2011 REU Projects

Collins, Landon (Hampton University).  Mentor:  Barbara Abraham (Hampton University). 
Environmental effects on the foraging activity of bees.
Abrstact: The project examined the correlation of weather variables with the activity of several bee genera observed on Salt Pond Mountain in Giles County, Virginia.  The abiotic factors measured were temperature, wind speed, humidity, and sunlight intensity. The bee activity was tracked by spotting the number of bees on flowers in five areas of Salt Pond Mountain: 1) Moonshine Dell Trail, 2) Bear Cliffs, 3) War Spur Loop Trail, 4) Hedwig Trail, and 5) Bald Knob Road and summit.  Total diversity of local bees was obtained using bee bowls of fluorescent colors.  The main method used to capture bees was using vials held above the bee, then placing the vial cap on underneath the bee. When bee activity reaches its peak in each environmental condition  is important to their pattern of foraging. The bees captured and identified during each observation showed the impact of environmental conditions in which genera of social and solitary bees prefer to forage for nectar or pollen. It is important to understand the foraging pattern of bees, because the plants that are in need of insect pollination depend on them to carry out reproduction and humans and other animals are dependent upon these food sources for survival. Ultimately climate change disrupts the interactions between plants and their pollinators causing mismatches of insect and plant phenology.

Credicott, Abby (University of Virginia).  Mentors: Henry Wilbur and Becky Wilbur (University of Virginia). 
The community structure of an old growth Hemlock forest in Virginia. 
Abrstact: Studies of old-growth forests have changed significantly since the early 1900’s when Clements first developed his climax theory, in which old-growth forests were seen as stable, resilient ecosystems. Today, however, they are considered dynamic systems susceptible to disturbances and change at some scale. This research studied the community structure of a cool-mountain cove old-growth Hemlock forest in Giles County, Virginia. Field research consisted of 120 vegetation sampling plots that recorded the occurrence of species. This data was analyzed for species distribution and richness using frequency evaluations. Each species was assigned an abundance class from Wofford’s Flora of the Blue Ridge and entered into an abundance matrix of plots by abundance class frequencies. The matrix was run through a Nonmetric Multidimensional Scaling ordination to maximize spatial relationships among pairs of plots in a 3 dimensional projection. Various environmental and biological variables were collected for each sample and run through various statistical tests to determine if each covariate accounted for the spatial distribution of plots in the ordination space. We found that stream distance, slope, and deer sign presence all account for the distribution of plots at some scale. These findings can be further applied to the relationship between the respective variables and the community structure and vegetation spatial patterns found in Pond Drain Valley. These results will support future studies of old-growth forest systems on the discrete and temporal community structures.

Donald, Hannah (University of Virginia).  Mentor:  Corlett Wood (University of Virginia). 
Effects of host community composition on patterns of genetic differentiation in Forked Fungus Beetles (Bolitotherus cornutus).
Abrstact: The environment of an organism can influence patterns of diversity by restricting gene flow. One way that the environment acts as a barrier to gene flow is through resource-associated differentiation. Through resource-associated differentiation, organisms become more adapted to local habitats. These habitats, however, are not always evenly distributed throughout the landscape. This study addresses the relationship between the habitat composition and genetic differentiation in forked fungus beetles (Bolitotherus cornutus). Forked fungus beetles are polyphagous insects that live in a host community composed of three fungi species: Ganoderma applanatum, Ganoderma tsugae, and Fomes fomentarius. Host community composition was determined by calculating evenness using the Shannon Diversity Index. The degree of genetic differentiation was then quantified by calculating the average FST (an estimate of genetic differentiation based on neutral alleles). Preliminary results indicate that there is no relationship between host community diversity and genetic differentiation. Although this study shows no relationship between population structure and host community with forked fungus beetles, other species with known genetic differentiation associated with a habitat could infer more about the role of the movement of genes due to the environment.

Greenlee, Anna (University of Virginia).  Mentor:  Courtney Thomason (Texas Tech University).  
Baseline immune state: How it changes with altered parasite communities in Peromyscus leucopus.
Abrstact: Wild immunological studies provide an understanding of concomitant infections which is applicable to real-life situations.  Using a wild study population of Peromyscus leucopus, baseline stress levels were related to life history factors to determine that variation exists in the immune states in the population. In comparison to data from clinical studies, this highlights the need to continue to study immunology in wild populations. Additionally, immune stress was used as a method of observing how the anti-parasitic drugs, ivermectin and fipronil affect animals that are not in controlled laboratory situations. Our study found adult females that are not reproductive responded with lowed stress when treated with either drug.  Since these drugs are widely used in veterinary applications in the natural world, understanding the variation in mammalian responses to these drugs is important.

