圈养小熊猫遗传多样性与种群遗传结构分析

小熊猫是亚洲特有的珍稀濒危动物,目前受到栖息地减少、片断化和人类活动干扰等威胁。中国圈养小熊猫已经有60 多年历史,约55 个机构曾经饲养过小熊猫,现今圈养数量有400 多只,评估小熊猫圈养种群的遗传多样性和遗传结构对科学维持圈养种群和保存遗传种质资源意义重大。本研究利用19 个微卫星座位,对中国境内11 个小熊猫圈养种群的116 只个体进行了遗传多样性评估及遗传结构分析。结果显示11 个种群都具有较高的遗传多样性,平均基因丰富度3.505 ± 1.033 (北京)至4.026 ± 1.219 (冕宁),期望杂合度0.631 ± 0.225(黄山)至0.782 ±0.171 (温岭)。其中福州和无锡种群极显著偏离Hardy-Weinberg 平衡。整个圈养群体内各个种群遗传分化系数为0.055,呈显著分化,表明11 个种群遗传分化水平较高。Bayesian 遗传聚类分析将11 个种群聚为三个遗传簇,与野生种群的遗传聚类结果一致。结论:小熊猫圈养种群与野生种群相比,同样具有较高的遗传多样性。因此,圈养小熊猫遗传管理的重点不再是引进野生个体充实圈养种群,应制订科学的繁殖计划,避免近交,从而维持圈养种群的遗传多样性。     

卧龙圈养大熊猫遗传多样性现状及预测

以中国最大的大熊猫圈养种群—四川卧龙中国大熊猫保护中心的圈养种群为对象,以８个大熊猫微卫星位点为分子标记, 探讨了大熊猫圈养种群的遗传多样性, 并与邛崃野生种群及其他７个濒危物种进行比较。微卫星数据表明, 圈养种群的遗传多样性水平(A＝5.5, He ＝0.620, Ho＝0.574) 低于邛崃野生种群(A＝9.8,He＝0.779,Ho＝0.581),但高于其他7 个濒危物种的种群(He＝0.13~0.46)。在此数据的基础上对未来100个世代内圈养种群遗传多样性的变化情况做出了预测。结果表明假设种群数量比现在扩大一倍, 经历100个世代后也只会使平均等位基因数少减少0.4。因此继续增加野生个体对保持遗传多样性的意义已经不大, 建议该圈养种群的保护策略应将重点放到制定更有效的繁殖计划以避免近交上。     

A population genetic study in the Ochamchir region, Abkhazia, SSR

The reported longevity of residents of the Soviet Socialist Republic of the Caucasus has focused considerable attention on this population. However, little is known of the genetic composition of this population. With this in mind, several village populations of the Ochamchir Region, Abkhazia, SSR, were typed for 37 discrete genetic blood groups, erythrocyte and plasma protein loci. Gene and haplotype frequencies calculated for the polymorphic markers were determined and the results used in an analysis of intervillage heterogeneity and genetic distance analysis comparing the Abkhazians to European and Asian reference populations. The Abkhazians are approximately equal distance from European and West Asian populations in a genetic sense, and this is consistent with their geographical location. In addition to the usual genetic polymorphisms, rare electrophoretic variants were encountered at the lactate dehydrogenase A and phosphohexose isomerase loci. These results suggest that the population of the Ochamchir Region is relatively homogeneous and not distinctly different from its geographical neighbors.     

