Microsatellite analysis reveals interpopulation differentiation and gene flow in the endangered tree Changiostyrax dolichocarpa (Styracaceae) with fragmented distribution in central China

Polymorphic simple sequence repeat (SSR) markers were used to investigate the impact of habitat fragmentation on the population structure and gene flow of Changiostyrax dolichocarpa, a critically endangered tree in central China. Intrapopulation genetic diversity, population structure and gene flow in the five extant populations of this species were analysed by eight SSR markers. Intrapopulation genetic diversity results suggest that C. dolichocarpa remnants maintained a relatively high degree of genetic diversity despite severe fragmentation. Low genetic differentiation among populations was found based on Wright's F(ST) and amova analysis. Both the F(ST)-based estimate and private allele method revealed high historical gene flow among the remnant populations. Recent immigrants, detected by assignment tests, tend to decrease from the grandparent generation to the current generation. The potentially highly restricted current gene flow among fragments may render the fragmented populations of C. dolichocarpa at a higher risk of local extinction several generations after fragmentation. Both in situ and ex situ conservation management for the remnant populations of C. dolichocarpa are therefore urgently needed to rescue remaining genetic diversity.     

Fragmentation can increase spatial genetic structure without decreasing pollen-mediated gene flow in a wind-pollinated tree

Fragmentation reduces population sizes, increases isolation between habitats and can result in restricted dispersal of pollen and seeds. Given that diploid seed dispersal contributes more to shaping fine-scale spatial genetic structure (SGS) than haploid pollen flow, we tested whether fine-scale SGS can be sensitive to fragmentation even if extensive pollen dispersal is maintained. Castanopsis sclerophylla (Lindley & Paxton) Schottky (Fagaceae), a wind-pollinated and gravity seed-dispersed tree, was studied in an area of southeast China where its populations have been fragmented to varying extents by human activity. Using different age classes of trees in areas subject to varying extents of fragmentation, we found no significant difference in genetic diversity between prefragmentation vs. postfragmentation C. sclerophylla subpopulations. Genetic differentiation among postfragmentation subpopulations was also only slightly lower than among prefragmentation subpopulations. In the most fragmented habitat, selfing rates were significantly higher than zero in prefragmentation, but not postfragmentation, cohorts. These results suggest that fragmentation had not decreased gene flow among these populations and that pollen flow remains extensive. However, significantly greater fine-scale SGS was found in postfragmentation subpopulations in the most fragmented habitat, but not in less fragmented habitats. This alteration in SGS reflected more restricted seed dispersal, induced by changes in the physical environments and the prevention of secondary seed dispersal by rodents. An increase in SGS can therefore result from more restricted seed dispersal, even in the face of extensive pollen flow, making it a sensitive indicator of the negative consequences of population fragmentation.     

喀斯特耐阴灌木淡黄金花茶的精细空间遗传结构与基因流

淡黄金花茶(Camelia flavida)是一种具有淡黄色花瓣的金花茶植物,为喀斯特典型的耐阴灌木。基于广西弄岗喀斯特季节性雨林15 hm2(300 m×500 m)监测样地,利用13对微卫星(SSR)标记,探讨喀斯特地貌对淡黄金花茶的精细空间遗传结构(SGS)、基因流和小尺度范围遗传分化的影响。结果表明:(1)淡黄金花茶在50 m距离内产生显著的SGS,在灌木类型和依赖种子传播的物种中具有中等程度的SGS强度(Sp=0.0248);(2)淡黄金花茶种子和花粉传播平均距离较短,分别为12.47 m和29.03 m,72.2%花粉和81.0%种子的传播距离均主要是在20 m内;(3)淡黄金花茶在小尺度范围(种群间距离1 km)的4个种群,甚至相距100 m的两个斑块产生了显著的遗传分化。喀斯特生境地貌对淡黄金花茶的基因流产生阻碍作用,从而导致淡黄金花茶在小尺度范围产生遗传分化。     

