Molecular and paleo-climatic data uncover the impact of an ancient bottleneck on the demographic history and contemporary genetic structure of endangered Pinus uliginosa

With the current rate of biodiversity loss, conservation management practices require a comprehensive understanding of eco-evolutionary relationships, history, and genetic structure of species. Assessments of genetic diversity are crucial, especially in rare, endemic, or threatened forest tree species with small and isolated populations, such as peat bog pine (Pinus uliginosa N.). Here, we used a novel approach, combining genetic diversity assessment, ecological niche modeling, and population demography inference to explore the complex history of a few remnant populations of this endangered pine. To asses the relative influence of isolation and fragmentation on genetic diversity in the taxonomic context, the patterns of genetic variation found in P. uliginosa were contrasted with those observed in its close relatives with much bigger distribution ranges and larger populations (Pinus sylvestris, Pinus mugo, and Pinus uncinata). We found a similar level of genetic diversity across the species at nuclear loci but contrasting patterns of variability distribution at chloroplast markers. We detected the signatures of an ancient genetic bottleneck dated at around 26 400 years ago, indicating a drastic reduction in the population size of P. uligionosa during the Last Glacial Maximum. In addition, we found substantial differentiation between current populations as a result of enhanced genetic drift during long-lasting isolation. The research suggests potential conservation management strategies for peat bog pine and emphasizes the importance of using complementary approaches for their successful development.     

滇杨种群遗传多样性与遗传结构

滇杨(Populus yunnanensis)是我国西南地区的特有树种, 具有速生、易无性繁殖、适应性强等优良特性, 是典型的南方型杨属树种。研究滇杨遗传多样性及种群结构对其种质资源的收集、保存和利用具有重要的意义。本研究从我国滇杨主要分布区云南和四川共采集了6个种群, 包括云南的昭通(ZT)、会泽(HZ)、嵩明(SM)、洱源(EY)、拉市海(LS)以及四川的美姑(MG), 共64个个体, 利用34对SSR分子标记和3对cpDNA叶绿体标记开展遗传多样性与遗传结构研究。SSR引物共检测到154个等位基因, 平均等位基因数为4.529, 观测杂合度(Ho)与期望杂合度(He)分别为0.552和0.472, 遗传分化系数(Fst)平均值为0.238, 多态性信息含量指数(PIC)平均值为0.421, 基因流(Nm)为0.806。滇杨的遗传结构分析(DAPC)与遗传距离的主坐标分析(PCoA)、UPGMA聚类分析均将6个种群划分为3个亚类: 第І亚类包括昭通种群、会泽种群和嵩明种群的4个个体, 第ІІ亚类包括嵩明种群的6个个体以及洱源种群和拉市海种群, 第III亚类为美姑种群; 嵩明种群包含第І和第ІІ两个亚类的混合遗传成分。3个cpDNA联合序列中共检测到35个变异位点, 分为13个单倍型, 其中单倍型H5在种群中分布最为广泛, 其余的单倍型均为种群特有的单倍型。分子方差分析(AMOVA)表明种群内的遗传变异大于种群间变异。研究表明滇杨不同种群的遗传分化具有地域性, 可选择就地保护; 昭通种群遗传多样性最高, 且包含7种叶绿体单倍型, 单倍型类型最多, 应优先保护。     

普达措国家公园四种针叶树径向生长对气候因子的响应

运用树木年代学的原理和方法,对普达措国家公园大果红杉、长苞冷杉、高山松和麦吊云杉4个优势针叶树种的年轮宽度进行测量,建立年轮宽度差值年表。分析年表与香格里拉气象站的日、月气候数据的相关性,研究4个优势针叶树种的径向生长对气候因子的响应。结果表明: 大果红杉的年生长速率最高,长苞冷杉的年生长速率最低;4种针叶树径向生长对气候因子的响应存在物种特异性,大果红杉与气候因子的相关性最强,麦吊云杉的径向生长对气候因子的响应不敏感;长苞冷杉树轮宽度年表与上年冬季(11、12月)和当年夏季(7月)的平均温度呈显著正相关;大果红杉树轮宽度年表与生长季早期(6月)温度呈显著正相关,与同期降水量和相对湿度呈显著负相关;而高山松树轮宽度年表与生长季早期(5月)的降水量和相对湿度呈显著正相关,与同期最高温度呈显著负相关,表明高山松的径向生长主要受生长季早期水分可利用性的影响。     

