Allozyme Variation and the Genetic Structure of Populations of the Rare Sedge Carex misera (Cyperaceae)

Abstract Carex misera is a rare sedge, endemic to rocky outcrops and mountain summits within the southern Appalachian Mountains from northern Georgia to northern North Carolina. We assessed allozyme diversity for 406 individuals from nine populations over most of the geographic range. Twenty-seven putative loci were assayed and eight (30%) were found to be polymorphic. Nei's gene diversity statistics ( H _T =0.043, H _S =0.019, G _ST =0.551) indicated low levels of variation but relatively highly differentiated populations, suggesting little gene flow. Significant deviations from genotypic expectations under Hardy-Weinberg equilibrium, high positive fixation indices, and the existence of small genetic neighborhoods within populations suggest that at least some inbreeding occurs. Cluster analysis of Nei's genetic identity statistics and principal component analysis of allele frequency data showed high similarity among the six southern populations with the two northern populations more differentiated from them and from each other. These results suggest that preservation of the northern populations is necessary to conserve the already low levels of genetic diversity within the species.     

Direct evidence for biased gene diversity estimates from dominant random amplified polymorphic DNA (RAPD) fingerprints

The relevance of using dominant random amplified polymorphic DNA (RAPD) fingerprints for estimating population differentiation was investigated when typically small population sample sizes were used. Haploid sexual tissues were first used to determine genotypes at RAPD loci for 75 eastern white pines ( Pinus strobus L.) representing five populations. Dominant RAPD fingerprints were then inferred from genotypic data for each individual at each locus, and gene diversity estimates from both sources of data were compared. Genotypic information at RAPD loci indicated little or no differentiation among populations, similar to allozyme loci. However, estimates of population differentiation derived from dominant RAPD fingerprints according to various common methods of analysis were generally inflated, especially when all fragments were considered. Simulations showed that an increase in loci sampling and population sample sizes did not significantly alleviate the biases observed.     

Allozyme, mitochondrial-DNA, and morphometrie variability indicate cryptic species of anchovy (Engraulis encrasicolus)

Previous surveys of population structure in the Atlantic-Mediterranean anchovy Engraulis encrasicolus L. have reported heterogeneity in morphology, allozyme frequencies, and mitochondrial DNA haplotype frequencies at a regional scale. In particular, two stocks of anchovy have been detected in the Adriatic Sea. In this paper, the available data is reviewed with the aim to relate genetic variation to geography at the widest possible geographical scale, for investigating the evolutionary mechanisms underlying stock structure in anchovy. Correspondence analysis of allozyme frequencies (24 samples, three polymorphic loci) compiled from the literature indicates three distinct entities in the Mediterranean Sea. Open-sea or oceanic anchovy populations are genetically different from inshore-water populations within a region (Nei's ^ G _ST = 0.035–0.067), while broadscale geographical variation is weak for each of these two habitat-specific forms (^ G _ST = 0.005–0.006). Mitochondrial-DNA haplotype frequencies support the distinction between an inshore form and an oceanic form (^ G _ST = 0.067–0.107), with virtually no genetic differences among oceanic populations across the Gulf of Biscay, the western Mediterranean and the Ionian Sea (^ G _ST = −0.001). If natural selection on marker loci is unimportant, these results indicate the occurrence of two parapatric, genetically distinct, habitat-specific forms that are widely distributed throughout the Mediterranean Sea. Persistent allele and haplotype-frequency differences between these forms indicate reproductive isolation and the presence of an E. encrasicolus species complex in the Mediterranean. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society 75 : 261–269.     

