2023 REU Projects

Altamirano Chavez, Maria (California State University - San Marcos), Mentor: Corlett Wood (University of Pennsylvania).
Medicago lupulina: Defense traits why are they so variable?
Abstract: To better understand the variations of defensive traits in plants, we will be using Medicago lupulina as a study system due to its variance in defense trait: Secreting trichomes. A field survey was conducted to test the different variations and possible trade-offs with producing Secreting Trichomes. Twenty individuals from eleven different populations were collected and then examined to evaluate the presence and absence of Secreting Trichomes as well as to determine any possible difference the distinct individuals had. To discover if the traits were perhaps a genetic trait passed down from parents, a Common Greenhouse Garden was tested. Offspring from both Secreting Trichomes and Non- Secreting Trichomes parents were grown. There was more variation in Secreting Trichomes than originally hypothesized yet there was no trade-off determined or any environmental factors associated with producing these specific defense traits. The genetic component is still undergoing research and will soon be known.

Cowing, Quinn (Brown University), Mentor: Sarah McPeek (University of Virginia).
How toxin distribution in fly poison (Amianthium muscitoxicum) guides the evolution of nectar and leaf toxicity
 Every species must mediate multiple species interactions throughout its lifetime, sometimes simultaneously. Studies that investigate the effects of multiple interactions on a single trait provide more insight on indirect pathways of selection that could occur from multiple selection agents. By looking at a plant-pollinator-herbivore system, we can explore how the evolution of defense traits can be affected by selection from multiple species. When plants evolve toxic chemical defense traits that end up in their nectar source, questions arise on the role of pollinators in defense trait evolution. Specifically, by studying the toxin distribution in a plant called fly poison, we can explore the potential effects of direct and indirect pollinator selection on plant toxicity. In order to do this, we selected 30 fly poison plants, excluded its pollinators and herbivores, took nectar and leaf samples, and analyzed our samples for toxin concentrations and sugar/volume measurements. We saw no relationship between nectar and leaf toxin levels nor nectar toxins and nectar sugar/volume levels. This lack of a relationship between nectar and leaf toxins suggests there is no constraint on the evolution of nectar toxicity by leaf toxin levels. In addition, this lack of a relationship between plant traits suggests that the loading of nectar toxins is not physiologically linked to leaf toxin transport. Further, the lack of a relationship between nectar toxin and sugar concentration suggests that the nectar toxin transport is not physiologically linked to the nectar sugar loading process. Finally, the lack of a significant relationship between nectar and leaf toxin levels suggests that indirect selection on plant toxicity by fly poison’s beetle pollinators is unlikely. Each interacting species is likely limited to selection only on the toxicity of their own food source.

Ferguson, Mikhaela (Shepherd University), Mentor: Corlett Wood (University of Pennsylvania).
Microbial effects on resource use and production traits in black medick
 Many organisms serve as hosts of microbial communities, whereby they regularly rely on microbes to facilitate crucial processes. The goal of this study was to investigate how microbes influence traits in their hosts using the well-studied Black Medick- Rhizobia mutualism as a study system. To show how different microbes can influence plant traits, we planted Black Medick in five different soil treatments. One of these treatments was a soil sample with a depleted microbial population, two treatments with intact soil communities, and two treatments with differing strains of rhizobia. We found that microbes did impact the resource use and production traits studied, but in a microbe and trait-specific manner. Composition of microbial community was more of a determinant of trait difference than presence or absence. Results indicate that microbial manipulations can be successfully implemented in the field, and that inoculations of soil microbial communities can enrich the environment for pathogens and parasites.

Griffith, Zaria (University of Rhode Island), Mentor: Sarah McPeek (University of Virginia).
The role of toxins in resource use among consumers of fly poison Amianthium Muscitoxicum
 This summer, we investigated the purpose of toxins in consumer-resource interactions by observing the foraging behavior of various consumers and the effects of aphids on inflorescences on the toxic plant fly poison (Amianthium muscitoxicum) at Mountain Lake Biological Station. During the first part of our experiment, we manipulated toxic nectar concentrations in fly poison and observed the amount of time consumers spent foraging. We then compared the mean time each species spent foraging for two manipulated treatments. In the second part of our experiment, we collected inflorescences with and without aphids and compared them by quantifying the concentration of toxins within each inflorescence. The results of our study allowed us to understand the role of toxins in consumption patterns among herbivores and pollinators.

McLaren, Ella (Case Western Reserve University), Mentor: Clara Stahlmann Roeder (University of Virginia).
Impact of contest outcome on reproductive effort and female preference in the forked fungus feetle (Bolitotherus cornutus)
 Male competition has been shown to make an impact on various behaviors, such as future contests outcomes and male association with a female. The question still stands: How does male competition impact intersexual selection in the form of male courting behaviors (male reproductive effort), and female preference? In this study, we observed the male courting, copulation, and guarding behaviors of Bolitotherus cornutus who have competed. We found that winners spend more time courting than losers (p = 0.0403), and winners had more copulation attempts than losers (p=0.0487). However, winning did not affect the success of copulation in the form of presence of guarding (df=1, p= 0.815). Winning also did not affect length of time spent guarding (p= 0.383). These results show that winners increase their precopulatory reproductive effort, but not postcopulatory reproductive effort. These results could imply a chemical change caused by competition that increases reproductive effort, followed by copulatory chemical change that counteracts the effects. This study also found that winning experience does not impact female preference. This could be because females are adverse to increased male pre copulatory behaviors. This study will aid in our understanding of male competition’s impact on female choice.

