«Strengthening the Nation through Diversity, Innovation & Leadership in STEM San Antonio,Texas · October 3-6, 2013 Get Connected! Connect with the ...»
CAN PREEXISTING TRAIT VARIATION PREDICT THE OUTCOMES OF PARASITOID COMPETITION IN NOVELHABITATS Gabriela Hamerlinck, Andrew Forbes.
University of Iowa, Iowa City, IA.
Parasitoid wasps often specialize on just one or a few hosts, and shifts to new hosts may explain the tremendous amount of parasitoid diversity if parasitoids using novel hosts become reproductively isolated from their source population. In this study, we ask whether, when different parasitoids compete for a novel resource, some species possess preexisting trait variations that enable them to better colonize particular novel hosts. Further, we ask whether we can predict successful host shifts based on analyses of ancestral characters. To this end, we have designed a mathematical model to describe the population dynamics of parasitoid populations competing for a novel host. As a case study to parameterize this general model, we use races of the wasp Diachasma alloeum that attack Rhagoletis larvae in hawthorn and blueberry fruit to determine their ability to attack Rhagoletis larvae in a new plant host, apple. Specifically, this model evaluates preexisting morphological characters that may allow one D. alloeum race to successfully use its host in a novel fruit over the other. Preliminary analyses focus on the interaction between ovipositor length and host habitat characteristics, and how this interaction may predict the outcome of competition.
Preliminary results show threshold values of ovipositor lengths result in competitive exclusion and no instances of coexistence, though coexistence is possible within the model. While the empirical evidence used to parameterize the model comes from a specific system, the model is broad in scope and can be expanded for use in other models of insect host shifts.
DOES WHITE-TAILED-DEER BROWSING AFFECT FOREST SONGBIRD COMMUNITIESVitek Jirinec, Matthias Leu, Daniel Cristol.
College of William & Mary, Williamsburg, VA.
White-tailed deer (Odocoileus virginianus) numbers in the eastern United States have increased dramatically over the past 3 decades. Human-induced forest fragmentation, extirpation of natural predators, and the setting aside of expansive areas in which hunting of deer does not occur have all contributed to this population boom. While impacts on natural ecosystems are predictable, few empirical, large-scale studies have examined the effects of deer browsing on avian community composition. The objective of our study was to evaluate the effects of deer abundance on forest bird communities in both rural and suburban landscapes. To correlate deer habitat use with avian species composition, we used point counts to survey birds: Virginia Peninsula, n = 125; Shenandoah River Valley, n = 99;
and deer fecal pellet transects (same sample sizes as point counts) to estimate relative use of habitat by deer. We estimated bird and deer pellet densities based on distance sampling to correct for imperfect detections. We predicted Graduate Oral that the densities of species nesting and foraging in the shrub layer would be negatively correlated with deer pellet abundance. Preliminary analyses indicate that the avian community varies with deer habitat use. High deer use was correlated with low densities for bird species breeding and foraging in understory vegetation. Our results suggest that habitat modification by deer browsing promotes measurable changes in bird community composition, with conservation implications for declining forest songbirds. The results of our study can be used to inform land use planning within a context of bird conservation.
335 ORAL ABSTRACTS
ANALYSIS OF THE LINEAGE-SCALE GENETIC STRUCTURE OF THE CORAL PORITES LOBATA IN
MAUNALUA BAY, HAWAIIKaho Tisthammer, Robert Richmond.
University of Hawaii at Manoa, Honolulu, HI.
Corals in Maunalua Bay, Hawaii, are under chronic pressures from sedimentation and terrestrial run off containing multiple toxicants. However, some individuals thrive despite the prolonged exposure to environmental stressors, which suggests that these individuals may have been under selection to withstand such stresses. A recent study shows increasing levels of cellular stress response in the coral Porites lobata along the environmental gradient that exists from the mouth of the bay toward offshore. Therefore, the lineage-scale genetic structure of P. lobata was investigated to understand the genetic basis for observed differential stress responses. The genetic structure was analyzed for indication of selection using known mitochondorial and nuclear DNA markers as well as using newly isolated candidate genes specifically related to stress responses. Preliminary results suggest that genetic differentiation in P. lobata is expected to be present due to selection in Maunalua Bay. The individuals near shore are likely to have genotypes associated with higher tolerance to toxicants, which will be further investigated by laboratory exposure experiments. Understanding the little-known genetic structure may be a key for saving severely degraded corals in Maunalua Bay, since the ability of corals to cope with environmental stressors depends on the underlying genetic networks. The results may also provide critical information for successful coral reef conservation as well as estimating the effects of climate changes on coral reefs.
INTERTIDAL FORAGING HABITS OF FISHED AND PROTECTED CALIFORNIA SPINY LOBSTERS OF
CATALINA ISLAND, CALIFORNIAMary McCormick1, Corey Garza1, Steve Litvin2.
California State University, Monterey Bay, Seaside, CA, 2Hopkins Marine Station, Leland Stanford Junior University, 1 Pacific Grove, CA.
In efforts to combat overfishing of valuable species like the California spiny lobster (Panulirus interruptus), managers have increasingly implemented marine protected areas. During nighttime high tides, the rocky intertidal zone, both in and external to these protected areas, serves as an important foraging habitat. There, lobsters feed on mussels, chiton, and limpets. However, on Catalina Island, this pattern of intertidal foraging may vary where protection from fishing has spurred increased lobster abundance and shifts in their population size structure, potentially impacting the types and size of prey targeted. We compared protected and fished populations by estimating spiny lobster trophic position using nitrogen stable-isotope analysis. We also inferred the relative importance of prey species that comprise the diet of spiny lobsters by applying carbon and nitrogen stable-isotope data to Bayesian mixing models. We predict that protected spiny lobster muscle tissues will exhibit depleted δ15N, indicative of feeding at a lower trophic level.
