ESR 3:125-132 (2007)  -  doi:10.3354/esr003125

Evaluating stability in Ziziphus celata, a highly endangered clonal shrub endemic to Lake Wales Ridge, central Florida

Martha M. Ellis1,*, Carl W. Weekley2, Eric S. Menges2

1Wildlife Biology Program, University of Montana, Missoula, Montana 59812, USA
2Archbold Biological Station, PO Box 2057, Lake Placid, Florida 33862, USA

ABSTRACT: Florida ziziphus Ziziphus celata is a self-incompatible clonal shrub comprising fewer than a dozen remnant, uniclonal populations in south-central Florida, USA. We model the population viability of this highly endangered species based on 9 yr of data from 2 populations. The matrix projection model is based on hypothetically independent ‘plants’ defined as clumps of ramets within a 25 cm radius. Seedling recruitment is unknown in the uniclonal study populations 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 yr are as high as 20% in one population. 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 through the translocation of cross-compatible genotypes is a long-term necessity for the persistence of Florida ziziphus populations.


KEY WORDS: Population viability analysis · Florida ziziphus · Clonal reproduction · Endangered species · Rare plant conservation


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