Mathematical Biology Seminar Linh Huynh, U of U Mathematics, Wednesday, Sept. 14, 2022 3:05pm in LCB 225 Harnessing stochastic fluctuations to disambiguate underlying mechanisms for the same observed dynamics Abstract: Density dependence is important in the ecology and evolution of microbial and cancer cell populations. Typically, we can only measure net growth rates, but the underlying density-dependent mechanisms can be feedbacks in birth rates, death rates, or both. We utilize the mean and variance of cell number fluctuations to separately identify birth and death rates from time series that follow logistic birth-death processes, and provide in detail an error analysis of our method. We apply our method to the scenario where a homogeneous cell population goes through three stages: (1) grows naturally to its carrying capacity, (2) is treated with a drug that reduces its carrying capacity, and (3) overcomes the drug effect to restore its original carrying capacity. In each stage, we disambiguate whether it happens through the birth process, death process, or some combination of the two, which contributes to understanding drug resistance mechanisms. Our method can be applied to other biological systems at different scales.