Clonal diversity in the rare Calamagrostis porteri ssp. insperata (Poaceae): comparative results for allozymes and random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR) markers

Four populations of the rare, highly clonal grass Calamagrostis porteri ssp. insperata were examined using allozymes and the two polymerase chain reaction (PCR)-based markers, random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR) bands. Only one of the 15 allozyme loci was variable and two alleles were detected, both of which were found in two populations, while only one genotype was detected in the other two populations. ISSR and RAPD markers detected more genotypes within populations than did allozymes. ISSR markers detected more diversity than RAPD markers in three of the four populations examined. In one population, no RAPD diversity was found whereas eight different genotypes were found among the 10 plants with ISSR markers. This diversity is present despite rare flowering, no documented occurrence of seed set in natural populations and very low seed set with experimental pollinations, all of which suggest that sexual reproduction rarely occurs. The subspecies is self-compatible, but seed initiation is lower in selfed ovules; also, there is high embryo abortion regardless of pollen source. Variation detected by RAPD and ISSR primers may reflect higher levels of sexual reproduction in the past, very rare sexual reproduction in extant populations, somatic mutations, or a combination of the three. Although the PCR-based markers identify several multilocus genotypes within populations, it is not known whether these all represent distinct genets generated by sexual reproduction or result from somatic mutations in the old, perennial and highly clonal plants.     

Multilocus DNA fingerprinting detects population differentiation in the outbred and abundant fish species Poecilia latipinna

Several workers have suggested that multilocus multilocus variable number of tandem repeat (VNTR) based 'DNA fingerprints' are not useful in detecting differentiation among outbred populations. They suggest that the extremely high mutation rates and complexity associated with multilocus VNTR fragments make detection of interpopulation differences against a background of extremely high intrapopulation variation unlikely. This paper shows that DNA fingerprinting with the multilocus VNTR probes (GACA)₄ and (CT)₉ reveal significant population differences in VNTR frequencies between Florida and Georgia populations of the outbred, abundant and vagile fish species Poecilia latipinna. Differences in mutation rates among some VNTR loci may account for the ability to detect interpopulation differentiation with these probes. These results suggest that appropriate species/probe combinations would allow investigations of population structure on a microgeographical scale even in outbred species with multilocus VNTR probes where less-sensitive techniques have failed.     

Genomic DNA fingerprinting of clinical isolates of Helicobacter pylori using short oligonucleotide probes containing repetitive sequences

The ability of oligonucleotide probes containing short repetitive sequence motifs to differentiate between isolates of Helicobacter pylori was investigated. Genomic DNA preparations from H. pylori were digested with the restriction enzyme Hind III, electrophoresed in agarose gels and transferred to nylon filters. Five separate oligonucleotide probes were tested for hybridization sequentially to fingerprint the digested DNA from a panel of 29 clinical isolates and one type strain of H. pylori , and their relative discriminatory abilities were assessed. Four probes, (GACA)₄, (GT)₈, (GTG)₅ and (GGAT)₄, were each shown to yield highly informative hybridization band profiles allowing differentiation of H. pylori isolates. The DNA fingerprints of individual isolates obtained with each probe were distinct and reproducible. Direct comparison with ribotyping revealed that oligonucleotide fingerprinting had far superior discriminatory power. Computer-assisted similarity analysis of (GGAT)₄-generated hybridization profiles of pairwise combinations of H. pylori isolates revealed that there was no correlation between ribotype and oligonucleotide fingerprint patterns. The results of this study demonstrate that oligonucleotide probes containing microsatellite sequences provide a new and powerful tool for isolate discrimination of H. pylori .     

Genetic variation, its assessment and implications to the conservation of seagrasses

