We modeled the
population viability of the endangered clonal shrub Florida ziziphus (Ziziphus celata)
based on nine years of data from two populations to identify management priorities.
Modeling a critically rare species, such
as Florida
ziziphus, requires additional consideration for both small sample sizes in
parameterization and short-term consequences for persistence in population
dynamics. We compare projection models
within these uniclonal populations based on hypothetically
independent “plants”. Seedling
recruitment is unknown in the study populations because of
cross-incompatibility and is not modeled. The populations modeled here have
stable demographies characterized by high survival
and stasis, but variable levels of new plant production (clonal
recruitment). Population growth rates suggest protracted long-term declines in
population size, but predicted extinction rates over 50 years greatly increased
when one favorable year is removed from simulations. Changes in new plant
production and survival had greater effects on population growth rates than did
changes in growth rates of individual plants. Augmenting clonal
plant production and protecting survival of new “plants” are short-term
management goals. The establishment of
sexually reproducing populations using augmentations and introductions is a
long-term necessity for the survival of Florida
ziziphus.