Department of Biology

Lauren Albert is a second-year Ph.D. student in the Evolution, Ecology, and Behavior Graduate Program. She is a member of Professor Spencer Hall’s lab.

Albert’s research questions are centered on advances in the community ecology of stage-structured interactions with disease dynamics. Stage-structure integrates competition for resources between and within life stages—linked through growth, development, reproduction, and mortality. From this framework, she focuses on the competitive asymmetries between stages that arise and how disease epidemics cause or affect these asymmetries. By doing this, Albert seeks to connect stage asymmetries with interesting population-level feedbacks that can influence the timing, size, and destructive power of epidemics. She addresses these individual and population-level questions using a planktonic host-fungal parasite system. The zooplankton host, Daphnia dentifera, becomes infected by spores of the fungal parasite Metschnikowia bicuspidata while feeding on algal resources. Virulence of spores on growth, fecundity, and survival likely causes or exacerbates stage asymmetries. For example, infection reduces adult size at first reproduction, affecting energy for reproduction and development. Further, Albert studies the various stage-structured interspecific interactions involving predators and algal resources of hosts, which can reveal additional consequences for asymmetries and disease. Her work tests predictions from mathematical models using mesocosm experiments and field surveys to ensure relevance to natural lake populations.

In addition to her research in the EEB Graduate Program, Albert works with a team of graduate students and researchers on the Modeling and Evidence Mapping Environment through the IU School of Education’s Learning Sciences program. This modeling interface helps elementary school students build models while making connections to scientific phenomena.

Kasie Chappell is a second-year Ph.D. student in the Evolution, Ecology, and Behavior Graduate Program. They are a member of Professor Spencer Hall’s lab.

Chappell is broadly interested in how sexual reproduction alters epidemic and population dynamics. Often, infected hosts allocate more resources to sexual reproduction—though it remains mechanistically unclear why hosts allocate more to sex. This ‘sicker-sexier’ response is predicted by the ‘abandon ship’ hypothesis, in which hosts produce more males that create diapause life stages to avoid stressors (colder temperature, disease, lower light). Chappell aims to explore: 1) what factors shape allocation to sex during epidemics, 2) whether higher frequency of males catalyze or constrain epidemics, and 3) how consumer (host-)resource dynamics are altered by changing sex ratios. Chappell will utilize the facultative parthenogenic system of Daphnia and their virulent fungal parasite Metschnikowia bicuspidata. This summer, they will conduct a field experiment coupled with a field survey to determine to what extent individual allocation to sex and population-level structure are altered by disease epidemics at intermediate seasonal conditions.

Stephen M. Dreyer is a second-year Ph.D. student in the Evolution, Ecology, and Behavior Graduate Program. He is a member of Associate Professor Erik Ragsdale’s lab. 

Dreyer’s research centers on developmental plasticity, the production of multiple phenotypes by a single genotype in response to environmental factors. Specifically, he is working to identify the genetic architecture of a plastic developmental response that harbors natural variation across populations in the wild. He utilizes the nematode Pristionchus pacificus—which exhibits a polyphenism (or plasticity resulting in discrete, alternative phenotypes) in its feeding structures. Environmental cues such as starvation and crowding influence the developmental decision between two adult feeding forms in this species, namely a microbivorous (“stenostomatous”) and a predatory (“eurystomatous”) morph. Dreyer has performed crosses between phenotypically similar lines to produce new, transgressive phenotypes, thereby uncovering combinations of alleles that can, in principle, be mapped and functionally validated. From these genotypes, he has used self-crosses in subsequent generations, while selecting upon the extreme phenotypes, to produce a panel of recombinant inbred lines. He will perform quantitative trait analysis, using the re-sequenced genomes of this panel, to identify regions of the genome that associate with difference in the polyphenism phenotype. In this way, Dreyer can reveal natural variation that influences the molecular mechanisms of a polyphenism and test how such alleles contribute to evolution of the polyphenism in nature.

Logan Geyman is a first-year Ph.D. student in the Microbiology Graduate Program. He is a member of Associate Professor Julia van Kessel’s lab.

Geyman investigates how using quorum sensing inhibitors impacts the evolution of Vibrio bacteria to understand how future use of these compounds will contribute to the evolution of their target bacteria over time. He also uses computer modeling to understand how heterologous bacterial populations impact the overall efficacy of quorum sensing inhibitors.

Holly Anderson is a second-year Ph.D. student in the Microbiology Graduate Program. She is a member of Associate Professor Ankur Dalia’s lab.

Anderson studies the systems that Vibrio cholerae uses to sense and respond to its environment. The facultative human pathogen V. cholerae is commonly found in the ocean, where it can colonize the chitinous surfaces of shellfish and zooplankton then degrade that chitin for use as a carbon source. The bacterium’s ability to sense chitin plays an important role in its pathogenicity, as this colonization behavior initiates a modulation of gene-expression-controlling biofilm formation, virulence factors, and natural transformation machinery within the cell. Her project focuses on the membrane-bound chitin sensor kinase ChiS and its periplasmic regulator periplasmic Chitin Binding Protein (CBP). ChiS is a transcriptional regulator for the expression of chitin catabolism and natural transformation genes in V. cholerae. In the absence of chitin, CBP will repress the DNA-binding activity of ChiS, but when chitin is present, chitin-bound CBP with activate ChiS transcriptional activity. Anderson seeks to characterize this dual-regulatory function that CBP exerts on ChiS in response to changing environmental conditions, thus giving insight into the diverse mechanisms prokaryotes employ to regulate sensor kinase activity.

As part of her graduate degree, Anderson is minoring in College Pedagogy, exploring her passion for teaching higher education, with a focus on helping non-traditional students navigate careers in STEM research.