Maintenance and natural regeneration of Castanopsis sclerophylla populations on islands of Qiandao Lake Region, China

Qiandao Lake was formed in 1959 when the Xin'anjiang Hydroelectric Plant was built. There are 1078 islands with areas larger than 2500 m² and many smaller islands. The population structure of C. sclerophylla was investigated to reveal whether it can sustain on islands so as to provide suggestions for ecological restoration. C. sclerophylla can be found on islands with a water level higher than 105.4 m, whereas the highest water level of Qiandao Lake was 108.2 m. Number of individuals on islands, with a range from 4 to more than 4000, was significantly related to the areas or altitudes of the islands. Population structure indicated that, at genet level, C. sclerophylla on large and most medium-size islands could be self-sustainable, whereas on small and some medium-size islands C. sclerophylla could not be self-sustainable and would decline. However, at the ramet level, almost all the C. sclerophylla populations, no matter on large, medium or small islands, seem to be self-sustainable. Further analysis indicated that re-sprouting contributed to more than 81.6% of the genets and 94.8% of the shoots formed after the creation of the Lake. The results above indicated that although small size of populations exist on some islands, these populations might be sustained via vegetative reproduction, especially re-sprouting, for a long period under the present situation without human disturbance and dramatic environmental changes. Conditions of most islands meet the standards necessary for the survival and growth of C. sclerophylla. Therefore, lack of seed or seedling is the main limitation for the ecological restoration of evergreen broad-leaved forests on islands of Qiandao Lake. However, that no individual was reproduced from sexual reproduction on some medium and small islands indicates that environmental condition might be another limiting factor for restoration.     

千岛湖岛屿化对社鼠的肥满度之影响

2008年5月以夹夜法对千岛湖区部分岛屿开展小型兽类种群数量调查,对其间捕获的优势鼠种——社鼠（Niviventer confucianus）进行解剖观察以及相应的测量,计算其肥满度指标K值（K=100W/L³）;同时对岛屿化环境下,社鼠的肥满度与性别、年龄、生境类型、岛屿面积和捕获率等生态因子的关系进行了研究。结果显示：岛屿化对社鼠两性之间的肥满度产生影响,其差异程度由大型岛屿的显著差异（P=0.015）至中小型岛屿的无显著差异（中：P=0.063;小：P=0.288）;年龄组间,除个别相邻年龄组差异显著（大：♂,I与II,P=0.042;中：♀和♂皆为II与III,P=0.013和P=0.044）或极显著（大：♀,III与IV,P=0.000）外,其余均未达到显著水平（P>0.05）。社鼠肥满度年龄组间的变化主要与其自身生理特征变化有关,与岛屿化关系不明显;岛屿的隔离作用,致使不同类型岛屿上的植被优势种及丰富度存在明显差异,从而影响到社鼠的肥满度差异;各岛捕获率所示的社鼠种群的相对数量与其肥满度并无显著相关性（Pearson-test,♀,r=−0.226,P=0.437;♂,r=−0.019,P=0.949）,岛屿化对其种群数量不产生影响;不同面积岛屿之间社鼠的肥满度差异极显著（P=0.000）,且肥满度均值与岛屿面积呈显著正相关（Pearson test,r=0.561,P=0.037）,岛屿面积不同,对社鼠的肥满度之变化产生影响。总之,千岛湖岛屿社鼠的肥满度差异的产生,除了性别、年龄等因素外,与岛屿的面积、生境及种群压力有直接或间接的关系,从侧面也反映了社鼠对岛屿环境的适应性。     

