岛屿特有种全缘冬青遗传多样性的ISSR分析

全缘冬青(Ilex integra)为岛屿特有植物,主要分布于浙江舟山群岛,被列为浙江省珍稀濒危植物。作者运用ISSR分子标记对舟山群岛的6个全缘冬青种群(5个自然种群和1个栽培种群)共57个个体进行了遗传多样性分析。采用9条随机引物扩增出78条清晰谱带,其中45条为多态性条带,多态位点百分比(PPL)为57.7%。经POPGENE软件分析,全缘冬青种群平均多态位点百分比(PPL)为42.1%,Nei’s基因多样度(HE)为0.153,较其他海岛植物的遗传多样性偏低。5个自然种群遗传分化系数Gst=0.316,AMOVA测度Fst=0.295,Shannon多样性分化系数S=0.304,遗传分化程度较高。全缘冬青种群间地理距离与遗传距离具有正相关性(r=0.649,P<0.05),岛屿间地理隔离对种群间遗传分化产生了较为显著的影响。UPGMA聚类分析显示,朱家尖岛与普陀岛种群亲缘关系较近,而舟山岛栽培种群是由桃花岛自然种群移植而来。针对全缘冬青种群遗传多样性较低及遗传分化程度较高的现状,应加强现有自然种群的就地保护,促进种群自然更新;建立种质资源库,收集不同岛屿的种源进行混合繁殖,促进基因交流。     

一个通用岛屿生物地理学模型

MacArthur-Wilson的平衡理论是生态学中最有影响力的理论之一,尽管进化的重要性早已认识到,但进化因素一直没有很好地整合到岛屿生物地理学模型中.本文通过在经典MacArthur-Wilson模型中整合成种及其他相关因素提出了一个更通用的综合模型.模型证实成种对岛屿上物种丰富度和特有种的形成具有重要作用,并且在满足一定条件时成种对局域物种多样性的作用可超过迁入的作用,这些条件与平均每物种成种率、绝灭率以及岛屿特征有关,但与迁入率无关.当其他参数固定时,模型预测,大岛具较大但不是最大的特有种比例.基于这一模型,可以预测海洋岛上物种丰富度和特有种的变化,预测结论与实际观察的一致.本文提出的模型为重新评估成种的作用和岛屿物种多样性数据,尤其是对那些偏离MacArthur-Wilson模型的数据进行重新分析提供了一个新方法.     

Study on population genetic diversity of Camellia japonica in 5 islands between China and Japan

运用ISSR分子标记法对中、日两国5个岛屿天然山茶种群共150个个体进行遗传多样性分析.结果表明:筛选出的20条引物扩增得到205条清晰条带,其中183条为多态性条带,多态位点百分比(PPB)为89.27％.经POPGENE软件分析,山茶种群平均多态位点百分比(PPB)为72.00％,Nei's基因多样性指数(HE)为0.2743,Shannon信息多态性指数(H)为0.4023,种群水平遗传多样性较高.基因分化系数Gst=0.2033,表明遗传变异主要存在于种群内个体间.Mantel检验(r=0.7989,P＜0.05)和UPGMA聚类表明岛屿地理隔离对山茶种群遗传分化具有重要影响.基于岛屿山茶种群遗传结构的分析,建议加强我国岛屿自然种群的就地保护力度.     

通过遗传多样性探讨极小种群野生植物的致濒机理及保护策略: 以裸子植物为例

遗传多样性是生物多样性的重要组成部分, 然而由于资源的过度开发利用和生境的破碎化影响了物种的遗传多样性, 甚至威胁到物种的生存适应性和生物多样性。极小种群野生植物是亟待保护的国家重点保护濒危植物,遗传多样性研究对揭示极小种群致濒机理及保护策略具有重要意义。生境破碎化会造成物种遗传多样性降低、种群间分化增加、基因流减少等, 使种群濒危。但在某些物种中, 繁殖特征、进化历史等生物和生态因素的不同也可能造成近期生境破碎化后遗传效应的延迟。裸子植物进化历史悠久, 包含许多孑遗物种, 由于生活史周期长, 遭受生境破碎化后可能短期内显示不出遗传效应的改变, 但长期很难恢复。本文以裸子植物为例综述了濒危植物的遗传多样性研究的案例, 探讨了濒危裸子植物应对环境恶化的维持机制、致濒因素和保护方案, 旨在说明通过遗传多样性研究充分认识极小种群致濒机理对高效保护极小种群野生植物的重要性。     