Spatial and temporal population genetic variation and structure of Nothotsuga longibracteata (Pinaceae), a relic conifer species endemic to subtropical China

Nothotsuga longibracteata, a relic and endangered conifer species endemic to subtropical China, was studied for examining the spatial-temporal population genetic variation and structure to understand the historical biogeographical processes underlying the present geographical distribution. Ten populations were sampled over the entire natural range of the species for spatial analysis, while three key populations with large population sizes and varied age structure were selected for temporal analyses using both nuclear microsatellites (nSSR) and chloroplast microsatellites (cpSSR). A recent bottleneck was detected in the natural populations of N. longibracteata. The spatial genetic analysis showed significant population genetic differentiation across its total geographical range. Notwithstanding, the temporal genetic analysis revealed that the level of genetic diversity between different age class subpopulations remained constant over time. Eleven refugia of the Last Glacial Maximum were identified, which deserve particular attention for conservation management.     

Fine-scale genetic structure and gene dispersal inferences in 10 neotropical tree species

The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift-dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies.     

Fine-scale spatial genetic structure of Dalbergia nigra (Fabaceae), a threatened and endemic tree of the Brazilian Atlantic Forest

The Atlantic Forest is one of the most diverse ecosystems in the world and considered a hotspot of biodiversity conservation. Dalbergia nigra (Fabaceae) is a tree endemic to the Brazilian Atlantic Forest, and has become threatened due to overexploitation of its valuable timber. In the present study, we analyzed the genetic diversity and fine-scale spatial genetic structure of D. nigra in an area of primary forest of a large reserve. All adult individuals (N = 112) were sampled in a 9.3 ha plot, and genotyped for microsatellite loci. Our results indicated high diversity with a mean of 8.6 alleles per locus, and expected heterozygosity equal to 0.74. The co-ancestry coefficients were significant for distances among trees up to 80 m. The Sp value was equal to 0.017 and indirect estimates of gene dispersal distances ranged from 89 to 144 m. No strong evidence of bottleneck or effects of human-disturbance was found. This study highlights that long-term efforts to protect a large area of Atlantic Forest have been effective towards maintaining the genetic diversity of D. nigra. The results of this study are important towards providing a guide for seed collection for ex-situ conservation and reforestation programmes of this threatened species.     

Pollen flow in fragmented landscapes maintains genetic diversity following stand-replacing disturbance in a neotropical pioneer tree,Vochysia ferruginea Mart

In forests with gap disturbance regimes, pioneer tree regeneration is typically abundant following stand-replacing disturbances, whether natural or anthropogenic. Differences in pioneer tree density linked to disturbance regime can influence pollinator behaviour and impact on mating patterns and genetic diversity of pioneer populations. Such mating pattern shifts can manifest as higher selfing rates and lower pollen diversity in old growth forest populations. In secondary forest, where more closely related pollen donors occur, an increase in biparental inbreeding is a potential problem. Here, we investigate the consequences of secondary forest colonisation on the mating patterns and genetic diversity of open-pollinated progeny arrays for the long-lived, self-compatible pioneer tree, Vochysia ferruginea, at two Costa Rican sites. Five microsatellite loci were screened across adult and seed cohorts from old growth forest with lower density, secondary forest with higher density, and isolated individual trees in pasture. Progeny from both old growth and secondary forest contexts were predominantly outcrossed (t_m=1.00) and experienced low levels of biparental inbreeding (t_m−t_s=0.00–0.04). In contrast to predictions, our results indicated that the mating patterns of V. ferruginea are relatively robust to density differences between old growth and secondary forest stands. In addition, we observed that pollen-mediated gene flow possibly maintained the genetic diversity of open-pollinated progeny arrays in stands of secondary forest adults. As part of a natural resource management strategy, we suggest that primary forest remnants should be prioritised for conservation to promote restoration of genetic diversity during forest regeneration.     

