Interactive effects of herbivores, habitat and fire on the population dynamics of a rare plant endemic to the Florida scrub
The interaction of multiple types of disturbance is a common feature of many systems. These interactions may alter dynamics of populations within these systems and are thus critically important to study. We examined the interactive effects of three types of disturbance (vertebrate herbivory, fire, and anthropogenic disturbance along sand roads) on the demography of an endangered and narrowly endemic herb, Liatris ohlingerae. We used integral projection models to examine the effects of these factors on each vital rate. We additionally constructed megamatricies to determine the coupled dynamics of herbivorized and non-herbivorized individuals.
We found noticeable differences in overall population growth in populations with differing time-since-fire and in roadside populations. The estimated population growth rate was consistently higher in roadside populations as well as in recently burned plots. Increasing rates of herbivory increased the differences due to anthropogenic disturbance and largely eliminated differences due to time-since-fire. The results of this study show that differing levels of a disturbance may both amplify and dampen the effects of other disturbances on population dynamics. It is thus critical to take these potential effects into account when estimating the effects of disturbance on population persistence.