2018 REU Projects and SciComm Videos

Albert, Jamie (University of Tennessee), Mentor: Chloe Lash (University of Tennessee).
Ant chemical secretions do not deter rodent seed predation
Abstract: Seed dispersal not only contributes to the success of a seed but is crucial in defining plant species density and community structure. Though there are many means of seed dispersal, many plant species in eastern North America rely on ants to distribute seeds away from the parent plant. This is known as myrmecochory. During this dispersal process, ants remove the elaiosome (fleshy seed coat appendage) from the main seed body, which greatly reduces the likelihood of rodent predation. However, ant chemistry may further impact seed selection by rodents. Ants have several glands that secrete chemicals, which may coat the seed during the dispersal process and further deter seed predators after the ant has discarded the seed body. Preliminary data from our lab indicates the presence of pentadecane from gland secretions of Aphaenogaster ants. To analyze whether the presence of pentadecane on seeds influences rodent predation, we conducted field trials at Mountain Lake Biological Station to investigate rodent response to various treatments of ant dispersed plants. This research aimed to determine the effects of ant secretions on secondary dispersers and predators, as well as examined the impact that this process has on seed dispersal effectiveness. We found that the presence of pentadecane did not influence rodent seed predation. Additionally, follow up trials were conducted to analyze the susceptibility of seeds when in proximity to elaiosomes. These trials indicated that ant-handled seeds were not at a greater risk of predation when located adjacent to seeds with remaining elaiosomes. Additionally, the removal of elaiosomes may be less influential in determining seed mortality from rodent predators. However, there may be different aspects of the seed dispersal system that are affected by ant-handling and chemical secretions.

Bubrig, Louis (University of Alabama), Mentors: Elizabeth Ostrowski (Massey University and University of Houston) and Michael Miller (University of Houston).
To cooperate or not to cooperate: Competition and incompatibility in Dictyostelium discoideum chimeric slugs
 Territorial animals typically exhibit differential competitive behaviors toward neighbors and strangers. Tolerance toward neighbors and increased competitiveness toward strangers is termed the “dear enemy effect,” and is considerably more common than the reverse, which is the “nasty neighbor effect.” The model organism Dictyostelium discoideum, a social amoeba, has been previously used to study social behaviors typically found in communal animals. This experiment sought to find evidence of differential behavior toward geographic neighbors and strangers in these single-celled organisms by mixing strains isolated from sites throughout the Appalachian Mountains and observing their collective performance. I hypothesized that D. discoideum would perform worse with geographic strangers, in line with the dear enemy effect. Mix performance was found to be significantly correlated to geographic distance but instead showed that increasing geographic distance improved performance, supporting the existence of the nasty neighbor effect in D. discoideum.

DavisAustin (Virginia Wesleyan University), Mentor: Chloe Lash (University of Tennessee).
Grooming behaviors and survival in differently-sized Aphaenogaster colonies exposed to Beauveria bassiana
Generally, higher concentrations of individuals result in more rapid spread of pathogens. However, in eusocial insects, such as ants, behaviors like allogrooming, self-grooming and the application of chemical secretions may exhibit a reversal of the expected trend. Allogrooming (or grooming of a nestmate), as well as self-grooming, are behaviors that exists in a variety of ant species and serve as one form of defense against pathogens. Beauveria bassiana is an entomopathogen that parasitizes many insects, including Aphaenogaster ants, which are keystone seed dispersers in eastern North America. Here, we investigate whether allogrooming increases in frequency in Aphaenogaster exposed individuals, and whether survival is affected by colony size. We performed a behavior analysis in which seven ants were placed inside of small containers and exposed to either B. bassiana or a control. Separately, we performed a survival analysis in which 60 colonies of ants of varying colony sizes were exposed to B. bassiana. Allogrooming behavior did significantly increase in Aphaenogaster ants exposed to B. bassiana, and survival did differ by colony size and pathogen exposure. The survival analysis results for the control treatment displayed higher survival for large colonies than medium. In exposed colonies, small colonies survived significantly more than medium. Thus, social immunity in Aphaenogaster is complex and has components in addition to colony size, such as grooming behaviors.