千岛湖岛屿小型兽类群落的多样性

2007 年秋季和2008 年春季,选取千岛湖地区14 个岛屿和2 个半岛作为样地,采用夹夜法进行小型兽类群落组成调查。两季度共布夹20 400 个,捕获小型兽类1 141 只,隶属2 目3 科9 属13 种,啮齿目(Rodentia)鼠科(Muridae)10 种和仓鼠科(Cricetidae)1 种,食虫目(Insectivora)鼩鼱科(Soricidae)2 种。利用以上结果分析其群落多样性,结果显示:14 个岛屿小型兽类群落春、秋两季的多样性指数、均匀度指数和优势度指数均呈现极显著差异且优势种发生变化;对可能影响岛屿小型兽类群落多样性的岛屿面积、距最近陆地距离、距最近大岛距离和植物丰富度等因素进行逐步回归分析,发现只有植物丰富度对小型兽类群落的物种丰富度有显著影响;对16 个样地按照物种组成比进行聚类,许源半岛样地与14 个岛屿聚为一类,姚家半岛样地单独归为一类,相似性指数比较结果亦显示姚家半岛样地与其它样地的相似性指数偏低。结论:景观破碎化导致千岛湖岛屿小型兽类群落的稳定性下降,物种多样性季节变化强烈;随岛屿面积的增加,小型兽类物种丰富度并非总是增加的,而是出现反复,呈现明显的小岛效应;14 个岛屿的物种与许源半岛样地物种构成比接近,推断在水库未形成前属同一生境。     

基于Ecopath模型的千岛湖生态系统结构和功能分析

为探索千岛湖生态系统现状及其历史变化, 根据2016年千岛湖的渔业资源与生态环境调查数据, 构建了千岛湖生态系统的 Ecopath 模型, 综合分析系统的能量流动过程、营养级结构和生态系统总体特征。2016年千岛湖 Ecopath 模型由18个功能组组成, 有效营养级范围为1—3.41, 牧食食物链的能量流动占系统总能量的56%。系统杂食指数(SOI)、联结指数(CI)、Finn循环指数分别为0.13, 0.26和5.15%。千岛湖与其他湖泊和水库比较, 其生态系统的各功能组的聚合度较高, 联结程度较为紧密, 物质再循环比例较高, 系统较为成熟。但千岛湖的系统总流量较低为24698.27 t/(km2·a), 总初级生产量与总呼吸量的比值为6.51, 表明系统总体规模较小且仍处于发展阶段。根据千岛湖生态系统历年变化趋势分析: 千岛湖生态系统的总体规模有变大趋势, 稳定性和复杂性有所增强, 但营养交互关系变弱, 系统抵抗外界干扰的能力仍较低。同时, 千岛湖生态系统的初级生产者转化效率较低, 食物网趋于简单, 应采取适当的管理措施, 以保障千岛湖生态系统的健康发展。     

千岛湖岛屿小型兽类群落分布格局及其影响因素

2007年秋季和2008年春季,采用夹夜法对千岛湖14个岛屿进行小型兽类群落组成调查,研究其群落空间分布格局及其影响因素。两季度共布置夹16 800只,捕获小型兽类1 037只,隶属2目2科7属11种。其中啮齿目（Rodenria）鼠科（Muridae）9种,食虫目（Insectivora）鼩鼱科（Soricdae）2种。结果显示：千岛湖小型兽类群落呈非随机分布格局;嵌套分析表明,千岛湖岛屿小型兽类群落呈现极显著嵌套格局,植物丰富度和生境专属性两项参数对其嵌套格局的形成具有显著影响,从而使适应力强的物种能够在多样的环境中生存,而适应力弱的物种则局限在特定的环境中。由于取样强度差异会过高地估计嵌套程度,故在研究中应尽量去除取样强度的干扰。     

