valley oak galls, and simple management decisions in cities (such as contiguous plantings, irrigation, and no litter removal) can increase gall diversity on oaks. 
  • A time series meets a habitat model: using a long-term perspective to understand species-environment relationships – Libby Porzig (Ecology)
          Habitat-suitability models describe species’ presence or abundance using physical habitat characteristics. While these models have accurately predicted spatial distribution, their ability to predict distributions through time has often been unsatisfactory. Because habitat-suitability models are usually created using data collected across space rather than through time, their poor performance may result in part from their failure to incorporate temporal demographic or environmental dynamics. I expand the scope of these models beyond a short-term snapshot of habitat characteristics. Using data spanning 1982-2005 from the Palomarin field station of PRBO Conservation Science, I evaluate the relative role of vegetation change, weather variability, and population processes in affecting local density of eight bird species through time. I then evaluate the ability of different model types to predict the subsequent five years. Incorporating rainfall into models improves model fit for five of the eight species relative to models based solely on vegetation characteristics. This investigation highlights the importance of including features other than physical habitat characteristics when predicting future abundance as well as the importance of model structure. 
  • Spatial and temporal patterns of pest and pathogen-caused forest canopy gaps in Yosemite Valley, California – Heather Mehl (Plant Pathology)
         As little as 150 years ago, the landscape of Yosemite Valley was one of open meadows and scattered woodlands. However, practices of fire suppression and meadow draining initiated in the 1850’s created conditions favoring conifer recruitment and today, dense mixed-conifer forests occupy a high proportion of the valley. One consequence of this altered vegetation structure is an increase in the frequency of endemic pests and pathogens, particularly two root-rotting fungi, Heterobasidion annosum and Armillaria mellea. These fungi alter forest structure through the creation of dynamic tree mortality centers, which frequently increase in size over time due to pathogen spread between the roots of adjacent trees, resulting in expanding gaps in the forest canopy. Today, there are hundreds of pathogen-associated canopy gaps in Yosemite Valley, and tree mortality caused by H. annosum and A. mellea is the primary source of forest disturbance. The o bjectives of this project are to document the current impacts of pests and pathogens on forest structure in Yosemite Valley and examine changes in pathogen dynamics over time. This research will provide both a greater appreciation of the ecological roles of pathogens in mixed-conifer forests, and provide useful information for vegetation management in Yosemite Valley National Park.
  • Population persistence in dynamic landscapes: the role of spatiotemporal connectivity – Katharina Ullmann (Entomology)
         Metapopulation theory provides a framework for exploring how spatial factors influence population persistence. Traditional metapopulation theory assumes that habitat patches are static in space and time. However, these assumptions are not always met because in real landscapes, disturbance and succession cause habitat patches to disappear and reemerge. If a species is mobile and able to track its habitat, then spatiotemporal connectivity may be essential for population persistence in highly dynamic landscapes. The squash bee (Pepopnapis pruinosa) is a specialist, annual, solitary ground-nesting bee. It collects pollen only from Cucurbita sp. (e.g. squash and pumpkins) and nests in or near Cucurbita sp. fields. To explore the role of spatiotemporal connectivity in determining population dynamics, I sampled squash bee abundance at 25 Cucurbita sp. fields that spanned a spatiotemporal connectivity gradient in the Sacramento Valley of California. I used existing GIS crop data and grower interviews to determine where Cucurbita sp. fields were located in current and previous years. Preliminary analyses indicated that the distance to nearest 2009 Cucurbita sp. field helped to explain 2010 squash bee abundance. This study supports the hypothesis that both spatial and temporal habitat connectivity contribute to population dynamics in such highly dynamic landscapes.