In a study of the widespread Australian endemic seagrass Posidonia australis , allozyme analysis identified a wide range in population genetic structure assessed using the multilocus genotype diversity statistic ( D _G). Values of D _G between zero and one were obtained; however, RAPD analysis generally detected higher levels of diversity, where D _G values were all greater than 0.5 ( D _G = 0.67 – 1). Some populations were allozymically monomorphic using allozyme analysis yet were highly polymorphic using RAPD analysis. The differences observed between methods, particularly among allozymically uniform populations, demonstrate the importance of choosing an appropriate method when assessing genotypic diversity. Different methods may reflect different historical aspects of population processes where allozymes reflect broader-scale gene flow and population establishment and DNA fingerprinting methods such as RAPDs may reflect fine-scale local recruitment events and shorter-term population processes. Using either method alone, particularly in genotypically depauperate organisms such as seagrasses and other clonal organisms, will be problematic in assessing their population genetic potential, a parameter being used by conservation managers to decide upon management strategies in rare and endangered organisms. It is recommended that the impact of disturbance assessed using genotypic diversity measures requires more than one technique to provide the most appropriate information for designing subsequent conservation strategies.     

Allozyme Variation and Genetic Relationships among Species of Cimicifuga (Ranunculaceae) from Korea

Allozyme investigation of the five Cimicifuga taxa in Korea was conducted to assess genetic and clonal diversity within populations and genetic divergence among populations and taxa. Levels of allozyme variation maintained in Korean Cimicifuga taxa were comparable to those for most herbaceous perennials. In general, samples excluding copies of the same multilocus genotype maintained higher levels of genetic diversity than the total samples within populations. Copies of homozygous genotypes at several loci resulting from clonal spread lead to decreased levels of genetic diversity within populations, indicating that clonal reproduction found in Cimicifuga affects population genetic structure. In general, more widely distributed species such as C. dahurica and C. japonica harbored higher levels of allozyme diversity than the other taxa examined. Although two varieties of C. heracleifolia are geographically and reproductively isolated, the genetic and clonal structure of var. bifida seems to resemble var. heracleifolia, indicating that the two varieties may have had a similar evolutionary history. However, the allozyme data strongly indicate that the two morphological types (Groups I and II) of C. simplex should be treated as separate species.     

LOCAL GENETIC AND CLONAL STRUCTURE IN THE TROPICAL TERRESTRIAL BROMELIAD,AECHMEA MAGDALENAE

The genetic structure of populations of the clone-forming tropical terrestrial bromeliad, Aechmea magdalenae, was examined by electrophoretic analyses in nine populations occurring on and near Barro Colorado Island, Republic of Panama. For the nine populations as a whole, 33% of the loci were polymorphic and the genetic diversity was 0.121. Within populations, the mean percent of polymorphic loci was 24.1% and the mean genetic diversity was 0.084. About one-third of the total allozyme diversity resided among populations (mean G_ST = 0.356). The distribution of A. magdalenae was patchy in the study area. This, coupled with the relatively small effective population sizes and the possible founding of populations by few individuals may have contributed to the large among-population component of genetic diversity. The extent of clonal growth was inferred by examining the relationship between the proportion of rosette-pairs sharing identical multilocus genotypes and distance between pairs. This method indicates that clonal spread is local; individuals sharing multilocus genotypes most often occur within 10 m of each other.     

Genetic variation at allozyme and RAPD loci in sessile oak Quercus petraea (Matt.) Liebl.: the role of history and geography

The nuclear genetic variation within and among 21 populations of sessile oak was estimated at 31 RAPD loci in conjunction with previous estimates of variation at eight allozyme loci. The aim of the study was to assess the relative role of isolation-by-distance and postglacial history on patterns of nuclear variation. Because of its small effective population size and maternal transmission, the chloroplast genome is a good marker of population history. Both kinds of nuclear variation (RAPD and allozyme) were therefore compared, first, to the geographical distances among populations and, secondly, to chloroplast DNA restriction polymorphism in the same populations. Multiple Mantel tests were used for this purpose. Although RAPDs revealed less genetic diversity than allozymes, levels of genetic differentiation ( G _ST) were identical. The standard genetic distance calculated at all RAPD loci was correlated with geographical distances but not with the genetic distance calculated from chloroplast DNA data. Conversely, allozyme variation was correlated with chloroplast DNA variation, but not with geography. Possibly, divergent selection at two allozyme loci during the glacial period could explain this pattern. Because of its greater number of loci assayed, RAPDs probably provided a less biased picture of the relative role of geography and history.     