Fraser, Linnea (Oberlin College), Mentors: Catherine Debban and Laura Galloway (University of Virginia).
Searching for reproductive isolation: Is reinforcement occurring in Campanula americana
Speciation research has historically focused on the reproductive barriers that arise in allopatry, but recent studies have begun to show that reinforcement, which acts through reproductive barriers that arise in sympatry, can complete speciation. Reinforcement is the selection for traits that prevent hybridization when the cost of hybrids is high, leading to speciation.  However, it is still poorly understood how often and among what groups reinforcement is occurring. In Campanula americana, the American bellflower populations of two distinct lineages exist in sympatry and allopatry, allowing a comparison between sympatric and allopatric populations of the lineages. Two regions of sympatry, one in North Carolina (NC) and one in Pennsylvania (PA) show evidence of different levels of gene flow indicating lineages may be on different evolutionary trajectories in different regions. In our study we looked for reproductive isolation between lineages due to pollinator preference and pollen-style interactions.  We set out arrays of plants of the two lineages and observed transitions between plants. We also crossed plants with pollen from within and between lineages cutting at 5h and 6h to prevent slow growing pollen from fertilizing ovules. Pollinators did not discriminate between the two lineages  in PA indicating no reproductive isolation due to pollinator preference. In NC pollinators preferred Western lineage plants, indicating pollinator preference could lead to reproductive isolation but this reproductive isolation is not consistent with reinforcement. We found that there is no reproductive isolation between lineages in sympatry due to pollen-style interactions however, relative to allopatric pollen-style interactions which increase hybridization, there is some indication that reinforcement may be occurring.

Horr, Daisy (Trinity University), Mentor: David McLeod (James Madison University).
The study of amphibians and reptiles at Mountain Lake Biological Station
Biological field stations are important to the scientific community for their role in education, outreach, and research. Mountain Lake Biological Station, Virginia (MLBS) is located on Salt Pond Mountain in the South-Eastern Appalachia, a hotspot for amphibian and reptile diversity, therefore making MLBS an incredible resource for herpetological research. MLBS has a rich legacy of amphibian and reptile-related research, and their own consortium of amphibian and reptile museum collections information, yet none of this information is readily or reliably accessible. The goals of this project were to create and build upon the herpetological resources present at MLBS and to create a comprehensive reference collection for future herpetology-related research work. In this study we conducted 1) historical research involving (a) collecting and archiving years of herpetological literature conducted at the station, and (b) documenting available museum specimens found at MLBS and the surrounding areas of Giles County. Additionally, we executed 2) current studies to address the present status of the herpetofauna community MLBS, which involved (a) implementing field surveys to collect presence/absence data on amphibian and reptiles, (b) collected between 5–10 individuals of each species for museum specimen and tissue collection for DNA barcoding documentation.

Hueston, Rita (University of Virginia), Mentors: Elizabeth Ostrowski (Massey University and University of Houston) and Michael Miller (University of Houston).
Altruism investment and chimeric conflict in Dictyostelium discoideum
Animal populations often  react differently to interactions with members of neighboring (sympatric) populations with whom they come into contact frequently than they do to interactions with members of populations they have never met before (allopatric). Two effects describe these interactions: Dear Enemy, in which sympatric populations are tolerated: this allows them to reduce the amount of energy lost through constant competition, and instead focus that energy on defending against the occasional allopatric invader; and Nasty Neighbor, in which sympatric populations are in constant conflict, but infrequent allopatric interactions are tolerated. The social amoeba Dictyostelium discoideum is an ideal model organism to study these interactions because entire population interactions are contained within a single multicellular microbial organism. This project expands on previous work in which slug fitness is decreased when allopatric chimeras are created (Votaw and Ostrowski, 2017). 19 chimeric mixes were created, 10 from allopatric populations along a distance gradient ranging from a few meters to 1500 km, and 9 from sympatric populations from ten different sites. Stalk height and spore number were measured as signals of levels of conflict or cooperation, as investment in stalk height is seen as an altruistic investment and a result of cooperation. I found that stalk height increased and spore number decreased as expected with genetic distance, but that overall sympatric mixes produced larger stalks and fewer spores than allopatric mixes.

