Wild sunflower diversity in Argentina revealed by ISSR and SSR markers: an approach for conservation and breeding programmes

Wild sunflower Helianthus annuus originates from North America and has naturalised in Argentina where it is considered invasive. The present study attempts to assess the genetic diversity using two different molecular marker systems to study the wild genetic patterns and to provide data applicable to conservation and breeding uses. Ten natural populations sampled throughout the wild range and six inbred lines were studied using inter‐simple sequence repeat (ISSR) and simple sequence repeats (SSR) markers. A total of 64 ISSR bands and 29 SSR alleles were produced from 106 wild and cultivated plants. We found 9 ISSR private bands and 21 SSR private alleles in wild accessions, but no private bands/alleles were found in cultivated sunflowers. Molecular variability in wild populations was approximately 60% higher than in inbred lines. Local wild sunflowers kept considerable diversity levels in comparison with populations in the centre of origin (approximately 70%) and therefore they might possess a potential for adaptive evolutionary change. Analysis of molecular variance (AMOVA) indicated population structure with nearly 20% of genetic variability attributable to between‐population differentiation. Principal coordinate analyses (PCO) grouped wild populations from different geographic locations, and a Mantel test showed low congruence between genetic distance (GD) and geographic distances (GGD); hence, molecular data could not rule out multiple wild introduction events. Low correlations were found between ISSR and SSR GD at individual and population levels; thus, divergent evolutionary groups were not evident in local wild sunflowers. Several genetic diversity criteria were utilised to assign conservation value and certain wild populations emerged as interesting sites for more extensive sampling.     

Genetic relationships among South-East Turkey wild barley populations and sampling strategies of Hordeum spontaneum

To assess the genetic diversity and the genetic structure of Turkish wild barley (Hordeum spontaneum Tell.) populations, 76 genotypes from ten ecologically and geographically different locations were analyzed by means of amplified fragment length polymorphism (AFLP) markers. Five primer combinations produced 187 scorable bands, of which 117 (62.6%) were polymorphic. Several population-specific and genotype-specific bands were identified, which differentiate populations or genotypes. Genetic distance, determined by Nei’s distance coefficient, varied from 0.07 to 0.21 with an average of 0.13. In the UPGMA dendrogram based on Nei genetic distances, the Hordeum spontaneum populations were separated into two major clusters. Genetic diversity was larger among (68%) than within (32%) populations. Eight AFLP bands were strongly correlated to the altitude of the collecting site, while no clear trend was detected between geographical origin and genetic diversity. Our results strongly suggest the need for a change in Hordeum spontaneum sampling strategy: more populations, rather then more individuals within population, should be sampled to appraise and safeguard genetic diversity in the wild barley gene pool.     

Development of two spotted spider mite (Acari: Tetranychidae) populations on strawberry and raspberry cultivars

Five strawberry (Fragaria sp.) and five raspberry (Rubus ideaus L.) cultivars were evaluated for resistance to two spotted spider mite (Tetranychus urticae Koch.). Two methods of assessing the development of two spotted mite populations using detached leaves were compared. The number of eggs laid and mites which developed were compared. The strawberry cvs Hapil and Pegasus had significantly greater development of two spotted mite populations than the cvs Rhapsody, Symphony and Elsanta. The raspberry cv. Joan Squires had higher populations of two spotted mite whilst the raspberry cv. Leo the least, when compared with cvs Glen Clova, Glen Moy and Glen Prosen. Differences were observed in oviposition sites and mite distribution when comparing raspberries with strawberries. The method of assessing the populations development of two spotted mite which involved maintaining the cut leaf stem in water may be of potential use for studying population dynamics of both two spotted mite and possible predators over extended periods of time.     