Population genetic structure of wild rice Oryza glumaepatula distributed in the Amazon flood area influenced by its life-history traits

Wild plant species develop their own way of living to adapt to the specific environment of their habitats. Their life-history traits strongly affect the genetic structure of the population. The wild species Oryza glumaepatula Steud. growing in the Amazon basin seems to have characteristic life-history traits suited for the flood condition. At the vegetative growth stage, the culms frequently break at internodes. With no roots anchoring on the ground, plant bodies floating in the water move downriver by water current and wind. To examine the association between the life-history traits and genetic population structure of Amazonian O. glumaepatula , we analysed allozyme variability at 29 loci of 16 enzymes using 37 populations from five regions. Allozymes were not so variable (total gene diversity H _E = 0.044) compared with Asian wild rice, O. rufipogon Griff. The bottleneck effect and rare opportunity of interspecies gene flow may prevent the development of allozyme variability. Population genotypes tended to be differentiated among geographically isolated regions. Observed heterozygosities were much lower than expected heterozygosities, or gene diversity ( H _O = 0.003 for whole population) and F _IS over polymorphic loci was 0.931, indicating that O. glumaepatula has developed an inbreeding system. But, the intrapopulation gene diversity ( H _S) was higher than interpopulation gene diversity ( D _ST), as generally observed in outbreeding populations. The migration ability of O. glumaepatula makes long-distance seed dispersal possible. This might have led to frequent gene flow among populations.     

珠芽蓼种群克隆多样性及克隆结构的初步研究

珠芽蓼(Polygonum viviparum)是青藏高原东缘广泛分布的克隆植物,具有有性和无性(根状茎和珠芽)两种生殖方式。该研究采用RAPD技术对分布于不同海拔的珠芽蓼7个自然种群进行了克隆结构和克隆多样性(是单克隆种群还是多克隆种群)以及克隆多样性与海拔因子之间的相关性研究,为了解高山克隆植物对环境的适应性策略及揭示克隆植物的繁殖和分布特点提供科学依据。研究结果表明:1)采用13条RAPD引物对珠芽蓼7个种群共140个样本进行扩增分析,共扩增到117个位点,其中多态性位点84个,多态位点百分率PPL达到71.79%,检测到43个基因型,且全部为局限型基因型;2)与Ellstrand和Roose(1987)总结的克隆植物的克隆多样性平均值相比(PD=0.17,D=0.62),珠芽蓼种群克隆多样性水平稍高,Simpson指数平均为0.639,基因型比率PD平均为0.307;3)克隆结构分析表明,珠芽蓼种群内克隆之间的镶嵌明显,这可能与珠芽蓼过渡型的克隆构型有关。研究中珠芽蓼种群的构型有游击型、密集型以及这两者之间的过渡类型;4)采用SPSS软件对珠芽蓼种群的克隆多样性与海拔高度进行相关性分析,结果显示它们之间并无明显的相关性。     

Analysis of genetic structure of a Suillus grevillei population in a Larix kaempferi stand by polymorphism of inter-simple sequence repeat (ISSR)

Clones of ectomycorrhizal fungi can colonize new areas through production of vegetative mycelium or spore dispersal, but the relative importance of these processes in nature is not known. In this study, sporocarps of an ectomycorrhizal fungus, Suillus grevillei , were mapped and sampled from a Larix kaempferi stand at the foot of Mt Fuji. DNA was extracted directly from each sporocarp, and DNA polymorphism was analysed by polymerase chain reaction (PCR) amplification of inter-simple sequence repeat (ISSR) regions primed by (GTG)₅, (GCC)₅ and (GACA)₄. Different sensitivities to detect polymorphism were found among the three primers, with (GACA)₄ showing the highest sensitivity. Forty seven sporocarps were analysed by the three ISSR primers and divided into 34 genets based on combination of PCR fingerprints. In the population 28 genets were represented by individual sporocarps. In most cases, sporocarps grown in aggregation (within a circle of 50 cm diameter) showed some different ISSR band patterns. These results suggest that genets of S. grevillei at the test site are relatively small. The genetic similarities between the 34 genets were also calculated and similarity groups were determined by the criterion that all similarity F values of genets within a group were not <80%. In general, the genets within a similarity group located close to each other. The results of multiple different but highly related genets in a small area suggest that the population of S. grevillei in this stand is not spread and maintained by clonal mycelium extension but is reproduced by spore dispersal.     