森林砍伐对苦槠种群遗传结构的影响

人类活动严重干扰着自然生态系统,其中砍伐是对森林生态系统最常见的干扰之一,它导致森林退化,植物种群变小,甚至灭绝,遗传多样性也随之下降。当被破坏的森林未被转换性利用时,则会逐渐恢复,但由于瓶颈效应,恢复起来的生态系统中植物种群的遗传结构可能会改变。恢复种群遗传组成的改变一方面与干扰的强度、频度和持续时间有关,另一方面,也受植物生活史特点的深刻影响。然而,我国对于砍伐后恢复起来的森林生态系统中生物多样性的改变,尤其是遗传多样性的改变的研究并不多见。研究在浙江省宁波市天童国家森林公园及周边地区选择了5个苦槠种群,采用SSR微卫星标记来分析砍伐对苦槠种群遗传结构的影响。5对多态SSR引物共得到了29个等位基因。种群内维持了较高的遗传多样性,种群间遗传分化程度较低,基因流达8．68。恢复林和成熟林种群的遗传多样性相差不大,以阿育王寺地区恢复种群的最高;表明砍伐对于苦槠种群遗传多样性的影响不大,这与苦槠较强的萌条能力有关。尽管如此,在恢复种群中观察到近期的种群瓶颈,显示出砍伐对种群遗传组成的影响;而在一个成熟林中也观察到种群瓶颈,这是因片断化导致种群变小之故。植被保存最好的天童国家森林公园内苦槠种群的遗传多样性却较低,这可能与成熟林中苦槠优势度较低有关。     

演替研究在常绿阔叶林抚育和恢复上的应用

以浙江天童国家森林公园常绿阔叶林动态过程为例,比较研究了常绿阔叶林演替系列主要树种白栎（Quercus fabri）、马尾松（Pinus massoniana）、苦槠（Castanopsis sclerophylla）、石栎（Lithocarpus glaber）、木荷（Schima superba）和栲树（C.fargesii）的群落生态学特征、种群生态学特征和生理生态学特性。阐明了常绿阔叶林演替系列间的相互更替过程;探讨了主要优势种群的植株结构及其更新能力的演变规律;揭示了演替系列群落主要优势种相互更替的原因。     

Population dynamics of shrews on small islands accord with the equilibrium model

Three of the six species of shrew in Finland, Sorex araneus, S. caecutiens, and S. minutus , are common on the mainland and widespread on islands in lakes. The islands range from 0.01 to 500 ha in area, and from 10 to 3000 m in isolation (distance from the mainland). The species-area relationship, the lack of importance of habitat diversity, the increasing frequency of unoccupied small islands with isolation, and direct observations of small populations, all suggest that populations on small islands have a high extinction rate. Demographic stochasticity is the main cause of extinctions in the superior competitor, S. araneus , which occurs consistently on islands greater than 2 ha. The small species, S. caecutiens and S. minutus , are more sensitive to environmental stochasticity than is S. araneus , and are inferior to it in interspecific competition; these factors probably contribute to the absence of the small species from many islands tens of hectares in area. Frequent colonization of islands less than 500 m from the mainland is indicated by large numbers of shrews trapped from tiny islets where breeding is not possible, by increasing epigenetic divergence of island populations with isolation, and by observations of dispersal to and colonization of islands. Dispersal ability decreases with decreasing individual size, which may partly explain the absence of the small shrews from many relatively large islands. The shrew populations persist in a dynamic equilibrium on the islands. Epigenetic morphological variation is a useful tool in ecological studies of island populations.     

The roles of geological history and colonization abilities in genetic differentiation between mammalian populations in the Philippine archipelago