Genetic structure and gene flow in a metapopulation of an endangered plant species,Silene tatarica

We investigated the distribution of genetic variation within and between seven subpopulations in a riparian population of Silene tatarica in northern Finland by using amplified fragment length polymorphism (AFLP) markers. A Bayesian approach-based clustering program indicated that the marker data contained not only one panmictic population, but consisted of seven clusters, and that each original sample site seems to consist of a distinct subpopulation. A coalescent-based simulation approach shows recurrent gene flow between subpopulations. Relative high FST values indicated a clear subpopulation differentiation. However, amova analysis and UPGMA-dendrogram did not suggest any hierarchical regional structuring among the subpopulations. There was no correlation between geographical and genetic distances among the subpopulations, nor any correlation between the subpopulation census size and amount of genetic variation. Estimates of gene flow suggested a low level of gene flow between the subpopulations, and the assignment tests proposed a few long-distance bidirectional dispersal events between the subpopulations. No apparent difference was found in within-subpopulation genetic diversity among upper, middle and lower regions along the river. Relative high amounts of linkage disequilibrium at subpopulation level indicated recent population bottlenecks or admixture, and at metapopulation levels a high subpopulation turnover rate. The overall pattern of genetic variation within and between subpopulations also suggested a 'classical' metapopulation structure of the species suggested by the ecological surveys.     

Spatial and demographic population genetic structure in Catasetum viridiflavum across a human-disturbed habitat

Spatial and temporal genetic structures were examined across sites on islands and mainland (continuous forest) populations of an epiphytic orchid, Catasetum viridiflavum, using 17 polymorphic allozyme loci. I tested whether patches on islands or at mainland sites comprised small local populations or a large population. Low among population differentiation was observed across the landscape suggesting that the species-specific pollinator and tiny wind-dispersed seeds maintain interconnections among distant patches. Temporal genetic structure among stage classes, and among breeding individuals are important components of the maintenance of genetic variation in this orchid. The natural history of this species including small breeding populations, probable high frequency of mating among relatives, and the high rates of seed movement among sites contribute to the high FIS. These data show that physically isolated patches in this epiphytic orchid comprise a single larger genetic population, which is independent of the physical distances among sites. Although quite different in ecological and life history characteristics, the genetic structure of this orchid demonstrates a pattern similar to temperate and tropical trees in fragmented landscapes.     

利用RAPD标记分析濒危植物白豆杉种群的遗传结构

以我国特有的濒危裸子植物白豆杉为材料,采用RAPD标记对其分布于浙江、江西、湖南和广西的11个天然种群予以检测,通过贝叶斯法估测了种群的遗传分化程度,并和由其他算法得出的结果进行了比较.求出的θ^B（Hickory）、GST（Nei）及φST（AMOVA）值分别为0.5018、0.5865和0.5436;而经由Shannon指数计算出的种群间遗传多样性所占比例为0.4839,同贝叶斯法估计出的结果最为接近.和其他松杉类植物相比,白豆杉种群间发生了极其显著的遗传分化,这可能是因为：（1）种群长期处于星散分布状态;（2）雌雄异株,而生于林下的雌株经常不能正常受粉;（3）种群取样跨越的地理范围宽广.Mantel检验表明,种群间的遗传分化程度和地理距离之间显著相关（r=0.719,P=0.003）.此外还发现白豆杉的遗传变异水平偏低,推测瓶颈效应和遗传漂变对小种群的作用是造成这一后果的重要因素.对白豆杉种群的保育和管理提出了建议.     

