Genetic diversity within and among 11 juvenile populations of green alder (Alnus crispa) in Canada

Germinated seeds from 11 populations of green alder [ Alnus crispa (Ait.) Pursh] sampled in four Canadian provinces were analysed for electrophoretically demonstrable diversity of 10 enzymes encoded by 15 structural loci. Of these, nine were polymorphic, and on average, 52% of the loci per population were polymorphic. Assuming a diploid model of expression, average level of expected heterozygosity was 0.11 with nearly all populations in Hardy-Weinberg equilibrium for the set of polymorphic loci analysed. No significant inbreeding and associated subpopulation structuring were noted. Rates of gene flow appeared high within and among populations. Although little divergence was observed among populations, genetic and geographical distances between populations were related. Discriminant and cluster analyses revealed a pattern of genetic variation associated with geography. Populations from northern Quebec were poorly differentiated, whereas western populations from Alberta exhibited a larger degree of genetic differentiation. Introgresive hybridization with the sympatric species Alnus sinuata (Regel) Rydberg and partial isolation in the West are suggested as an explanation for this larger differentiation. The occurrence and significance of rare alleles is discussed in relation to the importance of geographical distance in the process of population differentiation in this species.     

Genetic Diversity and Population Structure of Alnus hirsuta (Betulaceae) in Korea

Alnus hirsuta in Korea was measured to estimate the amount and pattern of genetic diversity and population structure. The mean genetic diversity within populations was 0.166. Korean alder populations have slightly high levels of genetic diversity compared to those of two Canadian alder species. The genetic differentiation among populations accounted for 9% of the total variation. The rate of gene flow was estimated high (Nm=2.63). Analysis of inbreeding coefficient, calculated for all polymorphic loci in each population, showed a substantial heterozygote deficiency relative to Hardy-Weinberg expectations. The mean G _ST value of A. hirsuta in Korea was 0.087. The low value of G _ST in this species, reflecting little spatial genetic differentiation, may indicate extensive gene flow. A relationship between the mean heterozygosity and annual rainfall showed a positive relationship (r ²=0.54, F=4.67). Received 8 August 1998/ Accepted in revised form 7 July 1999     

Genetic variation and population structure ofCarex breviculmis (Cyperaceae) in Korea

We determined the genetic diversity and population structures ofCarex breviculmis (Cyperaceae) populations in Korea, using genetic variations at 23 allozyme loci.C. breviculmis is a long-lived herbaceous species that is widely distributed in eastern Asia. A high level of genetic variation was found in 15 populations. Twelve enzymes revealed 23 loci, of which 11 were polymorphic (47.8%). Genetic diversity at the speciesand population levels were 0.174 and 0.146, respectively. Total genetic diversity (H_T = 0.363) and within-population genetic diversity (H_s = 0.346) were high, whereas the extent of the population divergence was relatively low (G_ST = 0.063). Deviation from random mating (Fis) within the 15 populations was 0.206. An indirect estimate of the number of migrants per generation(Nm = 3.69) indicated that gene flow was extensive among Korean populations of this species. Analysis of fixation indices revealed a substantial heterozygote deficiency in some populations and at some loci. Genetic identity between popu-lations was high, exceeding 0.956.     

Isolation and characterization of microsatellite loci in Ostryopsis davidiana (Betulaceae)

Ostryopsis (Betulaceae) is a samll genus endemic to China with only two species. Both of them play an important role in restoring the local ecosystems. The distribution of genetic diversity between and within populations in each species are important to further utilize the wild genetic resources and explore the interspecific divergence. In this study, we developed 10 microsatellite loci from O. davidiana by the combining biotin capture method for the first time. A total of 27 microsatellite sequences were recovered through screening the library and 10 of them are polymorphic. The number of alleles per locus in 18 sampled individuals ranged from 3 to 6, expected heterozygosity and observed heterozygosity ranged from 0.2958 to 0.4767 and from 0.1591 to 0.2997, respectively. In addition, all markers have been crossly checked in the other congeneric species. These microsatellite markers would together provide a useful tool for investigating the genetic diversity and structure of both species and speciation mechanism between them.     

