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Ziziphus celata Species Account

Scientific Name: Ziziphus celata Judd & D. W. Hall (Rhamnaceae)

Common Name: Florida ziziphus

Conservation Status: Federally and state listed Endangered.

Description: Florida ziziphus is a clonal shrub to 2 m in height. "Plants" (= presumably physiologically independent ramets) may be single-stemmed arborescent individuals or dense multi-stemmed clumps. The latter condition is often a response to mowing, but unmowed plants may also develop multiple stems. Plants resprout following fire and generally recover their pre-burn heights within two to three years. In the absence of fire (or mowing) plants may die back and resprout either at the base of the old plant or within a meter or two of the old plant. Populations generally comprise one or a few genetic individuals encompassing many separate “plants” spread out over an area covering dozens to hundreds of square meters.

Like many other shrubs adapted to xeric habitats, Florida ziziphus has spiny, geniculate branches and small leaves that are shed in the dry season. Flowers are about 1/2 cm in diameter, have five sepals, petals and stamens, and are fragrant. As in many other members of the buckthorn family, there is a nectar ring surrounding the pistil and the anthers are initially enclosed by clasping petals that reflex at anthesis to release pollen. The fruit is a single-seeded yellow drupe.

Distribution and Habitat: Florida ziziphus is known from 14 wild populations, all on the Lake Wales Ridge in Polk and Highlands Counties. Its range extends from Lake Wales in the north to Sebring in the south, a distance of 50 km. All populations occur on yellow sands (Tavares, Astatula and Candler), which historically supported longleaf pine/wiregrass sandhill, turkey oak sandhill or yellow sand oak/hickory scrub. Seven populations now occupy sites that have been converted to pastures. Most other populations occur in remnant longleaf pine/wiregrass sandhills or oak/hickory scrub. There is also a captive population in the Center for Plant Conservation National Collection at Bok Tower Gardens.

Genetics: Although several Florida ziziphus populations comprise dozens to hundreds of plants, nine of the 14 wild populations are uniclonal. Before 2007, when five new populations were discovered, genetic analyses including allozyme electrophoresis (Godt et al. 1997), RAPDs (Weekley et al. 2002), AFLPs (M. Gitzendanner, unpubl. data) and microsatellites (Weekley et al. 2007, Gitzendanner et al. 2012) concurred in recognizing that most populations consist of a single clone. However, four of the five populations discovered in 2007 are multi-clonal (Gitzendanner et al. 2012). Most importantly, two large pasture populations located near Lake Wales include at least 25 genotypes. In total, we now recognize more than 40, based on 8-loci microsatellite genotyping (Gitzendanner et al. 2012). However, some genotypes in the multi-genotype populations are closely related and may represent somatic mutants. A more conservative estimate of genetic diversity based on multi-locus lineages includes ~30 wild clones.

Breeding System and Pollination: Florida ziziphus is self-incompatible (Weekley and Race 2001) and many genotypes are also cross-incompatible (Weekley et al. 2002). Genotypes sharing the same self-incompatibility (S-) alleles belong to the same S-allele mating type and cannot reproduce sexually. To date, only two S-allele mating types have been confirmed in the wild, but a third mating type has been identified from the multi-genotype captive population at Bok Tower Gardens. Production of viable fruits has only been confirmed in three wild populations; the multi-genotype captive population at Bok has produced fruits annually since 1994.

Mating type assignments in Florida ziziphus are currently based on inferences from hundreds of hand-pollinations carried out over several years. Determination of mating type using a genetic approach would be much faster and easier than using hand pollinations; however, genetic mating-type assignment requires the identification and characterization of the genes that underlie the self-incompatibility reaction. To identify these genes in Florida ziziphus, we DNA-sequenced floral genes that are 'turned on' during anthesis, but we were not able to identify the self-incompatibility genes. However, this work enabled our collaborators to develop a large number of microsatellite markers for use in parentage analysis (Edwards et al. 2012). Identifying the parents of seedlings will provide additional insights into the cross-compatibility of wild genotypes and allow us to assign genotypes to the appropriate mating type. Knowing the mating types of all genotypes will enhance the design of future experimental introductions.

Florida ziziphus’s floral characteristics (fragrance, presence of nectar ring) indicate a generalist insect pollination syndrome. Floral visitors include a variety of bees, flies and butterflies. Flowering occurs in January-February when plants are mostly leafless. Flowers open throughout the day and remain open for three or four days. Mature plants often produce tens of thousands of flowers.

Life History: In 17 years of monitoring all known Florida ziziphus populations, neither seedling recruitment nor genet mortality has been recorded in the wild. In addition, genetic analysis of the large multi-genotype populations discovered in 2007 found no evidence for seedling recruitment (Gitzendanner et al. 2012). Thus, both single- and multi-genotype populations apparently persist and spread entirely through clonal recruitment. Although many “plants” (i.e., physiologically independent ramets) die (or die-back and resprout), some “plants” have survived for at least 20 years. Many of these long-lived individuals have flowered annually. Ellis et al. (2007) found that population growth rates indicate protracted long-term declines in population sizes, with extinction probabilities as high as 20% within 50 years. Ellis et al. (2007) concluded that the long-term persistence of Florida ziziphus populations requires the translocation of cross-compatible genotypes to establish sexually reproducing populations.

Recovery Program: The USFWS recovery program for Florida ziziphus (1999) calls for the establishment of sexually reproducing populations in appropriate habitat on publicly protected lands. Since most wild populations occur on private lands unlikely to be acquired for conservation, implementation of the recovery program requires the genetic augmentation of extant uniclonal populations and/or the creation of new multi-genotype populations capable of reproducing sexually. Since 2002, genetic augmentations have been carried out in two protected uniclonal populations and we have also carried out five introductions. Annual survival rates in translocated populations have generally been at least as high as survival rates in wild populations, but plant growth has been negligible. Most translocated populations have not flowered, suggesting that sexual maturation may be protracted in plants grown from seed in contrast to clonal resprouts in wild populations. However, since 2010,we have obtained fruits annually from several plants in one population introduced in 2006.

