RAPD Profiling in Detecting Genetic Variation in Endemic Coelonema (Brassicaceae) of Qinghai-Tibet Plateau of China

Random amplified polymorphic DNA (RAPD) markers were used to measure genetic diversity of Coelonema draboides (Brassicaceae), a genus endemic to the Qilian Mountains of the Qinghai-Tibet Plateau. We sampled 90 individuals in 30 populations of Coelonema draboides from Datong and Huzhu counties of Qinghai Province in P.R. China. A total of 186 amplified bands were scored from the 14 RAPD primers, with a mean of 13.3 amplified bands per primer, and 87% (161 bands) polymorphic bands (PPB) was found. Analysis of molecular variance (AMOVA) shows that a large proportion of genetic variation (84.2%) resides among individuals within populations, while only 15.8% resides among populations. The species shows higher genetic diversity between individuals than other endemic and endangered plants. The RAPDs provide a useful tool for assessing genetic diversity of rare, endemic species and for resolving relationships among populations. The results show that the genetic diversity of this species is high, possibly allowing it to adapt more easily to environmental variations. The main factor responsible for the high level of differentiation within populations and the low level of diversity among populations is probably the outcrossing and long-lived nature of this species. Some long-distance dispersal, even among far separated populations, is also a crucial determinant for the pattern of genetic variation in the species. This distributive pattern of genetic variation of C. draboides populations provides important baseline data for conservation and collection strategies for the species. It is suggested that only populations in different habitats should be studied and protected, not all populations, so as to retain as much genetic diversity as possible.     

Genetic Diversity and Genetic Structure of an Endangered Species, Trillium tschonoskii

The genetic diversity and genetic structure of Trillium tschonoskii (Maxim) were investigated using amplified fragment length polymorphism markers. Eight primer combinations were carried out on 105 different individuals sampled from seven populations. Of the 619 discernible DNA fragments generated, 169 (27.3%) were polymorphic. The percentage of polymorphic bands within populations ranged from 4.52 to 10.50. Genetic diversity (H_E) within populations ranged from 0.0130 to 0.0379, averaging 0.0536 at the species level. Genetic differentiation among populations was detected based on Nei's genetic diversity analysis (53.03%) and analysis of molecular variance (AMOVA) (52.43%). AMOVA indicated significant genetic differentiation among populations (52.43% of the variance) and within populations (47.57% of the variance) (p < 0.0002). Gene flow was low (0.4429) among populations. Species breeding system and limited gene flow among populations are plausible reasons for the high genetic differentiation observed for this species. We propose an appropriate strategy for conserving the genetic resources of T. tschonoskii in China.     

Unexpectedly high genetic diversity and divergence among populations of the apomictic Neotropical tree Miconia albicans

• Since tropical trees often have long generation times and relatively small reproductive populations, breeding systems and genetic variation are important for population viability and have consequences for conservation. Miconia albicans is an obligate, diplosporous, apomictic species widespread in the Brazilian Cerrado, the savanna areas in central Brazil and elsewhere in the Neotropics. The genetic variability would be, theoretically, low within these male‐sterile and possibly clonal populations, although some variation would be expected due to recombination during restitutional meiosis.
• We used ISSR markers to assess genetic diversity of M. albicans and to compare with other tropical trees, including invasive species of Melastomataceae. A total of 120 individuals from six populations were analysed using ten ISSR primers, which produced 153 fully reproducible fragments.
• The populations of M. albicans presented mean Shannon's information index (I) of 0.244 and expected heterozygosity (H_e) of 0.168. Only two pairs of apparently clonal trees were identified, and genetic diversity was relatively high. A hierarchical amova for all ISSR datasets showed that 74% of the variance was found among populations, while only 26% of the variance was found within populations of this species. Multivariate and Bayesian analyses indicated marked separation between the studied populations.
• The genetic diversity generated by restitutional meiosis, polyploidy and possibly other genome changes may explain the morpho‐physiological plasticity and the ability of these plants to differentiate and occupy such a wide territory and different environmental conditions. Producing enormous amounts of bird‐dispersed fruits, M. albicans possess weedy potential that may rival other Melastomataceae alien invaders.