Population Genetic structure ofPotentilla fragariodes var.major (Rosaceae) in Korea

The genetic diversity and population structure of eighteenPotentilla fragariodes var.major (Rosaceae) populations in Korea were determined using genetic variations at 22 allozyme loci. The percent of polymorphic loci within the enzymes was 66.7%. Genetic diversity at the species level and at the population level was high (Hes = 0.203; Hep = 0.185, respectively), whereas the extent of the population divergence was relatively low (G_ST = 0.069). F_IS, a measure of the deviation from random mating within the 18 populations, was 0.075. An indirect estimate of the number of migrants per generation (Nm = 3.36) indicated that gene flow was high among Korean populations of the species. In addition, analysis of fixation indices revealed a slight heterozygote deficiency in some populations and at some loci. Wide geographic ranges, perennial herbaceous nature and the persistence of multiple generations are associated with the high level of genetic variation. AlthoughP. fragariodes var.major usually propagated by asexually-produced ramets, we could not rule out the possibility that sexual reproduction occurred at a low rate because each ramet may produce terminal flowers. Mean genetic identity between populations was 0.983. It is highly probable that directional movement toward genetic uniformity in a relatively homogeneous habitat operates among Korean populations ofP. fragariodes var.major.     

Ecotypes of an ecologically dominant prairie grass (Andropogon gerardii) exhibit genetic divergence across the U.S. Midwest grasslands' environmental gradient

Big bluestem (Andropogon gerardii) is an ecologically dominant grass with wide distribution across the environmental gradient of U.S. Midwest grasslands. This system offers an ideal natural laboratory to study population divergence and adaptation in spatially varying climates. Objectives were to: (i) characterize neutral genetic diversity and structure within and among three regional ecotypes derived from 11 prairies across the U.S. Midwest environmental gradient, (ii) distinguish between the relative roles of isolation by distance (IBD) vs. isolation by environment (IBE) on ecotype divergence, (iii) identify outlier loci under selection and (iv) assess the association between outlier loci and climate. Using two primer sets, we genotyped 378 plants at 384 polymorphic AFLP loci across regional ecotypes from central and eastern Kansas and Illinois. Neighbour‐joining tree and PCoA revealed strong genetic differentiation between Kansas and Illinois ecotypes, which was better explained by IBE than IBD. We found high genetic variability within prairies (80%) and even fragmented Illinois prairies, surprisingly, contained high within‐prairie genetic diversity (92%). Using Bayenv 2, 14 top‐ranked outlier loci among ecotypes were associated with temperature and precipitation variables. Six of seven BayeScan F_ST outliers were in common with Bayenv 2 outliers. High genetic diversity may enable big bluestem populations to better withstand changing climates; however, population divergence supports the use of local ecotypes in grassland restoration. Knowledge of genetic variation in this ecological dominant and other grassland species will be critical to understanding grassland response and restoration challenges in the face of a changing climate.     

Inter- and intraspecific genetic variation inHippophae (Elaeagnaceae) investigated by RAPD markers

Genetic diversity has been investigated by the application of molecular markers in, for the first time, all the taxa recognised in recent treatises of the genusHippophae. RAPD (random amplified polymorphic DNA) analyses were conducted with 9 decamer primers, which together yielded 219 polymorphic markers. We found 16 fixed RAPD markers, i.e. markers that either occurred in all plants of a population or were absent from all plants. Several of these markers were useful for analysis of interspecific relationships, whereas others can be considered as taxon-specific markers. Clustering of taxa and populations in our neighbour-joining based dendrogram was in good agreement with some recently suggested taxonomic treatises ofHippophae. Amount and distribution of genetic variability varied considerably between species. Partitioning of molecular variance withinH. rhamnoides supported earlier findings that a considerable part of the total variance resides among subspecies (59.6%) Within-population variability also differed considerably. Percentage polymorphic RAPD loci and Lynch and Milligan within-population gene diversity estimates showed relatively high values for some species close to the geographic centre of origin in Central Asia, e.g.H. tibetana and the putatively hybridogenousH. goniocarpa. Spatial autocorrelation analyses performed on 12 populations ofH. rhamnoides revealed positive autocorrelation of allele frequencies when geographic distances ranged from 0 to 700 km, and no or negative autocorrelation at higher distances. At distances between 700 and 1900 km, we observed deviations from the expected values with strongly negative autocorrelation of allele frequencies. A corresponding relationship between geographic and genetic distances could not be found when the analysis instead was based on one population from each of 8 species.     

Isolation and characterization of microsatellite loci in the Amami rabbit (Pentalagus furnessi)

We report on the isolation and characterization of eight polymorphic and five monomorphic microsatellites in the Amami rabbit (Pentalagus furnessi). Microsatellite polymorphism was determined using 25 individuals. There were 2–11 alleles for each polymorphic locus with heterozygosity ranging between 0.08 and 0.76. Linkage disequilibrium was not suggested between any pairs among the eight polymorphic loci. We suggest that these primers be used in future studies to monitor population size, determine dispersal patterns, and genetic diversity within and between populations of this and related species.     