Comparative phylogenetic analyses of Chinese Horsfieldia (Myristicaceae) using complete chloroplast genome sequences

The biologist's ruler for biodiversity is the species; accurate species identification is fundamental to the conservation of endangered species and in-depth biological scientific exploration. However, the delimitation and affinities of Horsfieldia in China has been controversial, owing in part to very low levels of molecular divergence within the family Myristicaceae. Because species boundaries and phylogenetic relationships within Horsfieldia are also unclear, 13 samples were collected across its distribution in China and their genomes were subjected to shotgun sequencing using Illumina platforms. A total of 40 487 994–84 801 416 pair-end clean reads were obtained and, after assembly, the complete chloroplast genome was recovered for all samples. Annotation analysis revealed a total of 112 genes, including 78 protein-coding genes, 30 transfer RNA, and 4 ribosomal RNA genes. Six variable loci (petN-psbM, trnH-psbA, ndhC-trnV, psbJ-psbL, ndhF, and rrn5-rrn23) were identified. Phylogenetic analyses strongly support the presence of four distinct species of Horsfieldia in China. In addition, samples that had been identified previously as Horsfieldia kingii (Hook. f.) Warb. were indistinguishable from those of H. prainii (King) Warb., suggesting that if H. kingii does occur in China, it was not collected in this study. Similarly, the chloroplast genome of one H. hainanensis Merr. sample from Guangxi province was identical to H. tetratepala C. Y. Wu, suggesting that the distribution range of H. hainanensis might be narrower than assumed previously. The phylogenetic relationships between the Chinese Horsfieldia species based on the whole chloroplast genomes was supported strongly, indicating the potential for using entire chloroplast genomes as super-barcodes for further resolution of the phylogeny of the genus Horsfieldia.     

A genetic diversity study of endangered Psiadia species endemic from Mauritius Island using PCR markers

The genus Psiadia Jacq. represents the most important indigenous genus, by the number of species present, in the Mascarene archipelago (Mauritius, Reunion, Rodrigues), and is a typical example of adaptive radiation in oceanic islands. The Mauritius species are used in traditional pharmacopoeia for their expectorant properties, and most of them are heavily threatened. Molecular genetic relationships between representatives of eight endangered endemic Psiadia species from Mauritius, conserved in Le Mondrain Reserve, and P. dentata (Cass.) DC, endemic from Reunion island, were studied. The absence of length variations of the 5s rDNA non-transcribed spacer demonstrated the recent common origin of all the species surveyed. RAPD analysis revealed a relatively high intra-specific variability in accordance with the outcrossing mode of reproduction of Psiadia species. Moreover, RAPD analysis showed the existence of four major phenetic groups: (A) P. arguta (Pers.) Voigt, P. dentata, (B) P. penninervia D. C., P. terebinthina A.J. Scott, P. lithospermifolia (Lam.) Cordem, (C) P. viscosa (Lam.) A.J. Scott, P. canescens A.J. Scott, P. cataractae A.J. Scott, and (D) P. pollicina A.J. Scott. These groups were consistent with the chemical composition of the essential oils of the species as well as with their floral characteristics, based on literature. A molecular germplasm database for Psiadia species was established, which will allow further characterisation of new samples being introduced in Le Mondrain Reserve for conservation purpose.     

