Davis, Kathryn (Nash Community College), Mentor: David Beamer (Nash Community College).
Environmental correlates of population density and home range size of an introduced population of terrestrial salamander
Abstract: Woodland salamanders (Genus: Plethodon) are widely distributed across the eastern U.S. Over the southern Appalachians, they occur sympatrically and allopatrically; the allopatric distribution of large Plethodon species has been hypothesized to be the result of competition. Plethodon montanus was introduced around 1940 to Mountain Lake Biological Station (MLBS) where it is now sympatric with Plethodon glutinosus. We examined environmental correlates of P. montanus presence and absence at MLBS by establishing transects, measuring soil temperature, leaf litter depth, and estimating percent canopy cover and percent rock cover. We compared its population density with that of its source population. We established plots wherein we performed mark-recapture to estimate the home range size of P. montanus at MLBS.
Fristoe, Mason (University of Virginia), Mentor: Sarah McPeek (University of Virginia).
The patriarchy of pollination: Mixed evidence of sexual conflict in Amianthium muscitoxicum
Abstract: Sexual conflict results when the two sexes engage in differing strategies for maximizing their reproductive success. These different strategies may result in an evolutionary arms race in which males evolve mating strategies that force females to mate at rates beyond their optimum and females evolve resistance to these strategies. Levels of sexual conflict may be especially elevated in simultaneous hermaphrodites such as angiosperm plants because individuals possess both male and female reproductive function. Many species of angiosperms require an intermediate vector in the form of a pollinator to facilitate their reproduction. While pollinators benefit both sexual components to some degree, over-investment in pollinator-attracting traits may cause female function to mate at a rate beyond her optimum at the expense of her reproductive success. This may select for increased plasticity in traits associated with resource allocation to female function for more flexible reproductive investment. I used these plastic responses of nectar production and non-foliar photosynthesis to empirically quantify sexual conflict in a hermaphroditic angiosperm. I used Amianthium muscitoxicum (fly poison) as a model system. I measured standing nectar volume in the presence and absence of male function. I also measured rate of conversion of floral tissue to photosynthetic tissue with respect to inflorescence size. Flowers with male function removed produced significantly less nectar than intact flowers (p = 0.008). I observed no correlation between rate of conversion of floral tissue to photosynthetic tissue and inflorescence size. These results suggest that sexual conflict was present in nectar production in fly poison.
Medina Valencia, Alejandro (Iowa State University), Mentor: Phoebe Cook (University of Virginia).
How do resource quality and age structure within demes change over time?
Abstract: Metapopulations are temporally dynamic communities composed of subpopulations on resource patches that appear and disappear. Individuals within these patches may be under different pressures which can alter their behavior and overall fitness. This project’s purpose was to understand how resource quality and age structure in metapopulations of forked fungus beetles, Bolitotherus cornutus, changes over time and to see if there was any correlation between them. The questions we asked was which age group was founding new resource patches? How does resource quality change over time? How does age structure change over time? To answer our first question, we created 10 artificial resource patches of newly grown host fungus Ganoderma tsugae around previously aged metapopulations of B. cornutus. To answer the other two questions, we used data collected from 2015-2021 in the Brodie Formica Lab at Mountain Lake Biological Station in Giles County, Virginia. Our results for which age group disproportionately establishes new demes was inconclusive as only five individual beetles were ever seen on the artificial resource patches; something of note was that all these individuals were identified to be one-year-olds which gives rise to a possible trend, but more information would be needed to prove this. For our fungus quality analysis, we saw a decline in live growth as demes age. In our age structure analysis, we saw an increase in the proportion of one-year-old beetles as demes age. We also saw that the percent of live growth on a population did not correlate with the proportion of new beetles. Our conclusion is that time can explain some of the variation within this metapopulation in both resource quality and age structure, yet resource quality does not predict age structure in this system. This suggests that these processes are independent of one another in this system.
Mullins, Colleen (University of Virginia), Mentor: Adam Fudickar (Indiana University).
Birds reared in longer photoperiod are larger and eat more: implications for response of species to climate change
Abstract: The growth rate and body size of a species often vary geographically. Growth rates of an organism positively correlate with latitude and migratory tendencies of the species. In birds, a longer photoperiod is known to increase the time in which a nestling is fed each day, and increased food supply has been positively correlated with growth rate. In addition, the overall body size of migrants is typically smaller than their resident counterparts. Whether photoperiod, and thus the amount of time in which an organism is fed during development, drives this variation in growth rate and morphology is unknown. We explored this question using the dark-eyed junco (Junco hyemalis) by rearing nestlings of a sedentary junco subspecies, J. h. carolinensis, under the natural photoperiods of either a closely related migratory subspecies (J. h. hyemalis) or the natural photoperiod of carolinensis and compared the amount of food they consumed during development, growth rate, and morphology. Total daily food consumption, growth rate, fasted mass, and body size were all greater in birds that were hand-reared under the more northern photoperiod treatment. This suggests the variation in growth rate and morphology among different photoperiods was caused by differential total daily food consumption and has implications for species breeding in more northern latitudes in response to climate change.
Roark, Megan (University of Virginia’s College at Wise), Mentors: David McLeod (University of Virginia) and Chloe Lahondère (Virginia Tech).
Understanding the interactions between frogs and the mosquito species, Cx. territans at Mountain Lake Biological Station
Abstract: The unique interactions between ectotherm-feeding mosquitoes and their amphibian hosts are generally understudied. Understanding these interactions can elucidate mosquito biology and their role in pathogen transmission. This study focuses on Culex territans, a mosquito species that feeds primarily on amphibians. In the project, I pursued three objectives: 1) determine the hosts of Cx. territans at Mountain Lake Biological Station, Pembroke, VA; 2) assess the prevalence of various pathogens in two frog species; and 3) determine the prevalence of the fungal pathogen, Batrachochytrium dendrobatidis (Bd), at the station and whether Cx. territans is a potential vector for it. These objectives were addressed using DNA (Sanger) sequencing for mosquito blood meal host identification, PCR assays for trypanosome detection, qPCR for Bd detection, and a Bd contact transmission assay. DNA extracted from 36 mosquito blood meals indicated Cx. territans fed on L. catesbeianus (61%), L. clamitans (33%), L. sylvaticus (3%), and Nerodia sipedon (3%). Analysis of 83 Bd swabs resulted in detection of infection in a single individual L. catesbeianus (of 23 samples) and in four P. crucifer (of 9 samples). Mosquito blood meals also tested positive for trypanosome DNA. In summary, I found that Cx. territans feeds on a variety of hosts, may be harboring trypanosomes, and Bd prevalence at MLBS is relatively low.