     

Genetic diversity of Mexican brook lamprey <Emphasis Type="Italic">Lampetra (Tetrapleurodon) geminis</Emphasis> (Alvarez del Villar, 1966)

Lampreys are the only surviving representatives of the oldest known vertebrates. The Mexican lamprey L. geminis (nonparasitic), is particularly interesting, because it is an endemic, biogeographical relict, and a threatened species. RAPD markers were used to describe genetic diversity in L. geminis A total of 77 specimens were collected from five populations, three in the R'o Grande de Morelia-Cuitzeo basin and two in the R'o Duero-Lerma-Chapala basin, Mexico. Eighty-eight RAPD markers were obtained from eight primers. Genetic diversity within each population was estimated using Shannon's index (S), heterozygosity (H) and gene diversity (h). These estimates revealed significant variation within populations, although a variance homogeneity test (HOMOVA) showed no significant differences among populations or between basins. Nei genetic distance values indicate a low genetic differentiation among populations. Analysis of molecular variance (AMOVA) indicates that most of the genetic diversity occurs within populations (91.4%), but that a statistically significant amount is found among populations (P0.001). Principal coordinates and cluster analyses of RAPD phenotypes show that specimens are not grouped by geographical origin. The genetic diversity found within L. geminispopulations may be explained by its breeding system and an overlapping of generations. The scarce genetic differentiation among populations is likely to the low rate of DNA change that characterizes the lamprey group.     

Assessing genetic diversity of Elymus sibiricus (Poaceae: Triticeae) populations from Qinghai-Tibet Plateau by ISSR markers

Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population structure in eight populations of Elymus sibiricus L. from the southeast of Qinghai-Tibet Plateau of China. Of the 100 primers screened, 13 produced highly reproducible ISSR bands. Using these primers, 193 discernible DNA fragments were generated with 149 (77.2%) being polymorphic, indicating considerable genetic variation at the species level. In contrast, there were relatively low levels of polymorphism at the population level with the percentage of polymorphic bands (PPB) ranging from 44.04 to 54.92%. The mean gene diversity (H_E) was estimated to be 0.181 within populations (range 0.164–0.200), and 0.274 at the species level. A high level of genetic differentiation among populations was detected based on Nei's genetic diversity analysis (33.1%), Shannon's index analysis (34.5%), Bayesian method (33.2%) and AMOVA analysis (42.5%). No significant statistical differences (analysis of molecular variance [AMOVA], P = 0.08) in ISSR variation were found between the sample collection regions. However, among populations (42.5% of the variance) and within populations (57.5% of the variance), there were significant differences (P < 0.001). Populations shared high levels of genetic identity. This pattern of genetic variation was different from that for most of inbreeding Triticeae species reported. In addition, a geographical pattern of population differentiation, where the populations from south and north of sampling sites were clearly separated from each other, was revealed by both the cluster and principal coordinates analyses. Generally, the result of this study indicates that E. sibiricus contains high molecular variation in its populations. The implications of these results for the conservation of the species are discussed.     

Genetic Diversity and Population Structure in Fragmented Natural Populations of Melia dubia Cav. Revealed by SSR Markers—Its Implications on Conservation

