Genetic variability within and between the troops of toque macaque,Macaca sinica,in Sri Lanka

Genetic variability within and between the troops of toque macaque in Sri Lanka was studied from a population genetical perspective. Studies were made using electrophoretical blood protein variations as markers in order to clarify the genetic characteristics of the population of this species. A total of 256 samples from 20 troops which were collected in the field in 1981 to 1982 and 1983 to 1984 were examined for 32 blood protein loci. Eleven loci, that is, Tf, Alb, TBPA, Hb-α, PHI, PGM-II, CA-I, IDH, AK, ADA, and Ch-E showed the polymorphism in one or more troops. Of these 11 loci, 7 loci, that is, Tf, TBPA, Hb-α, PHI, PGM-II, CA-I, and IDH were highly polymorphic in most troops. The genetic variability within troops were quantified as H=0.0782 in average and this value was on higher level than other primates and comparable with that of continental macaques,Macaca fascicularis, in Thailand. The genetic differentiation between troops was quantified byG _ST andF _ST and these values were relatively smaller than those of other insular macaques.     

Conservation genetics of the endangered endemic Sambucus palmensis Link (Sambucaceae) from the Canary Islands

Five polymorphic microsatellites (simple sequence repeat; SSR) markers were used to estimate the levels of genetic variation within and among natural populations from different islands of the endangered endemic from the Canary Islands Sambucus palmensis Link (Sambucaceae). Genetic data were used to infer potential evolutionary processes that could have led to present genetic differentiation among islands. The levels of genetic variability of S. palmensis were considerably high; proportion of polymorphic loci (P = 100%), mean number of alleles per locus (A = 6.8), average expected heterozygosity (He = 0.499). In spite of its small population size and endemic character, 58 different multilocus genotypes were detected within the 165 individuals analyzed. All samples located in different islands always presented different multilocus genotypes. Principal Coordinates Analysis, genetic differentiation analysis (F _ST and G _ST ′) and Bayesian Cluster Analysis revealed significant genetic differences among populations located in different islands. However, this genetic differentiation was not recorded among Tenerife and La Gomera populations, possibly revealing the uncontrolled transfer of material between both islands. AMOVA analysis attributed 77% of the variance to differences within populations, whereas 8% was distributed between islands. The levels of genetic differentiation observed among populations, and the genetic diversity distribution within populations in S. palmensis, indicate that management should aim to conserve as many of the small populations as possible. Concentrating conservation efforts only on the few large populations would result in the likelihood of loss of genetic variability for the species.     

Genetic diversity in the threatened insular endemic plantAster asa-grayi (Asteraceae)

Genetic diversity in an insular endemic plantAster asa-grayi was examined using enzyme electrophoresis. Distribution ofA. asa-grayi is restricted to only four subtropical islands of Japan, and this species is listed as vulnerable to extinction in the Red Data Book of Japanese wild plants. A total of 161 individuals were sampled from five populations on four islands. Genetic diversity values at the population level were very low, compared to other plant species with a similar life history. Genetic variability at the species level is comparable to the mean value of endemic species. Genetic differentiation among populations is extremely high (G_ST= 0.71), indicating that the gene flow among populations is highly impeded, and pollen and seed dispersal is limited due to the pollinators and the seed morphology. This is because the four islands are geographically isolated. Fixation indices suggested that most populations do not randomly cross. To conserve the genetic diversity of the species, artificial crossings among different island populations are necessary.     

Population genetics of Japanese monkeys: III. Ancestry and differentiation of local populations

Genetic variability in local populations of the Japanese macaque (Macaca fuscata) was quantified by the proportion of polymorphic loci (P_poly) and the average heterozygosity per individual ( ) from the starch- and polyacrylamide-gel electrophoreses of blood proteins controlled by 32 independent genetic loci. P_poly averaged 13.6% and 2.1%, the values being at lower level compared with other mammalian species. Geographical distribution of the genetic variations was not uniform in the whole species but its local differentiation was remarkable. Genetic variability tended to be lower in the southern localities, especially in the southernmost island of Yaku, than in the central and northern localities. The genetic distance and the principal component analyses showed that the most divergent local populations were the population in the Shimokita peninsula at the northernmost distribution area of the species and the populations on the Yaku island at the southernmost. The most contributory loci to the genetic divergence were the PGM-II, Gc, and Hb-β, the variant allele at the first locus being concentrated in the Yaku island, in the Shimokita peninsula, and in the easternmost Boso peninsula, and the variant allele at the latter two loci having high frequencies in the Shimokita and the Izu peninsulas. The Hennigian cladistic analysis, for which the Chinese rhesus macaque (M. mulatta) was used as the outgroup, revealed that the number of presence of derived (apomorphic) alleles was conspicuously smaller in southern islet populations than in central and northern populations, whereas any areal tendency was not recognized in the number of loss of ancestral (plesiomorphic) alleles. The observed distribution pattern that the plesiomorphic variant allele at the PGM-II locus concentrated only in the peripheral (southernmost, northernmost, and easternmost) ranges of the species, would indicate, as a possibility, the occurrence of two or more waves of immigration of ancestors of the present-day Japanese macaque from the Asian continent.     

