2019 REU Projects

Bowen, John (Lawrence Technological University), Mentors: Elizabeth Ostrowski (Massey University and University of Houston) and Michael Miller (University of Houston).
Geographic variation in Dictyostelium discoideum altruism and selfishness
In nature, there is often a wide variation in the sociality of organisms, even within the same genus or species. We can develop an understanding of the variable social structures that allow individuals to be successful in a population by examining cooperation and conflict variation in different populations. Social amoeba Dictyostelium discoideum naturally creates opportunities for different strains to behave either cooperatively or competitively since some cells die to form a stalk that supports spore cells that go on to reproduce in the fruiting body stage of its lifecycle. This study worked to uncover natural variation in cooperation of D. discoideum populations from diverse geographic locations that cover a large portion of the species range. To accomplish this, an enrichment process for cooperative and competitive strains from each geographic location was carried out. While and after applying selection pressure for several rounds, we ran several experiments to better understand the natural variation of cooperation and competition in the different populations. Overall, this study showed that spore-biased enrichment may actually select for more selfish strains in D. discoideum populations and that cooperative variation likely exists both within and between these populations.

Cox, Madeline (Asbury University), Mentor: David McLeod (James Madison University).
Founder effect and morphological variation in Plethodon montanus 
Species that occupy the same niche compete for limited resources. These species can exist stably if they differentiate their niche, for example, by consuming different nutrients. At Mountain Lake Biological Station, Plethodon glutinosus and P. montanus occupy the same niche at Hunter’s Branch. The stomach contents of the syntopic salamanders were compared to the stomach contents of P. glutinosus from another community that had little interference with P. montanus. There was no difference in the diet of P. glutinosus and P. montanus from Hunter’s Branch (Pr (>F) = 0.489). There was no difference in the diet of P. glutinosus from Hunter’s Branch and P. glutinosus from the allopatric location (Pr(>|z|) = 0.471). If food was a limited resource, then P. glutinosus and P. montanus from Hunter’s Branch are in competition with each other and show no signs of niche partitioning.

Fan, Will (Emory University), Mentors: Elizabeth Ostrowski (Massey University and University of Houston) and Michael Miller (University of Houston).
Unequal sex ratio and mating behavior in Dictyostelium discoideum
The sex ratio of an organism is explained by its life history. For organisms whose life histories are difficult to observe directly, sex ratios may inform us a great deal about their reproductive behavior. Building on a previous study by Douglas et al. (2016), I examined the mating type distribution of Dictyostelium discoideum, a cellular slime mold with three mating types. When starved, D. discoideum amoebae of opposite mating types may undergo sexual reproduction and form structures called macrocysts. Many aspects of this behavior are currently unknown, and they have implications on the sex ratio of D. discoideum. In my study, I compared the sequences of 179 clones to the sex-determining locus of the three mating types. I discovered that the distribution patterns of mating types are unequal and site-dependent. These findings suggest that D. discoideum population is structure by mating type. My results also shed light on the frequency of sex, the relationship between the macrocyst stage and the fruiting body stage, and the type of interaction that occurs between two parental strains during macrocyst formation.

Gellinger, Madeleine (Indiana University), Mentor: Laura Galloway (University of Virginia).
Understanding arbuscular mycorrhizal symbiosis: does light indirectly affect Campanula americana?
Microbial symbionts, specifically arbuscular mycorrhizal fungi (AMF), are important for the maintenance of biodiversity and for individual plant fitness. These mutualists condition the soil but can also be influenced by abiotic factors and can ultimately alter aspects of plant fitness. Here I investigated the influence of light on AMF and other microbial populations to determine how these plant-microbial interactions may influence phenological and vegetative traits in Campanula americana using a field and greenhouse experiment. C. americana is a monocarpic herb that is found in partial shade and nutrient-rich soils. I evaluated vegetative and reproductive traits on plants growing in shade and open habitats as well as those with light environments altered by canopy defoliation and additional shading. I also conducted a greenhouse experiment in which field soil from the shade and open habitats were used as inoculum and seedlings were allowed to grow in open sun or shaded environments. In the field, increased light resulted in thicker leaves, larger plants, and earlier and more abundant flowering. In the greenhouse, light increased rosette biomass and the root-to-shoot ratio of plants, and shade-acclimated microbial populations increased plant biomass and lessened the time it took for a plant to produce its first leaf. This exemplifies that understanding microbe-plant interactions are important for understanding C. americana and potentially many other plant systems.