Study of the variability of erythrocyte enzymes in captive and wild populations of the black lemur (Eulemur macaco macaco). An indispensable preliminary in captive breeding programmes

A study of ten erythrocyte enzymes (PGM I, II, III, G6PD, 6PGD, GLO I, ADA, Est D, DIA, AcP, CA II, and AK) performed on 89 wild and 32 captiveEulemur macaco macaco shows that most systems are monomorphic except four (GLO I, CA II, 6PGD, and NADH DIA). The polymorphism of these markers allows us to make a satisfactory analysis of the variability on this species, especially on the view of comparing wild and captive populations, and shows that: (1) the population does not contain all phenotypes existing in the wild CA_a, CA_{a + b}, DIA_IV, GLO I_{B − C}, and PGD_c are completely absent in all captive populations and DIA_{III + IV} is only present in three out of 32 animals; (2) in the Nosy-komba Island, the PGD_c and DIA_IV are absent and DIA_{III + IV} and GLO I_{B − C} are only present in 1 out of 46 analyzed samples, showing that this population constitutes an isolate. The possibility to use these data for a strategy of Lemur conservation is discussed.     

Population structure and genetic diversity in two species of Hawaiian picture-winged Drosophila

Over the last several decades many picture-winged Drosophila have become less common in both geographical distribution and local population size (pers. obs., Foote pers. comm., Montgomerey pers. comm.). Here we report on a study of two Hawaiian Drosophila species, D. engyochracea, and D. hawaiiensis, to determine the impact that changes in population sizes over the past thirty years have had on the genetic diversity of these species. D. engyochracea is known from only two locations on the Island of Hawai'i (Kipuka Ki and Kipuka Pua'ulu), while D. hawaiiensis is currently more wide spread across Hawai'i Island. We collected 65 D. hawaiiensis and 66 D. engyochracea from two forest patches (kipuka) isolated by a 400 year old volcanic ash deposit. DNA sequence data for 515 bases of the mitochondrial gene COII was analyzed for both species to estimate relative total genetic diversity as well as inter-kipuka gene flow. The more wide spread species, D. hawaiiensis, has more genetic diversity (23 vs. 11 unique haplotypes) than the rarer species, D. engyochracea. The distribution of haplotypes in the kipuka is consistent with more gene flow in D. engyochracea than in D. hawaiiensis. Phylogenetic analysis indicates a small number of individuals morphologically identified as one species but have DNA sequence diagnostic for the other species. These results are consistent with these individuals being descendant from hybrids between species.     

Mitochondrial DNA analysis reveals hidden genetic diversity in captive populations of the threatened American crocodile (Crocodylus acutus) in Colombia

Identification of units within species worthy of separate management consideration is an important area within conservation. Mitochondrial DNA (mtDNA) surveys can potentially contribute to this by identifying phylogenetic and population structure below the species level. The American crocodile (Crocodylus acutus) is broadly distributed throughout the Neotropics. Its numbers have been reduced severely with the species threatened throughout much of its distribution. In Colombia, the release of individuals from commercial captive populations has emerged as a possible conservation strategy that could contribute to species recovery. However, no studies have addressed levels of genetic differentiation or diversity within C. acutus in Colombia, thus complicating conservation and management decisions. Here, sequence variation was studied in mtDNA cytochrome b and cytochrome oxidase I gene sequences in three Colombian captive populations of C. acutus. Two distinct lineages were identified: C. acutus‐I, corresponding to haplotypes from Colombia and closely related Central American haplotypes; and C. acutus‐II, corresponding to all remaining haplotypes from Colombia. Comparison with findings from other studies indicates the presence of a single “northern” lineage (corresponding to C. acutus‐I) distributed from North America (southern Florida), through Central America and into northern South America. The absence of C. acutus‐II haplotypes from North and Central America indicates that the C. acutus‐II lineage probably represents a separate South American lineage. There appears to be sufficient divergence between lineages to suggest that they could represent two distinct evolutionary units. We suggest that this differentiation needs to be recognized for conservation purposes because it clearly contributes to the overall genetic diversity of the species. All Colombian captive populations included in this study contained a mixture of representatives of both lineages. As such, we recommend against the use of captive‐bred individuals for conservation strategies until further genetic information is available.     