Fine-scale genetic structure of a long-lived reptile reflects recent habitat modification

Anthropogenic habitat fragmentation — ubiquitous in modern ecosystems — has strong impacts on gene flow and genetic population structure. Reptiles may be particularly susceptible to the effects of fragmentation because of their extreme sensitivity to environmental conditions and limited dispersal. We investigate fine-scale spatial genetic structure, individual relatedness, and sex-biased dispersal in a large population of a long-lived reptile (tuatara, Sphenodon punctatus) on a recently fragmented island. We genotyped individuals from remnant forest, regenerating forest, and grassland pasture sites at seven microsatellite loci and found significant genetic structuring (R_ST = 0.012) across small distances (< 500 m). Isolation by distance was not evident, but rather, genetic distance was weakly correlated with habitat similarity. Only individuals in forest fragments were correctly assignable to their site of origin, and individual pairwise relatedness in one fragment was significantly higher than expected. We did not detect sex-biased dispersal, but natural dispersal patterns may be confounded by fragmentation. Assignment tests showed that reforestation appears to have provided refuges for tuatara from disturbed areas. Our results suggest that fine-scale genetic structuring is driven by recent habitat modification and compounded by the sedentary lifestyle of these long-lived reptiles. Extreme longevity, large population size, simple social structure and random dispersal are not strong enough to counteract the genetic structure caused by a sedentary lifestyle. We suspect that fine-scale spatial genetic structuring could occur in any sedentary species with limited dispersal, making them more susceptible to the effects of fragmentation.     

群体遗传结构中的基因流

群体遗传结构上的差异是遗传多样性的一种重要体现,对群体遗传结构的研究已有较久的历史,而其中的基因流研究近些年来越来越受到重视。它对群体遗传学、进化生物学、保护生物学、生态学有着极其重要的作用。虽然传统的群体遗传学能估测基因流大小,但它的精确性还有很大局限性。随着生物技术的进步,对基因流的研究逐渐向分子水平过渡,应用蛋白质电泳技术、分子标记技术(RAPD、RFLP、VNTR、ISSR、DNA测序等)方法对群体间基因流的流动水平进行了深入细致的研究。通过综述群体遗传结构的几种模式:陆岛模式、海岛模式、阶石模式、距离隔离模式、层次模式,以及在群体遗传结构的几种模式基础上的基因流的研究方法、作用、地位和近些年来研究者的研究成果,并指出了这些方法的局限性。     

Landscape connectivity influences gene flow in a roe deer population inhabiting a fragmented landscape: an individual-based approach

Changes in agricultural practices and forest fragmentation can have a dramatic effect on landscape connectivity and the dispersal of animals, potentially reducing gene flow within populations. In this study, we assessed the influence of woodland connectivity on gene flow in a traditionally forest-dwelling species--the European roe deer--in a fragmented landscape. From a sample of 648 roe deer spatially referenced within a study area of 55 x 40 km, interindividual genetic distances were calculated from genotypes at 12 polymorphic microsatellite loci. We calculated two geographical distances between each pair of individuals: the Euclidean distance (straight line) and the 'least cost distance' (the trajectory that maximizes the use of wooded corridors). We tested the correlation between genetic pairwise distances and the two types of geographical pairwise distance using Mantel tests. The correlation was better using the least cost distance, which takes into account the distribution of wooded patches, especially for females (the correlation was stronger but not significant for males). These results suggest that in a fragmented woodland area roe deer dispersal is strongly linked to wooded structures and hence that gene flow within the roe deer population is influenced by the connectivity of the landscape.     

High genetic diversity vs. low genetic differentiation in Nouelia insignis (Asteraceae), a narrowly distributed and endemic species in China, revealed by ISSR fingerprinting

BACKGROUND AND AIMS: Nouelia insignis Franch., a monotypic genus of the Asteraceae, is an endangered species endemic in Yunnan and Sichuan Provinces of China. Most of the populations are seriously threatened. Some of them are even at the brink of extinction. In this study, the genetic diversity and differentiation between populations of this species were examined in two drainage areas. METHODS: DNA fingerprinting based on inter-simple sequence repeat polymorphisms was employed to detect the genetic variation and population structure in the species. KEY RESULTS: Genetic diversity at species level was high with P=65.05% (percentage of polymorphic loci) and Ht=0.2248 (total genetic diversity). The coefficient of genetic differentiation among populations, Gst, which was estimated by partitioning the total gene diversity, was 0.2529; whereas, the genetic differentiation between populations in the Jinsha and Nanpan drainage areas was unexpectedly low (Gst=0.0702). CONCLUSIONS: Based on the genetic analyses of the DNA fingerprinting, recent habitat fragmentation may not have led to genetic differentiation or the loss of genetic diversity in the rare species. Spatial apportionment of fingerprinting polymorphisms provides a footprint of historical migration across geographical barriers. The high diversity detected in this study holds promise for conservation and restoration efforts to save the endangered species from extinction.     