Sayles, Molly (Oberlin College), Mentors: Robin Costello and Butch Brodie (University of Virginia). 
No support for the preference performance hypothesis in forked fungus beetles
Abstract: The preference performance hypothesis states that females oviposit in such a way that maximizes offspring fitness. Two of the factors that may influence offspring fitness are resource competition and larval cannibalism, yet the relationship of these factors to oviposition has not yet been investigated. The number of eggs laid is expected to increase offspring competition and cannibalism and affect female oviposition site choice. This study investigates whether female forked fungus beetles (Bolitotherus cornutus) follow the preference performance hypothesis by exploring how the presence of pre-existing eggs affects female oviposition site choice. Females lay eggs singly on pieces of fungus called brackets that grow on decaying logs in the forests east of the Mississippi. The beetles experience resource competition when sharing their discrete piece of fungus, making them a good study system to explore female oviposition site choice and pre-existing egg density. Data from an observational study reveals that females lay more eggs on less crowded brackets. Thus, females oviposit in a way that follows the preference performance hypothesis. However, females also lay more eggs through time, suggesting that following the preference performance hypothesis may not actually maximize offspring fitness.  Data from a female choice experiment indicates that females do not choose to lay more eggs on empty versus crowded brackets, contradicting the results from the observational study by suggesting tat females do not follow the preference performance hypothesis. suggesting that following the preference performance hypothesis may not actually maximize offspring fitness. This study demonstrates that oviposition site choice is perhaps not an adaptive maternal effect.

Shaffer, Olivia (Frostburg State University), Mentors: Phoebe Cook and Butch Brodie (University of Virginia).
Subsocial insect networks show stable connections between individuals
Persistent associations in a population can be an important feature of social structures. Understanding whether associations are formed in a population can help give insight as to how these individuals interact as well as how they could be influencing each other’s fitness. We sought to find whether associations formed between individuals were predictable between time periods, as well as which relationships persist by asking whether mating or non-mating partners are more likely to be repeated. Observational data were taken of populations of Bolitotherus cornutus over the course of two three-week trials. Overall, in both trials for the 12 populations it was found that associations formed in the first eight days significantly predicted associations formed in the last eight days. When comparing different types of interactions, it was found that mating partners are better predicted by past mating interactions than non-mating partners by past non-mating interactions. This study suggests these subsocial insects are forming a non-random social structure by repeatedly interacting and mating with the same individuals.

Sklaver, Katherine (Eckerd College), Mentor: David McLeod (James Madison University).
A historical review of ornithology at MLBS
Biological field stations are important to the scientific community for their role in education, outreach, and research. Mountain Lake Biological Station (MLBS), is located in the southern Appalachian Mountains and its location endows upon it a wealth of diverse bird species. Given the description of MLBS, one would expect that the station has a sizable amount of data on ornithological study locations, behavior, and physiology, as well as an extensive specimen collection. However, there has only been one long term ornithology project at the station in the last 40 years, on Dark Eyed Juncos. This lack of research is, in part, because of the ornithological data at the station, little of it is reliably accessible. The goal of this project is to make the ornithological resources at the station more accessible for future researchers, students and citizen ornithologists, as well as to design and implement sustainable protocols for future data organization. To achieve this goal, the project has two stages. First, the ornithological data will be organized. Second, the ornithological data will be published and publicized in appropriate databases and websites. The ultimate goal of this project is to make it easier for people to use the ornithological data at the station. The expectation is that because the ornithological data will be made more accessible, more people who are interested in studying birds will use the resources of and ultimately contribute to MLBS research.

Vilella-Pacheco, Zorimar (University of Puerto Rico-Arecibo), Mentors: Lisa Mitchem and Butch Brodie (University of Virginia).
Do winners stink? Females discern the outcome of male combat using chemical cues
Male competition often selects for large males with extravagant displays or armaments, but traits of dominant males do not always indicate quality mates. In Bolitotherus cornutus (forked fungus beetle) there is competition for access to females.Copulation requires the females’ approval, suggesting that female choice also influences sexual selection in the species. . Previous research suggests that female choice is not a function of male traits used in competition (size and horn length). Females may use chemical signals to assess mate quality.  In this study we use behavioral trials to ask: 1) Do females perceive males using chemical signals? Similarly, because male signals can change after competition (Bunting & Hedrick, 2018), we ask: 2) Do females choose to associate with winning males? We performed female choice trials to test whether female beetles use chemical signals to detect and distinguish between potential mates. Our study provides the first evidence of chemical communication within B. cornutus. Females can perceive males using chemical signals and prefer to associate with scent of winning males.