LTREB Renewal: Instability, contingency, and global change in a terrestrial food chain

Michigan Technological University, Houghton MI

Investigators

Abstract

Isle Royale National Park is an island inhabited by wolves and moose, studied continuously for the past six decades. Recently, the wolf population collapsed to near extinction and the National Park Service responded by relocating mainland wolves to the island. One goal of this research is to test a long-standing idea in ecology that population fluctuations are driven by random events (such as extreme climate events and outbreaks of disease) more so than by predictable patterns such as the availability of food or mortalities due to predation. Knowing which influence is stronger – random events or predictable patterns – has important consequences for ecology and conservation. A second goal of this research is premised on the idea that relationships between carnivores and herbivores are indirectly affected by herbivores’ relationship with the plants they eat. Plants naturally produce chemicals (in varying amounts) that are unpalatable to herbivores and help the most fit plants from being overbrowsed. This research aims to understand how those herbivore-plant relationships reach up the food chain to affect carnivores. The research team will be involved with educational outreach, public engagement, and innovative art-science collaborations, focused on species of broad public interest. The first goal of the research is to test the Historical Contingency Hypothesis: population dynamics are largely the result of a series of random events characterized by (i) legacy effects that are comparable in length to the waiting time between such events and (ii) the disparate nature of individual random events. This goal will be achieved through analysis of field data with recently developed statistical methods. Support for this hypothesis could explain why ecological surprises are common, why ecologists are better at explaining the past than forecasting the future, and why populations tend to exhibit weak density dependence over longer periods of time. The second goal is to test the hypothesis that predation and the chemical ecology of herbivory have comparably strong influences on food chains. Recent theory indicates the hypothesis is plausible, and an empirical test of this requires a system like Isle Royale, where the influence of predation is well-documented. The test involves parameterizing a “toxin-dependent functional response” by quantifying how plant secondary compounds influence foraging by moose within and between foraging patches. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.