Aim To test hypotheses that: (1) late Pleistocene low sea‐level shorelines (rather than current shorelines) define patterns of genetic variation among mammals on oceanic Philippine islands; (2) species‐specific ecological attributes, especially forest fidelity and vagility, determine the extent to which common genetic patterns are exhibited among a set of species; (3) populations show reduced within‐population variation on small, isolated oceanic islands; (4) populations tend to be most highly differentiated on small, isolated islands; and (5) to assess the extent to which patterns of genetic differentiation among multiple species are determined by interactions of ecological traits and geological/geographic conditions. Location The Philippine Islands, a large group of oceanic islands in Southeast (SE) Asia with unusually high levels of endemism among mammals. Methods Starch‐gel electrophoresis of protein allozymes of six species of small fruit bats (Chiroptera, Pteropodidae) and one rodent (Rodentia, Muridae). Results Genetic distances between populations within all species are not correlated with distances between present‐day shorelines, but are positively correlated with distances between shorelines during the last Pleistocene period of low sea level; relatively little intraspecific variation was found within these ‘Pleistocene islands’. Island area and isolation of oceanic populations have only slight effects on standing genetic variation within populations, but populations on some isolated islands have heightened levels of genetic differentiation, and reduced levels of gene flow, relative to other islands. Species associated with disturbed habitat (all of which fly readily across open habitats) show more genetic variation within populations than species associated with primary rain forest (all of which avoid flying out from beneath forest canopy). Species associated with disturbed habitats, which tend to be widely distributed in SE Asia, also show higher rates of gene flow and less differentiation between populations than species associated with rain forest, which tend to be Philippine endemic species. One rain forest bat has levels of gene flow and heterozygosity similar to the forest‐living rodent in our study. Main conclusions The maximum limits of Philippine islands that were reached during Pleistocene periods of low sea level define areas of relative genetic homogeneity, whereas even narrow sea channels between adjacent but permanently isolated oceanic islands are associated with most genetic variation within the species. Moreover, the distance between ‘Pleistocene islands’ is correlated with the extent of genetic distances within species. The structure of genetic variation is strongly influenced by the ecology of the species, predominantly as a result of their varying levels of vagility and ability to tolerate open (non‐forested) habitat. Readily available information on ecology (habitat association and vagility) and geological circumstances (presence or absence of Pleistocene land‐bridges between islands, and distance between oceanic islands during periods of low sea level) are combined to produce a simple predictive model of likely patterns of genetic differentiation (and hence speciation) among these mammals, and probably among other organisms, in oceanic archipelagos.     

蓖齿眼子菜繁殖多样性研究

 繁殖是影响水生植物生存竞争、分布以及群落结构动态变化的关键因素。通过野外观察和室内试验,较详细地介绍了蓖齿眼子菜(Potamogeton pectinatus)的繁殖策略。研究结果表明:蓖齿眼子菜有性繁殖中具有水表和水下气泡两种传粉方式;种子发生量较大,但种子发芽率低,不到6%,种子繁殖对种群恢复贡献不大,其主要作用在于远程传播和保持持久的种子库。蓖齿眼子菜具有广泛而高效的无性繁殖系统,可以通过断株、根状茎、地上块茎、地下块茎、地上茎节以及叶腋基部进行繁殖,其中最重要的是地下块茎和根状茎,次年种群恢复主要来自于地下块茎和根状茎。此外,对采用蓖齿眼子菜进行沉水植被恢复与重建提出了建议。     

千岛湖次生林优势种植物光合生理生态特性

对千岛湖次生林优势种马尾松(Pinus massoniana)、苦槠(Castanopsis sclerophylla)、石栎(Lithocarpus glaber)、青冈(Cyclobalanopsis glauca)在不同季节的光合作用日变化、光响应、CO2响应以及相对叶绿素含量进行了分析,以期了解群落演替的内在机制。结果表明:(1)马尾松的净光合速率(Pn)日变化在4个季节均呈"单峰"曲线;苦槠在8月呈"双峰"曲线,其他3个月份均呈"单峰"曲线;石栎和青冈在5月、8月和11月的Pn日变化均为"双峰"曲线,有明显的光合"午休"现象,2月为"单峰"曲线。(2)马尾松和苦槠的Pn日积累值为8月最高,石栎和青冈为11月最高,且均与其他3个月均差异显著。4种优势种在4个季节的Pn日积累值的平均值大小为马尾松苦槠青冈石栎,差异显著。(3)4个季节中,光饱和点(LSP)、光补偿点(LCP)、最大净光合速率(Amax)、暗呼吸速率(Rd)、最大羧化速率(Vcmax)、最大电子传递速率(Jmax)均以马尾松最高,表观量子效率(AQY)为马尾松最低。青冈在4个季节中具有最低的LSP、Rd和最高的AQY。苦槠和石栎的光合特性介于马尾松和青冈之间。(4)相对叶绿素含量以青冈最高,马尾松最低。总之,马尾松属强阳性树种,苦槠为阳性树种,石栎具有一定的耐荫性,青冈的耐荫性较强。     