Genetic diversity of Typha latifolia (Typhaceae) and the impact of pollutants examined with tandem-repetitive DNA probes

Genetic diversity at variable-number-tandem-repeat (VNTR) loci was examined in the common cattail, Typha latifolia (Typhaceae), using three synthetic DNA probes composed of tandemly repeated “core” sequences (GACA, GATA, and GCAC). The principal objectives of this investigation were to determine whether: (1) the previously reported almost complete lack of polymorphism at allozyme loci in this species was indicative of a reduced amount of genetic diversity at VNTR loci as well; (2) VNTR markers were informative about possible clonal propagation; and (3) significant differences in genetic structure of sampling sites were associated with differences in environmental levels of pollutants at those sites. Previously, widespread sampling across the eastern United States, surveying across ten allozyme loci, has detected only two genotypes, involving a difference at a single locus, among 104 populations. In this study, the amount of genetic diversity detected at VNTR loci: (1) among ramets (N = 40; 40 genotypes detected) collected at ∼8-km intervals along a 320-km transect; (2) among ramets (N = 220; 117 genotypes detected) from five study sites separated by 50–3000 m; and (3) even among ramets within each study site [N = 44 per site; from 13 to 34 genotypes detected per site (270 m²)] exceeds that previously found in those more geographically widespread allozyme surveys. Among the 260 ramets analyzed here, the mean number of bands scored per individual was 48.61 (SD = 2.80). Mean genetic similarity among ramets collected along the 320-km transect was 0.91, which was within the range of mean genetic similarity within the five study sites (range: 0.89–0.95). Among the five study sites, 61% of the samples analyzed appeared to be clonal ramets, with up to 12 clones detected for 44 ramets sampled within a site. Clones grew intermingled and ranged up to 39 m in extent. Permutation tests of genetic similarity revealed significant genetic differentiation between each of the five study sites. Consistent with the previous allozyme studies, T. latifolia was characterized by extremely low genetic variation relative to levels of polymorphism detected at VNTR loci in other plant species. Estimated heterozygosity among ramets along the 320-km transect ranged from 0.11 to 0.13, while that within the five study sites ranged from 0.05 to 0.12. Estimates of F_st (0.32–0.41) also indicated considerable genetic subdivision among these stands. Significantly higher genetic diversity was detected at the two study sites that chemistry and toxicity data indicate to be the most severely impacted by pollutants. Although this correlation does not establish cause and effect, the results of this study indicate that the analysis of genetic diversity at VNTR loci may be a useful tool for monitoring anthropogenic-induced changes in the genetic structure of natural populations of plants.     

Intron size polymorphism of the Adh1 gene parallels the worldwide colonization history of the Mediterranean fruit fly, Ceratitis capitata