在韩国境内Potentilla fragarioides var .sprengeliana的遗传多样性和种群结构(英文)

根据 2 2个等位酶位点遗传变异 ,探讨了韩国境内委陵菜 (PotentillafragarioidesL .var.sprengeliana)的遗传多样性和种群结构。酶位点的多态位点百分比为 5 9 1%。种和种群水平上的遗传多样性比较高 ,分别为Hes=0 .2 10 ,Hep=0 .199;而种群的分化水平则相对较低 (GST=0 .0 74)。 19个种群中随机交配的偏差为FIS=0 .331。每代迁移数的间接估计 (Nm=3.15 )表明该种在韩国的种群间基因流较高。另外 ,固定指数分析显示在一些种群和位点有轻微的杂合子缺乏。种群间平均遗传一致度为 0 985。这些韩国委陵菜种群存在于较为均一的生境 ,这很有可能是造成其种群遗传一致性较高的原因。     

Maintenance of genetic and morphological identity in two sibling Syrrhopodon species (Calymperaceae,Bryopsida) despite extensive introgression

Bryophytes are a group of land plants in which the role of hybridization has long been challenged. Using genotyping by sequencing to circumvent the lack of molecular variation at selected loci previously used for phylogeny and morphology, we determine the level of genetic and morphological divergence and reproductive isolation between the sibling Syrrhopodon annotinus and S. simmondsii (Calymperaceae, Bryopsida) that occur in sympatry but in different habitats in lowland Amazonian rainforests. A clear morphological differentiation and a low (0.06), but significant Fst derived from the analysis of 183 single nucleotide polymorphisms were observed between the two species. Conspecific pairs of individuals consistently exhibited higher average kinship coefficients along a gradient of geographic isolation than interspecific pairs. The weak, but significant genetic divergence observed is consistent with growing evidence that ecological specialization can lead to genetic differentiation among bryophyte species. Nevertheless, the spatial genetic structures of the two species were significantly correlated, as evidenced by the significant slope of the Mantel test based on kinship coefficients between pairs of interspecific individuals and the geographic distance separating them. Interspecific pairs of individuals are thus more closely related when they are geographically closer, suggesting that isolation‐by‐distance is stronger than the interspecific reproductive barrier and pointing to interspecific gene flow. We conclude that interspecific introgression, whose role has long been questioned in bryophytes, may take place even in species wherein sporophyte production is scarce due to dioicy, raising the question as to what mechanisms maintain differentiation despite weak reproductive isolation.     

Patterns of Genetic Diversity and Population Structure of the Clonal Herb,Potentilla fragarioides var. sprengeliana (Rosaceae) in Korea

The genetic diversity and population structure of Potentilla fragarioides var. sprengeliana(Rosaceae) in Korea were investigated using genetic variation at 22 allozyme loci. The percent of polymorphic loci within the enzymes was 59.1%. The genetic diversity at the species level and at the population level was high (Hes=0.210; Hep=0.199, respectively), whereas the extent of the population divergence was relatively low (GST=0.074). FIS, a measure of the deviation from random mating within the 19 populations, was 0.331. An indirect estimate of the number of migrants per generation (Nm=3.15) indicates that gene flow is high among Korean populations of the species. In addition, analysis of fixation indices revealed a slight heterozygote deficiency in some populations and at some loci. The mean genetic identity between populations was 0.985. It is highly probable that the trend of genetic uniformity in a relatively homogeneous habitat is thought to be operated among Korean populations of P. fragarioides var.sprengeliana.     

GENETIC VARIATION AND DIFFERENTIATION IN THE GENUS MABRYA (SCROPHULARIACEAE-ANTIRRHINEAE): SYSTEMATIC AND EVOLUTIONARY INFERENCES

Nine populations of the five species of Mabrya have been examined for allozyme variation at 22 loci using enzyme electrophoresis. The species are homoploid (n = 12), herbaceous perennials and occur in small populations in canyons and barrancas in North American desert scrub and thorn scrub habitats. Although of ancient polyploid origin, the number of isozymes considered typical for diploids is encountered except for a probable duplication at a TPI locus. The average interspecific pairwise comparisons of genetic identities (range 0.434–0.731) are very dissimilar to intraspecific values (range 0.886–0.968). The uniformly low interspecific genetic divergence estimates (average I value of 0.593), large number of unique alleles (average of five per species), pronounced morphological differences, reduced interspecific cross-compatibilities, and (usually) allopatric distributions support recently proposed specific and infrageneric delimitations and hypotheses of a geographical speciation mode, a long period of reproductive isolation, and relictual endemism. Estimates of populational genetic variation are concordant with previous reproductive observations and suggest an outcrossing breeding system for M. geniculata and a mixed mating system for the other species. Because of approximately similar divergence values, phylogenetic relationships in the genus remain unresolved.     