Keclik, Julieanna (Florida State University), Mentor: Adriana Herrera Montes (University of Puerto Rico - Río Piedras).
Changes in ecosystem services due to increase in building areas: A case study in the Appalachian region
Ecosystem services are the benefits that the ecosystem naturally provides but due to the increase in human population and the continual alteration of the earth, has the potential to be affected. Which is why the focus of this study will be to evaluate the changes of ecosystem services along a forest to peri urban gradient. This will be studied in the Appalachian forest region, forest, Mountain lake Biological station for rural sites, and Blacksburg to account for Peri-Urban sites. In this study I will specifically quantify the changes in supporting, provisioning, and regulating services. I will describe habitat structure as an estimate of supporting services, composition of woody vegetation for regulating service, and describe the community of salamanders and composition of soil invertebrates to measure biodiversity to quantify provisioning services. In my findings I found that that there was a change in habitat structure, it is shifting from natural landscapes with native woody vegetation to areas more manicured and with more ornamental species of woody vegetation and increasing in spatial heterogeneity. As habitat structure shifts along this gradient there is a decline in salamander populations. No significant change of regulating services were found along the gradient, but further studies should be done to quantify what factors of woody vegetation increase regulating services.

Martínez-Oquendo, Pamela (Pontifical Catholic University of Puerto Rico), Mentor: Adriana Herrera Montes (University of Puerto Rico - Río Piedras).
Changes in the morphology of the red-backed salamander in building areas
Increasing of human population associated to land use transformation is a general trend around the world. Human activities promote that natural areas to be transformed into more anthropogenic landscapes, which could critically affect the organisms adaptation capacity and response to the environmental challenges associated with landscape transformation. This started happening in the Appalachian Mountains when they were occupied by Europeans that used the land for farming and lumbering. Today, they are the home of millions of people and are also the touristic attraction of visitors from around the world that have impacted the area.  Therefore, it is necessary to address this situation, because these mountains are known for their great diversity of organisms, including amphibians such as salamanders. Which is why, my study focused on the effect of humans on the salamander morphology in the Appalachian mountain. For this, I evaluated the consequences of disturbances in the salamander Plethodon cinereus. I used a disturbance gradient that represented undisturbed and disturbed areas. My undisturbed area was a forest and my undisturbed areas were peri-urban/urban areas. Each one of these categories had at least three replicas with ten P. cinereus individuals. I measured the body size and weight of each salamander to evaluate the hypothesis that heavily habitat transformation have consequences in the salamanders morphology. I found that the length and weight of individuals inhabiting forested and rural areas were similar when comparing forest versus rural areas, but were different when compared just the forests sites together, and when I compared just only the rural sites among each other.