Moloney, James (Truman State University), Mentors: Chloé Lahondère and Forde Upshur (Virginia Tech).
Aedes japonicus phytophagy of fly poison (Amianthium musictoxicum) and analysis of floral volatiles
Abstract: Although it is popular belief that all mosquitoes consume blood for energy, this is not the case.  Only females of some species of mosquitoes are known to consume blood meals, but regardless of species, both male and female mosquitoes primarily get their energy from plant carbohydrates.  Mosquitoes use a combination of olfactory and visual cues to locate nectar meals.  At Mountain Lake Biological Station, the invasive Aedes japonicus mosquito was observed landing on the native fly poison plant, Amianthium muscitoxicum.  To better understand this plant-insect interaction, I performed three experiments.  First, I released lab-reared and sugar-starved Ae. japonicus mosquitoes into enclosures containing one fly poison inflorescence and recorded the number of surviving mosquitoes after 16 hours.  Second, I scanned each mosquito for pollen grains on its body and processed them for an anthrone chemical fructose assay to determine whether they fed on the plant nectar.  Third, I collected the volatile organic compounds (VOCs) that make up the floral scent using porapak traps and analyzed them using GC/MS.   I found that 29% of mosquitoes tested positive for fructose.  I believe pollen was primarily collected during sugar feeding, but not all positive pollen mosquitoes were positive for fructose.  I found that nonanal and ⍺-pinene make up the majority of the floral extract of fly poison.  This work provided essential insights to help develop an attractive toxic sugar baits (ATSBs) using nonanal and ⍺-pinene to control the population of Ae. japonicus, including both males and females.  Controlling the mosquito population will become increasingly important from a public health perspective as the climate warms and mosquito range increases.

Roeske, Isabella (Emory University), Mentors: Chloé Lahondère and Joanna Reinhold (Virginia Tech).
Exploring Culex territans mosquitoes host seeking and their role in trypanosome transmission to frogs
 This project explores the host-seeking behavior of Culex territans mosquitoes and their potential role as vectors of Trypanosoma to frogs. The study was conducted at Mountain Lake Biological in conjunction with the Biochemistry Department at Virginia Tech. Culex territans is a unique mosquito species in that it primarily feeds on ectotherms, with green frogs and American bullfrogs as its preferred hosts. The investigation of host-seeking behavior involved assessing the responses of Cx. territans to differing scents, such as live and dead frogs, carbon dioxide (CO2), feces, and urine, using a specially designed olfactometer. Results indicated that CO2 was not a primary host-seeking cue, but urine may be a potential attractant. Furthermore, visual behavioral assays revealed that this species might use visual cues to detect and feed on their hosts, despite Cx. territans being nocturnal. The study also explored the prevalence of Trypanosoma spp. in Cx. territans and its frog hosts. Sanger sequencing confirmed the presence of Trypanosoma ranarum in both mosquitoes and frogs. Subsequently, experiments were conducted to explore the potential transmission pathways of Trypanosoma within Cx. territans. The results provided strong evidence supporting the hypothesis that trypanosomes are transmitted through mosquito saliva. Overall, this study sheds light on the host-seeking behaviors of Cx. territans and highlights the potential role of these mosquitoes as vectors of Trypanosoma to frogs. The findings contribute to understanding the behavior and potential vector competency of a mosquito that primarily feeds on ectotherms.

Westermann Salas, Lukas (University of Maryland), Mentor: Clara Stahlmann Roeder (University of Virginia).
The chemical communication of age and its role in partner choice and assortment in forked fungus beetles (Bolitotherus cornutus)
 Social organization affects every organism at some level, whether it be a colonial invertebrate or a solitary mammal. An individual’s social environment and partner choice can directly influence their fitness, meaning optimal partner choice can maximize fitness. This paper explores how animals choose their social partners, and the extent that chemical cues are used in that regard. Forked fungus beetles (Bolitotherus cornutus) are an ideal system to address the topic of partner choice because they have been shown to assort by age and use chemical cues to choose partners. This allowed us to ask the question: do these beetles know each other’s age and assort accordingly due to chemical cues? These questions will be addressed by conducting sets of behavioral trials to see if young and old males and females prefer scents of males of different ages. This was measured by recording the time that the beetles associate with the scents of male beetles assorted by age. Beetles from different age and sex groups showed varying preferences for the smells of old and young males, but not aligned with their own age. These results suggest that the beetles can recognize and respond to each other’s age, but it does not match how they assort.  This study emphasizes the importance of chemical communication for assorting into social groups and choosing partners, also highlighting how an individual’s fitness is affected by its choice of partners. These chemical cues may have evolved to be able to better assess and choose social partners to improve fitness. As such, the traits expressing chemical signals may be under selection where the chemicals function as a medium for partner choice.