Polymorphic dinucleotide microsatellites in tongue sole (Cynoglossus semilaevis)

The tongue sole, Cynoglossus semilaevis, is a rare marine flatfish distributed in Chinese coastal waters. From a (GT)_n‐enriched genomic library, 57 microsatellites were isolated and characterized. Seventeen of these loci were polymorphic in a test population with alleles ranging from three to 13, and observed and expected heterozygosities from 0.1613 to 1.0000 and from 0.2126 to 0.8983, respectively. Five loci deviated from the Hardy–Weinberg equilibrium in the sampled population, and linkage disequilibrium between two loci was significant after applying Bonferroni correction. Three additional fish species assessed for cross‐species amplification revealed that only one locus was also polymorphic in one species. These polymorphic microsatellite loci should provide sufficient level of genetic diversity to evaluate the breeding strategy and investigate the fine‐scale population structure in C. semilaevis.     

Genetic divergence and introgressive hybridization betweenAlnus sinuata andA. crispa (Betulaceae)

The actinorhizal genusAlnus contains numerous taxa that have been morphologically classified into different subgenera, species and subspecies. The genetic divergence has been evaluated within subg.Alnobetula between the parapatric taxaAlnus sinuata andA. crispa, using diversity of allozyme markers at 15 structural loci among 20 populations. Evidence for introgressive hybridization at the overlap of their ranges was noted in three populations. However, the width of the hybrid zone appeared tenuous. The average genetic distance derived from the comparisons of conspecific populations was much smaller than the interspecific distance (D = 0.047). This allelic divergence was also paralleled with larger amounts of allelic and genotypic diversity within and among populations ofA. sinuata, which are occupying a more heterogenous ecological niche. It is proposed that the repeated advances and retreats of the ice sheet during the Pleistocene may have promoted the divergence and allopatric evolution of these subspecies, and that secondary contact may have occurred repeatedly during the interglacial periods. The dynamic-equilibrium model would predict in such cases that narrow hybrid zones, formed at the contact of parapatric ranges, would impede gene exchange between parental taxa by selection against hybrids. The results obtained in this study seemed concordant with this hypothesis, as they were also in agreement with the existent taxonomical treatment of these taxa based on morphology.     

Cross‐amplification of 10 new isolated polymorphic microsatellite loci for red mullet (Mullus barbatus) in striped red mullet (Mullus surmuletus)

Ten polymorphic dinucleotide microsatellite loci were isolated and characterized for the red mullet (Mullus barbatus). Allele variability was tested on both the red mullet and its congener the striped red mullet (Mullus surmuletus). Characterization of 30 individuals of both species from the western Mediterranean showed moderate to high allelic diversity ranging from two to 26 alleles per locus (mean 10.9). Three loci showed departures from Hardy–Weinberg proportions. No evidence of significant association between genotypes at pairs of loci was observed. These polymorphic loci could be suitable for population genetic assessments of both species.     

GENETIC RELATIONSHIPS AND PATTERNS OF ALLOZYMIC DIVERGENCE IN THE IPOMOPSIS AGGREGATA COMPLEX AND RELATED SPECIES (POLEMONIACEAE)

The Ipomopsis aggregata complex consists of diploid, outcrossing, perennial herbs. The group is highly variable morphologically and is treated as three species: I. aggregata, I. tenuituba, and I. arizonica. Geographic races of I. aggregata and I. tenuituba are recognized as subspecies. Enzyme electrophoresis was used to examine genetic relationships among populations and taxa in the Ipomopsis aggregata complex and some related species. Genetic data for 23 allozyme loci from 60 populations were also used to determine how genetic variation is distributed geographically. Populations in the southwestern United States were more variable than those in the northwest: the center of genetic diversity corresponded to the center of species diversity. Allozymic data provided no evidence of loss of genetic variability associated with recent and rapid divergence. Genetic relationships based on Nei's genetic identity did not correspond to taxonomic relationships. For example, populations of both I. arizonica and I. tenuituba clustered within I. aggregata. Despite relatively high levels of genetic diversity among populations, diversity among taxa was low. Results indicated that floral divergence and concomitant speciation have occurred recently in the Ipomopsis aggregata complex. Allozymic patterns also reflected convergent evolution for floral morphology and possible introgression. Despite morphological differences among species, insufficient evolutionary time has elapsed for allelic fixation at neutral or near-neutral allozyme loci.     