Integrating coalescent-based species delimitation with ecological niche modeling delimited two species within the Stewartia sinensis complex (Theaceae)

Accurate species delimitation is the key to precise estimation of species diversity and is fundamental to most branches of biology. Unclear species boundaries within species complexes could lead to the underestimation of species diversity. However, species delimitation of species complexes remains challenging due to the continuum of phenotypic variations. To robustly examine species boundaries within a species complex, integrative approaches in phylogeny, ecology, and morphology were applied to the Stewartia sinensis complex (Theaceae) endemic to China. Multispecies coalescent-based species delimitation using 572 nuclear ortholog sequences (anchored enrichment) supported reciprocal phylogenetic monophyly of the northern lineage (NL) and southern lineage (SL), which were not sister clades. Niche equivalency and similarity tests demonstrated significant climatic niche differentiation between NL and SL with observed Warren et al.'s I = 0.0073 and Schoener's D = 0.0021. Species distribution modeling also separated their potential distribution. Morphometric analyses suggested significant interlineage differentiation of multiple traits including the ratio of length and width, leaf width, and pedicel length, although overall similarity did not differ. Based on the integrative species concept, two distinct species were proposed with legitimate names of Stewartia gemmata for SL and S. sinensis for NL. Our empirical study of the S. sinensis complex highlights the importance of applying multiple species criteria, in particular the underappreciated niche differentiation, to species delimitation in species complexes pervasive in plants.     

Development and characterization of 43 microsatellite markers for the critically endangered primrose Primula reinii using MiSeq sequencing

Primula reinii (Primulaceae), a perennial herb belonging to the Primula section Reinii, occurs on wet, shaded rocky cliffs in the mountains of Japan. This threatened species comprises four varieties; these plants are very localized and rare in the wild. In this study, 43 microsatellite markers were developed using MiSeq sequencing to facilitate conservation genetics of these critically endangered primroses. We developed novel microsatellite markers for three varieties of P. reinii, and tested its polymorphism and genetic diversity using natural populations. These novel markers displayed relatively high polymorphism; the number of alleles and expected heterozygosities ranged from 2 to 6 (mean=3.2) and 0.13 to 0.82 (mean=0.45), respectively. All loci were in HardyeWeinberg equilibrium. These microsatellite markers will be powerful tools to assess P. reinii genetic diversity and develop effective conservation and management strategies.     

中国西北地区天然胡杨群体遗传多样性及核心保护单元的构建

胡杨(Populus euphratica)是极端干旱荒漠区的珍稀乔木树种。为了确定天然胡杨群体遗传多样性保护单元并挖掘优异的种质资源, 本研究以中国西北地区新疆、青海、甘肃、宁夏、内蒙古的58个天然胡杨群体为研究对象, 利用120个位点的SNPs标记对这些胡杨群体进行群体遗传结构和遗传多样性分析, 并根据不同群体间Nei’s遗传相似度, 采用逐步聚类优先取样法对初始群体、遗传多样性保护单元和剩余群体进行t检验。群体结构和主成分分析表明, 胡杨群体可分为新疆南疆(SX)、新疆北疆(NX)、青海(QH)和混合群(甘肃、宁夏和内蒙古混合群, GNM) 4个分支, 遗传多样性分析表明新疆南疆(SX)遗传多样性高于其他群体。分子方差分析(AMOVA)表明天然胡杨群体的遗传变异主要分布在各个群体内。构建了天然胡杨群体一级核心保护单元3个群体(CU3), 二级核心保护单元33个群体(CU33)。南疆存在较多优异抗逆的天然胡杨古树资源, 南疆分布区的平均遗传多样性水平最高。综上所述, 南疆地区胡杨古树遗传多样性整体高于北疆及疆外地区, 结合新疆地区干旱严重指数等生境信息, 建议加大对南疆胡杨古树群体的保护力度, 重视北疆胡杨林的更新换代。     

Phylogenetic relationships and the maternal donor of Roegneria (Triticeae: Poaceae) based on three nuclear DNA sequences (ITS,Acc1, and Pgk1) and one chloroplast region (trnL-F)