An AFLP-based survey of genetic diversity and relationships of major farmed cultivars and geographically isolated wild populations of <Emphasis Type="Italic">Saccharina japonica</Emphasis> (Phaeophyta) along the northwest coasts of the Pacific

The genetic diversity and relationships of six representative cultivars and six geographically isolated wild populations of Saccharina japonica along the northwest coasts of the Pacific Ocean were investigated using AFLP markers. A total of 547 bands were generated across all samples by ten primer combinations. At the cultivar or population level, the percentage of polymorphic loci (P), gene diversity (H), and Shannon’s information index (I) was highest in Dalian population (P 59.05%; H 0.2057; I 0.3062) and lowest in Lianjiang cultivar (P 9.87%; H 0.0331; I 0.0497). At the species level, P, H, and I were 85.01%, 0.1948, and 0.3096, respectively. Unique bands were detected in all the six wild populations, with Dalian being the most. In comparison, only Yanza cultivar possessed one unique band. The G _ST value was 0.6226 and the gene flow (N _m ) was 0.1515, indicating strong genetic differentiation among cultivars and populations. Two UMPGA dendrograms were constructed based on the Dice similarity coefficients among individuals and on genetic distances among cultivars and populations, which generally revealed three major clades corresponding to three countries. Analysis of molecular variance revealed that a larger proportion (60.21%) of the total genetic variation was attributable to differences among cultivars and populations. The Mantel test suggested that genetic differentiation was positively correlated with geographic distance (r = 0.7962, P = 0.011) in the six wild populations, agreeing with the isolation by distance model. On the whole, low to moderate genetic diversity within cultivars and populations (except Dalian population) and high genetic differentiation among cultivars and populations were detected.     

Conservation Genetics of Jacquemontia reclinata (Convolvulaceae), an Endangered Species from Southern Florida: Implications for Restoration Management

Guidelines designed to aid in the restoration of rare species have been previously proposed using two primary strategies to select individuals for augmentation and reintroduction: mixing progeny from different populations or separating individuals from different populations. Understanding the genetic structure and diversity of an endangered species can offer insights into conservation management strategies. We used random amplified polymorphic DNA markers to assess the genetic structure and diversity of Jacquemontia reclinata , a federally endangered species endemic to Southeastern Florida. We sampled 20 percent of total number of individuals from eight of the ten known wild populations. Across individuals high levels of polymorphic loci (94.7%) were found and larger populations had greater genetic diversity. Cluster and ordination analyses found that one population was genetically differentiated from all the others; this population grows in a unique habitat. Most genetic variation (77.5%) was found within populations, and genetic distances between populations were not explained by their geographic distances. We recommend the use of two management units in restoration programs for J. reclinata , one consisting of the genetically differentiated population and the second consisting of the other seven populations sampled.     

Microsatellite markers reveal genetic diversity of wild soybean in different habitats and implications for conservation strategies (Glycine soja) in China

Wild soybean individuals were sampled from ten habitat sites in Beijing region, China and were assessed using 36 SSR markers for the genetic variation among the habitat subpopulations. AMOVA analysis showed 57.46 % inter-population and 42.54 % intrapopulation genetic variation. The genetic variation had geographical regionality. The drought-stressed and founder subpopulations intensively reduced genetic diversity, and along-river system habitats appeared to have closer genetic similarity. The bottleneck impact of drought stress appeared to be inferior to the founding effect on subpopulation genetic diversity but superior on genetically geographical grouping. Here, all the subpopulations were found to contain unique alleles. The phenotypic and genetic diversities had similarly fluctuated patterns across the subpopulations. These results here suggest that a conservation strategy should be taken: theoretically as many as possible populations are sampled to maximize the genetic diversity in ex situ conservation of wild soybean within an area in China. Spatial distance should be considered for isolating wild soybean populations when genetically modified soybeans are cultivated in China.     