日本岛屿山茶种群遗传结构的ISSR分析

为查明日本岛屿山茶种群的生存状况及了解岛屿隔离对山茶种群遗传结构的影响,采用ISSR分子标记,利用筛选的20条引物对日本5个山茶（Camellia japonica）种群的遗传结构进行分析。结果表明：山茶种群的多态位点百分比（PPB）为70.29％,Nei’s基因多样性指数（H_E）为0.281 9,Shannon信息多态性指数（H）为0.409 5,与其它岛屿种群相比遗传多样性水平较高,表明山茶种群的生存状况较好。基因分化系数G_st=0.205 7,种群间具有较高的遗传分化;地理距离与遗传距离具有显著相关性（r=0.821 7,p<0.05）,UPGMA也将同岛种群聚在一起,表明岛屿隔离对山茶种群的遗传分化具有重要影响。借鉴日本岛屿山茶种群的保护经验,建议加强我国岛屿山茶种群的就地保护力度,同时建立山茶种质资源库,促进基因交流。     

中日5个岛屿山茶种群遗传多样性研究

运用ISSR分子标记法对中、日两国5个岛屿天然山茶种群共150个个体进行遗传多样性分析。结果表明:筛选出的20条引物扩增得到205条清晰条带,其中183条为多态性条带,多态位点百分比(PPB)为89.27%。经POPGENE软件分析,山茶种群平均多态位点百分比(PPB)为72.00%,Nei’s基因多样性指数(HE)为0.2743,Shannon信息多态性指数(H)为0.4023,种群水平遗传多样性较高。基因分化系数Gst=0.2033,表明遗传变异主要存在于种群内个体间。Mantel检验(r=0.7989,P<0.05)和UPGMA聚类表明岛屿地理隔离对山茶种群遗传分化具有重要影响。基于岛屿山茶种群遗传结构的分析,建议加强我国岛屿自然种群的就地保护力度。     

昌化江河谷隔离对海南岛特有植物盾叶苣苔遗传多样性的影响

为评估盾叶苣苔的遗传多样性与遗传分化格局,探索影响盾叶苣苔遗传变异地理分布的因素,该研究采集盾叶苣苔(Metapetrocosmea peltata)11个种群172份材料,通过PCR扩增和测序分析核糖体转录间隔区(ITS)序列的变异式样。结果表明:(1)盾叶苣苔物种水平的遗传多样性很高(H_T=0.998, π=0.023 5),种群间基因流很弱(N_m=0.04)且存在强烈的遗传分化(G_ST=0.375)。(2)单倍型分析显示,盾叶苣苔的单倍型大多是种群特异的,仅白马岭与南茂岭种群有共享单倍型。(3)Mantel test表明,遗传距离和地理距离存在一定相关性(相关系数r=0.322,P=0.010)。(4)Structure聚类分析将盾叶苣苔划分为6种遗传成分,其地理分布与昌化江河谷导致的隔离样式基本一致,基于Nei遗传距离的种群聚类分析支持这一结果,显示盾叶苣苔遗传多样性的分布受到昌化江河谷的隔离作用。(5)AMOVA分析确定67%的变异来自地区间,表明地理隔离是盾叶苣苔种群分化的重要因素。这表明昌化江及其支流所引起的海南岛山地内部隔离是盾叶苣苔种群发生强烈遗传分化的重要原因,从而导致盾叶苣苔在物种水平具有较高的遗传多样性。上述研究结果为海南特有苦苣苔资源盾叶苣苔的保护和可持续利用提供了理论指导,将有助于理解海南岛特有植物和其他海岛植物遗传变异的地理分布及其影响因素。     