Melia dubia, a fast-growing tree species with multi-various uses, is suitable species for agro and farm forestry. In an extensive survey in eight districts of Karnataka, India, it was observed that the majority of M. dubia natural populations are fragmented and tree number is very less. Sixty trees were selected to assess the genetic variability using SSR markers. Analysis revealed a moderate level of genetic diversity (Ho?=?0.47; He?=?0.69) and inbreeding as evinced by overall positive fixation index of 0.30. Mean Fst observed was 0.16 indicating moderate genetic differentiation among populations. The analysis of molecular variance ascribed 99% of total genetic diversity to within population variation. Cluster analysis by unweighted pair group method and genetic differentiation through structure analysis did not differentiate 10 populations as per geographic location, showing that moderate genetic diversity was not due to geographic distance. As genetic diversity was more within population, selection of individual plants would be more effective for genetic improvement to capture the natural variation within the population. An understanding of genetic diversity and differentiation of M. dubia natural populations will help in exploiting the genetic resource for tree improvement and also in formulating management and conservation strategies for this 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.     

我国盾叶薯蓣居群遗传结构分析

利用随机扩增多态DNA(RAPD)标记,分析研究了中国11个盾叶薯蓣居群82个个体的遗传多样性与遗传结构,15个寡聚核苷酸引物扩增共得到108条带,其中96条为多态带,占88．89％。Shannon多样性指数(I)为0．3093,居群水平的变异从0．1564到0．3098,物种水平的Nei基因多样度(h)为0．2499,居群水平的变化范围为0．1607到0．2137。遗传变异分析表明,物种水平的基因分化系数Gst为0．3415,居群间的基因流Nm为0．9641,居群间遗传交换小。分子方差分析(AMOVA)表明,居群内变异为68．96％,地区间变异为19．45％,居群问变异为11．58％。聚类结果以长江为界,将盾叶薯蓣分为南北两个大类群。研究结果对盾叶薯蓣种质的迁地保护有重要意义。     

Genetic diversity and phylogenetic relationships in alder,Alnus firma, revealed by AFLP

Molecular markers for alder,Alnus firma Sieb. et Zucc, have not been studied extensively. Here, we used amplified fragment length polymorphism (AFLP) to investigate genetic relationships among 15 natural populations. EcoRI-ACG + Msel-CTG combinations revealed the highest polymorphism (62.2%). A total of 171 DNA fragments were identified. On average, 58.1% of the AFLP markers that were generated using four primer pairs were polymorphic. Diversity was insignificant among the populations. The combination of a wind-pollinated, outcrossing breeding system along with large population sizes, and the ability to regenerate by stump sprouting may explain the high level of genetic diversity within this species. The majority (98%) of the genetic variance resided within populations. The average number of individuals that were exchanged between populations per generation was very high (N _em = 12.3). Gene dispersal in alder is apparently by seed dispersalvia water and human activity as well as through pollen. Five individuals per population were claded in the same cluster.     

Low genetic diversity and high genetic differentiation in the critically endangered Omphalogramma souliei (Primulaceae): implications for its conservation

Omphalogramma souliei Franch. is an endangered perennial herb only distributed in alpine areas of SW China. ISSR markers were applied to determine the genetic variation and genetic structure of 60 individuals of three populations of O. souliei in NW Yunnan, China. The genetic diversity at the species level is low with P=42.5% (percentage of polymorphic bands) and Hsp=0.1762 (total genetic diversity). However, a high level of genetic differentiation among populations was detected based on different measures (Nei's genetic diversity analysis: Gst=0.6038; AMOVA analysis: Fst=0.6797). Low level of genetic diversity within populations and significant genetic differentiation among populations might be due to the mixed mating system in which xenogamy predominated and autogamy played an assistant role in O. souliei. The genetic drift due to small population size and limited current gene flow also resulted in significant genetic differentiation. The assessment of genetic variation and differentiation of the endangered species provides important information for conservation on a genetic basis. Conservation strategies for this rare endemic species are proposed.     

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.     