Gene flow between cultivated and wild sunflowers

With the development of transgenic crops, concern has been expressed regarding the possible escape of genetically-engineered genes via hybridization with wild relatives. This is a potential hazard for sunflowers because wild sunflowers occur as weeds in fields where cultivated sunflowers are grown and hybridization between them has been reported. In order to quantify the potential for gene escape, two experimental stands of sunflower cultivars were planted at two sites with different rainfall and altitude profiles. Populations of wild plants were planted at different distances from each cultivar stand. An allele homozygous in the cultivar (6Pgd-3-a), but absent in the wild populations, was used as a molecular marker to document the incidence and rate of gene escape from the cultivar into the wild populations of sunflowers. Three-thousand achenes were surveyed to determine the amount of gene flow from the cultivated to the wild populations. The marginal wild populations (3 m from the cultivar) showed the highest percentage (27%) of gene flow. Gene flow was found to decrease with distance; however, gene flow occurred up to distances of 1000 m from the source population. These data suggest that physical distance alone will be unlikely to prevent gene flow between cultivated and wild populations of sunflowers.     

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.     

Randomly amplified polymorphic DNA-polymerase chain reaction analysis of two different populations of cultured Korean catfishSilurus asotus

Genetic similarity and diversity of cultured catfishSilurus asotus populations collected from two areas in western Korea were examined using randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Out of 20 random primers tested, 5 produced 1344 RAPD bands ranging from 8.2 to 13.6 polymorphic bands per primer. The polymorphic bands in these populations ranged from 56.4% to 59.6%. Polymorphic bands per lane within populations ranged from 4.9% to 5.3%. The similarity within the Kunsan population varied from 0.39 to 0.82 with a mean (± SD) of 0.56 ± 0.08. The level of bandsharing values was 0.59 ± 007 within the catfish population from Yesan. The genetic similarity in cultured catfish populations may have been caused because individuals from two populations were reared in the same environmental conditions or by inbreeding during several generations. However, in view of bandsharing values, polymorphic bands and also the specific major bands that were inter-population-specific, significant genetic differentiation between these populations were present even if bandsharing (BS) values were somewhat numerically different. Therefore, the number of RAPD polymorphisms identified in this study may be sufficient to permit estimating genetic similarity and diversity. However, in future, additional populations, sampling sites and individuals will be necessary to make up for these weak points.     

北京地区野生大豆种群SSR标记的遗传多样性评价

 使用40对SSR引物分析了北京地区野生大豆(Glycine soja)天然种群的遗传结构与遗传多样性。10个种群共检测到526个等位变异, 平均每对引物等位基因数为13.15个, 种群平均Shannon指数(I)为0.658, 群体平均位点预期杂合度(H_e)为0.369, 群体平均位点杂合度(H_o)为1.29 %。平均种群内遗传多样度(H_s)为0.362, 平均种群间遗传多样度(D_ST)为0.446, 基因分化程度(G_ST)为0.544。该研究显示, 中-西部生态区种群比北部和东部山区种群有较高的遗传多样性。在地理上, 环绕北京地区的太行山和燕山两大余脉区域野生大豆种群遗传分化表现出地理差异。可能是经过干旱选择而形成的有抗旱潜力的种群在遗传上表现单一化。期待该种群提供耐旱基因。     

Effects of Didymella applanata and Botrytis cinerea on axillary buds, lateral shoots and yield of red raspberry

The viability of axillary buds and the growth and potential yield of lateral shoots at nodes of red raspberry (Rubus idaeus) infected naturally by Didymella applanata or Botrytis cinerea were measured on excised nodes, decapitated nursery canes or on canes from fruiting plantations. In comparison with lesion-free nodes, buds at infected nodes were smaller and fewer of them were capable of growth when excised and ‘forced’, although the difference in growth between infected and uninfected nodes decreased during late winter. After February, those buds at infected nodes which were capable of forced growth did so as early and with a similar growth rate as those at lesion-free nodes. In April, 70% of buds at infected nodes were capable of growth compared with 94% of those at lesion-free nodes. When nursery canes of cv. Mailing Delight were decapitated above infected nodes the emergence of lateral shoots from the terminal infected node did not differ significantly from that at lesion-free nodes. On a range of farm sites in Scotland the emergence of shoots at infected nodes in the cropping region of canes was significantly poorer than from uninfected nodes but substantially better at infected nodes of cv. Glen Clova than at those of cvs Mailing Jewel and Mailing Orion. It is suggested that cv. Glen Clova is relatively tolerant of spur blight and cane botrytis. The length and potential yield of laterals which developed at infected nodes in the cropping region of canes in these three cultivars did not differ significantly from those at lesion-free nodes. In all tests there was no significant difference in growth at nodes infected by D. applanata and B. cinerea which may indicate a common mechanism for suppression of buds.     