岛屿植物舟山新木姜子居群遗传多样性的RAPD分析

基于随机扩增多态 DNA(RAPD)方法分析了舟山群岛濒危植物舟山新木姜子 (N eolitsea sericea) 6个居群的遗传多样性及分化程度。 10条随机引物扩增出 84个可分析位点 ,多态位点百分比 (PPL)为 3 8.10 %。经 POPOGENE分析发现 ,舟山新木姜子居群平均水平的多态位点百分比 (PPL )为 2 3 .18% ,Nei' s基因多样度 (HE)为 0 .0 793 ,Shannon信息指数 (H )为 0 .12 0 1,与其它岛屿植物比较具有中等偏低水平的遗传多样性 ;岛屿各居群间遗传分化程度较高 (Gst=0 .3 646) ;地理距离与遗传距离之间具有显著相关性 (r=0 .7697,P=96.62 % ) ,岛屿隔离效应是导致居群间遗传分化的重要因素。结合居群遗传多样性及UPGMA聚类分析 ,推测普陀山岛舟山新木姜子部分个体可能为大猫岛迁入的后裔 ,而朱家尖岛舟山新木姜子则由人为移植自普陀山岛。基于舟山新木姜子的物种保护及资源利用 ,建议加强现有自然居群的就地保护 ,促进居群自然更新 ;建立种质资源库 ,收集不同岛屿的种源进行混合繁殖 ,促进基因交流 ;选育优良品系用于海岛植被恢复及园林观赏     

植物边缘种群遗传多样性研究进展

边缘种群指地理分布边缘可检测到的一定数量的同种个体集合, 准确评价其遗传多样性对于理解第四纪冰期后气候变化对物种边缘扩展或收缩、遗传资源保护与利用以及物种形成等有重要意义。该文探讨了维持植物边缘种群遗传多样性的进化机制, 分析交配系统对物种边缘及其遗传多样性的影响, 比较了边缘与中心种群遗传多样性的差异及其形成的生态与进化过程, 并探讨了边缘种群遗传多样性与其所在的群落物种多样性的关系及理论基础。该文提出今后研究的重点是应用全基因组序列或转录组基因序列研究前缘-后缘种群之间或边缘-中心种群之间的适应性差异, 边缘种群与所在群落其他物种之间相互作用的分子机制, 深入解析边缘种群对环境的适应及边缘种群遗传多样性与群落物种多样性关系的生态与进化过程。     

沿海岛屿与内陆藓类植物遗传多样性和分化的比较研究——以真藓(Bryum argenteum Hedw.)为例

基于11个内陆居群和32个岛屿居群的252份标本,采用ISSR分子标记技术对真藓（Bryum argenteum Hedw.）的遗传多样性进行了研究。结果显示：岛屿与内陆居群间的遗传多样性差异显著,岛屿居群间的分化程度（G_st=0.453）大于内陆居群（G_st=0.387）,岛屿居群的遗传分化与地理来源间存在极显著相关性（r=0.478,n=175,P<0.001）。地理隔离效应是导致岛屿居群间遗传分化的重要因素。岛内居群间的遗传分化水平较低,仅有29.4%~29.7%的遗传多样性存在于居群间。聚类分析表明,43个居群可划分为10大类群,真藓遗传关系受地理因素和生境异质性的影响,水域隔离影响了真藓繁殖体在岛屿间的传播。     

The world in a grain of sand: evolutionarily relevant,small‐scale freshwater bioregions on subtropical dune islands

1. Conservation plans are required to safeguard freshwater biodiversity in the face of increasing threats. Traditionally plans have used surrogates for biodiversity that do not account for the evolutionary process, but genetic data in the form of comparative phylogeography can fulfil this role. 2. Comparative phylogeographic analyses of multiple freshwater fish and decapod crustacean species were carried out with specimens from two model systems, namely the sand dune islands of Fraser and North Stradbroke in eastern Australia. 3. Almost all of the species studied from both islands displayed an intraspecific evolutionary split between sides of the island (east/west on North Stradbroke Island, and north/south on Fraser Island), indicating that each side of each island hosts its own distinct community of populations of freshwater animals. 4. The probable process responsible for both of these divergent communities is different source populations for each side of each island. 5. This study shows that biodiversity will not always follow obvious geography and that significant diversity may exist at small scales within multiple species. These evolutionarily relevant units of biodiversity should be incorporated at the beginning of the conservation and resource management planning process.     

In and out of Madagascar: Dispersal to Peripheral Islands, Insular Speciation and Diversification of Indian Ocean Daisy Trees (Psiadia, Asteraceae)