The exon-primed intron-crossing (EPIC) PCR technique was used to analyse the size variation at the first intron of the Ceratitis capitata Adh ₁ gene. A total of 27 samples from 16 natural populations was analysed from five geographical regions in the species range: Africa, Mediterranean Basin, Latin America, Hawaii and Australia. The Adh ₁ first intron varies extensively in length with at least 18 size variants ranging from 1400 bp to 3450 bp. These variants can be grouped into four distinct size categories: short, medium, long and very long. The majority of these variants are present only in the African populations. Only a subset of the ancestral variants appear to have succeeded in migrating from Africa during the medfly colonization process. The medfly population structure inferred from the intron size polymorphism is congruent with that observed from the analysis of allozyme variation. The geographical dispersal of the medfly from its source area is associated with a gradual and great reduction in intron variability which parallels the trend of decreasing variability evaluated at 26 biochemical loci. The intron phylogenetic tree is in agreement with allozyme data in portraying the dynamic population history of the medfly. Stochastic evolutionary forces such as drift, bottleneck effects and migration seem to have played the major roles in the dispersion pattern of Adh ₁ intron variation during the colonization of the medfly.     

POLYPHYLETIC ORIGINS OF ASEXUALITY IN DAPHNIA PULEX. II. MITOCHONDRIAL-DNA VARIATION

Allozyme studies of the cladoceran Daphnia pulex have shown that most populations reproduce by obligate parthenogenesis, although some cyclically parthenogenetic populations remain throughout the southern portion of its range. Clonal diversity within the obligate parthenogens is extremely high and has been attributed to the polyphyletic origin of asexuality. Specifically, it has been proposed that the clonal diversity in the obligate parthenogens was generated via the spread of a sex-limited meiosis suppressor through populations of a cyclically parthenogenetic ancestor. In this study, analysis of polymorphism of restriction-endonuclease sites in the mitochondrial genome, in conjunction with allozyme analysis, was used to determine whether obligate parthenogenesis has a monophyletic or polyphyletic origin in D. pulex. An allozyme survey of 77 populations from Ontario and Michigan was first conducted to determine breeding systems and levels of clonal diversity (Hebert et al., 1989). Mitochondrial-DNA variation was then surveyed in one isolate of each clone from each population reproducing by obligate parthenogenesis and in 2–4 isolates from each population reproducing by cyclic parthenogenesis. Seventeen restriction enzymes were used in this analysis. Thirty-five mitochondrial genotypes were found among the 36 obligate clones (as identified by allozyme analysis), while 17 mitochondrial genotypes were identified among 40 cyclic isolates from 14 populations. Five mitochondrial genotypes were found in both groups. Parsimony and phenetic-clustering methods were used to construct trees showing the genetic relationship among mitochondrial genotypes. The results clearly show that obligate parthenogenesis had a polyphyletic origin in this species. The close relationship between cyclic and obligate parthenogens in the Great Lakes region suggests that many obligate clones have recently been derived from cyclic populations and that the generation of clones is still occurring in this area. Patterns of clonal diversity based on the joint consideration of allozyme and mitochondrial-DNA data are discussed.     

Population genetics of Dioon edule Lindl. (Zamiaceae, Cycadales): biogeographical and evolutionary implications

Dioon edule Lindl. (Zamiaceae) is a cycad endemic to Mexico, that occurs as one species D. edule and the geographical variety D. edule var. angustifolium (Miq.) Miq. Dioon edule has a north to south distribution in eastern Mexico. In this study, we analysed 14 allozymic loci in eight populations of D. edule from its total distribution range by sampling all known populations. Patterns of diversity and genetic variability, within and among populations, were obtained. The mean number of alleles per locus ( A ) was 1.44 and the percentage of polymorphic loci was relatively high ( P  = 54.78). The mean observed ( H _O ) and expected heterozygosity ( H _E ) were 0.27 and 0.24, respectively. F -statistics revealed an excess of heterozygous genotypes, locally and globally ( F  = −0.17 and f  = −0.27, respectively). The genetic variation explained by differences among populations was only 7.5%. We also detected a negative relationship between genetic diversity and latitude. On average, the gene flow between population pairs was relatively high ( Nm  = 2.98); furthermore, gene flow between population pairs was significantly correlated with geographical distances ( r  = −0.38, P  = 0.025). Therefore, patterns of genetic diversity in D. edule appear to be associated with the post-Pleistocene spread of the species, from its southerly (origin) to its northerly range (derived populations, including its central distribution). The biogeographical and evolutionary aspects of the results of this study are discussed. We recognize Dioon angustifolium Miq. for the northernmost disjunct populations.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80 , 457–467     

