黄花蔺的繁育系统研究

黄花蔺Limnocharis flava(Linn．)Buch．的蝎尾状聚伞花序上通常产生两性花2∽13朵,单花花期5～13h。自然居群中观察到,花开放后有两种甲虫访花,但外围数轮无花药的退化雄蕊限制了花粉向外散布,内轮雄蕊上花药开裂后花粉直接落在自花的柱头上。花被片闭合后内轮花被片萎蔫成液体,促进了花粉在柱头上萌发。花粉与胚珠的比值为930±180(650∽1120),属于较经济的自花传粉类型。果实成熟后花序倒伏,其顶端产生的营养芽萌发形成新的营养苗。一个基株一年内可产生6∽20个营养苗。黄花蔺自花传粉结实率达80％,每果实产生种子470～640枚。黄花蔺近距离扩散以营养繁殖形成的新植株完成,长距离扩散或占领新生境以及抵抗干旱则依靠种子。人工去雄、套袋及授粉实验表明,黄花蔺的繁育系统是以自交为主的混合交配类型,并可能是由异交向自交演化的。     

江西野生寒兰居群遗传结构与遗传多样性研究

该研究采用叶绿体基因组片段(petB-petD)和核基因组ITS序列,对分布于江西的寒兰17个自然居群的252个体进行遗传结构与遗传多样性分析,以明确江西野生寒兰遗传多样性水平与居群遗传结构特征,为探寻江西寒兰资源数量锐减以及保护提供理论依据。结果表明:(1)nrDNA ITS序列长度652～658 bp,总变异位点140处,变异位点百分率为21.3%～21.5%,(G+C)含量为58.9%～67.1%。cpDNA序列长度522～529 bp,有变异位点9处,变异位点百分率为1.70%～1.72%,(G+C)含量为32.9%～33.7%。(2)分子方差分析(AMOVA)表明,种群内的遗传变异大于种群间变异,cpDNA片段居群间的遗传变异为40.76%,居群内为59.24%;ITS居群间的遗传变异为28.96%,居群内为71.04%;基因流(N_m)较大,cpDNA片段N_m为1.226 5; ITS N_m为0.726 7。(3)ITS和cpDNA数据失配分析和中性检验均表明江西寒兰野生居群在历史近期经历了扩张事件,nrDNA ITS序列较叶绿体序列进化较快,变异速率也较快。     

用RAPD检测华山新麦草自然居群的遗传结构和居群分化

华山新麦草特产于我国陕西华山,为国家一级重点保护植物。应用RAPD技术,用2 0条随机引物对黄埔峪、仙峪、华山峪3个居群不同海拔的13个亚居群共2 6 6个华山新麦草取样个体进行扩增,共得12 2个扩增片段。平均每个引物得到的扩增片段数为6 .1(2～10 )。实验数据的统计分析表明:黄埔峪居群的多态性位点比率为6 0 .6 6 % ,仙峪居群的多态性位点比率为90 .98% ,华山峪居群的多态性位点比率为95 .0 8% ,总的多态性位点比率为95 .0 8% ,说明华山新麦草具有较高的遗传变异性。Shannon多样性指数(0 .330 6 )和基因分化系数(GST=0 .32 6 3)揭示了华山新麦草居群遗传变异多存在于亚居群内。华山新麦草亚居群间的基因流N m=1.0 32 2 ,低于一般风媒传粉植物(N m=5 .2 4 )的基因流水平。亚居群间平均的遗传距离为0 .15 71(变化范围:0 .0 0 2 2～0 .2 90 1) ,最大的遗传距离值出现在黄埔峪亚居群(hp1)和华山峪高海拔亚居群(h8)之间,仙峪亚居群与华山峪高海拔亚居群之间以及华山峪高海拔亚居群与低海拔亚居群之间的遗传距离值也较大。遗传距离与海拔垂直距离之间的相关性分析表明二者有显著的相关性(p<0 .0 1)。聚类分析和主成分分析也显示华山新麦草自然居群已发生明显分化,主要表现为黄埔峪居群、仙峪居群与华山峪居群     