Madagascar is surrounded by archipelagos varying widely in origin, age and structure. Although small and geologically young, these archipelagos have accumulated disproportionate numbers of unique lineages in comparison to Madagascar, highlighting the role of waif-dispersal and rapid in situ diversification processes in generating endemic biodiversity. We reconstruct the evolutionary and biogeographical history of the genus Psiadia (Asteraceae), a plant genus with near equal numbers of species in Madagascar and surrounding islands. Analyzing patterns and processes of diversification, we explain species accumulation on peripheral islands and aim to offer new insights on the origin and potential causes for diversification in the Madagascar and Indian Ocean Islands biodiversity hotspot. Our results provide support for an African origin of the group, with strong support for non-monophyly. Colonization of the Mascarenes took place by two evolutionary distinct lineages from Madagascar, via two independent dispersal events, each unique for their spatial and temporal properties. Significant shifts in diversification rate followed regional expansion, resulting in co-occurring and phenotypically convergent species on high-elevation volcanic slopes. Like other endemic island lineages, Psiadia have been highly successful in dispersing to and radiating on isolated oceanic islands, typified by high habitat diversity and dynamic ecosystems fuelled by continued geological activity. Results stress the important biogeographical role for Rodrigues in serving as an outlying stepping stone from which regional colonization took place. We discuss how isolated volcanic islands contribute to regional diversity by generating substantial numbers of endemic species on short temporal scales. Factors pertaining to the mode and tempo of archipelago formation and its geographical isolation strongly govern evolutionary pathways available for species diversification, and the potential for successful diversification of dispersed lineages, therefore, appears highly dependent on the timing of arrival, as habitat and resource properties change dramatically over the course of oceanic island evolution.     

Vicariance and marine migration in continental island populations of a frog endemic to the Atlantic Coastal forest

The theory of island biogeography is most often studied in the context of oceanic islands where all island inhabitants are descendants from founding events involving migration from mainland source populations. Far fewer studies have considered predictions of island biogeography in the case of continental islands, where island formation typically splits continuous populations and thus vicariance also contributes to the diversity of island populations. We examined one such case on continental islands in southeastern Brazil, to determine how classic island biogeography predictions and past vicariance explain the population genetic diversity of Thoropa taophora, a frog endemic to the Atlantic Coastal Forest. We used nuclear microsatellite markers to examine the genetic diversity of coastal and island populations of this species. We found that island isolation has a role in shaping the genetic diversity of continental island species, with island populations being significantly less diverse than coastal populations. However, area of the island and distance from coast had no significant effect on genetic diversity. We also found no significant differences between migration among coastal populations and migration to and from islands. We discuss how vicariance and the effects of continued migration between coastal and island populations interact to shape evolutionary patterns on continental islands.     

Biodiversity dynamics in isolated island communities: interaction between natural and human-mediated processes

The flora and fauna of oceanic islands have inspired research since the early scientific explorations. Islands can be considered 'nature's test tubes'- simple systems with multiple replicates. Our research has used the simplicity of island systems to understand ecological community dynamics and to compare the properties of island communities with those in more complex mainland systems. Here, we present three topics: (i) current patterns of biodiversity on isolated islands of the Pacific; (ii) current patterns of disturbance and invasion on islands; and (iii) future trajectories inferred from these patterns. We examine features of islands (in particular, topography and isolation) that have allowed for given levels and distribution of endemicity. The extent to which island communities are impacted by, resist or accommodate disturbance and/or invasions by nonindigenous species appears to be dictated to a large extent by properties of the native communities and how these communities were originally assembled. Accordingly, patterns of disturbance and invasion are very different for high (montane) islands that are extremely isolated compared to those that are nearer to a source of natural migrants. As with all biotas, those on islands are dynamic entities. However, the unique aspect of islands is their isolation, and extreme isolation has largely been lost over the course of the last few centuries due to the development of transportation routes. We argue that such a modified dynamic will affect the future of the biota and the processes that gave rise to the biota. Specifically for isolated habitats, ecological processes will become increasingly more likely to generate biodiversity than evolutionary processes which have been relatively more important in the past. In the short term, island biotas and other similar biotas that occur in montane habitats may fare well as species are often abundant locally in the habitat to which they are indigenous, and may demonstrate considerable resistance and resilience to invasion. However, island biotas - and other biotas that show high local endemism - will likely not fare well in the face of prolonged disturbance. The biotas in these areas generally display a relatively low dispersal capacity; therefore, under conditions of long-term habitat modification, isolated biotas are likely to be swamped by non-natives, which - simply because of random processes and higher propagule pressure - will move more readily into available habitats. Thus, despite the importance of incorporating the evolutionary process into conservation efforts, we must also be careful to evaluate the likely form that the processes will take when the context (specifically, extent of isolation) has been highly modified.     