Assessment of genetic diversity and population differentiation of Achyranthes bidentata (Amaranthaceae) in Dao Di and its surrounding region based on microsatellite markers

Identifying genetic diversity patterns is fundamentally important for effective species management and conservation. In this study, we used five microsatellite loci to investigate the genetic diversity and population differentiation of Achyranthes bidentata in Dao Di and its surrounding region. Our analysis of microsatellite data indicated the level of genetic diversity of A. bidentata (H_T = 0.333) was lower than other plants. The results showed no significant genetic diversity differences and population genetic differentiation between the Dao Di and surrounding region. Significant temperature differences (Bio2: mean diurnal range and Bio7: temperature annual range) were found between the Dao Di and surrounding region, which may improve the accumulation of medicinal ingredients of populations in the Dao Di. The populations of A. bidentata were divided into two genetic groups, which was caused by five temperature variables (Bio1, Bio4, Bio7, Bio9, and Bio11). This study thus provides an important case for over-collecting within limited ranges in affecting population diversity and bioclimate variables for different producing area in driving population differentiation.     

Genetic diversity and population structure of Buddleja crispa Bentham in the Himalaya-Hengduan Mountains region revealed by AFLP

Buddleja crispa Benth. is one of the most morphologically variable species in genus Buddleja, and it is widely distributed in the Himalaya-Hengduan Mountains (HHM) region. This study used AFLPs as a tool to examine the genetic variation among and within 25 populations of B. crispa. Analysis of population genetics of the species aimed to clarify morphological variation, current distribution patterns, strong adaptability to habitats, and the effects of geological factors in the HHM region. The genetic structure results, based on PCoA and NJ cluster analyses, revealed that the populations of B. crispa were divided into two genetic groups. Furthermore, the peripheral populations had lower genetic diversity than the populations in the center of the distribution areas (Three Parallel Rivers). We conclude that the gene flow (predominantly seed and pollen flow) and the population differentiation of B. crispa might be more affected by the barriers formed by rivers and mountains than by geographic distance.     

Assessment of genetic diversity and population structure of Chinese wild almond, Amygdalus nana, using EST- and genomic SSRs

Amygdalus nana L., commonly known as wild almond, is an endangered wild relative of cultivated almond, which has great potential in almond crop breeding. In this study, we used microsatellite (SSR) loci derived from both expressed sequence tag (EST) and anonymous genomic sequence to explore the genetic diversity and population structure of A. nana in Xinjiang of China. Seven natural populations were collected across the whole distribution of A. nana in China, including populations from both inside (four populations) and outside (three populations) the established protected areas. A total of 22 and 19 alleles were detected from the seven pairs of EST and genomic SSR loci, respectively. Generally, the genomic SSRs showed lower levels of variation than EST-SSRs, which may partially due to the higher cross-species transferability in EST-SSRs than in genomic SSRs. The population-level genetic diversity (A = 1.84, P = 50.00%, H_o = 0.3491, H_E = 0.2271) was lower than cultivated almond and several wild fruit species with similar breeding system. Most of the genetic variation (82.16%) was partitioned within populations. In particular, the population collected from Tacheng County (outside the protected areas) had the highest levels of genetic diversity and had significantly different genetic constitution from other populations.     

Mitochondrial genetic diversity and population structure of a vulnerable freshwater fish,rock carp (Procypris rabaudi) in upper Yangtze River drainage

Rock carp (Procypris rabaudi (Tchang)) is an endemic species in the upper Yangtze River drainage. The genetic variability and population structure of eight populations (Mudong (MD), Hejiang (HJ), Wanzhou (WZ), Xishui (XS), Nantan (NT), Cangxi (CX), Tongjiang (TJ) and Wulong (WL)) were investigated based on mitochondrial DNA control region. According to the river dimensions, MD, HJ, WZ, WL and CX were defined as large river populations, while TJ, XS and NT were defined as small. The total genetic diversity level of rock carp was moderate (h = 0.858, π = 0.0079). Genetic differentiations among populations in small rivers were greater than those among populations in large rivers, and small rivers showed significant differentiation from large rivers. Analysis from the coalescent-based method showed that there were asymmetric gene flows among four large river populations (CX, HJ, MD and WZ). Demographic analyses suggested that the species as a whole and the WZ population experienced population expansion, while the HJ, NT, and MD populations experienced bottlenecks. The analysis of genetic diversity and population structure suggested that the WL, TJ, CX, NT and XS populations should be protected and managed separately, and that the HJ, MD and WZ populations should be considered as a genetic management unit.     

