Data from: Seed predation has the potential to drive a rare plant to extinction

1. Pre-dispersal seed predation is sometimes considered unlikely to
dramatically affect plant population growth because plants are generally
expected to produce more seeds than there are safe sites for germination.
Lupinus constancei is a rare herb of limited distribution, with fewer than
400 reproductive individuals restricted to a single square kilometre of
north-western California, USA. In addition to the vulnerability resulting
from its extremely small population size, L. constancei faces heavy seed
predation by small mammals. 2. As a stop-gap measure to prevent population
decline, managers began covering a large number of the reproductive plants
with herbivory exclosures in 2003, but the population-level effects of
seed predation and the effectiveness of this caging treatment were
unknown. We used ten years of demographic data to compare the population
dynamics of plants inside herbivory exclosures with those sustaining
ambient rodent seed predation. 3. We found that the stochastic population
growth rate would be robust without seed predation (λs = 1.17), but
without continued human intervention (i.e. use of exclosures), the current
rate of predation would result in a decline towards extinction (λs =
0.92). 4. After our study concluded, high mortality due to two extreme
winter droughts followed by a wildland fire reduced the number of
reproductive plants to ~103, making extinction of L. constancei more
likely. 5. Synthesis and applications. The prevalence of consumer-driven
population decline is largely unknown, but this study demonstrates that
pre-dispersal seed predation by rodents can have powerful population-level
effects, and represents one set of conditions under which consumer
pressure has the potential to drive plant extinction. However, with
continued management to limit the effects of seed predation in the
short-term and investigation into the ultimate drivers of this high seed
predation rate in the long-term, the Lassics lupine population could be
restored to a robust rate of growth.