Effects of ecogeographic variables on genetic variation in montane mammals: implications for conservation in a global warming scenario

Aim Evolutionary theory predicts that levels of genetic variation in island populations will be positively correlated with island area and negatively correlated with island isolation. These patterns have been empirically established for oceanic islands, but little is known about the determinants of variation on habitat islands. The goals of this study were twofold. Our first aim was to test whether published patterns of genetic variation in mammals occurring on montane habitat islands in the American Southwest conformed to expectations based on evolutionary theory. The second aim of this research was to develop simple heuristic models to predict changes in genetic variation that may occur in these populations as a result of reductions in available mountaintop habitat in response to global warming. Location Habitat islands of conifer forest on mountaintops in the American Southwest. Methods Relationships between island area and isolation with measures of allozyme variation in four species of small mammal, namely the least chipmunk (Tamias minimus), Colorado chipmunk (Tamias quadrivittatus), red squirrel (Tamiasciurus hudsonicus), and Mexican woodrat (Neotoma mexicana), were determined using correlation and regression techniques. Significant relationships between island area and genetic variation were used to develop three distinct statistical models with which to predict changes in genetic variation following reduction in insular habitat area arising from global warming. Results Patterns of genetic variation in each species conformed to evolutionary predictions. In general, island area was the most important determinant of heterozygosity, while island isolation was the most important determinant of polymorphism and allelic diversity. The heuristic models predicted widespread reductions in genetic variation, the extent of which depended on the population and model considered. Main conclusions The results support a generalized pattern of genetic variation for any species with an insular distribution, with reduced variation in smaller, more isolated populations. We predict widespread reductions in genetic variation in isolated populations of montane small mammals in the American Southwest as a result of global warming. We conclude that climate‐induced reductions in the various dimensions of genetic variation may increase the probability of population extinction in both the short and long term.     

Conservation of oceanic island floras: Present and future global challenges

Current threats to the planet's biodiversity are unprecedented, and they particularly imperil insular floras. In this investigation, we use the threat factors identified by the Millennium Ecosystem Assessment as the main drivers of biodiversity loss on islands to define and rank 13 current, continuing threats to the plant diversity of nine focal archipelagos where volcanic origin (or in the Seychelles a prolonged isolation after a continental origin) has produced a high degree of endemicity and fragility in the face of habitat alteration. We also conduct a global endangerment assessment based on the numbers of insular endemic plants in the endangered (EN) and critically endangered (CR) IUCN categories for 53 island groups with an estimated 9951 endemic plant species, providing a representative sample of the world's insular systems and their floristic richness. Our analyses indicate that isolation does not significantly influence endangerment, but plant endemics from very small islands are more often critically endangered. We estimate that between 3500 and 6800 of the estimated 70,000 insular endemic plant species worldwide might be highly threatened (CR+EN) and between ca. 2000 and 2800 of them in critical danger of extinction (CR). Based on these analyses, and on a worldwide literature review of the biological threat factors considered, we identify challenging questions for conservation research, asking (i) what are the most urgent priorities for the conservation of insular species and floras, and (ii) with the knowledge and assets available, how can we improve the impact of conservation science and practice on the preservation of island biodiversity? Our analysis indicates that the synergistic action of many threat factors can induce major ecological disturbances, leading to multiple extinctions. We review weaknesses and strengths in conservation research and management in the nine focal archipelagos, and highlight the urgent need for conservation scientists to share knowledge and expertise, identify and discuss common challenges, and formulate multi-disciplinary conservation objectives for insular plant endemics worldwide. To our knowledge, this is the most up-to-date and comprehensive survey yet to review the threat factors to native plants on oceanic islands and define priority research questions.     