Mixing models may indicate variation in the order of importance of prey species between fished and protected sites and between sites with and without mussel beds, a key foraging habitat for lobsters. The strategy of closing areas to fishing can impact local trophic dynamics, but habitat quality, regardless of fishing pressure, remains an important factor in determining prey availability and community trophic dynamics. For coastal management, this study highlights the value of incorporating a variety of habitats, such as intertidal habitat, into the design of marine reserves.
AN ASSESSMENT OF MERCURY CONTAMINATION IN FISH AND WILDLIFE OF LAKE CHAPALA:
IMPLICATIONS FOR HUMAN AND ENVIRONMENTAL HEALTHZaria Torres, Miguel Mora, Robert Taylor.
Texas A&M University, College Station, TX.
The Lerma-Chapala Basin has industrial, agriculture, and urban areas that contribute a variety of environmental contaminants into the Rio Lerma and ultimately, Lake Chapala. It is the largest tropical lake in Mexico and is a primary water source for the city of Guadalajara. It is also a popular wintering area for the American White Pelican (AWPE, Pelecanus erythrorhynchos), a species of concern in the United States. This project assesses the effects
336 ORAL ABSTRACTS
of mercury (Hg) on fish and wildlife of Lake Chapala over a 2-year period. We measured mean Hg concentrations for water, sediments, and 3 fish species: silverside, Christoma spp.; carp, Cyprinus carpio; and tilapia, Oreochromis
mossambicus. Mean Hg concentrations were also measured in feathers from migratory AWPEs and resident birds:
the great egret(GREG), Ardea alba; and snowy egret, (SNEG), Egretta thula; as well as feathers from AWPE collected in North Padre, Texas. Our results show mean Hg concentrations as follows: water = 15.3 ± 2.05 ng/kg, sediment = 0.705 ± 0.185 µg/kg dry wt, carp = 0.373 ± 0.125 µg/g wet wt, charal = 0.1505 ± 0.015 µg/g wet wt, and tilapia =
0.0407 ± 0.028 µg/g wet wt. Carp samples, also taken from a nearby reservoir, San Antonio Guaracha, Michocan, had mean Hg concentration levels of 0.0787 ± 0.035 µg/g wet wt. Lake Chapala AWPE feathers = 4.08 ± 2.485, GREG/ SNEG = 5.104 ± 2.846, and North Padre AWPE = 2.871 ± 0.870. Further analysis will help to determine risks to wildlife and human populations that use resources from the lake.
CLIMATE WARMING AND NUTRIENT ADDITION INCREASES EXOTIC PLANT COMPETITIVE ABILITY AND
EXOTIC APPLE SNAIL REPRODUCTION (POMACEA MACULATA) IN NATIVE WETLAND COMMUNITIESMaria Meza-Lopez, Evan Siemann.
Rice University, Houston, TX.
Habitats are often invaded by multiple invasive species, which may result from common responses to environmental conditions. Climate warming has been predicted to enhance invasion success. Our current knowledge on warming effects on invasions is primarily based on bioclimatic models that often neglect other environmental factors and their interactive effect. In this study we asked how nutrient addition, warming, and their interaction influence exotic plant and herbivore invasions and whether herbivore invasions depend on plant origin. We addressed these questions using a 2 x 2 x 2 factorial mesocosm experiment with 5 replicates for 16 weeks. Forty freshwater, native wetland communities were established and randomly assigned to 3 classes: warming, ambient or increased 2 °C;
nutrient addition, control or 6 ppt N and 1.7 ppt PO4; and plant origin, second round of planting with exotic plants or additional native plants. All mesocosms received apple snails (Pomacea maculata). Results showed that apple snail reproduction increased 4 fold with warming and was independent of other factors, while snail mass was higher with nutrients only and warming. These results suggest that warming will increase snail population growth rate, and that warming with nutrients will contribute to snail invasions but are limited in current climate conditions. Native plant biomass increased with nutrients without exotic plants, while warming reduced native plant fitness with no effect on exotic plants. This suggests that, independently, nutrients and warming would accelerate plant invasions in wetlands.
This study emphasized that interactive effects among multiple environmental factors are critical to predict invasion success and invader impacts on native species.
PREDICTION OF THE KEY DEVELOPMENTAL STAGES OF WINE GRAPESDiana Zapata Rojas, Melba Ruth Salazar, Lynn Mills, Markus Keller, Gerrit Hoogenboom.
Washington State University, Prosser, WA.
Weather conditions are considered significant in affecting crop development. The main controlling factor is temperature, which controls the rate of development in plants. Phenological models such as thermal time models have been widely applied to predict the development of several species. They are expected to be successfully applied to wine grapes by including specific cultivar parameters in order to describe their complete development. In addition, to help in decision making for management and site selection, phenological models optimize vineyard production systems for cost, quality, and environment, tending to indicate sustainability over time. This study evaluated the starting date and threshold temperature for the prediction of 4 growing stages and 4 Vitis vinifera L. cultivars. Heat requirements for individual consecutive growing stages were used to run a complete model from budbreak until veraison. The model’s performance was tested at several interactions of starting date and threshold temperature.
Results found significant differences in heat demands between cultivars and developmental stages in an early and late cultivar. The highest requirements were obtained for the growth stages of bud burst to first bloom and full bloom Graduate Oral to veraison where major changes in phenology occurred during the transition period from vegetative to reproductive.