Genetic Structure of Rhizobium etli biovar phaseoli Associated with Wild and Cultivated Bean Plants (Phaseolus vulgaris and Phaseolus coccineus) in Morelos, Mexico

The genetic structure of Rhizobium etli biovar phaseoli was determined for five populations in three different locations in the state of Morelos, Mexico, by using starch gel electrophoresis for five to nine polymorphic loci. Two populations were sampled during two different years from nodules of cultivated and wild common bean plants (Phaseolus vulgaris). The three other populations were associated with wild runner beans (P. coccineus) and sampled during 1988. The Rhizobium populations differ genetically both among sites and among populations within the same site in different years, as shown by differences in allelic frequencies, genetic differentiation analysis, and differences in electrotypes. The total genetic diversity for the five populations during 1988 was H = 0.487; there were also high levels of genetic variation within each population. We found the highest linkage disequilibrium in a global analysis for all the populations. At a local scale, we also found significant linkage disequilibrium in two populations, although the distribution of the D' suggest some recombination at a local scale. The other three rhizobium populations exhibit low linkage disequilibrium. A cluster analysis (UPGMA) of pairwise genetic distances showed that bacteria isolated from most wild Phaseolus spp. are grouped by population, whereas those obtained from cultivated P. vulgaris are very heterogeneous. The analysis of the genetic structure of Rhizobium strains may allow the identification of strains that are naturally well adapted to a wide range of different environments, which may be useful for agricultural purposes or as a starting point for developing improved Rhizobium strains.     

Distinction between cultivated and wild chicory gene pools using AFLP markers

The cultivation area of industrial chicory, Cichorium intybus L. cv Sativum, coincides with the natural distribution area of its wild relative, C. intybus L., which could lead to gene flow between wild and cultivated types. The genetic diversity within and between the two types has therefore been studied using AFLP genotyping of samples from 12 wild populations collected in Belgium and ten commercial varieties. The genotyping of 233 individuals allowed the identification of 254 AFLP markers. Similar levels of genetic diversity were observed within wild populations and cultivated varieties, suggesting the absence of any strong bottleneck in the history of the cultivated types. The phylogenetic analysis pointed to a monophyletic origin of cultivated varieties as compared to the local wild populations studied, hence the two types of chicory form two separate gene pools. The genotyping of some individuals sampled in ruderal sites clearly showed that they belong to the cultivated gene pool, which suggests the existence of feral or weedy types. The low differentiation observed among wild populations indicates that gene flow might be important in this species.     

The role of ethylene and cell wall modifying enzymes in raspberry (Rubus idaeus) fruit ripening

This study focuses on four raspberry ( Rubus idaeus ) genotypes from two different genetic backgrounds: cvs Glen Prosen and Glen Clova, bred at the Scottish Crop Research Institute (SCRI) and genotypes bred at Horticulture Research International (HRI), East Malling (EM), EM 4997 and EM 5007. The ripe fruit of each genotype pair were characterised subjectively by raspberry breeders as relatively firm or soft, respectively. Different stages of fruit development from each genotype were used to quantify fruit firmness, rates of ethylene evolution and ripening rate. Penetrometry data confirmed suspected firmness differences. Firmness correlated with rates of ethylene evolution. Rates of ethylene production also correlated with receptacle size. Storage of green fruits in 20 μl l⁻¹ ethylene reduced fruit firmness, enhanced respiration rate and colour (anthocyanin) development and stimulated the development of cell wall hydrolase activities. However, during natural ripening in the field, fruit respiration rate declined, which indicates a non-climacteric ripening pattern. In drupelets, the activities of polygalacturonase (PG), pectin methylesterase (PME), C x -cellulase (C x ) and β -galactosidase ( β -gal.) increased substantially as ripening progressed. More detailed studies with ripe fruit of cv. Glen Clova indicated major isoforms of PG at pIs 3.3, 8.6 and 10.1; of PME at pIs 7.2, 8.5, 8.7, 8.8; of C x at pI 2.4; and of β -gal. at pIs 6.3 and 6.7.     