Development of twelve polymorphic microsatellite loci in polyploid endangered Omphalogramma vincaeflora Franch. (Primulaceae)

A total of twelve polymorphic microsatellite loci were developed from polyploid endangered species, Omphalogramma vincaeflora (Primulaceae). These loci were screened for variability among 45 individuals from three populations in China. The primers amplified loci with allele number ranging from 3 to 9, with an average of 4.25 per locus. Polymorphism information content ranged from 0.23 to 0.86. Nei’s genetic diversity ranged from 0.34 to 0.86. These primers provide an opportunity to use polymorphic DNA markers to study the population genetic structure and its breeding system in this species.     

Allozyme variation and population differentiation of the Aconitum delavayi complex (Ranunculaceae) in the Hengduan Mountains of China

The Aconitum delavayi complex is a group of four climbing species with trisect-leaves occurring in the Hengduan Mountains. The species of this complex are highly localized on very narrow regions with quite small population sizes. Because of rapid environmental changes recently in the Hengduan Mountains, this complex shows complicated morphological variability, which makes it difficult to delimit species. In the present study, 10 enzyme systems coding for 14 putative loci were employed to detect the interspecific and intraspecific genetic variation of the complex. In addition to low genetic diversity within all eight populations surveyed, the results indicate that A. episcopale is a distinct species because of high genetic identities among its three populations. Very low genetic divergence among populations of A. stapfianum and A. delavayi suggests that the two species should be treated as a single one.     

Comprehensive analysis of population genetics of Phoxinus phoxinus ujmonensis in the Irtysh River: Abiotic and biotic factors

As a widely distributed species along the Irtysh River, Phoxinus phoxinus ujmonensis (Kaschtschenko, 1899) was used as a model to investigate genetic diversity and population structure as well as the influence of environmental factors on population genetics. In this study, we specifically developed 12 polymorphic microsatellite loci. The analysis of microsatellite and mtDNA markers revealed a high and a moderate genetic diversity across seven populations, respectively. Moderate differentiation was also detected among several populations, indicating the impact of habitat fragmentation and divergence. The absence of isolation by distance implied an extensive gene flow, while the presence of isolation by adaptation implied that these populations might be in the process of adapting to divergent habitats. Correlation analysis showed that abiotic factors like dissolved oxygen, pH, total dissolved solids, and conductivity in water as well as biotic factors like plankton diversity and fish species diversity had impact on genetic diversity and divergence in P. phoxinus ujmonensis populations. The results of this study will provide an insight into the effect of environmental factors on genetic diversity and contribute to the study of population genetics of sympatric species.     

Allozyme diversity in the federally threatened golden paintbrush, <Emphasis Type="Italic">Castilleja levisecta</Emphasis> (Scrophulariaceae)

Castilleja levisecta (Scrophulariaceae), the golden paintbrush, is an insect-pollinated herbaceaous perennial found in the Pacific Northwest. Currently restricted to two island populations off British Columbia and nine populations (eight on islands) in Washington, C. levisecta is a rare species threatened with extinction. Allozymes were used to describe genetic diversity and structure in these eleven populations. Despite its threatened status and small geographic range, exceptionally high levels of genetic diversity are maintained within C. levisecta. All sixteen of the loci resolved were polymorphic within the species (P_s=100%), while the mean percentage of loci polymorphic within populations (P_p) was 65.7%. The mean number of alleles per polymorphic locus (AP_s) was 2.94 within the species and averaged 2.38 within populations (AP_p). Genetic diversity (H_es) was 0.285 for the species, whereas mean population genetic diversity (H_ep) was 0.213. Smaller populations had, on average, fewer observed alleles and less genetic diversity. A significant negative correlation (r = –0.72) was found between genetic identity and geographic distance, indicating reduced gene flow between distant populations. The most geographically isolated population was one of the larger populations, one of the most genetically diverse and the most genetically divergent. A wide range of pairwise population genetic identities (I = 0.771 – 0.992) was found, indicating considerable genetic divergence between some populations. Overall, 19% of the total genetic diversity was distributed among populations. Results of this survey indicate that genetic augmentation of existing populations is unnecessary. The high allelic diversity found for the species and within its populations holds promise for conservation and restoration efforts to save this rare and threatened plant species.