THE INFLUENCE OF DISPERSAL PATTERNS AND MATING SYSTEM ON GENETIC DIFFERENTIATION WITHIN AND BETWEEN POPULATIONS OF THE RED HOWLER MONKEY (ALOUATTA SENICULUS)

The relationship between social structure and partitioning of genetic variance was examined in two red howler monkey populations (W and G) in Venezuela, one of which (G) was undergoing rapid growth through colonization by new troops. Rates and patterns of gene flow had been determined through radiotelemetry and direct observation data on solitary migrants, and 10 years of troop censusing. Standard electrophoresis techniques were used to examine 29 loci in blood samples taken from 137 of the study animals. Analysis of genetic variance demonstrated: (1) a significantly high level of genetic variation among troops within populations (F_ST = 0.225 for W and 0.142 for G), and (2) a significant excess of heterozygosity within troops relative to expected (F_IS = -0.136 for W and -0.064 for G), despite relatively high levels of observed and inferred inbreeding in W. Differences between the populations in F_ST values conformed to those predicted based on differences in colonization rate. Comparison of partitioning of genetic variance among different genealogical subsets of troops demonstrated that the pattern of genetic differentiation observed among troops within populations was promoted by an essentially single-male harem breeding structure, a very low rate of random exchange of breeding males among troops, and a high degree of relatedness among troop females. Between-troop genetic differentiation (F_ST) was thereby increased relative to that expected from other types of social organization, while the correlation between uniting gametes within troops (F_IS) was decreased. Genetic differentiation between populations (2%) corresponded to that predicted from migration rates. Such a mosaic of genetic variation, combined with differences in reproductive success observed among troops and a high troop failure rate, create conditions in which interdemic selection could result in more rapid spread of advantageous gene combinations than would be expected in a panmictic population, particularly in a colonizing situation in which the founder population is small.     

Blood protein variation of a new population of gelada baboons (Theoropithecus gelada), in the Southern Rift Valley, Arsi Region, Ethiopia

Blood protein polymorphism of gelada baboon (Theropithecus gelada) to the south of the Rift Valley, Arsi Region, were examined for 36 genetic loci using three electrophoresis techniques for 48 blood samples from three localities, and compared with the northern geladas. New variant alleles and genetic markers of Hb-α, PA-2, and TBPA loci were detected. The distribution patterns of the variant alleles of Hb-α, PA-2, TBPA, Pi, Gc, PGM-II, and TBPA loci were localized in the geographic regions of south and north gelada populations, respectively. Genetic variability of southern geladas was estimated as P_poly=0.083 and , which was comparable to northern geladas. A remarkably high genetic differentiation between the two geographic populations was shown byNei's genetic distance=0.071 and G_ST value=0.420. Our results of genetic analysis suggest that the southern and northern gelada populations have been separated for several hundred thousand years, and gene flow between the two geographic populations is severely restricted. The southern gelada baboon may be regarded as a distinct subspecies.     

Multiple-population versus hierarchical conifer breeding programs: a comparison of genetic diversity levels

Advanced-generation domestication programs for forest-tree species has raised some concerns about the maintenance of genetic diversity in forest-tree breeding programs. Genetic diversity in natural stands was compared with two genetic conservation options for a third-generation elite Pinus taeda breeding population. The breeding population was subdivided either on the basis of geographic origin and selection goals (multiple-population or MPBS option) or stratified according to genetic value (hierarchical or HOPE option). Most allelic diversity in the natural stands of loblolly pine is present in the domesticated breeding populations. This was true at the aggregate level for both multiple-population (MPBS) and the hierarchical (HOPE) populations. Individual subpopulations within each option had less genetic diversity but it did not decline as generations of improvement increased. Genetic differentiation within the subdivided breeding populations ranged from 1 to 5%, genetic variability is within each subpopulation rather than among subpopulations for both MPBS (>95%) and the HOPE approaches (>98%). Nei's G_st estimates for amongpopulation differentiation were biased upwards relative to estimates of from Weir and Cockerham (1984).     

