WEEKLEY, CARL W.* AND TAMMERA RACE. Plant Ecology Lab, Archbold Biological Station, Lake Placid, FL 33852. - The breeding system of Ziziphus celata Judd and D. Hall (Rhamnaceae), a rare endemic shrub of the Lake Wales Ridge, Florida: implications for recovery.
While the rarity of an endangered plant species can seldom be ascribed
to its breeding system, knowledge of its breeding system may be
critical to its recovery. The federally-listed endangered Ziziphus
celata, a woody clonal shrub endemic to xeric upland habitats of
the Lake Wales Ridge in central Florida, is known from only five
populations, four of which are sterile and perhaps uniclonal.
Altogether only eleven genotypes of Z. celata have been
identified, based on allozyme electrophoresis. We conducted field
experiments, including hand-pollinations of bagged flowers, over a
four year period to determine the breeding system of Z. celata.
We found that it is an obligate outcrosser and that some genotypes
appear to be cross-incompatible. Determination of cross-compatibility
is complicated by the high percentage of seed abortion and by the
presence of parthenocarpic fruit. Germination trials and seed
dissections are therefore required to confirm cross-compatibility.
While eleven of 44 test crosses performed to date have yielded fruit,
we have obtained germinants from only four crosses. Our objective is
the identification of cross-compatible genotypes to be used for the
genetic enhancement of sterile populations and the creation of new
fertile populations. The translocation of compatible mating types to
create reproductively viable populations is essential for the recovery
of Z. celata.
Key words: breeding system, endangered species restoration, Lake Wales Ridge, rarity, Ziziphus celata