Contrasting demographic history and population structure in Capsella rubella and Capsella grandiflora, two closely related species with different mating systems

Both mating system and population history can have large impacts on genetic diversity and population structure. Here, we use multilocus sequence data to investigate how these factors impact two closely related Brassicaceae species: the selfing Capsella rubella and the outcrossing C. grandiflora. To do this, we have sequenced 16 loci in approximately 70 individuals from 7 populations of each species. Patterns of population structure differ strongly between the two species. In C. grandiflora, we observe an isolation-by-distance pattern and identify three clearly delineated genetic groups. In C. rubella, where we estimate the selfing rate to be 0.90-0.94, the pattern is less clear with some sampling populations forming separate genetic clusters while others are highly mixed. The two species also have divergent histories. Our analysis gives support for a bottleneck approximately 73 kya (20-139 kya) in C. rubella, which most likely represents speciation from C. grandiflora. In C. grandiflora, there is moderate support for the standard neutral model in 2 of 3 genetic clusters, while the third cluster and the total data set show evidence of expansion. It is clear that mating system has an impact on these two species, for example affecting the level of genetic variation and the genetic structure. However, our results also clearly show that a combination of past and present processes, some of which are not affected by mating system, is needed to explain the differences between C. rubella and C. grandiflora.     

Contrasting population genetic structure of two sympatric species of Anthurium (Araceae) along elevation in an Andean mountain forest

The topography of the tropical Andean forest is steep, resulting in physical conditions that change with the elevation, thus driving a high turnover of insect pollinator species over short distances, which may lead to localized gene dispersal, promoting genetic divergence between plant populations distributed along the elevation gradient. In this study, we characterized the population genetic structure of Anthurium caucanum and A. panduriforme, two closely related species that coexist along the elevation gradient in the Andean forest but differ in inflorescence size and abundance of flower visitors. The sampling of both species covered seven elevation bands, from 2,200 to 2,900 MASL. Five microsatellite loci were used to genotype the sampled individuals. Our results indicated that heterozygosity was high for both species. Genotypic richness was significantly lower for A. caucanum (G/N = 0.45) compared with A. panduriforme (G/N = 0.88), while population differentiation was strong for A. caucanum (F_st = 0.23) but low for A. panduriforme (F_st = 0.03). Assignment analysis suggested a low rate of immigration events for A. caucanum populations and a high gene flow between A. panduriforme populations. Based on the seed production of bagged inflorescences, A. caucanum demonstrated the ability to self-pollinate, while A. panduriforme was considered self-incompatible. In addition, genotypic richness decreased with elevation for A. caucanum. In summary, the contrasting population genetic structure of the two Anthurium species along the elevation gradient appear to be the result of different gene flow rates, mating systems, and life-history traits, such as clonal growth, flowering phenology, and density.     

海南岛海菖蒲种群克隆多样性和遗传结构

海草是生长在潮间带和潮下带的单子叶植物,由海草植物组成的海草床是生态系统服务价值最高的生态系统之一.然而,近几十年人类活动干扰、全球气候变化等因素导致海草床衰退严重.海菖蒲是分布于热带、体型最大的雌雄异株海草,我国位于该物种的分布北缘,本文对其克隆多样性和遗传结构进行研究,以期为该海草的保护提供参考.采用4对多态微卫星标记对采自海南岛4个地点的现存海菖蒲种群的样品进行基因型分型.结果表明:海菖蒲种群克隆多样性和遗传多样性较低,这与所研究种群处于分布区北缘有关;种群间遗传分化值范围较大(0.073~0.309),这可能是由于分布于不同港湾的种群间距离范围较大以及局域绝灭/再拓殖的遗传漂变效应所致;各种群未发现近期经历种群瓶颈的信号,很可能是由于种群内遗传多样性已经很低,种群减小未能导致遗传多样性明显降低.根据种群遗传特征,提出了重点保护种群的建议,鉴于目前我国海菖蒲等海草快速衰退的局面,应强化海草保护并实施海草床生态恢复.     

