Biodiversity and Conservation 11: 2027–2046, 2002. 2002 Kluwer Academic Publishers. Printed in the Netherlands. Genetic impoverishment and cross-incompatibility in remnant genotypes of Ziziphus celata (Rhamnaceae), a rare shrub endemic to the Lake Wales Ridge, Florida C.W. WEEKLEY1,* , T.L. KUBISIAK 2 and T.M. RACE 3 1 Archbold Biological Station, P.O. Box 2057, Lake Placid, FL 33862, USA; 2US Department of Agriculture Forest Service, Southern Research Station, Southern Institute of Forest Genetics, 23332 Highway 67, Saucier, MS 39574, USA; 3Trout Lake Nature Center, P.O. Box 641, Eustis, FL 32727, USA; *Author for correspondence (e-mail:
[email protected]; fax: 11-863-699-1927) Received 19 July 2001; accepted in revised form 7 December 2001 Key words: Cluster analysis, Cross-incompatibility, Endangered species, Genetic diversity, Genetic impoverishment, Lake Wales Ridge, RAPDs, Sexual reproductive failure, Ziziphus celata Abstract. The loss of genetic diversity in fragmented populations of self-incompatible plant species may result in sexual reproductive failure and local extinctions. Florida ziziphus (Ziziphus celata)isa self-incompatible clonal shrub known only from five genetically depauperate populations on the Lake Wales Ridge, Florida, USA. Recovery of this species requires identification of cross-compatible genotypes that can be used to create viable (i.e., sexually reproducing) populations. To further development of a recovery program for this highly imperiled species, we investigated its genetic structure and sexual reproductive viability. We used random amplified polymorphic DNAs (RAPDs) to investigate genetic variability within remnant populations and we conducted experimental compatibility trials to determine the cross-compatibility of remnant genotypes. One hundred and ninety-nine unique stem samples collected from one ex situ and five in situ populations were assayed for the presence or absence of a band for 32 RAPD markers.