我国盾叶薯蓣居群遗传结构分析

利用随机扩增多态DNA(RAPD)标记,分析研究了中国11个盾叶薯蓣居群82个个体的遗传多样性与遗传结构,15个寡聚核苷酸引物扩增共得到108条带,其中96条为多态带,占88．89％。Shannon多样性指数(I)为0．3093,居群水平的变异从0．1564到0．3098,物种水平的Nei基因多样度(h)为0．2499,居群水平的变化范围为0．1607到0．2137。遗传变异分析表明,物种水平的基因分化系数Gst为0．3415,居群间的基因流Nm为0．9641,居群间遗传交换小。分子方差分析(AMOVA)表明,居群内变异为68．96％,地区间变异为19．45％,居群问变异为11．58％。聚类结果以长江为界,将盾叶薯蓣分为南北两个大类群。研究结果对盾叶薯蓣种质的迁地保护有重要意义。     

板栗和锥栗同域居群的空间遗传结构

采用微卫星技术研究了板栗(Castanea mollissima)和锥栗(C. henryi)同域分布居群的空间遗传结构, 探讨了它们的遗传变异空间分布特征及其形成机制。结果表明,采用的7个微卫星在两物种中共扩增出173个等位基因,两物种都具有较高的遗传多样性且种间遗传分化水平较低(F_ST=0.051), 但空间自相关分析揭示板栗和锥栗在同域居群中具有不同的空间遗传结构,锥栗在100 m内有空间遗传结构,而板栗没有;同时,基于亲缘关系系数F_ij的Sp统计值也显示锥栗具有比板栗更强的空间遗传结构(板栗的Sp=0.002;锥栗的Sp=0.018)。居群遗传变异的空间结构是其传粉和种子散播及生境共同作用的结果,其中种子的近距离散播和居群密度可能是主要的因素。板栗和锥栗居群在小尺度上空间遗传结构的差异可能反映了它们种子的大小及扩散过程的差异。     

鹅掌楸居群遗传结构及其保护对策

鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎ ｃｈｉｎｅｎｓｅ（Ｈｅｍｓｌ．）Ｓａｒｇ．）１０个位点上的等位基因电泳结果表明：鹅掌楸种内遗传多样性水平较高,种内遗传变异的２０．６％分布在居群间,７９．４％分布在居群内,东部分布亚区的多样性水平和基因流低于西部,居群间分公程度则高于西部;其遗传我样性随纬度增加而递减,形成南高北低格局。针对我掌楸居群遗传结构的形成原因及现状提出了适宜的保护措施。     

岷江柏野生居群和迁地保护居群的遗传多样性比较

通过分析岷江柏的迁地保护居群和野生居群的遗传多样性、遗传结构及居群间基因流,判断迁地保 护岷江柏居群的遗传多样性水平,为其迁地保护提供理论基础。本研究利用GBS（Genotyping-by-Sequencing） 测序技术获得的SNP位点对四川大渡河双江口岷江柏迁地保护移栽苗、苗圃播种苗及3个野生居群进行主成分分析（PCA分析）、聚类分析、分子进化树、遗传多样性和遗传结构分析。经过GBS测序共获得高质量Clean Data 118 321 514 728 bp,并开发了1947 047个tags,从中鉴定到了1 259 610个SNP位点。系统发育进化树显示大部分移栽岷江柏居群和野生岷江柏聚在一起,居群结构分析结果显示交叉验证错误率的谷值确定最优分群数为1。4个岷江柏居群的观测杂合度（H_o）、期望杂合度（H_e）、Shannon信息指数I（S_hi）、近交系数（F_is）、多态信息含量（P_ic）的值分别为0.181 5~0.272 0、0.223 2~0.300 3、0.331 0~0.464 9、0.178 0~0.246 5和0.272 2~0.309 2,说明岷江柏居群的遗传多样性水平较高。移栽岷江柏居群的H_e=0.300 3,S_hi=0.464 9,岷江柏居群迁地保护居群遗传多样性总体水平略高于野生居群。野生岷江柏居群中白湾隧道（BW）_vs_松岗镇（SA）的遗传分化指数（F_st）较大,基因流（N_m）较小（F_st=0.091,N_m=2.496）,而迁地保护的岷江柏居群与野生岷江柏居群没有明显的遗传分化,居群间的基因交流频繁（F_st<0.05,基因流N_m>4）,说明没有明显的分群现象,岷江柏居群迁地保护居群遗传多样性较高。因此,移栽濒危植物是迁地保护过程中较好的方法,本文为以后野生岷江柏迁地保护提供参考,为其他树木种质资源的保存提供理论依据。     