An analysis of G matrix variation in two closely related cricket species,Gryllus firmus and G. pennsylvanicus

An important issue in evolutionary biology is understanding the pattern of G matrix variation in natural populations. We estimated four G matrices based on the morphological traits of two cricket species, Gryllus firmus and G. pennsylvanicus, each reared in two environments. We used three matrix comparison approaches, including the Flury hierarchy, to improve our ability to perceive all aspects of matrix variation. Our results demonstrate that different methods perceive different aspects of the matrices, which suggests that, until more is known about these methods, future studies should use several different statistical approaches. We also found that the differences in G matrices within a species can be larger than the differences between species. We conclude that the expression of the genetic architecture can vary with the environment and that future studies should compare G matrices across several environments. We also conclude that G matrices can be conserved at the level of closely related species.     

Genetic diversity and genetic structure of Decalobanthus boisianus in Hainan Island,China

Decalobanthus boisianus is a native plant of Hainan Island, China, which has caused considerable damage to tropical forest ecosystems in recent decades. Understanding the genetic diversity and structure of this species can facilitate uncovering the molecular mechanism of its invasive ability. Here, we collected 77 individuals of D. boisianus spanning 8 distribution areas with a gradient of human disturbance intensity (i.e., low, moderate, and high disturbance intensity groups) to assess patterns of genetic diversity and structure using inter simple sequence repeat (ISSR) markers. We found that a total of 220 loci were scored with 13 primers using ISSR methods, and that 198 loci were polymorphic. The genetic diversity of D. boisianus among these eight forests decreased with increasing human disturbance intensity. Over 70% of the total genetic variation was present within populations, while less than 30% of variation was found among populations. There was a high gene flow (1.27) among them due to a lack of effective geographic barriers. The mean Nei's genetic distance of D. boisianus populations was found to be relatively small (i.e., 0.07), and the average genetic similarity of the eight populations was high (i.e., 0.93). Our findings indicate that the genetic diversity of D. boisianus correlated to human disturbance density, and that D. boisianus populations in Hainan Island have frequent gene exchange. We suggest that reduce deforestation to decrease human disturbance may be a good way to prevent the invasion of D. boisianus.     

Contrasting phylogeographical patterns of two closely related species, Machilus thunbergii and Machilus kusanoi (Lauraceae), in Taiwan

Aim The purpose of this paper was to study the patterns of genetic variation, demographic history, haplotype relationships and potential location of diversity centres of two closely related species, Machilus thunbergii and Machilus kusanoi. Location The phylogeography of M. thunbergii and M. kusanoi was examined by sampling 110 and 106 individuals from 25 and 16 sampling sites, respectively, across their distributional range in Taiwan. Machilus thunbergii is distributed on the Asian mainland, South Korea, southern Japan, the Ryukyus, Taiwan and the Philippines, whereas M. kusanoi is endemic to Taiwan. These two species are closely related, and both are widely distributed in Taiwan but occupy different altitudinal zones and habitats. Methods The range‐wide variation of M. thunbergii and M. kusanoi in Taiwan was studied using chloroplast DNA (cpDNA) variations. A haplotype network was constructed with the computer program tcs . Nested clade analysis was conducted with the computer program ceodis , and various parameters of genetic diversity were calculated and neutrality tested by the computer program Dna SP. Population differentiation was estimated using the programs arlequin and hapstep . The contribution of the populations to gene diversity and to allelic richness was calculated using the software contrib . The level of divergence for each population from the remaining populations was calculated as the mean value of pairwise F_ST for each population against the rest of the populations. Results Extremely low levels of genetic differentiation were found for both species. This result suggested that these two species probably survived in multiple relict refugia with different population sizes throughout the island during low‐temperature periods of the Pleistocene. In addition, nested clade analysis (NCA) of cpDNA haplotypes indicated that restricted gene flow with isolation‐by‐distance characterized the recolonization after the Pleistocene by Tashueshan and Shiouhluan populations of M. thunbergii in the north‐central area west of the Central Mountain Range (CMR). In contrast, NCA analysis indicated that a major diversity centre on the southern tip of the island (Kending population) and contiguous range expansion characterized the recolonization by M. kusanoi of northern areas along the east side of the CMR. The major diversity centres found for the two species examined were further supported by the results of the mean F_ST for individual populations in comparison with other populations, and of the contribution of the divergence component to the total diversity. Main conclusions This research supports the multiple relict refugia hypothesis for both species investigated. Populations of M. thunbergii at Shiouhluan and Tashueshan in the north‐central area west of the CMR represent a diversity centre currently expanding its size. A diversity centre at the southern‐edge population of M. kusanoi, and a contiguous range expansion from Kending, were found. These results indicate that the M. thunbergii populations at Tashueshan and Shiouhluan and the M. kusanoi population at Kending, and even Soukar, are evolutionarily significant units for conservation programmes.     