Amplified fragment length polymorphism analysis of the population structure and genetic diversity of Phoebe zhennan (Lauraceae), a native species to China

Phoebe zhennan S. Lee et F. N. Wei (Lauraceae), is the main source of Gold Phoebe, a rare and extremely valuable wood in China. However it has undergone a dramatic decline. In this study, we used 12 amplified fragment length polymorphism primer combinations to assay 92 accessions, which were highly representative of the entire P. zhennan germplasm. It revealed that P. zhennan consisted of three genetic populations, named as SCZ (central Sichuan), CQH (eastern Sichuan, Chongqin, Hubei and Hunan) and YG (Yunnan and Guizhou), probably owing to natural selection caused by topography differences. The CQH population further diverged into two geographical sub-populations: CD-CQ (SCD and west region of Chongqin) and HB-HN (eastern side of Chongqin, Hubei and Hunan). The loci were moderately polymorphic (40.4%). The genetic distance between SCZ and YG was the highest, between CD-CQ and HB-HN the lowest. Pairwise fixation indices (Ф_PT) between any inferred populations were significant. This rare species exhibited low genetic diversity; therefore, the results provided significant data related to the conservation and management of P. zhennan. That is, with this genetic information, land managers are equipped with better tools allowing them to more effectively protect this species and its limited genetic diversity.     

Genetic diversity, population structure, effective population size and demographic history of the Finnish wolf population

The Finnish wolf population (Canis lupus) was sampled during three different periods (1996-1998, 1999-2001 and 2002-2004), and 118 individuals were genotyped with 10 microsatellite markers. Large genetic variation was found in the population despite a recent demographic bottleneck. No spatial population subdivision was found even though a significant negative relationship between genetic relatedness and geographic distance suggested isolation by distance. Very few individuals did not belong to the local wolf population as determined by assignment analyses, suggesting a low level of immigration in the population. We used the temporal approach and several statistical methods to estimate the variance effective size of the population. All methods gave similar estimates of effective population size, approximately 40 wolves. These estimates were slightly larger than the estimated census size of breeding individuals. A Bayesian model based on Markov chain Monte Carlo simulations indicated strong evidence for a long-term population decline. These results suggest that the contemporary wolf population size is roughly 8% of its historical size, and that the population decline dates back to late 19th century or early 20th century. Despite an increase of over 50% in the census size of the population during the whole study period, there was only weak evidence that the effective population size during the last period was higher than during the first. This may be caused by increased inbreeding, diminished dispersal within the population, and decreased immigration to the population during the last study period.     

安徽省扬子鳄饲养种群繁殖力的参数分析及种群增长预测

通过对宣城扬子鳄繁殖研究中心三代繁殖鳄1982—2003年繁殖力有关参数的分析,结果表明近三年来繁殖研究中心扬子鳄产卵量明显减少;亲代受精率为(83.80±2.37)%、孵化率为(89.53±0.86)%;发现F1受精率为(79.38±2.74)%、孵化率为(83.78±1.95)%;F2代个体受精率为(68.7±1.84)%、孵化率为(88.16±1.68)%;通过单因素方差分析F(受精率)=4.33(P<0.05)、F(孵化率)=4.56(P<0.05)差异显著。分析影响扬子鳄繁殖的因素发现:产卵量明显减少可能与亲代鳄逐渐退出繁殖期、F1代鳄整体产卵能力有下降趋势、F2代鳄没有大规模进入繁殖期有关;分析历史资料发现扬子鳄产卵窝数与4月份的温度相关性高(R=0.979,P<0.01);作者认为F1、F2代个体与亲代之间的受精率、孵化率有显著差异,近交衰退、遗传多样性的丧失有密切关系。利用时间序列分析建立理想状态下饲养扬子鳄种群数量估计模型,预测10年内扬子鳄饲养将可能达到19000尾;根据该种群增长模式及种群年龄结构特点,应扩大饲养规模,特别是育成鳄饲养池及幼鳄饲养池的建设。     