Genetic variation in populations of Populus davidiana Dode based on microsatellite marker analysis

Populus davidiana Dode, the only aspen in Korea, is useful for restoration because of its fast growth and vigorous reproduction. This study was conducted to estimate the genetic diversity and subdivision in populations of P. davidiana in South Korea using microsatellite markers. DNA from 113 individuals from five populations was amplified using five microsatellite primers. Fifty-three alleles were detected, and the expected heterozygosity was 0.603. The populations of P. davidiana in Korea have high genetic variation despite their peripheral distribution. R _ST (0.213) indicated a significant level of genetic subdivision among populations compared to the differentiation among other aspen populations. The high conservation value of the populations is attributed to its ecological and commercial importance.     

千岛湖社鼠种群遗传现状及与生境面积的关系

以千岛湖地区13个岛屿上的社鼠(Niviventer confucianus)种群为研究对象,利用13个微卫星位点分析了13个社鼠种群的遗传现状,并探讨了种群遗传现状与岛屿面积大小之间的关系。研究结果显示,13个社鼠种群的平均观测等位基因数(Na)与平均有效等位基因数(Ne)分别为7.385,5.952,平均期望杂合度(He)与平均观测杂合度(Ho)分别为0.819,0.930,平均多态信息含量(PIC)为0.760,说明13个社鼠种群均具有较高的遗传多样性。13个种群间的分化系数(Fst)为0.053,表明种群间的遗传分化较小。3个面积较大且相近岛屿上社鼠种群,即高仙阁种群 (Gaoxiange Island,G);乌石T岛种群 (Wushi T Island,WT);东门岛种群 (Dongmen Island,DM)间的Fst值均小于0.05,表明种群间无分化,而小岛种群与大岛种群间的分化却比较明显。此外,一元回归结果显示,多态信息含量(PIC)和Shannon多样性指数(I)与岛屿面积大小之间均存在显著地正相关关系。以上结果说明,在社鼠种群进化过程中,生境面积的缩小可能使种群的遗传结构发生改变,并有可能导致种群的快速进化。     

Demographic responses of arctic hares Lepus arcticus placed on two predominantly forested islands in Newfoundland

During January-April 1989. we monitored survival, reproduction, and body condition of 19 radio-collared arctic hares Lepus areticus introduced to two predominantly (80%) forested islands. Merchant (66 1 ha) and Burke (82 6 ha), in Placentia Bay, Newfoundland By late April, bone-marrow fat (42 7%) and kidney fat indices were lower than found in populations on the mountain barrens of western Newfoundland However, most island hares gained weight overwinter, and litter sizes (mean. 4 2 in utero) and testis weights (mean, 8 3 g) were as large or larger than recorded from other introduced and natural populations in Newfoundland The distribution of telemetry locations, tracks and feeding sites indicated that hares frequented the scattered barrens (totalling c 30 ha) on both islands in greater proportion than available These results suggest that, in the absence of snowshoe hares and mammalian predators, forested regions interspersed with small patches of barrens can sustain arctic hares     

Enhanced colour polymorphisms in island populations of the land snail Euhadra peliomphala