Roegneria is a polyploid perennial genus in the tribe Triticeae. Some species of Roegneria are morphologically similar to genus Elymus and have been classified in Elymus. To investigate the delimitation and phylogenetic relationships of Roegneria, nuclear (ITS, Acc1, and Pgk1) and chloroplast (trnL–trnF) DNA regions were sequenced for 38 allopolyploid species and 32 diploid species of Triticeae. Phylogenetic analyses of nuclear DNA revealed that all Roegneria species were included in the St and Y genome clades, and that the Y genome was closely related to the V and Xp genomes. The chloroplast DNA dataset showed that Roegneria species were grouped with Pseudoroegneria species. The Pseudoroegneria species from the Middle East (P. libanotica and P. tauri) and Central Asia (P. strigosa) were more closely related to Roegneria species. The results suggested that: (i) the species containing the St and Y genomes should be segregated from Elymus and treated as a distinct genus, Roegneria, based on the genomic constitution; (ii) P. libanotica, P. tauri, and/or P. strigosa potentially served as the maternal donor of the St genome in Roegneria; (iii) The Y genome of Roegneria originated from a diploid Y genome species, and the V and Xp genomes may have contributed to Y genome formation; (iv) among Roegneria species of previously uncertain genomic constitution, R. seriotina was tetraploid and possessed the StY genomes, E. calcicolus was hexaploid with the StYH genomic constitution and should be classified in Campeiostachys, R. glaucifolia possessed the StStY genomes, and R. tschimganica had the genomic constitution St₁St₂Y.     

典型黑土区主要树种根系构型特征及其对固土能力的影响

为量化典型黑土区主要树种根系构型特征,探究其对固土能力的影响,以该区分布较广的榆叶梅、小叶锦鸡儿、白桦、糖槭、红皮云杉、樟子松单株个体为研究对象,采用全根挖掘和WinRHIZO Pro LA2004分析系统相结合对其根系空间分布、几何形态、分形等特征进行测定,同时采用原位整株根系拉拔的方法量化根系垂直拉拔力。结果表明: 榆叶梅以倾斜根为主,小叶锦鸡儿、白桦、糖槭和红皮云杉以水平根为主,樟子松根系在水平和垂直分布上较为均衡;除白桦总根表面积和红皮云杉总根长外,灌木树种总根长、总根表面积显著大于乔木,落叶阔叶乔木总根长、总根表面积显著大于针叶常绿乔木,白桦总根体积显著大于小叶锦鸡儿、糖槭、红皮云杉和樟子松;榆叶梅、小叶锦鸡儿和白桦根系分形维数和分形丰度显著大于红皮云杉和樟子松;榆叶梅、小叶锦鸡儿和糖槭整株根系平均最大垂直拉拔力显著大于白桦、樟子松和红皮云杉。主要受根系总根长、总根表面积和倾斜根数量的影响,榆叶梅、小叶锦鸡儿和糖槭根系表现出较强的固土能力,可作为典型黑土区水土保持植被构建中优先选择的树种。     

基于DNA条形码技术对浙江省外来入侵福寿螺进行分子鉴定

外来入侵福寿螺对我国农业生产和水生生态系统平衡等造成严重危害。2010年, 种类鉴定研究首次揭示我国外来入侵福寿螺包括Pomacea canaliculata和P. maculata两个种, 而浙江省仅见P. canaliculata一种报道。P. canaliculata和P. maculata种间形态近似, 且受环境、食物源等因素影响, 同种内外壳形态特征多样, 因而基于形态特征进行种类的准确鉴定极为困难。本研究在采集浙江省7个区县的福寿螺样本的基础上, 利用DNA条形码技术扩增了101个不同个体的COI序列, 并从BOLD数据库下载了“P. canaliculata种团”的5个近缘种的55条COI序列用于分析, 其中包括P. lineata, P. dolioides和P. paludosa所有已发表序列, 以及P. canaliculata和P. maculata的南美洲样品的序列等。序列相似度比对、DNA条形码间隙和系统发育树等分析表明, COI序列可以实现近缘福寿螺的有效鉴别。待测的浙江省福寿螺样品中, 杭州江干区检测到P. canaliculata和P. maculata两种, 而舟山普陀区、绍兴上虞区和新昌县、温州瓯海区及杭州西湖区仅检测到P. canaliculata, 表明P. canaliculata在浙江省具有更广的分布范围。P. canaliculata和P. maculata分别形成4种和2种单倍型, 各区县样点分别包含1-3种单倍型, 浙江省各发生地呈现较低的遗传多样性。依据系统发育关系推测, 浙江省分布的P. canaliculata和P. maculata分别可能来源于阿根廷和巴西。     