Genetic diversity and population structure of the serpentine endemic Calystegia collina (Convolvulaceae) in northern California

We used enzyme electrophoresis to evaluate genetic diversity in 32 populations of Calystegia collina, a clonal plant species endemic to serpentine outcrops in northern California (USA). Of 34 loci examined 56% were polymorphic, but on average only 17% were polymorphic within local populations. Neither the total number of alleles nor the number of multilocus genotypes differed significantly between populations in small vs. large serpentine outcrops. Genetic and geographic distances between populations were positively correlated, but this relationship was not significantly affected by the isolation of serpentine outcrops. Populations were highly differentiated (F(st) = 0.417) and little genetic variation was explained by geographic region or serpentine outcrop.Observed heterozygosity within populations almost always exceeded Hardy-Weinberg expectations. In many populations, all 30 sample ramets were uniformly heterozygous at one or more loci yet were genetically variable at other loci. These results imply that many C. collina populations originate from one or a few genetic founders, with little recruitment from seeds. Genetic variation within uniformly heterozygous populations must be the product of multiple, closely related founders or somatic mutations within the population. We conclude that vegetative reproduction, perhaps coupled with somatic mutation, helps maintain genetic diversity in these isolated but long-lived populations.     

Genetic diversity and genetic structure of populations of Ranunculus japonicus Thunb. (Ranunculaceae)

Abstract In order to clarify the genetic diversity and population structure of Ranunculus japonicus , allozymic analysis was conducted on 60 populations in southwestern Japan. Considerable genetic variati ons were detected among the populations of R. japonicus . The genetic diversities within species ( H _es = 0.215) and within populations ( H _ep = 0.172) were slightly higher than those of other perennial herbs with widespread distribution and outcrossing plants. Significantly higher values of fixation index were detected in some populations, which might have arisen from restricted mating partners. The majority of genetic variation (approx. 80%) resided within a population and a moderate level of genetic differentiation ( G _ST = 0.203) was observed among populations. The F _ST value (0.203) suggests the existence of a substantial population structure in this species. The highly significant correlation between geographic distance and F _ST values indicates that isolation by distance has played an important role in the construction of the genetic structure of this species.     

Phylogeographical patterns of two closely related desert shrubs,Nitraria roborowskii and N. sphaerocarpa (Nitrariaceae), from arid north‐western China

To investigate the influence of climate aridification and oscillations on the genetic diversity and evolutionary processes of organisms in the Quaternary in north‐western China, we selected Nitraria roborowskii and N. sphaerocarpa and examined the geographical apportionment of genetic variation in their vast range. In the study, 21 plastid haplotypes were identified in N. roborowskii based on two plastid DNA regions. We found significant genetic differentiation between populations in both N. roborowskii and N. sphaerocarpa. We also found similar phylogeographical patterns of allopatric divergence and regional range expansion in both species, but the degree of allopatric divergence in N. roborowskii was lower. Finally, areas to the south of the Alxa Desert, the Hexi Corridor and Ningxia Province were identified as possible refugia for N. roborowskii.     

Genetic structure of the shrub Daphne laureola across the Baetic Ranges, a Mediterranean glacial refugium and biodiversity hotspot

Distribution margins constitute areas particularly prone to random and/or adaptive intraspecific differentiation in plants. This trend may be particularly marked in species discontinuously distributed across mountain ranges, where sharp geographic isolation gradients and habitat boundaries will enhance genetic isolation among populations. In this study, we analysed the level of neutral genetic differentiation among populations of the long-lived shrub Daphne laureola (Thymelaeaceae) across the Baetic Ranges, a glacial refugium and biodiversity hotspot in the western Mediterranean Basin. Within this area, core and marginal populations of D. laureola were compared with regard to their spatial isolation, size, genetic diversity and differentiation. A spatially explicit analysis conducted on the vast majority of the species' known populations in the study area (N = 111) showed that marginal populations (western and eastern) present larger spatial isolation than core populations, but are not smaller. We compared genetic diversity and differentiation between core and marginal populations using a subsample of 15 populations and 225 amplified fragment length polymorphism (AFLP) markers. Core and marginal populations did not differ in genetic diversity, probably because of the occurrence of large populations on the local margins. Western populations were strongly differentiated from the other populations. In addition, spatial and genetic differentiation among populations was larger on the western margin. Eastern populations constituted a genetically homogeneous group closely related to core populations, despite their greater spatial isolation. Results suggest that studies on phenotypic differentiation between core and marginal populations of D. laureola, and presumably other species having discontinuous distributions across the Baetic ranges, should take into account geographical differences in levels of genetic differentiation between the different distribution borders.     