Genetic differentiation among Hemarthria compressa populations in south China and its genetic relationship with H. japonica

Within and among populations genetic variance of twelve Hemarthria compressa populations and one Hemarthria japonica population from China were analyzed using inter simple sequence repeat (ISSR). Twelve primers amplified a total of 165 genomic DNA fragments across a total of 148 individuals of which 156 were polymorphic (94.55%). 75.76% of the bands were unique to each species, while the average genetic distance (GD) between one population of H. japonica and twelve populations of H. compressa was 0.44, which suggest that there was distinct differentiation between these two species. In H. compressa, twelve primers produced 145 bands across 145 individuals. High genetic diversity was observed at species level. The percentage of polymorphic loci (P) was 86.21% and Shannon's information index of diversity (I) was 0.357. In contrast, there were relatively low levels of genetic diversity within population (P=32.93%, I=0.174). Analysis of molecular variance (AMOVA) showed that a considerable proportion of genetic variation (48.02%) resided among populations. The coefficient of gene differentiation (G(ST)=48.6%) also suggested that there was strong genetic differentiation among H. compressa populations in southern China. An indirect estimate of the number of migrants per generation (N(m)=0.264) indicated that gene flow was low among populations of this species. Relative high clonal diversity was found, and all local genotypes were found.     

Genetic diversity and population structure of Culex modestus across Europe: does recent appearance in the United Kingdom reveal a tendency for geographical spread?

In mainland Europe, the mosquito species Culex modestus Ficalbi (1890) is a bridge vector for West Nile virus (WNV) from its natural bird-mosquito cycle to mammals. The present study assessed the genetic diversity of Cx. modestus, as well as related Culex species, using the mitochondrial COI DNA barcoding region and compared this with the population structure across Europe. A haplotype network was mapped to determine genealogical relationships among specimens. The intraspecific genetic diversity within individual Culex species was below 2%, whereas the interspecific genetic divergence varied from 2.99% to 13.74%. In total, 76 haplotypes were identified among 198 sequences. A median-joining network determined from 198 COI sequences identified two major lineages that were separated by at least four mutation steps. A high level of intraspecific genetic diversity was not detected in Cx. modestus in samples submitted from different European populations, which indicates that morphologically identified specimens represent a single species and not a species complex. Therefore, it is deduced that different populations of Cx. modestus will show a similar potential to transmit WNV, lending support to concerns that the population present in southeast England represents a risk of transmission to humans.     

The genetic structure of populations of the vulnerable aquatic macrophyte <Emphasis Type="Italic">Ranunculus nipponicus</Emphasis> (Ranunculaceae)

Ranunculus nipponicus (Makino) Nakai is a vulnerable aquatic macrophyte in the Kinki district, which is the southernmost distribution of this species in Japan. The genetic diversity and structure within and among eleven extant populations were assessed using the inter-simple sequence repeats (ISSR) polymerase chain reaction in association with combinations of propagation pattern (clonal and/or seeds) and genotypic geographical structure. In total, 53 bands were amplified, of which 18 (34%) were polymorphic. Analysis of the ISSR bands identified 46 genotypes among 81 individuals from one stream population and 72 distinct genotypes among 147 individuals in the Kinki district. An unweighted pair group method with arithmetic mean (UPGMA) dendrogram showed some unity among upstream and downstream subpopulations within one stream and eleven populations. The Shannon index of genetic diversity was 0.109 for one stream population and 0.313 for total genetic diversity, suggesting relatively high genetic diversity. Analysis of molecular variance (AMOVA) revealed that 84.1% of the total genetic diversity occurred among populations and the remaining diversity (15.9%) occurred within populations. Significant genetic differentiation occurred among populations in the Kinki district. These results suggest that conservation of each population is important for maintaining genetic diversity of R. nipponicus in this district. An erratum to this article can be found at     

Genetic analyses of the federally endangered Echinacea laevigata using amplified fragment length polymorphisms (AFLP)—Inferences in population genetic structure and mating system