Assessment of genetic diversity and population structure of Bergenia stracheyi (Saxifragaceae) in the Western Himalaya (India)

Genetic diversity and population structure in Bergenia stracheyi, a threatened medicinal herb in the Western Himalaya of India was analysed using directed amplification of minisatellite DNA (DAMD) and inter simple sequence repeats (ISSR) markers. A total of 41 accessions of B. stracheyi representing three populations (Khillenmarg –KLM, Jalori Pass-JLP and Rohtang-RTG) were considered in the present study. The cumulative data analysis for 26 (10 DAMD + 16 ISSR) markers revealed 87.1% polymorphism. The maximum inter-population genetic distance was found between KLM and JLP, whereas the minimum genetic distance was found between RTG and JLP populations. The analysis of molecular variance (AMOVA) revealed maximum percentage of variation among individuals within populations (75%) than among the populations (25%). Clustering pattern of the three sample populations in STRUCTURE and PCoA analyses showed high genetic variation at population level. The present study revealed that distribution patterns, high altitudinal ranges, high habitat specificity, relatively high gene flow, small and isolated population size have shaped the current population structure of B. stracheyi in the Western Himalayan region. DAMD and ISSR markers have provided significant insights into characterization of B. stracheyi populations, and facilitate selection of appropriate accessions for further utilization in conservation and bioprospecting programmes.     

Analysis of the genetic diversity and population structure of Perinereis aibuhitensis in China using TRAP and AFLP markers

Perinereis aibuhitensis is found in the coastal waters of northwestern Pacific. Different ecotypes are distributed throughout the coastal sea beach based on their ecology and behavior, but relatively little is known about the population structure of this species. In this study, we estimated the genetic relationships within P. aibuhitensis using Target Region Amplified Polymorphisms (TRAP) and Amplified Fragment Length Polymorphisms (AFLP) that were derived from related populations on the coasts of China. All populations were uniquely fingerprinted using the TRAP and AFLP marker method. The mean genetic distance was estimated to be 0.1859 based on the TRAPs and AFLPs. Using the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) by Molecular Evolutionary Genetics Analysis (MEGA) 6.06 software, Principal Coordinate Analysis (PCA) and STRUCTURE analysis, the phylogenetic tree of the ten P. aibuhitensis populations was separated into four major clusters; however, the mantel test indicated that there was no significant correlation between the genetic and geographical distances due to gene differentiation and gene flow (P > 0.005). The genetic diversity was low for P. aibuhitensis at the population level compared with the species level. Finally, an appropriate strategy for conserving the P. aibuhitensis germplasm is proposed.     

普通野生稻小种群的交配系统与遗传多样性

小种群的遗传动态是保育遗传学关注的核心问题之一,而种群遗传动态又与交配系统密切相关.普通野生稻(Oryza rufipogon Griff.)是具有重要经济价值的濒危物种,目前其种群规模都较小,研究其小种群交配系统与遗传变异性对普通野生稻的保护具有重要意义.运用7对SSR引物,对采自江西东乡普通野生稻小种群的36份种茎和其中20个家系共计601份子代进行了分析.结果显示:该种群的表观异交率为0.318,多位点法估计(MLTR)的多位点异交率为0.481;50%以上的子代共享亲本,非随机交配明显;东乡普通野生稻种群交配系统属于混合交配类型.比较亲本和子代种群的遗传变异性显示:子代种群比亲本种群遗传变异性更丰富;子代种群的杂合子不足与种群变小自交比例上升有关;而亲本种群杂合子过剩可能与杂合基因型的选择优势有关.这些结果说明创造条件扩大种群规模对普通野生稻的原生境保护显得尤为重要.     