Genetic structure and reproduction dynamics of Salix reinii during primary succession on Mount Fuji,as revealed by nuclear and chloroplast microsatellite analysis

The early stage of volcanic desert succession is underway on the southeastern slope of Mount Fuji. We used markers of nuclear microsatellites (simple sequence repeats; SSR) and chloroplast microsatellites (cpSSR) to investigate the population genetic structure and reproduction dynamics of Salix reinii, one of the dominant pioneer shrubs in this area. The number of S. reinii genets in a patch and the area of the largest genet within the patch increased with patch area, suggesting that both clonal growth and seedling recruitment are involved in the reproduction dynamics of S. reinii. Five polymorphic cpSSR markers were developed for S. reinii by sequencing the noncoding regions between universal sequences in the chloroplast genome. Nineteen different cpSSR haplotypes were identified, indicating that S. reinii pioneer genets were created by the long-distance dispersal of seeds originating from different mother genets around the study site, where all vegetation was destroyed during the last eruption. Furthermore, the clustered distributions of different haplotypes within each patch or plot suggested that newly colonized genets tended to be generated from seeds dispersed near the initially established mother genets. These results revealed that the establishment of the S. reinii population on the southeastern slope of Mount Fuji involved two sequential modes of seed dispersal: long-distance dispersal followed by short-distance dispersal.     

Genetic population structure and contemporary dispersal patterns of a recent European invader, the Chinese mitten crab, Eriocheir sinensis

Genetic studies of recently established populations are challenging because the assumption of equilibrium underlying many analyses is likely to be violated. Using microsatellites, we investigated determinants of genetic structure and migration among invasive European-Chinese mitten crab populations, applying a combination of traditional population genetic analyses and nonequilibrium Bayesian methods. Consistent with their recent history, invasive populations showed much lower levels of genetic diversity than a native Chinese population, indicative of recent bottlenecks. Population differentiation was generally low but significant and especially pronounced among recently established populations. Significant differentiation among cohorts from the same geographical location (River Thames) suggests the low effective population size and associated strong genetic drift that would be anticipated from a very recent colonization. An isolation-by-distance pattern appears to be driven by an underlying correlation between geographical distance and population age, suggesting that cumulative homogenizing gene flow reduces founder bottleneck-associated genetic differentiation between longer-established populations. This hypothesis was supported by a coalescent analysis, which supported a drift + gene flow model as more likely than a model excluding gene flow. Furthermore, admixture analysis identified several recent migrants between the UK and Continental European population clusters. Admixture proportions were significantly predicted by the volume of shipping between sites, indicating that human-mediated transport remains a significant factor for dispersal of mitten crabs after the initial establishment of populations. Our study highlights the value of nonequilibrium methods for the study of invasive species, and also the importance of evaluating nonequilibrium explanations for isolation by distance patterns.     

Genetic diversity and structure of the narrow endemic Wyethia reticulata and its congener W. bolanderi (Asteraceae) using RAPD and allozyme techniques

Wyethia reticulata is an edaphic endemic in the Sierra Nevada foothills. Its sympatric congener, W. bolanderi, is also restricted to the foothills, but has a north-south range of 275 km, compared to 14 km for W. reticulata. The goals of this study were to determine clonal diversity, population size, genetic variation, and spatial and generic structure for each species from paired populations in El Dorado County, California, using allozyme and RAPD (random amplified polymorphic DNA) methodologies. Wyethia reticulata, spreading by rhizomes, had populations dominated by a few large individuals, while W. bolanderi, with a basal caudex, had populations of a few hundred evenly sized individuals. Genetic analyses indicated that W. reticulata, compared to its congener, had somewhat less genetic diversity (H(T): 0.28 vs. 0.38), had more of its genetic variation partitioned among populations (F(ST): 0.25 vs. 0.07), and showed a complete absence of inbreeding (F(IS): -0.03 vs. 0.22). Population membership in accord with populations defined by geographical location resulted only when all markers were included in the analysis. Ecological limits on recruitment of genets appears to result in small population size in W. reticulata. Limited gene flow, drift within small populations, and sexual reproductive dominance of large clones result in the genetic divergence of populations in this species, while genetic diversity is maintained by the longevity of clones and outbreeding.     