Out of the Pan-Himalaya: Evolutionary history of the Paeoniaceae revealed by phylogenomics

Peonies (the Paeoniaceae, Paeonia L.) are famous garden flowers, medicinal plants, and edible oil crops, but their evolutionary history largely remains unknown. To probe into their phylogenetic relationships, evolutionary history, formation of present distribution pattern, and origins of tetraploids, we sequenced 25 fragments belonging to 20 single copy nuclear genes and 14 chloroplast regions of all species in the genus to reconstruct phylogenetic relationships, date the divergence times of lineages, infer the ancestral biogeographical regions, and document the parents of tetraploids. Our results show that Paeoniaceae separated from the other members in Saxifragales in the Campanian of the late Cretaceous and diverged into two clades, woody and herbaceous clades, in the late Oligocene or early Miocene. They survived and early diverged in the Pan-Himalaya where they migrated eastwards to East Asia and further to NW America, and northwards to Middle Asia, and further to Europe. The woody lineage differentiated into two sublineages with accelerated root or floral disk evolution, while the herbaceous lineage diverged into five sublineages. Multiple glacial and interglacial cycles in Europe in the late Pliocene and early Pleistocene created opportunities for the peony species to meet and hybridize in the Mediterranean refugia, giving rise to eight allotetraploid species and four infraspecific tetraploids. Paeonia daurica Andrews, P. obovata Maxim., and P. tenuifolia L. served as the most important parents. The phylogeny of Paeonia L. implies that a new taxonomic system with two subgenera and seven sections should be proposed.     

Phylogeography of Japanese water crowfoot based on chloroplast DNA haplotypes

Water crowfoot, Ranunculus subgenus Batrachium, are submerged macrophytes in the Ranunculaceae. We aimed to infer the Quaternary history of these aquatic macrophytes in the Japanese archipelago. We studied 212 individuals of three perennial and one annual species from 46 populations covering the entire geographic range and found eight haplotypes based on approximately 1800 bp of four spacers in chloroplast DNA. The relationships among haplotypes were resolved using maximum parsimony and parsimony network analyses. To identify the zones of clear genetic boundaries, Monmonier's algorithm was used. The eight haplotypes were distinguished from adjacent haplotypes by one substitution or indel. Each of the 46 populations was fixed for a single haplotype. Inconsistency between cpDNA haplotypes and Batrachium taxa was found, except in one annual species. The distribution of the haplotypes in perennial species was highly geographically structured. An abrupt genetic change was detected between the Tohoku region and more southerly regions. Since the perennial Batrachium are cold-adapted, this genetic differentiation may be due to historical changes in their distributions caused by Quaternary climatic oscillations: interglacial retreats in colder refugia and glacial range expansions. The single haplotype composition of each population may have been shaped by founder effects during colonization and/or by genetic drift. The interglacial refugial populations must have been small enough to deplete haplotype diversity. Inconsistency between cpDNA haplotypes and Batrachium taxa may be due to incomplete lineage sorting of ancestral polymorphic haplotypes.     

中国东北云杉属研究资料

本文通过分析云杉属的分类性状,找出其变异性状和稳定性状。并由此提出将东北云杉划分为2种,2变种的观点。     

Genetic discontinuity revealed by chloroplast microsatellites in eastern North American Abies (Pinaceae)

Development of conservation strategies for Fraser fir (Abies fraseri) in the southern Appalachian Mountains depends in part on recognition of the extent to which Fraser fir is genetically distinct from the closely related balsam (A. balsamea) and intermediate (A. balsamea var. phanerolepis) fir. These sibling species have exhibited intergrading, clinal variation in morphological, chemical, and genetic characteristics in prior research. Chloroplast microsatellite markers were polymerase chain reaction amplified from genomic DNA samples of 78 individuals representing the geographic ranges of Fraser, balsam, and intermediate fir. Gene diversity levels at two loci ranged among taxa from 0.65 to 0.84. Allele frequencies demonstrated significant differentiation among taxa, with R(ST) values of 0.36 and 0.10. Haplotype diversity and D(SH) were highest for balsam fir and lowest for intermediate fir. A haplotype network analysis based on allele size distribution for the two loci revealed two distinct clusters of haplotypes and population-specific haplotypes. Ninety-two percent of the haplotypes in one cluster were from balsam fir and intermediate fir, and 84% of the haplotypes in the other cluster were from Fraser fir and intermediate fir. The genetic differentiation of chloroplast DNA markers provides justification for the recognition of Fraser fir as a distinct Management Unit (MU) for conservation purposes, regardless of its taxonomic classification.     