Variability of allozyme and cpSSR markers in the populations of Siberian spruce

The variability of 21 allozyme and three microsatellite loci of chloroplast DNA (cpDNA) was studied in the populations of Siberian spruce (Picea obovata Ledeb.) from Irkutsk oblast, Magadan oblast, Buryatia, and Mongolia. It was demonstrated that the highest level of genetic diversity among the examined populations at both allozyme and microsatellite loci was observed in the Tulyushka population from Irkutsk oblast. The lowest level of genetic diversity was observed in marginal isolated populations of Bogd Uul and Magadan. In the relict spruce population from Olkhon Island, differing from the other populations in the lowest allelic diversity of both types of markers, no expected decline of expected heterozygosity and haplotype diversity was observed. In this population, the variability parameters mentioned were close to the population mean. The obtained intrapopulation and intraspecific variability parameters of allozyme and microsatellite loci of chloroplast DNA and the data on the population differentiation at these loci indicate that the given markers can be used for the analysis of the population structure of Siberian spruce.     

Population genetic analyses of an amphi-Atlantic species: Lychnis alpina (Caryophyllaceae)

Lychnis alpina is a perennial caryophyllaceous plant with an amphi-Atlantic distribution. 27 populations are described on the basis of allozyme data from 11 electro-phoretic loci. L. alpina has a relatively low level of genetic variation, 3 of the loci are polymorphic ( P.,_%= 20.2%) and the mean expected heterozygosity per indivindual is H³= 0.233 the three polymorphic loci included (H = 0.064, 11 loci included). Despite relatively low level of genetic variation, the genetic diversity among populations is relatively high with F_ST= 0.51. A hierarchial analysis of genetic diversity demonstrates that most of the genetic diversity exists as interpopulational, intra-regional diversity. Genetic identity is not associated with the intercontinental geographical distribution of the populations, neither is the diversity correspondant to taxonomic relationships.     

Microsatellite evidence for high clonality and limited genetic diversity in Ziziphus celata (Rhamnaceae), an endangered, self-incompatible shrub endemic to the Lake Wales Ridge, Florida, USA

Genetic data are often crucial for designing management strategies for rare and endangered species. Ziziphus celata is an endangered sandhill shrub endemic to the Lake Wales Ridge of central Florida. This self-incompatible clonal species is known from only 14 wild populations, most of which are small (under 100 plants). Focusing on the five populations discovered in 2007, we evaluate the level of genetic diversity and identify clonal lineages within the wild populations of the species with a set of microsatellite loci. To account for somatic mutations and genotyping errors, we identified clonal lineages using a threshold cutoff for pair-wise genetic distances among samples. The microsatellites had up to 18 alleles/locus, and, consistent with outcrossing, samples were highly heterozygous (average population level H _o  = 0.69). Most populations of Z. celata consist of a single clone, and the most diverse population has only 10 clones. Overall Z. celata comprises 41 multi-locus genotypes, and 30 clonal lineages. With nearly 1,000 recorded plants (595 genotyped) and only 30 clonal lineages, Ziziphus celata is highly clonal: clonal richness, R = 0.049. The pair-wise distance method facilitates identification of clonal lineages, avoiding overestimation of clonal diversity. In most cases, the samples that grouped into a lineage were one to four plants differing from a surrounding genotype by a single microsatellite repeat insertion/deletion mutation, consistent with these having arisen via somatic mutations. Our data will enable managers to incorporate extant diversity from wild populations into ex situ collections. Additionally, our research demonstrates the utility of microsatellites for conservation of imperiled species, identifying genotypes of high priority for preservation.