Genetic structure of two endangered pitcher plants,Sarracenia jonesii and Sarracenia oreophila (sarraceniaceae)

Sarracenia jonesii and S. oreophila arc insectivorous perennial plants of the southeastern United States. Both pitcher plant taxa arc rare and endangered. Allozyme diversity was assessed for eight of the ten extant populations of S. jonesii and 14 of the 35 remaining S. oreophila populations. Genetic diversity was low and comparable for both species (H_es = 0.086 and 0.082 for S. jonesii and S. oreophila, respectively). Mean population genic diversity (H_ep) was 0.061 for S. jonesii and 0.060 for S. oreophila. Estimates of genetic diversity were typical of those commonly associated with endemic species. Small populations of each species and geographically disjunct populations tended to maintain less genetic diversity. Indirect estimates of gene flow were comparable for S. oreophila (Nm = 1.62) and S. jonesii (Nm = 1.07).     

Comparative study of pollination biology of two closely related alpine Primula species,namely Primula beesiana and P.bulleyana (Primulaceae)

The comparative pollination biology of a population of Primula beesiana,a population of P.bulleyana,and an overlapping population of these two species in Yulong Shan,Yunnan Province,China,was studied in 2004 and 2005.The results indicate that both P.beesiana and P.bulleyana are typical heterostylous and obligate outcrossing species;the main pollinators of the two species were bees and butterflies.At the sites of all three populations,the main pollinating visitors of the two species showed preference for one...     

Comparative study of pollination biology of two closely related alpine Primula species,namely Primula beesiana and P. bulleyana (Primulaceae)

Abstract The comparative pollination biology of a population of Primula beesiana, a population of P. bulleyana, and an overlapping population of these two species in Yulong Shan, Yunnan Province, China, was studied in 2004 and 2005. The results indicate that both P. beesiana and P. bulleyana are typical heterostylous and obligate outcrossing species; the main pollinators of the two species were bees and butterflies. At the sites of all three populations, the main pollinating visitors of the two species showed preference for one of the two species, resulting in the ethological isolation of the two species by the pollinators. This ethological isolation contributes to the reproductive isolation of the two species, which supports the hypothesis that P. beesiana and P. bulleyana are two distinct species. The reproductive isolation of the two species (ethological isolation) is probably an important mechanism in maintaining species boundaries in the genus and has contributed to the species diversification of Primula in the area. In addition, gene exchanges between P. beesiana and P. bulleyana has occurred to some extent in the overlapping population, but whether natural hybridization has contributed to species diversification in Primula remains to be determined.     

Spatial genetic structure in Beta vulgaris subsp. maritima and Beta macrocarpa reveals the effect of contrasting mating system,influence of marine currents,and footprints of postglacial recolonization routes

Understanding the factors that contribute to population genetic divergence across a species' range is a long‐standing goal in evolutionary biology and ecological genetics. We examined the relative importance of historical and ecological features in shaping the present‐day spatial patterns of genetic structure in two related plant species, Beta vulgaris subsp. maritima and Beta macrocarpa. Using nuclear and mitochondrial markers, we surveyed 93 populations from Brittany (France) to Morocco – the southern limit of their species' range distribution. Whereas B. macrocarpa showed a genotypic structure and a high level of genetic differentiation indicative of selfing, the population genetic structure of B. vulgaris subsp. maritima was consistent with an outcrossing mating system. We further showed (1) a strong geographic clustering in coastal B. vulgaris subsp. maritima populations that highlighted the influence of marine currents in shaping different lineages and (2) a peculiar genetic structure of inland B. vulgaris subsp. maritima populations that could indicate the admixture of distinct evolutionary lineages and recent expansions associated with anthropogenic disturbances. Spatial patterns of nuclear diversity and differentiation also supported a stepwise recolonization of Europe from Atlantic‐Mediterranean refugia after the last glacial period, with leading‐edge expansions. However, cytoplasmic diversity was not impacted by postglacial recolonization: stochastic long‐distance seed dispersal mediated by major oceanic currents may mitigate the common patterns of reduced cytoplasmic diversity observed for edge populations. Overall, the patterns we documented here challenge the general view of reduced genetic diversity at the edge of a species' range distribution and provide clues for understanding how life‐history and major geographic features interact to shape the distribution of genetic diversity.     