Biodiversity in the Gulf of Guinea: an overview

Patterns of species-richness and endemism in the Gulf of Guinea reflect the region's biogeographic history. Bioko is a continental-shelf island that was recently connected to the African mainland, whereas Príncipe, São Tomé and Annobón are truly oceanic and have never been connected with each other or with the mainland. As a result, Bioko supports a much more diverse flora and fauna but with relatively low levels of endemism at the species level, whereas the oceanic islands are relatively depauperate because of their isolation but rich in endemic taxa. Species endemism is 0–3% on Bioko for angiosperms, bats, birds, reptiles and amphibians, compared with much higher values on Principe for these same taxa of 8% (plants) to 100% (amphibians), on São Tomé between 14% (plants) and 100% (amphibians), and on Annobón 0% (bats) to 71% (reptiles). On a global scale, for their size both Príncipe and São Tomé support unusually high numbers of single-island endemic species of birds, reptiles and amphibia. For its tiny size, Annobón is also notable for its endemic birds and reptiles. Among terrestrial molluscs the rates of endemism are in general higher than for plants and vertebrates, from ca 50% on Bioko to ca 80% on the oceanic islands. In contrast and as might be expected, only Bioko supports a rich freshwater fish fauna and it contains many endemic taxa, whereas the oceanic islands support only a few salt-tolerant species. The Gulf of Guinea islands are also important for their marine organisms, amongst which coral reef fish and marginellid molluscs show high levels of endemism, though they are not especially species-rich. The Gulf of Guinea islands are of great interest to conservationists and evolutionary biologists. Each island, of greatly differing size and degree of isolation, has acquired its unique sub-set of plants and animals separately from the neighbouring mainland, followed by adaptive radiations in situ. For this reason the conservation value of the archipelago as a whole is greater than the sum of the biodiversity contained in its individual islands. Conservation initiatives in the Gulf of Guinea should therefore ensure that representative terrestrial, freshwater and marine habitats and groups of organisms are targeted in a co-ordinated manner among the islands.     

Genetics of insular populations of mammals, with particular reference to differentiation and founder effects in British small mammals

Island populations are of interest for their differentiation as well as their species diversity; some of the earliest biological interest in islands was concerned with the number of 'endemics' thereon. There is dispute about the long-term evolutionary importance of island forms, but they are rich sources of data for studying the under-exploited interface of genetics, ecology and physiology. Differentiation of island populations may arise from genetic change after isolation, or from the chance collection of alleles carried by the colonizing group itself. The general reduction of genetic variance in island populations compared to continental forms of the same species suggests that founder events have played a major role in the formation of most island forms. However, there is ample evidence of adaptation in island populations despite this lower variation; this is relevant when using island biology as a base for the deriving of rules for genetic conservation.     

Dispersal is fundamental to biogeography and the evolution of biodiversity on oceanic islands

Vicariance biogeography emerged several decades ago from the fusion of cladistics and plate tectonics, and quickly came to dominate historical biogeography. The field has since been largely constrained by the notion that only processes of vicariance and not dispersal offer testable patterns and refutable hypotheses, dispersal being a random process essentially adding only noise to a vicariant system. A consequence of this thinking seems to have been a focus on the biogeography of continents and continental islands, considering the biogeography of oceanic islands less worthy of scientific attention because, being dependent on stochastic dispersal, it was uninteresting. However, the importance of dispersal is increasingly being recognized, and here we stress its fundamental role in the generation of biodiversity on oceanic islands that have been created in situ , never connected to larger land masses. Historical dispersal patterns resulting in modern distributions, once considered unknowable, are now being revealed in many plant and animal taxa, in large part through the analysis of polymorphic molecular markers. We emphasize the profound evolutionary insights that oceanic island biodiversity has provided, and the fact that, although small in area, oceanic islands harbour disproportionately high biodiversity and numbers of endemic taxa. We further stress the importance of continuing research on mechanisms generating oceanic island biodiversity, especially detection of general, non-random patterns of dispersal, and hence the need to acknowledge oceanic dispersal as significant and worthy of research.     

Genetic differentiation among populations of an oceanic island: The case of Metrosideros boninensis, an endangered endemic tree species in the Bonin Islands

Conservation of endemic species on oceanic islands is an essential issue for biodiversity conservation. Metrosideros boninensis (Myrtaceae) is an endangered tree species endemic to the Bonin Islands of the western North Pacific Ocean. This species is considered to be extremely rare with less than 400 adult individuals, a number that has fluctuated between the 1880s and 1980s through human influence. We analyzed the genetic diversity and genetic structure of this species using amplified fragment length polymorphism markers and microsatellite markers. Genetic diversity of M. boninensis was extremely low compared to related taxa and similar endemic species from small islands. This low genetic diversity might be attributed to a stepwise colonization process with repeated founder bottlenecks in the dispersal pathway to the Bonin Islands. Populations of M. boninensis showed significant genetic differentiation and isolation by distance over a small geographical scale, despite the fact that this species should have extensive gene dispersal ability. This genetic differentiation might be caused by limited gene flow via pollen and seed among populations and genetic drift amid a small number of remnant individuals. Taken together, these findings suggest that the genetic diversity and connectivity of tree populations on islands are more vulnerable to habitat fragmentation than previously thought. We offer some recommendations for management to ameliorate habitat fragmentation and biological invasion.