  • Extending species distribution modeling techniques: payoffs across ecological disciplines – David Harris (Population Biology)
         Understanding ecological communities and species interactions is one of the most fundamental and most challenging issues of ecology. Unfortunately, ecologists report that the statistical methods available to them cannot address a range of important questions about how species’ phenotypes and evolutionary history shape their interactions with the environment and with one another. With phenotypic and phylogenetic information in hand, however, extensions of current species distribution modeling (SDM) techniques could allow ecologists to ask more nuanced, biologically motivated questions about the structures of the communities they study than are available through more common alternatives like RLQ analysis. I will apply this extended SDM approach to two different ecological systems to show its utility. First, I will reanalyze the distribution of 56 Algerian plant species and compare my results with both of the recently developed approaches for understanding traits these complex relationships, both in terms of predictive performance and in terms of biological insight. Second, two collaborators and I will apply extended SDM to predicting the host range shifts of Central European caterpillars after the Columbian interchange, showing the value of the approach across traditional ecological disciplines 

Session 4:  Behavioral and Animal Ecology

  • Effects of weather on survival in Song Sparrows – Kristen Dybala (Ecology) 
            Resource management decisions require reliable projections of species’ responses to climate change. Current research predicts that many species ranges will contract or dramatically shift, so that populations may decline or be extirpated from the parks and refuges designed to protect them. However, this species-distribution approach to studying climate change cannot describe how or why a local population may decline, such as through a decline in survival or reproductive success rates. I examined the effects of weather on survival rates in a declining population of Song Sparrows in the Point Reyes National Seashore. Adults and juveniles will respond differently to climate change, and both direct and indirect effects of weather on survival are important to consider. Recognizing the demographic links between climate change and population dynamics is critical to identifying management actions that could minimize the effects of climate change.
  • Exploring a bioacoustic tool for mammals: extracting multiple information types from the alarm calls of two ground squirrel species, the Belding’s ground squirrel (Spermophilus beldingi) and the golden-mantled ground squirrel (Spermophilus lateralis) – Stacie Hooper (Ecology and Evolution)
           Acoustic signals can contain a wealth of information. Even seemingly simple signals, such as alarm calls, have been shown to include different types of information, including the caller’s identity. A bioacoustic approach which uses the information in signals has been used to survey and monitor bird and marine mammal populations. However, few studies have investigated the potential of this approach for use with terrestrial mammals. The purpose of this work was to explore the feasibility of a bioacoustic tool by testing for the presence of different kinds of information in the alarm calls of two ground squirrel species. Since sociality can affect the amount of information in signals, we chose species with differing levels: the highly social S. beldingi, and the relatively asocial S. lateralis. Neural networks were able to correctly and consistently classify alarm calls of both species to age class, individual, and in the case of Belding’s gr ound squirrels, to sex. The multiple types of information we found in the alarm calls of these species indicate that a bioacoustic approach which capitalizes on this information may be a useful tool for the tracking and monitoring of terrestrial mammal populations. 
  • Pallid Bat foraging behavior: Boys and girls don’t mix – Kate Ingram (Ecology)
          Sex differences in resource needs have been used to explain sexual segregation behavior in polygynous mammals. Many temperate bat species are polygynous, exhibit sex-biased dispersal and seasonal segregation. In order to test the hypothesis that Pallid bats (Antrozous pallidus) partition dietary resources during segregation, this study attempted to quantify dietary differences between the sexes. I preformed dietary analysis on individuals that were sampled for two years across a 750 km2 area in the American southwest. Initial analyses revealed diet differences between sexes that were influenced by region and year. These results suggest that seasonal segregation in Pallid bats may be due, in part, to resource needs differences between the sexes that vary with regional and yearly fluctuations in insect availability.
  • Why Humans Fight Like Ants (but not like chimpanzees) – Matt Zimmerman (Ecology)
           Ants, chimpanzees and humans engage in lethal intergroup violence, an activity rare in nature. Since humans and chimpanzees are close evolutionary relatives, many have inferred that human and chimpanzee intergroup violence has a common genetic origin. Chimpanzees fight in small groups and take few personal risks. Humans, however, fight like ants, in large groups and at great personal risk. Traditionally, evolutionary biologists understand this type of risk-taking through “inclusive fitness,” the idea that an individual will sacrifice more for a group if that group is composed of close genetic relatives. As sisters, ant colony soldiers are very closely related, which can explain their very risky behavior. Chimpanzee band-members are only moderately related, which explains their moderately risky behavior. Human armies, by contrast, are virtually unrelated, so genetic mechanisms can’t adequately explain their high-risk behavior. I argue that the evolutionary puzzle of human warfare can be resolved by examining cultural, as opposed to genetic, relatedness. Because cultural information can be transmitted more quickly than genetic information, humans in large groups can be close cultural relatives, which can also lead to high-risk behavior. Empirical measurements of cultural and genetic relatedness in humans, chimps and ants seem to support this argument.