Female mate choice and species recognition between two closely related cichlid fish of Lake Malawi,Metriaclima estherae and M. callainos

Cichlids are one of the most diverse and colourful groups of freshwater fishes in the world. Despite much investigation, the factors that promote speciation in these fishes are still uncertain. However, previous studies suggest that sexual selection on male colour is one of the main drivers of speciation among these fishes. Metriaclima estherae is a polymorphic cichlid species from Lake Malawi, and thus provides an ideal model for the investigation of the importance of colour as a species recognition cue. M. callainos is a closely related and morphologically similar species, with male colour pattern very similar to that of M. estherae. We tested female choice by giving females of the two species a choice between conspecific and heterospecific males in the presence and absence of visual (colour) and chemical cues. The results show that females of M. callainos were able to reliably recognize conspecific males, even when colour was eliminated as a cue. However, females of M. estherae did not prefer conspecific males, although they were able to discriminate between red and blue conspecific colour morphs by using chemical cues. These results suggest that species recognition cues may differ even among closely related species of cichlid fish, and that female preferences for male coloration may be weak in certain species.     

Comparative population structure of two dominant species,Shinkaia crosnieri (Munidopsidae: Shinkaia) and Bathymodiolus platifrons (Mytilidae: Bathymodiolus), inhabiting both deep‐sea vent and cold seep inferred from mitochondrial multi‐genes

Deep‐sea hydrothermal vents and cold seeps, limited environments without sunlight, are two types of extreme habitat for marine organisms. The differences between vents and cold seeps may facilitate genetic isolation and produce population heterogeneity. However, information on such chemosynthetic fauna taxa is rare, especially regarding the population diversity of species inhabiting both vents and cold seeps. In this study, three mitochondrial DNA fragments (the cytochrome c oxidase submit I (COI), cytochrome b gene (Cytb), and 16S) were concatenated as a mitochondrial concatenated dataset (MCD) to examine the genetic diversity, population structure, and demographic history of Shinkaia crosnieri and Bathymodiolus platifrons. The genetic diversity differences between vent and seep populations were statistically significant for S. crosnieri but not for B. platifrons. S. crosnieri showed less gene flow and higher levels of genetic differentiation between the vent and seep populations than B. platifrons. In addition, the results suggest that all the B. platifrons populations, but only the S. crosnieri vent populations, passed through a recent expansion or bottleneck. Therefore, different population distribution patterns for the two dominant species were detected; a pattern of population differentiation for S. crosnieri and a homogeneity pattern for B. platifrons. These different population distribution patterns were related to both extrinsic restrictive factors and intrinsic factors. Based on the fact that the two species were collected in almost identical or adjacent sampling sites, we speculated that the primary factors underlying the differences in the population distribution patterns were intrinsic. The historical demographics, dispersal ability, and the tolerance level of environmental heterogeneity are most likely responsible for the different distribution patterns.     

中国特有濒危树种毛红椿核心和边缘居群的遗传多样性

选用8对多态的微卫星引物, 研究了毛红椿(Toona ciliata var. pubescens)核心居群和边缘居群的遗传多样性。研究结果显示, 边缘居群的观察等位基因数和有效等位基因数并不比核心居群低, 甚至更高。普通广布和稀有地方等位基因在所有居群中均有分布, 而普通地方和稀有广布等位基因分别仅在5个和3个居群中有分布。从4种类型等位基因总数上看, 边缘居群高于核心居群, 特别是边缘居群的稀有地方等位基因数量明显多于核心居群。边缘居群的平均期望杂合度和观察杂合度都高于核心居群。核心居群间的基因分化系数为0.1520, 边缘居群间为0.3045, 边缘居群与核心居群的遗传分化差异达到显著水平。核心居群间基因流大于1, 而边缘居群间基因流小于1, 说明核心居群间基因交流频繁, 边缘居群由于片段化和地形影响, 基因流较小。Mantel检验结果显示, 居群间遗传距离与地理距离的相关性不显著, 说明地理距离对毛红椿居群遗传分化的影响不显著。