For my Ph.D. thesis, I worked on various projects that are united under a common theme: How do population processes percolate across different scales?
Monarch butterfly population dynamics.
Every year, the monarch butterfly (Danaus plexippus) population in the eastern North America makes a fantastic journey over many generations, from Mexico to Canada and back. Recent studies have shown a precipitous population decline in Mexico, which has been linked to the decline in milkweed host plants in the agricultural Midwest. Monarch caterpillars exclusively feed on milkweed, so it is not surprising that the milkweed decline appears to be locally impacting butterfly caterpillar abundance. Yet, it is not clear whether this local effect should scale-up to continental population decline. In this study (see Publications), I employed 4 different datasets (incl. citizen science data from NABA) and showed that the "milkweed limitation hypothesis" is not supported at the continental scale. Instead, different processes such as migration success seem to be dominating the population dynamics.
Drosophila microbiota population dynamics.
Recent technological advances have uncovered tremendous abundance and diversity of bacteria associated with plant and animal hosts. While there is great interest in basic ecological mechanisms structuring within host microbial populations and communities, an explicit test of traditional ecological theories is rare. A major challenge is observing microbial population dynamics in the host over time. In this project, I developed general model that links microbial population dynamics in the host gut, to statistics from widely collected data: fecal time-series data. I then apply this framework to Drosophila melanogaster - Acetobacter tropicalis model system, and test how host-microbial interaction changes under experimental treatments. We observe that A. tropicalis undergoes population reduction in the host gut due to both elimination and sequestration by the host, and higher microbial density leads to further reduction. Our dynamic models imply that the population decline occurs over narrow spatial range, and the ingested bacteria experience population bottleneck in few specialized compartments.
I have been working on theoretical models to elucidate how population dynamics affect speciation. Specifically, I am interested in understanding how the cost and benefit of choosiness may hamper or promote reinforcement. Moreover, it is not clear how choosiness evolves under asymmetrical population sizes. More to come.
Agrawal AA, Inamine H. (Accepted). Mechanisms behind the monarch's decline.
Inamine H, Ellner SP, Newell PD, Luo Y, Buchon N, Douglas AE. (2018). Spatiotemporally heterogeneous population dynamics of gut bacteria inferred from fecal time series data.
Inamine H, Ellner SP, Springer JP, Agrawal AA. (2016). Linking the continental migratory cycle of the monarch butterfly to understand its population decline.
Oikos 125: 1081-1091.
-- Cover Article
-- Press: NPR, PRI's Living on Earth, USA Today, Cornell Chronicle, etc.
Loweth J, Singer B, Baker L, Wilke G, Inamine H, Bubula N, Alexander J, Carlezon WA, Neve RL, Vezina P. (2010). Transient Overexpression of α-Ca2+/Calmodulin-Dependent Protein Kinase II in the Nucleus Accumbens Shell Enhances Behavioral Responding to Amphetamine.
The Journal of Neuroscience 30(3): 939-949.