Allozyme Variation and the Genetic Structure of Populations of Trochodendron aralioides, a Monotypic and Narrow Geographic Genus

Trochodendron aralioides Siebold & Zucc., a primitive angiosperm that is insect-pollinated, has wind-dispersed seeds and grows only in eastern Asia. Nineteen populations were analyzed, including 16 from Taiwan, two from the main islands of Japan and one from Iriomote Island in the Ryukyu Islands. Genetic variability (0.133) at the species level was more similar to that of a narrow geographic species than an endemic species. Based on genotype frequencies, mating within populations was non-random (F _{I s}=0.065) and there was significant genetic differentiation (F _ST =0.164) among populations. Genetic diversity was largely within, rather than among, populations (H _s =0.132, 85.14%). Bisexual flowers of T. aralioides exhibit synchronized dimorphism. The protogynous and protandrous morphs are self-incompatible, which probably promotes outcrossing and contributes to the high levels of heterozygosity within populations. Using a maximum likelihood tree, populations of T. aralioides were separated into two distinct clusters: Japan and Taiwan/ Iriomote Island. Populations of T. aralioides on Iriomote Island and in northern Taiwan exhibited a high degree of genetic similarity. The isolation-by-distance model does not fit populations in Taiwan, but suitably describes the relationship between populations of T. aralioides in Japan and Taiwan. Received 28 April 2000/ Accepted in revised form 13 December 2000     

RFLP studies of genetic relationships among inbred lines of the cultivated sunflower,Helianthus annuus L.: evidence for distinct restorer and maintainer germplasm pools

One-hundred-and-eighty-one nuclear DNA probes were used to examine restriction-fragment length polymorphism in inbred lines of the cultivated sunflower (Helianthus annuus L.). The probes were from six libraries: two genomic libraries — one made with PstI and the other with HindIII, and four cDNA libraries — from etiolated plantlets, green leaves, ovaries, petals and anthers. Total DNA from 17 inbred lines representing an overview of the genetic stocks of sunflower, including restorer and maintainer lines of the classical cytoplasmic male sterility, was digested with four different restriction enzymes and probed in 331 probe-enzyme combinations. Of 181 clones analysed, 73 probes were found to be polymorphic. Genetic distances between inbreds were calculated from the resultant proportion of shared bands and submitted to principal component analysis and the UPGMA tree-making method. The RFLP analysis allowed a clear differentiation between restorer and maintainer lines of the cytoplasmic male sterility, together with a grouping of some of the genotypes from the same origin. The analysis of the accuracy of distance estimation as a function of the number of probe-enzyme combinations used, indicates that 40–50 combinations ensure a confidence level of near 95%. Considering the inbreds as representatives of the range of cultivated inbreds, estimates of gene diversity, as well as estimates of average gene diversity between and within the sets of restorer and maintainer lines, were calculated. Estimation of gene diversity showed that the available genetic variability in cultivated sunflower, based on allelic frequencies, is lower than that of other plants (H=0.20). Moreover, we show that the proportion of genetic variability due to the difference between maintainer and restorer lines (D_m) is about 2%.     

Variability and differentiation of microsatellites in the genus Dasyurus and conservation implications for the large Australian carnivorous marsupials

All four species of Australian quolls (Dasyurusspecies) have declined since European settlement in terms of bothrange and population numbers. Six highly polymorphic simplesequence repeats (CA_n microsatellites) were used to estimate thegenetic variability and population differentiation within andamong twenty populations (including museum specimens from sixpopulations), as a preliminary means of assessing populationconservation status and relative levels of variability withinmembers of the genus. Overall mean expected heterozygosity (H_E)and corrected allelic diversity (A) were highest among westernquolls. Northern quolls, eastern quolls, and tiger quolls werenot significantly different from each other in either measure. There were also significant differences in diversity amongpopulations within species. Genetic differentiation wasestimated by a number of methods and showed that themicrosatellites used here were useful for defining differencesboth among species and populations. Allele frequency data weresummarised by two-dimensional MDS, which was able to partitionpopulations into distinct species clusters. Similarly, theassignment test was able to assign most individuals to both thecorrect species and population levels. Results of MDS and theassignment test may prove useful in forensic applications. Genetic distance and subdivision between pairs of populationswere assessed by two means based on different mutation models formicrosatellites: infinite alleles model (Nei's D, F_ST) andstepwise mutation model (Goldstein's mu;², R_ST). Pairwisemeasures of population subdivision indicate that most populationsshould be conserved as separate management units. We discussresults of these analyses in terms of applications toconservation for each of the four Australian species of quoll andprovide a genetic basis for future population monitoring in thesespecies.     