Species diversity and population density affect genetic structure and gene dispersal in a subtropical understory shrub

Aims The dispersal of pollen and seeds is spatially restricted and may vary among plant populations because of varying biotic interactions, population histories or abiotic conditions. Because gene dispersal is spatially restricted, it will eventually result in the development of spatial genetic structure (SGS), which in turn can allow insights into gene dispersal processes. Here, we assessed the effect of habitat characteristics like population density and community structure on small-scale SGS and estimate historical gene dispersal at different spatial scales.Methods In a set of 12 populations of the subtropical understory shrub Ardisia crenata, we assessed genetic variation at 7 microsatellite loci within and among populations. We investigated small-scale genetic structure with spatial genetic autocorrelation statistics and heterogeneity tests and estimated gene dispersal distances based on population differentiation and on within-population SGS. SGS was related to habitat characteristics by multiple regression.Important findings The populations showed high genetic diversity (H e = 0.64) within populations and rather strong genetic differentiation (F ′ ST = 0.208) among populations, following an isolation-by-distance pattern, which suggests that populations are in gene flow–drift equilibrium. Significant SGS was present within populations (mean Sp = 0.027). Population density and species diversity had a joint effect on SGS with low population density and high species diversity leading to stronger small-scale SGS. Estimates of historical gene dispersal from between-population differentiation and from within-population SGS resulted in similar values between 4.8 and 22.9 m. The results indicate that local-ranged pollen dispersal and inefficient long-distance seed dispersal, both affected by population density and species diversity, contributed to the genetic population structure of the species. We suggest that SGS in shrubs is more similar to that of herbs than to trees and that in communities with high species diversity gene flow is more restricted than at low species diversity. This may represent a process that retards the development of a positive species diversity–genetic diversity relationship.     

Low levels of realized seed and pollen gene flow and strong spatial genetic structure in a small,isolated and fragmented population of the tropical tree Copaifera langsdorffii Desf

Over the past century, the Brazilian Atlantic forest has been reduced to small, isolated fragments of forest. Reproductive isolation theories predict a loss of genetic diversity and increases in inbreeding and spatial genetic structure (SGS) in such populations. We analysed eight microsatellite loci to investigate the pollen and seed dispersal patterns, genetic diversity, inbreeding and SGS of the tropical tree Copaifera langsdorffii in a small (4.8 ha), isolated population. All 112 adult trees and 128 seedlings found in the stand were sampled, mapped and genotyped. Seedlings had significantly lower levels of genetic diversity (A=16.5±0.45, mean±95% s.e.; H_e=0.838±0.006) than did adult trees (A=23.2±0.81; H_e=0.893±0.030). Parentage analysis did not indicate any seed immigration (m_seeds=0) and the pollen immigration rate was very low (m_pollen=0.047). The average distance of realized pollen dispersal within the stand was 94 m, with 81% of the pollen travelling <150 m. A significant negative correlation was found between the frequency and distance of pollen dispersal (r=−0.79, P<0.01), indicating that short-distance pollinations were more frequent. A significant SGS for both adults (∼50 m) and seedlings (∼20 m) was also found, indicating that most of the seeds were dispersed over short distances. The results suggested that the spatial isolation of populations by habitat fragmentation can restrict seed and pollen gene flow, increase SGS and affect the genetic diversity of future generations.     

