Mast seeding, community dynamics, and tick-borne disease risk in forest ecosystems

Abstract

Tick-borne diseases are the most common vector-borne illnesses in the United States, with Lyme disease being the most frequently reported. Due to a warming climate, the incidence rates of tick-borne diseases are projected to increase — a risk exacerbated by the continued resilience of these diseases to the development of vaccines and treatments. Forecasting the risk of infection to prevent transmission in the first place remains the best approach for fighting tick-borne illnesses. Reservoir hosts, such as small mammals and deer, facilitate the transmission from the tick vector to humans with varying levels of success. Likewise, the population dynamics of reservoir host species may hinge on mast seeding events, or the synchronous, interannual variability in seed crop production within populations of perennial plants. The pulsed resource creates a trophic cascade through the food web that provides spatiotemporally separated niches for primary consumers of the mast. I explore the capacity of mast seeding events to explain, and therefore forecast, the distribution of ticks and the reservoir host species that facilitate tick-borne diseases in the eastern United States. I estimate the historic mast seeding events of individual trees with a state-space autoregressive model, synthesizing seed count data collected from sites for several decades. Based on these estimates, I determine the degree to which different genera of perennial plants affect reservoir host species, and in turn the degree to which different host species affect tick population dynamics.