Variations in visible genetic polymorphisms are assumed to decrease in populations on small islands because of intense founder effects, genetic drift and inbreeding. However, we have found evidence of a marked enhancement of colour polymorphisms within populations on small oceanic islands that were colonized from the mainland. The source populations on the mainland of the land snail Euhadra peliomphala in four oceanic islands were estimated by phylogenetic analysis of mitochondrial DNA sequences. Diversity of shell colour was higher in the island populations than in the source populations on the mainland. In addition, the shell colour morphs differed not only among populations from different islands but also between the island populations and the source populations on the mainland. By contrast, no mtDNA variations were found in any of the island populations, even though the source populations possessed high mtDNA diversity. Thus, components of colour morphs changed in the island populations after their colonization, and colour polymorphisms are enhanced in these islands despite the loss of genetic variation. The above findings suggest that ecological mechanisms such as morphological release owing to a release from competition may overcome the tendency toward reduced genetic variation in islands to enhance the colour polymorphism.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 417–425.     

Genetic and phylogenetic consequences of island biogeography

Abstract.— Island biogeography theory predicts that the number of species on an island should increase with island size and decrease with island distance to the mainland. These predictions are generally well supported in comparative and experimental studies. These ecological, equilibrium predictions arise as a result of colonization and extinction processes. Because colonization and extinction are also important processes in evolution, we develop methods to test evolutionary predictions of island biogeography. We derive a population genetic model of island biogeography that incorporates island colonization, migration of individuals from the mainland, and extinction of island populations. The model provides a means of estimating the rates of migration and extinction from population genetic data. This model predicts that within an island population the distribution of genetic divergences with respect to the mainland source population should be bimodal, with much of the divergence dating to the colonization event. Across islands, this model predicts that populations on large islands should be on average more genetically divergent from mainland source populations than those on small islands. Likewise, populations on distant islands should be more divergent than those on close islands. Published observations of a larger proportion of endemic species on large and distant islands support these predictions.     

Influence of pulsed resources and marine subsidies on insular rodent populations

Inputs of marine resources contribute to high consumer densities on small, barren islands in the arid Gulf of California, Mexico. Episodes of rainfall associated with El Niño Southern Oscillation (ENSO) events, however, stimulate plant growth and seed production and replenish soil detritus and seed banks. We studied the effects of marine inputs and pulsed ENSO resources on rodent populations on islands before, during and after the strong 1997–1998 ENSO event. Stable isotope analysis was used to determine rodent diets. During dry years, P. maniculatus consumed marine prey near shore and on small islands, and were much more abundant in these areas than farther inland and on larger islands. Captures were particularly concentrated near shore on three islands inhabited by Chaetodipus rudinoris, a granivore that was numerous in inland areas. Following the ENSO, Peromyscus maniculatus increased in abundance by 408%, compared to only 160% for C. rudinoris, and new individuals invaded inland areas. P. maniculatus populations declined sharply the following year, however, whereas C. rudinoris populations remained relatively stable. In response to ENSO conditions, P. maniculatus ate more seeds on islands with C. rudinoris than on islands without C. rudinoris. P. maniculatus also increased less markedly and declined more quickly in abundance where C. rudinoris was present. We speculate that P. maniculatus is capable of rapid numerical response to resource pulses but depends on marine foods during dry years. C. rudinoris is restricted to islands with sufficient seed resources, but maintains stable populations by exploiting low‐density seeds and caching seeds from wet years. On islands with both species, C. rudinoris restricts P. maniculatus to near‐shore areas via interference, but spillover consumption of seeds by subsidized P. maniculatus may limit the response of C. rudinoris to ENSO resources. Combined with differences in life history and dispersal abilities, these ecological factors help explain the distinct biogeographic distributions of these rodents on Gulf islands.     