Johnson, Rebecca (University of Idaho).  Mentors:  Vince Formica and Butch Brodie (University of Virginia).  
Comparison of behavioral and genetic Bateman gradients in Forked Fungus Beetles (Bolitotherus cornutus).
Abrstact: Bateman (1948) identified the relationship between mating and reproductive success as a means of empirically detecting the presence and intensity of sexual selection within a population. The Bateman gradient has become a useful tool, but the question of how to estimate mating success arises. Two methods are generally used: behavioral mating success (BMS) where number of mates and frequency of matings are directly observed, usually in a controlled environment, and genetic mating success (GMS) where only the number of mates are detected within an individual’s progeny through genetic analysis.  Though GMS is oftentimes the only way to detect number of mates in the field, possible biases exist with this estimate leading to false conclusions of the Bateman gradient or sexual selection acting on a population. In this study we examine the Bateman gradient in a sexually promiscuous wild forked fungus beetle, Bolitotherus cornutus, low-density population, making comparisons between gradients using BMS and GMS. In this study system, we were able to estimate BMS through daily observations and GMS by genotyping adults and collected eggs and then constructing a pedigree of the populations. We find that the estimates of mating success produce two very different stories of sexual selection within our population. GMS estimates indicate no difference in sexual selection intensity between sexes, while BMS estimates actually indicate females are undergoing sexual selection rather than males. We suggest caution in interpreting results from Bateman gradients constructed using GMS estimates; this estimate can be biased as more mates are inherently detected in more fecund females. This awareness could also potentially lead to a method of predicting BMS from the GMS data, avoiding the potential biases in the future.

Milano, Nelson (University of Massachusetts, Amherst).  Mentors:  Vince Formica and Butch Brodie (University of Virginia).  
No evidence for morphological trade-offs between body size and testes in Forked Fungus Beetles.
Abrstact: The development of exaggerated morphological structures in organisms has long been credited to competition among conspecifics for mate acquisition. However, in some organisms exaggerations in secondary sexual traits have developed in the expense of others. While many studies have reported the relationships between morphological structures in distinctively polymorphic organisms, the relationships between morphological structures in organisms that are continuously polymorphic are comparatively limited. Here we used forked fungus beetles to determine if there are relationships between external and reproductive morphological structures that may provide a signature for alternative mating tactics in organisms that are continuously polymorphic. We measured elytra length, thoracic horn length, clypeal horn length, wing length and width and pronotum width of 34 forked fungus beetles. Beetles were then dissected to measure the dry weight of testes and bean accessory glands. Comparing morphological structures to body size (elytra length), we found thoracic horns to be positively allometric with body size and wings were found to be negatively allometric with body size. In reproductive structures, bean glands were found to be positively allometric with body size. However, we found no relationships between testes weight and body size. The lack of a relationship between testes and body size may suggest that they are both evolving independently of one another and that they may be experiencing different developmental processes. In order to adequately understand the mechanisms behind development in insects, we may have to assess the selective pressures being experienced at the postembryonic stage.

Murphy, Asia (North Carolina State University).  Mentor:  Marcella Kelly (Virginia Tech). 
Carnivore coexistence and occupancy across the Mountain Lake landscape. 
Abrstact: The coyote (Canis latrans) has recently colonized the eastern United States. Its presence in the eastern ecological community could influence native carnivores in either positive or negative ways. Yet, there has been little research examining how coyotes might interact with other carnivores in the eastern US. Our objectives were to determine how coexisting carnivores are using resource partitioning to ameliorate competition. Additionally we examined whether coyotes have reached saturation or are continuing to expand their range on Salt Pond Mountain Giles County, VA. Using camera trapping, we focused on four carnivore species: black bears (Ursus americanus), bobcats (Lynx rufus), gray foxes (Urocyon cinereoargenteus) and coyotes. We surveyed an approximately 30km2 area for nine weeks (May-July 2011) using twenty remote trail camera stations and used historical data from 2004-2010 in our analyses. We examined 1) habitat selection at the macrohabitat and microhabitat scale; 2) the potential for habitat, spatial and temporal partitioning; 3) and changes in occupancy across the years of 2004 through 2011.We used Student’s T-tests to compare mean habitat values at present versus absent sites. From these results we formulated apriori hypotheses on habitat selection to enter into Program Presence for modeling occupancy via AIC model selection. We also ran single-season and multi-season analyses to estimate occupancy values of all carnivores across the landscape. We found that carnivores are selecting for and against habitat characteristics at both the macrohabitat and microhabitat scale, that there is evidence for habitat partitioning amongst bobcats and coyotes, with coyotes selecting for developed areas and bobcats selecting against developed areas. We also found that Salt Pond Mountain is nearly saturated with bears and that coyote occupancy continues to steadily increase  Based on the results of this study, we believe there is need for more research on the ecology of eastern coyotes and their effects on ecological communities.