Genetic variability and differentiation of three Russian populations of potato cyst nematode <Emphasis Type="Italic">Globodera rostochiensis</Emphasis> as revealed by nuclear markers

Genetic variability of yellow potato cyst nematode G. rostochiensis from three Russian populations (Karelia, Vladimir oblast, and Moscow oblast) was investigated using two types of nuclear markers. Using RAPD markers identified with the help of six random primers (P-29, OPA-10, OPT-14, OPA-11, OPB-11, and OPH-20), it was possible to distinguish Karelian population from the group consisting of the populations from two adjacent regions (Moscow oblast and Vladimir oblast). Based on the combined matrix, containing 294 RAPD fragments, dendrogram of genetic differences was constructed, and the indices of genetic divergence and partition (P, H, and G _st), as well as the gene flow indices N _m between the nematode samples examined, were calculated. The dendrogram structure, genetic diversity indices, and variations of genetic distances between single individuals in each population from Karelia and Central Russia pointed to genetic isolation and higher genetic diversity of the nematodes from Karelia.Based on polymorphism of rDNA first intergenic spacer ITS1, attribution of all populations examined to the species G. rostochiensis was proved. Small variations of the ITS1 sequence in different geographic populations of nematodes from different regions of the species world range did not allow isolation of separate groups within the species. Possible factors (including interregional transportations of seed potato) affecting nematode population structure in Russia are discussed.     

Odontometric variation among local populations of Kenyan olive baboons

This is a first report on a survey of local variations in genetic marker frequencies and morphometric features on Kenyan olive baboons. Data on dental casts of the upper dentitions of 207 baboons (115 males and 92 females) are analyzed with univariate and multivariate techniques. The materials represent 18 troops captured at 4 different localities. In general, levels of variability within and between localities are not great. The most marked variations present are in the premolar teeth. Females show greater variation than males. There are suggestive correlations between morphometric distance and geographic distance (positive) and morphometric distance and altitude difference (negative). There are some differences between this olive baboon sample and that of Swindler, McCoy & Hornbeck (1967) which lies close to a zone of olive-yellow baboon hybridization (Maples, 1972).     

Relationship among the genes, enzymes, and intermediates of the biosynthetic pathway of lysine in Saccharomyces

Summary Genetic lesions of 10 of the lysine loci in Saccharomyces have been provisionally correlated with the various enzymatic steps of the homocitric acid pathway for the biosynthesis of lysine. The characterization of mutational blocks in different mutants was made on the basis of the accumulation of appropriate intermediates, lack of enzymatic activity, and feeding experiments. Genetic lesions in mutants lys ₄, lys₇, lys₈, and lys ₁₂ correspond to the biochemical steps between homocitric acid and -amino-adipic acid. Similarly the genetic lesions in lys ₁, lys₂, lys₅, lys₉, lys₁₃, and lys ₁₄ correspond to the intermediate steps between -aminoadipic acid and lysine. Lysine-genes are not clustered, instead are mapped on different chromosomes of Saccharomyces. Some of the intermediate steps in the biosynthesis of lysine correspond to two or more unlinked genes.Supported by NSF Grant GB 28558X, Lilly Research Foundation, and Faculty Research Committee, Miami University.     

Investigation of genetic diversity in fragmented geometric tortoise (Psammobates geometricus) populations

Microsatellite DNA was used to investigatelevels of genetic variability in severelyfragmented populations of the geometrictortoise, Psammobates geometricus, themost endangered tortoise on mainland Africa.Eight microsatellite markers were used toassess genetic variability within and betweenthree naturally occurring populations of P. geometricus. These populations areseparated by the Cape Fold mountain ranges inthe western Cape region of South Africa. Levels of variability were quantified usingallelic diversity, genotypic frequencies andheterozygosity. Evidence for populationsub-structuring was examined using Fstatistics, R_st and ².High levels of variability were found in allthree populations. Low levels of populationdifferentiation were found suggestingsignificant gene flow between the populations.     