Echinacea laevigata (Boynton and Beadle) Blake is a federally endangered flowering plant species restricted to four states in the southeastern United States. To determine the population structure and outcrossing rate across the range of the species, we conducted AFLP analysis using four primer combinations for 22 populations. The genetic diversity of this species was high based on the level of polymorphic loci (200 of 210 loci; 95.24%) and Nei’s gene diversity (ranging from 0.1398 to 0.2606; overall 0.2611). There was significant population genetic differentiation (G_ST = 0.294; Ө^II = 0.218 from the Bayesian f = 0 model). Results from the AMOVA analysis suggest that a majority of the genetic variance is attributed to variation within populations (70.26%), which is also evident from the PCoA. However, 82% of individuals were assigned back to the original population based on the results of the assignment test. An isolation by distance analysis indicated that genetic differentiation among populations was a function of geographic distance, although long-distance gene dispersal between some populations was suggested from an analysis of relatedness between populations using the neighbor-joining method. An estimate of the outcrossing rate based on genotypes of progenies from six of the 22 populations using the multilocus method from the program MLTR ranged from 0.780 to 0.912, suggesting that the species is predominantly outcrossing. These results are encouraging for conservation, signifying that populations may persist due to continued genetic exchange sustained by the outcrossing mating system of the species.     

Allozyme diversity in relation to geographic distribution and population size inLathyrus vernus (L.) Bernh. (Fabaceae)

Lathyrus vernus (L.) Bernh. is a diploid, long-lived perennial and insect-pollinated herb with no special adaptation to long-distance dispersal. It occurs on neutral soil in deciduous forests throughout western Eurasia. Due to specific habitat preferences,L. vernus has a fragmented distribution with isolated populations. We investigated allozyme variation at eleven loci in 20 populations ofL. vernus from one geographically central region (the Czech Republic and the Slovak Republic) and two geographically marginal regions (southern and central Sweden) in the species present-day distribution. There was a clear differentiation between the three regions and the genetic distance between the populations was highly correlated with geographic distance. The total genetic diversity (H_T) was 0.354. The proportion of genetic diversity due to differentiation between regions, and to differentiation between populations within regions, accounted for 10% each. There was no difference in level of genetic diversity between the three regions. No significant difference in level of genetic diversity was found between small and large populations. The genetic diversity inL. vernus may either be a result of the long generation-time of the species or peculiarities in the post-glacial migration species, e.g. survival only in refugia far east of the sampled populations and/or migration as a continuous process not involving founder-events.     

Genetic variation within and among populations of a wild rice Oryza granulata from China detected by RAPD and ISSR markers

Genetic variation within and between five populations of Oryza granulata from two regions of China was investigated using RAPD (random amplified polymorphic DNA) and ISSR (inter-simple sequence repeat amplification) markers. Twenty RAPD primers used in this study amplified 199 reproducible bands with 61 (30.65%) polymorphic; and 12 ISSR primers amplified 113 bands with 52 (46.02%) polymorphic. Both RAPD and ISSR analyses revealed a low level of genetic diversity in wild populations of O. granulata. Furthermore, analysis of molecular variance (AMOVA) was used to apportion the variation within and between populations both within and between regions. As the RAPD markers revealed, 73.85% of the total genetic diversity resided between the two regions, whereas only 19.45% and 6.70% were present between populations within regions and within a population respectively. Similarly, it was shown by ISSR markers that a great amount of variation (49.26%) occurred between the two regions, with only 38.07% and 12.66% between populations within regions and within a population respectively. Both the results of a UPGMA cluster, based on Jaccard coefficients, and pairwise distance analysis agree with that of the AMOVA partition. This is the first report of the partitioning of genetic variability within and among populations of O. granulata at the DNA level, which is in general agreement with a recent study on the same species in China using allozyme analysis. Our results also indicated that the percentage of polymorphic bands (PPB) detected by ISSR is higher than that detected by RAPD. It seems that ISSR is superior to RAPD in terms of the polymorphism detected and the amplification reproducibility. Received: 29 March 2000 / Accepted: 15 May 2000     