Interesting Facts: Florida ziziphus was thought to be extinct before its rediscovery in 1987 (DeLaney and Wunderlin 1989). It is one of the rarest of Lake Wales Ridge endemics and also one of the most endangered. The nearest relative of Florida ziziphus, Ziziphus parryi, occurs in Baja California, Mexico.

Data Collected by Archbold Biological Station’s Plant Ecology Program: All known individuals of Florida ziziphus, including wild, captive and translocated plants, are monitored at least annually for survival, growth and sexual reproduction. The Plant Ecology Program (PEP) has also collected data on the autecology, breeding system, and seed germination requirements of Florida ziziphus. The PEP collaborates with conservation horticulturalists at Bok Tower Gardens, and plant geneticists and other researchers at several institutions including the University of Florida, Colorado State University, Cedar Crest College, Army Corps of Engineers.

Current reports and other relevant unpublished documents are available here.

Data Availability: Data on cross compatibility and germinability are available here.

Contact Person: Eric Menges

Last Updated: 10 May 2012

Bibliography of Florida Ziziphus:

DeLaney, K. R., R. P. Wunderlin, and B. F. Hansen.  1989.  Rediscovery of Ziziphus celata (Rhamnaceae). Sida 13:325-330.

Edwards, C.W., T.L. Parchman, and C.W. Weekley. 2012. Assembly, gene annotation and marker development using 454 floral transcriptome sequences in Ziziphus celata (Rhamnaceae), a highly endangered, Florida endemic plant. DNA Research 19: 1-9. pdf link

Ellis, M.M., C.W. Weekley, and E.S. Menges. 2007. Evaluating stability in Ziziphus celata, a highly endangered clonal shrub endemic to Lake Wales Ridge, central Florida. Endangered Species Research 3: 125-132. pdf link

Gitzendanner, M.A.  C.W. Weekley, C. C. Germain-Aubrey, D. E. Soltis, and P.S. Soltis, 2012. Microsatellite evidence for high clonality and limited genetic diversity in Ziziphus celata (Rhamnaceae), an endangered, self-incompatible Lake Wales Ridge, Florida, USA endemic. Conservtion Genetics 13: 223-234. pdf link

Godt, M.J.W., T. Race and J.L. Hamrick. 1997. A population genetic analysis of Ziziphus celata, an endangered Florida shrub. Journal of Heredity 88: 531-533.

Judd, W. S., and D. W. Hall.  1984.  A new species of Ziziphus (Rhamnaceae) from Florida. Rhodora 86:381-387.

Menges, E.S., C.W. Weekley, and M.A. Rickey. 2008. Sandhill restoration studies and experimental introduction of Ziziphus celata at Lake Wales Ridge National Wildlife Refuge. Annual Report to Florida Fish and Wildlife Conservation Commission, Gainesville, FL. pdf link

U.S. Fish and Wildlife Service. 1999. Florida Ziziphus.  Pages 1986-1999 in Multi-species recovery plan for the threatened and endangered species of South Florida. U.S. Fish and Wildlife Service, Atlanta, GA.

U.S. Fish and Wildlife Service. 2009. Florida Ziziphus (Ziziphus celata) 5-year review: summary and evaluation. U.S. Fish and Wildlife Service, South Florida Ecological Services Office, Vero Beach, FL.

Weekley, C. W. 2009. Recent developments boost recovery prospects of Florida ziziphus. Palmetto 26: 8-11. pdf link

Weekley, C., T. Race and D. Hardin. 1999. Saving Florida Ziziphus: Recovery of a rare Lake Wales Ridge endemic. Palmetto 19: 9, 12.  

Weekley, C.W. and E.S. Menges. 2008. Experimental introductions of Florida Ziziphus on Florida's Lake Wales Ridge, USA. Pages 256-261 in P. S. Soorae, editor. Global re-introduction perspectives: Re-introduction studies from around the Globe. IUCN/SSC Re-introduction Specialist Group, Abu Dhabi, UAE. pdf link

Weekley, C.W. and T. Race. 2001. The breeding system of Ziziphus celata Judd and D.W. Hall (Rhamnaceae), a rare endemic plant of the Lake Wales Ridge, Florida, USA: implications for recovery. Biological Conservation 100: 207-213. pdf link

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

Weekley, C.W, M.A. Gitzendanner, C. Germain-Aubrey, D.E. Soltis, P.S. Soltis, and E.S. Menges. 2007. Genetic research crucial to the recovery of Ziziphus celata. Final report to U.S. Fish and Wildlife Service, Vero Beach, FL.

Wiese, C. and M.E. Kane. 2007. A new method of propagation for Ziziphus celata (Florida ziziphus), a Florida endangered species. Palmetto 24: 4-7,15. pdf link

Center for Plant Conservation National Collection at Bok Tower Gardens contains a multi-genotype population of Florida ziziphus that produces several thousand fruits annually. (Photo by C. Weekley.)
Flowering branch of Florida ziziphus showing buds and freshly opened flowers. (Photo by R. Bowman.)
Florida ziziphus seedling from germination experiment. Sand grains adhere to cotyledon in foreground. (Photo by C. Weekley.)
Plant Ecology Program intern Julia Gehring (left) and Bok Tower Gardens intern Melissa Nietzel install Florida ziziphus transplant in the 2010 experimental introduction at Lake Wales Ridge State Forest. (Photo by C. Weekley.)