Strong genetic differentiation of the East-Himalayan <Emphasis Type="Italic">Megacodon stylophorus</Emphasis> (Gentianaceae) detected by Inter-Simple Sequence Repeats (ISSR)

Megacodon stylophorus (Clarke) Smith is a perennial alpine herb endemic to the species-rich eastern Himalayan region. Its populations are locally scattered as isolated patches throughout this region. Genetic variation within and among six populations of this species was assessed using ISSR fingerprinting with 13 primers. High levels of genetic diversity exist within species (P = 69.83%, H_T = 0.1949 and H_sp = 0.3047), while the within-population diversity is low (P = 11.21%, H_E = 0.0532 and H_pop = 0.0792). Extraordinarily high levels of genetic differentiation were detected among populations based on various statistics, including Neis genetic diversity analysis (72.7%), Shannons diversity index (74.01%) and AMOVA (80.70%). That is, populations shared low levels of genetic identity (I = 0.8203 ± 0.0430). This genetic structure was probably due to severe genetic drift of the small-sized patchy populations resulting from postglacial habitat fragmentations. The observed genetic structure of the populations implies that as many populations as possible should be considered for any in situ and ex situ conservation practice on this species.     

Genetic variation and natural hybridization betweenOrchis laxiflora andOrchis palustris (Orchidaceae)

Genetic divergence between population samples ofOrchis laxiflora and ofO. palustris from various European locations was studied by electrophoretic analysis of 25 enzyme loci. An average genetic distance of D_Nei = 1.24 was found between the two taxa, with 12 out of 25 loci showing alternative alleles (diagnostic loci). Genetic heterogeneity was observed within bothO. laxiflora andO. palustris, when northern and southeastern populations were compared, being lower in the former taxon (D = 0.06), than in the latter (D = 0.16). Karyologically, 2n = 36 was found for bothO. laxiflora andO. palustris. O. laxiflora andO. palustris produce hybrids, described asO. ×intermedia. Genotype analysis of several sympatric samples showed the presence of hybrid zones, including F₁ hybrids and, in low proportions, recombinant classes, putatively assigned to F_n and backcrosses, as well as a few introgressed individuals of both taxa. These data indicate that hybrids are only partially fertile, with a very limited mixing up of the two parental gene pools; this is also shown by the lack of significant lowering of genetic distances when sympatric and allopatric heterospecific samples are compared. Accordingly,O. laxiflora andO. palustris form a syngameon; nevertheless they can be considered as good taxonomic species, with virtually distinct gene pools, which evolve independently. The genetic variability inO. laxiflora andO. palustris is remarkably low ( _e = 0.05 and _e = 0.02, respectively). In particular, nearly complete absence of polymorphic loci was found inO. palustris from northcentral Europe. Two hypotheses are considered to explain the low genetic variability of this endangered species.     

SMALL POPULATION GENETIC VARIABILITY AT LOCI UNDER STABILIZING SELECTION

Genetic variability at a locus under stabilizing selection in a finite population is investigated using analytic methods and computer simulations. Three measures are examined: the number of alleles k, heterozygosity H, and additive genetic variance Vg. A nearly-neutral theory results. The composite parameter S = NV_M/V_s (where N is the population size, V_M the variance of new mutant allelic effects and V_s the weakness of stabilizing selection) figures prominently in the results. The equilibrium heterozygosity is similar to that of strictly neutral theory, H = 4N_μc/ (1 + 4N_μc), except that μ_c = where c is about 0.5. Simulations corroborate except for very low N. Genetic variability attains similar equilibrium values at both a “lone” locus and at an “embedded” locus. This agrees with my earlier work concerning molecular clock rates. These results modify the neutralist interpretation of data concerning genetic variability and genetic distances between populations. Low H values are proportional not to N but to . This may explain the narrow observed range of H among species. Heterozygosities need not be highly correlated to genetic variances. Genetic variances are not highly dependent on population size except in very small populations which are difficult to sample without bias because the smallest populations go extinct the fastest. Nearly neutral evolution will not be easily distinguished from strictly neutral theory under the Hudson-Kreitman-Aguade inter-/intraspecific variation ratio test, since a similar effective mutation rate holds for genetic distances and D = 2μ_ct, where . As with strictly neutral theory, comparisons across loci should show D and H to be positively correlated because of the shared μ_c. But unlike neutral theory, for a given locus, comparisons across species should show D and H to be negatively correlated. There is no obvious threshold of population size below which genetic variability inevitably declines. Extinction depends on both genetic variation and natural selection. Neither theory nor observation presently indicates the measure of genetic variability (k, H, V_G or other) that best indicates vulnerability of a small population to extinction.     

