Southern Research Station

Title: Genetic impoverishment and cross-incompatibility in remnant genotypes of Ziziphus celata (Rhamnaceae), a rare shrub endemic to the Lake Wales Ridge, Florida

Author: Weekley, C.W.; Kubisiak, Thomas L.; Race, T.M.

Date: 2002

Source: Biodiversity and Conservation 11: 2027-2046, 2002.

Description: The loss of genetic diversity in fragmented populations of self-incompalible plant species may result in sexual reproductive failure and local extinctions. Florida ziziphus (Ziziphus celata)is a self-incompetiblc 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 reproduclive 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. Based on unweightcd pair-group mean cluster analysis (UPGMA), only 11 multi-locus genotypes (MLGs) were identified. Eight of these MLGs correspond to MLGs identltied in an earlier allozyme study. In addition, we identified three new RAPD-based MLGs. Three of the five natural populations consisted of only one MLG, while the largest and most genetically diverse population comprised only four MLGs. Coefficients of similarity ranged from 96.6% for the most closely related MLGs to 20.7% fix the most distantly related. The compatibility trials demonstrated that most MLCs are cross-incompatible. With 69% of all possible one-way crosses tested (38/55) we have identified only eight compatible crosses via germination trials. Based on the results of the compatibility trials, we assigned MLGs to self-incompatibility (SI) mating types. On present evidence, the current breeding population of Florida ziziphus may comprise as few as two SI mating types. These SI mating types will be used to guide future breeding efforts and an experimental introduction.

Keywords: Cluster analysis, Cross-incompatibility, Endangered species, Genetic diversity, Genetic impoverishment, Lake Wales Ridge. RAPDs, Sexual reproductive failure, Ziziphus celata

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Citation

Weekley, C.W.; Kubisiak, Thomas L.; Race, T.M.  2002.  Genetic impoverishment and cross-incompatibility in remnant genotypes of Ziziphus celata (Rhamnaceae), a rare shrub endemic to the Lake Wales Ridge, Florida.   Biodiversity and Conservation 11: 2027-2046, 2002.