武夷山地伯乐树种群遗传多样性的ISSR分析

伯乐树（Bretschneidera sinensis Hemsl.）为我国特有单型科珍稀濒危植物,具重要的科研价值。本研究采用ISSR分子标记对武夷山脉分布的5个伯乐树天然种群和1个移栽种群进行遗传多样性分析。结果表明伯乐树物种水平遗传多样性较高（PPB：75.70%;H_ES：0.304 5;H：0.450 1）,种群水平则较低（PPB：60.13%;H_EP：0.238 1;H：0.347 5）,MJY种群和BSZ种群分别是所有种群中遗传多样性最高和最低的。5个地理种群间遗传分化程度较高（G_st=0.218 1）,原因可能源于伯乐树的繁殖方式及生境片段化,Mantel检验也证实了地理距离与遗传距离具有显著相关性（r=0.626 7,P＜0.05）。针对伯乐树种群遗传多样性现状,建议加强现有自然种群的就地保护,促进种群自然更新。     

Mitochondrial DNA diversity of Coilia mystus (Clupeiformes: Engraulidae) in three Chinese estuaries

We used sequences of mitochondrial cytb and 16SrRNA gene segments in order to clarify the genetic diversity and population structure in three Chinese estuary populations of Coilia mystus: 21 individuals from ChangJiang River (Yangtze River) estuary, 22 from MinJiang River estuary, and 22 from ZhuJiang River (Pearl River) estuary (65 individuals total). We obtained 607 base pairs of consensus cytb sequence. Thirty four distinct haplotypes were detected among the 65 cytb sequences. The indexes of nucleotide diversity (π) in these three populations were ChangJiang 0.533%, MinJiang 1.135%, and ZhuJiang 0.268%. MinJiang is the largest of the three populations. Genetic distances within the populations were between 0.3 and 1.2%, and 0.8 to 10.8% among populations. The largest genetic distance was 10.8% between the ChangJiang and ZhuJiang populations, and the smallest was 0.8% between MinJiang and ZhuJiang populations. Analysis of molecular variance (AMOVA) analysis revealed that variation among populations accounts for 90.25% of total variation, suggesting that this is the main source of total variance. We obtained 470 base pairs of consensus sequence of 16SrRNA. We detected 19 distinct haplotypes among the 65 sequences. The indexes of nucleotide diversity (π) in these three populations were ChangJiang 0.108%, MinJiang 0.843%, and ZhuJiang 0.097%. MinJiang is also the largest among these three populations. Genetic distances were between 0.1 and 0.9% within populations and 0.5 to 1.9% between populations. The largest genetic distance was the 1.9% between the ChangJiang and MinJiang populations, and the smallest was 0.5% between the MinJiang and the ZhuJiang populations. AMOVA analysis disclosed that variation among populations accounts for 74.61% of total variation, suggesting that this is the main source of total variation. The results of this study suggest that the three Coilia mystus populations, especially the most isolated Changjiang population, have developed significant genetic structure.     

Genetic Variation in the Endangered Endemic Species Cycas fairylakea (Cycadaceae) in China and Implications for Conservation

Cycas fairylakea is an endangered endemic species in China. Genetic diversity within and among four natural populations of this species in China was investigated using amplified fragments length polymorphism (AFLP). A moderate to low level of intraspecific genetic diversity was detected in this species (at population level: P = 39.57 %, H₀ = 0.244; at species level: P = 60.22%, H₀ = 0.356). The among-population component accounted for, respectively, 25.7 and 31.5% of the genetic variation, according to AMOVA and Shannon’s index, indicating most of the genetic variation was found between individuals within populations. All four populations have opposite pyramid age structure, and few coning individuals, which is still decreasing. Possibly because of habitat degradation and environmental pollution, plant diseases and insect pests in the populations were extremely serious, suggesting that the main factors threatening the survival of C. fairylakea populations were not genetic variation, but human activities and the breeding system of this species.