Research

A matrix population model with juvenile, non-breeding, and adult life stages

Demography in variable environments

Environmental variability can affect populations through changes in survival, reproduction, and movement. I use matrix population models and life-history theory to examine how variation across time and space, together with density dependence, shapes population dynamics. Using long-term data from Soay sheep, I found that population density reshapes life-history trade-offs and the distribution of lifetime reproductive success. In spatially structured populations, we derived conditions under which temporal variability can favor migration even when one habitat is best on average. Across hundreds of animal and plant species, we found that reproductive dispersion scales proportionally with mean age of reproduction, whereas damping time increases more slowly.

A transient dynamics diagram showing vectors moving away from and toward an equilibrium

Perturbations and ecological stability

Ecological systems respond differently to brief disturbances (pulse), sustained environmental change (press), and persistent stochastic fluctuations. I develop models using perturbation theory, stochastic processes, and time series analysis to understand how disturbances shape transient dynamics, recovery, and long-term stability. We show that transient responses to pulse disturbances accumulate to determine the long-term response to sustained press disturbances. Using long-term time series of Trinidadian guppies, we found that environmental noise interacts with density dependence to alter equilibrium structure and resilience in ways not captured by standard early-warning indicators. We also developed a method that partitions variation in population growth into contributions from changing vital rates and transient population structure.

Community members harvesting peas in a high-elevation field in the Indian Trans-Himalaya

Conservation and socio-ecological systems

I am interested in studying how ecological dynamics interact with human livelihoods in shared landscapes and traditional farming systems. I combine participatory field research and long-term population monitoring to study socio-ecological systems in the Indian Trans-Himalaya. We studied a neglected and understudied traditional crop (black pea) and barley and compared it with an introduced cash crop, finding that black peas outperform green pea in survival and reproduction across high-elevation sites. We generated the first whole genome sequencing data for black pea and find it has distinctive genetic and nutritional value. Using a 13-year time series from a pastoral landscape, we found that higher wild-prey density is associated with greater livestock depredation, suggesting snow leopard-mediated apparent competition and highlighting the need to combine prey recovery with livestock protection. I also contributed to one of the first systematic regional assessments of snow leopard and prey populations, using camera traps and prey counts across 26,112 km² of the Indian Himalaya.