Perkins-Taylor, Ian (Swarthmore College).  Mentor:  Vince Formica (University of Virginia).
Morphological correlates of courtship behavior.
Abrstact: Courtship is a key step in the mating process where potential mates can both display their own phenotypes and assess the phenotypes of potential partners. These displays are one way in which sexual selection can act upon a population; individuals can choose whether or not to mate with a potential partner based on assessment of phenotypes which increase reproductive success. Population level dynamics like intrasexual competition can also influence who mates with whom, so in order to isolate the effects of mate preference competition must be controlled. We examined the relationship between both male and female phenotypes and courtship behavior, and whether or not this relationship was different in the presence and absence of male competition using Bolitotherus cornutus as a study system. This species experiences sexual selection for males with larger horn size via male-male combat. We took field and laboratory observations of courtship behavior and measured body size variables for each individual. Laboratory trials paired 1 male with 1 female to eliminate the effects of intrasexual competition. Female body size, but not male body size, was significantly and positively related to courtship activity. Because of the passive role of female B. cornutus in initiating courtship, these results suggest that there is male preference for larger females. This is true in both the presence and absence of male competition. In a species with seemingly stereotypical sex roles, this finding shows that males are not always mating as indiscriminately as we might imagine. Mating with larger females may increase male reproductive fitness because larger females are more fecund, or, if body size is heritable, by increasing the body size, and therefore competitive ability, of offspring.

Roberts, Margaret (Appalachian State University).  Mentors:  Eric Nagy (University of Virginia) and Zack Murrell (Appalachian State University). 
The environmental distribution of morphological variation and hybridization in Vaccinium.
Abrstact: Observations of character expression/morphological traits allow hybridization to be observed in nature and are an important method used to study introgression (McDade 1990). Studying this variation in a spatial context allows the evolutionary dynamics of populations to be viewed as an active ongoing process. While general observations and sampling of the blueberry species have been done around Mountain Lake Biological Station, little is known about the distribution and hybridization dynamic of the many Vaccinium species present within the area.  This, coupled with the fact that Vaccinium is a highly polymorphic genus that readily hybridizes, makes it an ideal candidate to study introgression and hybridization. In this study we analyzed the character traits of species sampled uniformly throughout the Mountain Lake Biological Station property to better understand the hybridization and speciation dynamic of the taxonomic clusters in the area. Environmental factors including co-occurring tree species, tree diameter, percent canopy cover, soil temperature, soil moisture and soil pH were also sampled and mapped along with the variation found to explore possible environmental correlations.  An analysis of the distribution of morphological variation and clustering patterns was used to better understand the population and hybridization dynamic of multiple Vaccinium species across the landscape.  Distinct taxonomic clusters were found to be statistically significant yet showed extensive overlap with individuals of other species groups.  Geographic statistical GIS data displayed an area of high PC1 variance clustering along a distinct gradient of change in mean PC1 indicating a possible hybrid zone.  While no association was found between the occurrence of morphological variation and environmental factors, variation was found to both positively and negatively correlate with certain tree species.

Squibb, Cari Lynn (Virginia Tech).  Mentor:  Rachel Hanauer (Indiana University).  
The age-class distribution of coccidian infections in Dark-eyed Juncos (Junco hyemalis).
Abrstact: Parasites are used in numerous studies to investigate biological theories in a wide range of taxa, including avian systems.  However, little is known about how parasites are distributed throughout ontogeny, despite the fact that age classes experience different stressors that may impact their vulnerability to parasitism. To examine the host-parasite dynamics in an avian system, we measured coccidian (Protozoa: Isospora) infection intensities in a small passerine species, the dark-eyed junco (Junco hyemalis). Fecal samples and condition measurements were collected from wild individuals in nestling, juvenile, and adult age classes. Additionally, the coccidia loads of three captive juncos were monitored daily to examine daily variation in the number of oocysts released. Coccidian oocysts were not detected in the nestling age class, but were found in the juveniles (70.59%) and adults (43.33%). There was no significant difference in infection intensity between adults and juveniles. No significant correlation was found between condition (as measured by mass divided by wing length) and infection prevalence or intensity. Additionally, we found that there was a great deal of daily variation in oocyst production in the captive juncos. Our results suggest that coccidian infections may not result in a condition cost to juncos, but future studies should examine other variables to determine if there are costs of infection. Due to the amount of daily variation found in oocyst production, one fecal sample may not accurately reflect the individual’s coccidia load, which reduces the effectiveness of coccidia as a study parasite in field studies.

Tomé, Braian (Florida International University).  Mentor:  Barbara Abraham (Hampton University).
Foraging patterns of bees on shrubs in and around Mountain Lake Biological Station.
Abrstact: Insect pollinators have been declining in the past few decades due to habitat loss and fragmentation, and the increased use of synthetic pesticides and herbicides. The service these organisms provide is a key ecological process, which, if disrupted, has the potential to make food webs collapse from the bottom up.  Native bee species, especially bumble bees (Bombus spp.), are of great importance in supporting this system.  Blueberries (Vaccinium spp.) serve as a source of nectar and pollen for pollinators, food and habitat for mammals and birds, and a food crop for humans. It is of interest to determine the most important alternative floral resources used by blueberry pollinators throughout the season at high elevations in and around Mountain Lake Biological Station (MLBS), Giles County, Virginia. This is due to the lack of information on native bees in this area. The study consisted of observing different species of flowering shrubs, and collecting or noting the bees that landed on their flowers. The data collected contributed to a greater understanding of the sequence of floral resources being used by native bees to support their populations through the season. In consequence, this information is useful for the conservation of forest resources and wildlife, and the sustainable development of blueberry farms.