PayneDeanna (University of Colorado Boulder), Mentor: Sarah Budischak (Princeton University).
Exploring growth stunting and endoparasites in P. leucopus and P. maniculatus
In previous research, intestinal parasites have been linked to both mental and physical stunting in human children, however, when considering the prevalence of soil-transmitted helminthiases (out of 836 million children throughout the world who need treatment) only 517 million children received treatment in 2016 (WHO Reports). Intestinal parasites contribute to growth stunting by taking vital nutrients from its host, leading to malnutrition, creating a deficit in the necessary resources the host finds essential in growth functions or by causing damage that prevents the host from absorbing the nutrients it ingests. Growth stunting refers to the prevention or slowed development compared to a fully capable individual with unlimited resources or described by its genetic potential. The purpose of this research is to further understand the relationship between host-parasite interactions; specifically, how intestinal parasites might stunt the growth of young wild mice (Peromyscus leucopus and Peromyscus maniculatus) as individuals develop from juveniles into adults. By using mark and recapture techniques, data about physical characteristics and feces samples was collected from the Peromyscus populations surrounding the Mountain Lake Biological Station, in order to determine changes in body size and growth rates in mice from juvenile or sub-adult to adult. Data analysis (using linear mixed models) shows no significant relationship of number of intestinal parasites or types of intestinal parasites (coccidia, nematodes, or cestodes) to growth rate or body size, in either Peromyscus maniculatus or Peromyscus leucopus. Finally, no significance between number intestinal parasites and types of intestinal parasites compared to growth or body condition may indicate that similar experiments analyzing the relationship between intestinal parasites and growth stunting has a correlation rather than causation.

Stankovic, India (Waynesburg University), Mentor: Sarah Budischak (Princeton University).
The nematodes of Mountain Lake: what are they, how prevalent are they, and where are they coming from?
Disease ecology is defined as the efforts to understand pathogen transmission and spread over space and time, and the impact it has on host populations (Kilpatrick and Altizer, 2010). Parasite prevalence and trophic transmission in food webs has been extensively studied (Rossiter, 2013). In an effort to determine the prevalence of parasite transmission from an intermediate host to the definitive host within a specific food web, I will focus on the prevalence of nematodes in a potential intermediate host and across a range of Peromyscus leucopus populations. In a 2011 study conducted by Luong and Hudson, at the University of Pennsylvania, research verified the intermediate host of a common gastrointestinal nematode. Pterygodermatites peromysci infected 70% of C. pallidipes (camel crickets) increasing P. leucopus populations susceptibility as the camel crickets main predator. Peromyscus leucopus and camel crickets both cohabitate the Appalachian mountains of northern Virginia, yet there was not solid evidence to assume these crickets trophically transmit this nematode at Mountain Lake Biological Station. Trapped mice and insects, from dissections, sequenced parasites to see if they matched across species. The dissections of white footed mice revealed various white worms, red worms, tapeworms, and a few unrecognizable nematodes. Camel crickets and a beetle species (Carabus vinctus) were also dissected to determine if they too were infected with the same species of nematodes. Unfortunately, although the PCR amplification of the barcode region worked, the sequences showed signs of contamination and were unusable. Aspicularis americana, Syphacia peromysci, and Capillaria americana find refuge in P. leucopus on Mountain lake; still to be determined is what these parasite life cycles look like. My first goal being to use molecular barcoding to identify two here-to-unknown species, mysterious nematodes A and B. And my second goal being to use this information to determine whether or not an intermediate host is involved. My research is not clear in determining what these nematodes are or if there is an intermediate host involved.

Thoms, Rachel (University of Virginia), Mentors: Robin Costello and Butch Brodie (University of Virginia).
Home range mediates the effect of resource dispersion on social interactions​
Social interactions have important fitness consequences and are highly variable within and among populations. This variation in social interaction might be explained by the physical environment where the interactions take place. An individual’s home range is often a product of the environment, and home range overlap has been shown to predict sociality. This study investigates (1) if differences in environmental resource dispersion explains variation in social interactions and (2) whether the effect of resource dispersion on social interactions is mediated through home range size. We tested this through manipulation of fungal resource dispersion in twelve experimental populations of forked fungus beetles. Path modeling demonstrated that as resources become more clumped, individuals home range sizes decrease, and this decrease in home range size predicts an increase in the number of social interactions, but not in number of social partners.  While the physical environment does have a significant effect on patterns of social interaction, this effect is driven indirectly through changes in individual space use. This study provides a clear example of the mechanism through which the environment structures social interactions.