Fine-scale spatial genetic structure and gene dispersal in Silene latifolia

Plants are sessile organisms, often characterized by limited dispersal. Seeds and pollen are the critical stages for gene flow. Here we investigate spatial genetic structure, gene dispersal and the relative contribution of pollen vs seed in the movement of genes in a stable metapopulation of the white campion Silene latifolia within its native range. This short-lived perennial plant is dioecious, has gravity-dispersed seeds and moth-mediated pollination. Direct measures of pollen dispersal suggested that large populations receive more pollen than small isolated populations and that most gene flow occurs within tens of meters. However, these studies were performed in the newly colonized range (North America) where the specialist pollinator is absent. In the native range (Europe), gene dispersal could fall on a different spatial scale. We genotyped 258 individuals from large and small (15) subpopulations along a 60 km, elongated metapopulation in Europe using six highly variable microsatellite markers, two X-linked and four autosomal. We found substantial genetic differentiation among subpopulations (global F_ST=0.11) and a general pattern of isolation by distance over the whole sampled area. Spatial autocorrelation revealed high relatedness among neighboring individuals over hundreds of meters. Estimates of gene dispersal revealed gene flow at the scale of tens of meters (5–30 m), similar to the newly colonized range. Contrary to expectations, estimates of dispersal based on X and autosomal markers showed very similar ranges, suggesting similar levels of pollen and seed dispersal. This may be explained by stochastic events of extensive seed dispersal in this area and limited pollen dispersal.     

Strong population genetic structure of an invasive species,Rhynchophorus ferrugineus (Olivier), in southern China

The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier), was initially reported in China in the 1990s and is now considered one of the most successful invasive pests of palm plants in the country. A total of 14 microsatellite loci and one mitochondrial cytochrome oxidase subunit Ι (cox I) gene fragment were used to investigate the genetic characteristics and structure of R. ferrugineus in southern China. High levels of genetic differentiation among populations and significant correlations between genetic and geographical distances indicated an important role of geographical distance in the distribution of the RPW in southern China. High gene flow between Fujian and Taiwan province populations illustrated the increased effects of frequent anthropogenic activities on gene flow between them. Genetic similarity (i.e., haplotype similarity) indicated that RPW individuals from Taiwan and Fujian invaded from a different source than those from Hainan. To some extent, the genetic structure of the RPW in southern China correlated well with the geographic origins of this pest. We propose that geographical distance, anthropogenic activities, and the biological attributes of this pest are responsible for the distribution pattern of the RPW in southern China. The phylogenetic analysis suggests that the most likely native sources of the RPW in southern China are India, the Philippines, and Vietnam.     

Significant genetic boundaries and spatial dynamics of giant pandas occupying fragmented habitat across southwest China

Understanding population history and genetic structure are key drivers of ecological research. Here, we studied two highly fragmented and isolated populations (Xiaoxiangling and Daxiangling) of giant pandas (Ailuropoda melanoleuca) at the extreme southwestern edge of their distribution. This area also contains the Dadu River, national road 108 and various human infrastructure and development, providing an ideal region in which we can identify the effects of different barriers on animal movements. We used partial mitochondrial control region (mtDNA) and nine microsatellite loci (nuclear DNA) data derived from 192 faecal and one blood sample collected from the wild. We found 136 genotypes corresponding to 53 unique multilocus genotypes and eight unique control region haplotypes (653 bp). Significant genetic boundaries correlated spatially with the Dadu River (K = 2). We estimate that a major divergence took place between these populations 26,000 years bp, at around the similar time the rock surface of valley bottom formed in Dadu River. The national road has resulted in further recent population differentiation (Pairwise F(S) on mtDNA and nuclear DNA) so that in effect, four smaller sub-populations now exist. Promisingly, we identified two possible first-generation migrants and their migration paths, and recommended the immediate construction of a number of corridors. Fortunately, the Chinese government has accepted our advice and is now planning corridor construction.     

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。