Genetic diversity and population structure in Malus sieversii, a wild progenitor species of domesticated apple

Malus sieversii (Lebed.) M. Roem. is a wild progenitor species of the domesticated apple. It is found across a mountainous region of central Asia and has been the focus of several collection expeditions by the USDA-ARS-National Plant Germplasm System. This study used microsatellite variation at seven loci to estimate diversity and differentiation within M. sieversii using several complimentary approaches. Multilocus genotypes were amplified from 949 individuals representing seedling trees from 88 half-sib families from eight M. sieversii populations collected in Kazakhstan. Apportioning of genetic variation was estimated at both the family and site level. Analyses using a hierarchical model to estimate F _st showed that differentiation among individual families is more than three times greater than differentiation among sites. In addition, average gene diversity and allelic richness varied significantly among sites. A rendering of a genetic network among all sites showed that differentiation is largely congruent with geographical location. In addition, nonhierarchical Bayesian assignment methods were used to infer genetic clusters across the collection area. We detected four genetic clusters in the data set. The quality of these assignments was evaluated over multiple Markov Chain Monte Carlo runs using both posterior likelihood and stability of the assignments. The spatial pattern of genetic assignments among the eight collection sites shows two broadly distributed and two narrowly distributed clusters. These data indicate that the southwestern collection sites are more admixed and more diverse than the northern sites.     

Influences of habitat features and human disturbance on use of breeding sites by a declining population of southern fur seals (Arctocephalus australis)

Southern fur seals Arctocephalus australis in Peru have declined gradually over the past decade, and declined dramatically (72%) as a result of low food availability during the severe El Niño in 1997–98. In 1999, seals abandoned some historically important breeding sites. This is particularly alarming because new sites were not colonized. Our objective was to examine how habitat features and human disturbance influenced whether sites were currently used, abandoned or apparently not used in the past by fur seals for breeding. Data were collected on 14 variables at 70 potential breeding sites at three guano reserves in Peru. Discriminant analysis revealed significant multivariate differences among sites currently used for breeding, abandoned sites and unused sites ( F =5.97, P <0.00001), and the model classified 74% of sites correctly. Currently used sites were less likely to have human disturbance and more likely to have offshore islands, stacked rocks, tide pools and abundant shade. Separate discriminant analyses for each reserve produced similar results. Habitat associated with thermoregulation (e.g. shade or pools) may be more important to fur seals in Peru, which breed at lower latitudes and are at greater risk of overheating on land than other populations. Habitat with minimized human access may be especially important to seals in small populations in which individuals may perceive themselves as more vulnerable because of decreased vigilance and dilution effects. Seals in our study selected breeding habitat with stacked rocks, which create shade and tide pools for thermoregulation and make human access difficult; but pups might suffer higher mortality in this habitat. We hypothesize that fur seals in Peru may exhibit an Allee effect, whereby suitability of habitat varies with population abundance.     

Genetic diversity and population structure of silver pomfret (Pampus argenteus) in the Indo-West Pacific revealed by mitochondrial control region sequences

Sequence variation of the mitochondrial control region in silver pomfret (Pampus argenteus) among six populations from the Indo-West Pacific region was analyzed. A total of 309 polymorphic sites were detected in the 464–466 bp segment of the control region among 165 individuals which defined 72 haplotypes. Haplotype diversity was ranged from 0.800 to 0.943 and nucleotide diversity ranged from 0.333% to 1.886%. Genetic distance and the fixation index indicated significant differences among populations in different geographical groups (P < 0.05). Median-joining network analysis data showed distinct patterns of phylogeographic structure. The present results suggested that P. argenteus populations have developed significant genetic structure, especially among geographically isolated groups.