Population genetics of Japanese monkeys: II. Blood protein polymorphisms and population structure

Genetic variability in individual troops of the Japanese macaque (Macaca fuscata fuscata) was quantified by the proportion of polymorphic loci and the average heterozygosity per individual from the results of starch-gel electrophoreses of blood proteins controlled by 32 independent genetic loci. The former averaged 9.2% and the latter 1.3%, the values being remarkably lower than those estimated for other animal populations. Geographical distribution of the genetic variations was not uniform in the whole species but the variants occurred only in limited areas. Assuming the selective neutrality of segregating alleles and the two-dimensional stepping-stone model of population structure, the genetic migration rate between the local demes per generation could be estimated to average less than inverse of average effective deme size. Here, the local deme is not a troop itself, but it consists of several troops tightly connected with each other by frequent exchanges of reproductive males. Analyses of correlation between geographic and genetic distances between troops revealed that the gene constitutions of two troops apart more than 100 km on an island could be regarded as practically independent of each other. These results suggest that the population structure of the Japanese macaque species has a tendency to split into a number of local subpopulations in which the effect of random genetic drift is prevailing.     

Genetic diversity within and among populations of Shorea leprosula Miq. and Shorea parvifolia Dyer (Dipterocarpaceae) in Indonesia detected by AFLPs

The genetic diversity within and among populations of Shorea leprosula and Shorea parvifolia from Indonesia was investigated using amplified fragment length polymorphisms (AFLPs). The results indicated that S. leprosula is genetically more variable than S. parvifolia. At the population level, a higher level of genetic diversity was revealed for S. leprosula with a percentage of polymorphic loci (PPL_p) of 53.32% and an expected heterozygosity (H _ep) of 0.16 in comparison with S. parvifolia showing PPL_p of 51.79% and H _ep of 0.14. At the species level, S. leprosula showed PPL_s of 92.86% and H _es of 0.21, while S. parvifolia showed PPL_s of 85.71% and H _es of 0.21. Genetic differentiation (G _st) indicated that 25 and 31% of total genetic diversity in S. leprosula and S. parvifolia, respectively, were attributed to the differences among populations. An analysis of molecular variance (AMOVA) at two hierarchical levels exhibited that most genetic variation resided within populations with proportion of 70.2% for S. leprosula and 66.2% for S. parvifolia. The AMOVA at three hierarchical levels performed for S. leprosula and S. parvifolia together revealed that the genetic difference between the two species was remarkably higher with a proportion of 44.1% than the differences within and among populations (38.1 and 17.8%, respectively). The genetic differentiation between islands was significant for S. leprosula but not for S. parvifolia. The observed genetic diversity agreed with the life history traits of Shorea species. Highly differentiating individual AFLP markers were found for each species, which will serve as diagnostic markers for the identification of wood of different species, from different islands and regions.     

Genetic diversity in populations of Cronartium ribicola in plantations and natural stands of Pinus strobus

Genetic diversity was studied in 22 populations of the white pine blister rust fungus Cronartium ribicola from natural stands and plantations of eastern white pine, Pinus strobus. Pseudo-allelic frequencies were estimated at each of 7 putative RAPD loci by scoring for presence or absence of amplified fragments in dikaryotic aecidiospores. Analysis of genetic distance between all pairs of populations did not reveal any trend with regard to geographic origin or type of white pine stand. In addition, when hierarchical population structure was analysed, total genetic diversity (H _s =0.214) was mostly attributable to diversity within populations (H _s =0.199; AMOVA _st =0.121, P<0.01). Genetic diversity of populations relative to region of origin (east, centre, and west) or type of stand (natural stands vs plantations) was not significantly different from zero (P>0.10) Nevertheless, a significant proportion of genetic differentiation was found between populations within region or stand type (F _st =0.114; _sc =0.132, P<0.001). This result indicates that some population structure exists but that it appears to be independent of region of origin or type of stand. At least for 2 populations from white pine plantations, it appears possible that a recent introduction of a limited number of propagules was responsible for low levels of genetic diversity. We interpret these results as meaning that either long-distance dispersal is taking place between populations more than 1000 km apart or that these populations share a common recent ancestor. In addition, we suggest that C. ribicola may still be expanding its distribution by colonizing new plantations.