Genetic diversity and differentiation in Dalbergia sissoo (Fabaceae) as revealed by RAPD

Dalbergia sissoo, a wind-dispersed tropical tree, is one of the most preferred timber tree species of South Asia. Genetic diversity and differentiation among natural populations of D. sissoo were examined for the first time. We found a relatively high level of genetic diversity in D. sissoo, both at the species level (percentage of polymorphic bands = 89.11%; H = 0.2730; I = 0.4180) and the population level (percentage of polymorphic bands = 68.7%; H = 0.239; I = 0.358), along with a relatively low degree of differentiation among populations (GST = 0.1311; AMOVA = 14.69%). Strong gene flow among populations was estimated, N(m) = 3.3125. The Mantel test suggested that genetic distances between populations were weakly correlated with geographic distances (R = 0.3702, P = 0.1236). The high level of genetic diversity, low degree of differentiation, strong gene flow, and weak correlation between genetic and geographic distances can be explained by its biological character and wide-spread planting. This information will be useful for the introduction, conservation and further studies of D. sissoo and related species.     

Genetic comparisons between seed bank and <Emphasis Type="Italic">Stipa krylovii</Emphasis> plant populations

The soil seed bank represents the potential plant population since it is the source for population replacement. The genetic structure of a Stipa kryiovii (Roshev.) plant population and its soil seed bank was investigated in the Xilinguole Steppe of Inner Mongolia using random amplified polymorphic DNA (RAPD) analyses. The population was sampled at two sites that were in close proximity to each other (0.5 km apart). Thirty plants and 18 seed bank samples were taken from each site to determine the genetic diversity between sites and between sources (plant or seed). The material was analyzed using 13 primers to produce 92 loci. Eighty-six were multi-loci, of which 23 loci (26.74%) of allele frequencies showed significant differences (P ≤ 0.05). The genetic similarity between two seed bank sites was 0.9843 while the genetic similarity between two plant sites was 0.9619. Their similarities were all greater than that between the seed bank and plant populations. An analysis of their genetic structure showed that 87.86% of total variation was derived by two-loci. Genetic structures between plant and soil seed bank populations in S. krylovii were different due to the variance of mean gametic disequilibria and mean gene diversity. AMOVA results showed that the majority of variance (88.62%) occurred within sites, 12.75% was from between-groups. Further research is needed to investigate the selective function in maintaining the genetic diversity of Stipa krylovii plant populations.     

Genetic comparisons between seed bank and Stipa krylovii plant populations

The soil seed bank represents the potential plant population since it is the source for population replacement. The genetic structure of a Stipa krylovii (Roshev.) plant population and its soil seed bank was investigated in the Xilinguole Steppe of Inner Mongolia using random amplified polymorphic DNA (RAPD) analyses. The population was sampled at two sites that were in close proximity to each other (0.5 km apart). Thirty plants and 18 seed bank samples were taken from each site to determine the genetic diversity between sites and between sources (plant or seed). The material was analyzed using 13 primers to produce 92 loci. Eighty-six were multi-loci, of which 23 loci (26.74%) of allele frequencies showed significant differences (P < or = 0.05). The genetic similarity between two seed bank sites was 0.9843 while the genetic similarity between two plant sites was 0.9619. Their similarities were all greater than that between the seed bank and plant populations. An analysis of their genetic structure showed that 87.86% of total variation was derived by two-loci. Genetic structures between plant and soil seed bank populations in S. krylovii were different due to the variance of mean gametic disequilibria and mean gene diversity. AMOVA results showed that the majority of variance (88.62%) occurred within sites, 12.75% was from between-groups. Further research is needed to investigate the selective function in maintaining the genetic diversity of Stipa krylovii plant populations.     