天山雪岭云杉森林群落的密度制约效应

密度制约是维持自然森林群落物种共存的重要机制之一。雪岭云杉(Picea schrenkiana)是天山森林群落的单优种, 在我国温带森林中占有重要地位。本文基于对天山雪岭云杉8 ha森林动态监测样地的两次调查结果, 分析了该样地群落物种组成的动态变化, 运用点格局方法分析了雪岭云杉个体在不同龄级的空间分布格局及其关联性, 探讨了该群落的密度制约效应。结果表明: (1)该样地内, DBH ≥ 1 cm的木本植物在2009年有11,835株, 2014年为11,050株, 5年间的个体死亡率为8.82%, 补员率为2.19%, 个体株数净减少6.63%。(2)使用双关联函数g(r)分析了不同龄级雪岭云杉的空间分布格局, 发现幼龄树和中龄树在0-40 m尺度上主要呈现聚集分布, 但随着尺度增大聚集强度逐渐减小; 老龄树在0-2 m及4 m尺度上呈随机分布, 在其他尺度上呈聚集分布, 但聚集程度较小。(3)用“案例-对照”设计的方法, 排除生境异质性的影响后, 将幼龄树和中龄树作为案例, 老龄树作为对照, 对比幼龄树、中龄树与老龄树的分布格局, 发现雪岭云杉幼龄树和中龄树在0-40 m尺度上呈现额外的聚集, 随着径级的增大, 这种额外的聚集强度逐渐减小, 即表现出密度制约效应。(4)老龄树与中龄树、幼龄树的空间关联性相同, 在0-40 m尺度上均呈明显负关联。     

Are Polyommatus hispana and Polyommatus slovacus bivoltine Polyommatus coridon (Lepidoptera: Lycaenidae)? The discriminatory value of genetics in taxonomy

Taxonomic confusion exists in several sibling species groups. The Polyommatus coridon species complex (Chalk Hill Blues) serves as a model group of sibling species in which genetic analyses provide suitable means for taxonomic clarification. We studied the allozyme patterns of the two described bivoltine species of this complex, Polyommatus hispana and Polyommatus slovacus, and compared them to the two genetic lineages of the univoltine P. coridon. P. hispana is well distinguished from P. coridon (genetic distance: 0.081), and most probably is a sibling species that has evolved during glacial isolation on the Iberian Peninsula. P. slovacus is genetically indistinguishable from the eastern, Pontic–Mediterranean lineage of P. coridon; therefore we suggest that it represents a local bivoltine population only. Since the spring generation of P. slovacus was much less common than the summer generation and showed less genetic diversity, it is probable that uni-/bivoltinism is a dimorphism affecting only part of the whole population. We suggest that the higher genetic diversity of the second generation may be a consequence of gene flow from adjacent single-brooded populations.     

Spatial distribution patterns and association of Picea crassifolia population in Dayekou Basin of Qilian Mountains,northwestern China

