A fire-explicit population viability analysis of Hypericum cumulicola in Florida rosemary scrub

Land managers seeking to reestablish historical fire regimes need guidance on how to apply prescribed fire to promote the population persistence of endangered species. We explored extinction risks of Hypericum cumulicola , a fire-dependent plant endemic to the Lake Wales Ridge, Florida (U.S.A). Stochastic and deterministic matrix population models based on six censuses (1994-1999) and data from several germination and seedling survival experiments were used to compare H. cumulicola demography and extinction probabilities under different fire regimes. Environmental variation associated with site, year, and winter precipitation was included in these models. We estimated time to extinction of unburned populations of different sizes and the probabilities of extinction under no fire, different regular fire-return intervals, and alternating short and long fire-return intervals. Following an initial fire, even relatively large populations of thousands of individuals may become locally extinct within 300-400 years without additional fires. Extinction probability declined as intervals between fires decreased. Fire intervals of >50 years resulted in an appreciable extinction probability after 200 years. Cycles of highly staggered short and long fire-return intervals caused slightly higher chances of extinction than regular fire-return intervals. The simulations were sensitive to estimates of survival in the seed bank. Active management will be required to restore favorable fire regimes in areas where fire has been suppressed. To maintain biodiversity, managers should consider variable fire regimes to match the requirements of a variety of species with different life histories.