广西地不容种质资源的ISSR分析

采用简单序列重复区间扩增(ISSR)分子标记技术对广西地不容3个野生居群和1个引种居群共92个个体进行了遗传多样性研究。10个引物共扩增出61条带,其中60条具多态性,多态性位点百分率为98.36%。4个居群多态性百分率在73.77%～86.89%。Nei’s基因多样性指数(H)为0.3379,Shannon信息多样性指数(Ⅰ)为0.5055。3个野生居群Nei’s遗传分化系数(Gst)表明:83.87%遗传变异分布在居群内,16.13%的遗传变异分布在居群间。引种居群与3个野生居群间的遗传一致度达0.8846。引种居群有效地保护了广西地不容的遗传多样性。     

RAPD polymorphism of wild emmer wheat populations, Triticum dicoccoides, in Israel

 Genetic diversity in random amplified polymorphic DNAs (RAPDs) was studied in 110 genotypes of the tetraploid wild progenitor of wheat, Triticum dicoccoides, from 11 populations sampled in Israel and Turkey. Our results show high level of diversity of RAPD markers in wild wheat populations in Israel. The ten primers used in this study amplified 59 scorable RAPD loci of which 48 (81.4%) were polymorphic and 11 monomorphic. RAPD analysis was found to be highly effective in distinguishing genotypes of T. dicoccoides originating from diverse ecogeographical sites in Israel and Turkey, with 95.5% of the 100 genotypes correctly classified into sites of origin by discriminant analysis based on RAPD genotyping. However, interpopulation genetic distances showed no association with geographic distance between the population sites of origin, negating a simple isolation by distance model. Spatial autocorrelation of RAPD frequencies suggests that migration is not influential. Our present RAPD results are non-random and in agreement with the previously obtained allozyme patterns, although the genetic diversity values obtained with RAPDs are much higher than the allozyme values. Significant correlates of RAPD markers with various climatic and soil factors suggest that, as in the case of allozymes, natural selection causes adaptive RAPD ecogeographical differentiation. The results obtained suggest that RAPD markers are useful for the estimation of genetic diversity in wild material of T. dicoccoides and the identification of suitable parents for the development of mapping populations for the tagging of agronomically important traits derived from T. dicoccoides. Received: 13 July 1998 / Accepted: 13 August 1998     

Optimal sampling strategies for capture of genetic diversity differ between core and peripheral populations of <Emphasis Type="Italic">Picea sitchensis</Emphasis> (Bong.) Carr

In previous studies we reported that while core populations of Sitka spruce [Picea sitchensis (Bong.) Carr] have little within-population genetic structure, peripheral populations are strongly spatially structured at distances up to 500 m. Here we explore the implications of this difference in structure on ex situ gene conservation collections and estimates of genetic diversity from research collections. We test the effects of varying the number of individuals sampled and the total area they are sampled across on capture of neutral genetic variation in collections from core, continuous versus peripheral, disjunct populations. Bivariate response surface analysis of genetic marker data for eight sequence tagged site loci from core and peripheral populations suggest that a population sample from 150 trees covering at least 225 ha would be adequate for capturing 95% of the genetic diversity (as measured by allelic richness or expected heterozygosity) in core populations. However, a larger sample of 180 individuals from an area of at least 324 ha is needed in peripheral populations to capture the same proportion of standing variation because of stronger within-population spatial genetic structure. Standard population sampling protocols for estimating among and within-population genetic diversity would significantly underestimate the within-population allelic richness and expected heterozygosity of peripheral but not core populations, potentially leading to poor representation of genetic variation in peripheral populations as well as erroneous conclusions about their genetic impoverishment.