研究青海云杉(Picea crassifolia)种群不同发育阶段的空间分布格局及其关联性, 能揭示其种群的发展规律, 推断其潜在的生态学过程或影响机制, 进而为该种群的配置、种植和森林的经营与管理等提供指导。该研究基于祁连山大野口流域10.2 hm²青海云杉动态监测样地调查资料, 分析了青海云杉群落的物种组成和径级结构, 并采用点格局方法, 通过单变量成对相关函数和双变量成对相关函数对不同年龄阶段青海云杉种群的空间分布格局及其空间关联性进行分析。结果表明: (1)青海云杉种群的径级结构呈倒“J”型分布, 属增长型种群, 种群自然更新状况良好。(2)青海云杉种群4个径级的个体在小尺度上呈聚集分布, 但随着空间尺度的增大, 聚集强度逐渐减弱, 趋向随机分布; 较小径级的个体常呈聚集分布, 而随着径级增大, 也趋向于随机分布。(3)青海云杉大树个体在小尺度(<4 m)范围内与其他径级个体都呈负关联, 随着尺度的增加, 大树与幼树表现出正关联且关联性随尺度的增加而减弱, 而与小树、中树则表现为无关联或者微弱的负关联; 径级相近的个体空间关联性为正关联或无关联, 随着个体径级间差距增大, 空间关联性转变为无关联或负关联。研究表明, 祁连山大野口流域青海云杉种群的分布格局及其关联性随空间尺度和发育阶段而变化, 这是由种群自身的生物生态学特性、种内种间关系以及环境条件共同作用的结果。     

鹅掌楸贵州烂木山居群的微卫星遗传多样性及空间遗传结构

濒危植物鹅掌楸(Liriodendron chinense)目前仅零散分布于我国亚热带及越南北部地区, 残存居群生境片断化较为严重。研究濒危植物片断化居群的遗传多样性及小尺度空间遗传结构(spatial genetic structure)有助于了解物种的生态进化过程以及制定相关的保育策略。本研究采用13对微卫星引物, 对鹅掌楸的1个片断化居群进行了遗传多样性及空间遗传结构的研究, 旨在揭示生境片断化条件下鹅掌楸的遗传多样性及基因流状况。研究结果表明: 鹅掌楸烂木山居群内不同生境斑块及不同年龄阶段植株的遗传多样性水平差异不显著(P>0.05), 居群内存在寨内和山林2个遗传分化明显的亚居群。烂木山居群个体在200 m以内呈现显著的空间遗传结构, 而2个亚居群内的个体仅在20 m的距离范围内存在微弱或不显著的空间遗传结构。鹅掌楸的空间遗传结构强度较低(Sp = 0.0090), 且寨内亚居群的空间遗传结构强度(Sp = 0.0067)要高于山林亚居群(Sp = 0.0053)。鹅掌楸以异交为主, 种子较轻且具翅, 借助风力传播, 在一定程度上降低了空间遗传结构的强度。此外, 居群内个体密度及生境特征也对鹅掌楸的空间遗传结构产生了一定影响。该居群出现显著的杂合子缺失, 近交系数(F_IS)为0.099 (P < 0.01), 表明生境片断化的遗传效应正逐渐显现。因此, 对鹅掌楸的就地保护应注意维护与强化生境的连续性, 促进基因交流。迁地保护时, 取样距离应不小于20 m, 以涵盖足够多的遗传变异。     

Fine-scale phylogeographical analysis of Mediterranean Anacamptis palustris (Orchidaceae) populations based on chloroplast minisatellite and microsatellite variation

The phylogeographical history of the rare marsh orchid Anacamptis palustris (Orchidaceae) was reconstructed using highly polymorphic chloroplast minisatellite and microsatellite loci. Allelic variation at chloroplast microsatellite loci was due to length variation in poly(A/T) repeats and was informative on a regional scale, but was not sufficient to unravel relationships among populations on a local geographical scale. The minisatellite locus, however, was found to be highly variable. Nine distinct repeat types were found and variation in repeat number occurred in five repeat types. The distribution of chloroplast haplotypes, combining microsatellite and minisatellite repeat type variation, provided a clear phylogeographical picture on a large geographical scale, whereas length variation in one highly polymorphic minisatellite repeat type provided fine-scale phylogeographical information. Mediterranean populations could be divided into four main lineages, a western European lineage, a northern and central Italian lineage, a well-isolated southern Italian (Apulian) lineage, and an eastern European lineage. Variation at the most variable minisatellite repeat type N revealed 19 alleles and allowed the study of seed-mediated gene flow and an estimation of the ratio of pollen to seed flow among neighbouring populations.