Genetic variation and clonal diversity in island Cephalanthera rubra populations from the Biebrza National Park, Poland

Three populations of the orchid species Cephalanthera rubra localized on neighbouring mineral islands in the Biebrza National Park (north-east Poland) were examined using 16 allozyme loci. The percentage of polymorphic loci in these C. rubra populations ranged from 25 to 31.3% and the mean number of alleles per polymorphic locus from 1.25 to 1.31. The levels of observed heterozygosity at polymorphic loci were higher than expected for all populations. The overabundance of heterozygotes was noted in every population. The values of fixation indices were highly negative. The genetic differentiation among the three populations was small ( F _ST = 0.0173), albeit statistically significant ( P  < 0.001). The level of gene flow varied from 13 to 16. Fourteen multilocus genotypes were found among the 401 ramets sampled from the populations. Only four of them were common for all populations. The frequency of genotypes was different in these three populations of C. rubra . Some of the multilocus genotypes dominated in the given populations, others were found sporadically. Genetic variation within C. rubra populations is mainly the result of small population sizes and reflects the influences of breeding system and type of reproduction. On the other hand, these properties are also connected with habitat conditions.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 99–108.     

武汉东湖圆形盘肠溞种群遗传结构分析

为了评估人工堤坝分隔对武汉东湖浮游动物种群遗传结构的影响,以细胞色素氧化酶亚基Ⅰ（mitochondrial cytochrome coxidase subunit Ⅰ,COⅠ）基因为分子标记,通过PCR扩增和DNA测序技术并结合GenBank数据库中已有的相关序列,对武汉东湖圆形盘肠溞（Chydorus sphaericus）种群遗传多样性进行了分析。结果显示:7个样点采集的圆形盘肠溞并没有分为不同的类群,全局检验和种群间两两差异检验均显示7个圆形盘肠溞类群没有显著的遗传差异。构建的邻接树显示武汉东湖的圆形盘肠溞COⅠ基因聚为一枝,除加拿大育空地区Kookatsoon湖与武汉东湖的部分圆形盘肠溞COⅠ基因聚为一枝外,其他地区的圆形盘肠溞COⅠ基因都分别聚为不同的枝。对圆形盘肠溞COⅠ基因序列两两距离与样点间的地理距离进行相关分析显示,不论是东湖内的小空间尺度还是更大尺度上的圆形盘肠溞COⅠ基因都存在序列相似性随地理距离增加而降低（距离-衰减模式）,说明圆形盘肠溞存在分布限制。研究结果表明武汉东湖50年前修建的人工堤坝并未对武汉东湖圆形盘肠溞的种群遗传结构造成显著影响。       

Habitat loss other than fragmentation per se decreased nuclear and chloroplast genetic diversity in a monoecious tree

Generally, effect of fragmentation per se on biodiversity has not been separated from the effect of habitat loss. In this paper, using nDNA and cpDNA SSRs, we studied genetic diversity of Castanopsis sclerophylla (Lindl. & Paxton) Schotty populations and decoupled the effects of habitat loss and fragmentation per se. We selected seven nuclear and six cpDNA microsatellite loci and genotyped 460 individuals from mainland and island populations, which were located in the impoundment created in 1959. Number of alleles per locus of populations in larger habitats was significantly higher than that in smaller habitats. There was a significant relationship between the number of alleles per locus and habitat size. Based on this relationship, the predicted genetic diversity of an imaginary population of size equaling the total area of the islands was lower than that of the global population on the islands. Re-sampling demonstrated that low genetic diversity of populations in small habitats was caused by unevenness in sample size. Fisher's α index was similar among habitat types. These results indicate that the decreased nuclear and chloroplast genetic diversity of populations in smaller habitats was mainly caused by habitat loss. For nuclear and chloroplast microsatellite loci, values of F(ST) were 0.066 and 0.893, respectively, and the calculated pollen/seed dispersal ratio was 162.2. When separated into pre-and post-fragmentation cohorts, pollen/seed ratios were 121.2 and 189.5, respectively. Our results suggest that habitat loss explains the early decrease in genetic diversity, while fragmentation per se may play a major role in inbreeding and differentiation among fragmented populations and later loss of genetic diversity.