植物的繁育系统、遗传结构和遗传多样性保护

达尔文和最早的群体遗传学理论,都认为繁育系统对生物的遗传多样性和进化起重要作用。本文首先介绍用蛋白质电泳检测植物繁育系统的优点,然后讨论中外学者的实验结果,表明在植物众多特征中,如生活型、是有性繁殖还是无性繁殖等都能影响群体遗传结构,但最显著的是繁育系统和群体遗传分化两者间的关系。因此我们能从植物的繁育系统推测群体遗传结构,进而提出监测遗传多样性的取样策略,这对就地保护和移地保护都是十分重要的     

华木莲居群遗传结构与保护单元

华木莲(Sinomanglietia glauca)仅分布于江西宜春和湖南永顺, 是我国一级重点保护植物。前人采用RAPD、ISSR以及叶绿体SSCP(single-stranded conformation polymorphism)标记对华木莲进行了居群遗传学研究, 但未包括后发现的湖南居群或未检出居群内遗传变异。为了全面检测华木莲遗传多样性及其空间分布格局, 并据此确定保护单元, 本研究采用细胞核微卫星标记对华木莲所有4个居群共77个个体进行了居群遗传学分析。结果表明, 华木莲具有较低的遗传多样性(平均等位基因数A = 2.604, 平均期望杂合度H_E = 0.423)和较高的遗传分化(F_ST = 0.425)。STRUCTURE和主成分分析(Principal Coordinated Analysis, PCA)将4个居群首先分为江西、湖南两组, 江西的2个居群实际上是同一个自然繁育居群, 而湖南的2个居群则为2个分化明显的自然繁育居群。研究还发现湖南居群存在明显的杂合子过剩现象, 可能是小居群内随机因素造成的。研究结果表明华木莲可能在近期历史上遭受过强烈的瓶颈效应, 导致种群缩小、遗传多样性丧失和居群分化加剧, 需要加强对其进化潜力的保护。在制定保护措施时, 需要考虑其较高的遗传分化水平, 根据遗传结构可以将其划分为3个保护单元, 即湖南居群和江西居群分别为2个进化显著单元, 湖南居群进一步划分为2个管理单元(分别为朗溪乡云盘村和小溪乡鲁家村居群)。     

SYMMETRY AND DEVELOPMENT OF BUTOMUS UMBELLATUS (BUTOMACEAE) AND LIMNOCHARIS FLAVA (LIMNOCHARITACEAE)

The prostrate rhizome of Butomus umbellatus produces branch primordia of two sorts, inflorescence primordia and nonprecocious vegetative lateral buds. The inflorescence primordia form precociously by the bifurcation of the apical meristem of the rhizome, whereas the non-precocious vegetative buds are formed away from the apical meristem. The rhizome normally produces a branch in the axial of each foliage leaf. However, it is unclear whether the rhizome is a monopodial or a sympodial structure. Lateral buds are produced on the inflorescence of B. umbellatus either by the bifurcation or trifurcation of apical meristems. The inflorescence consists of monochasial units as well as units of greater complexity, and certain of the flower buds lack subtending bracts. The upright vegetative axis of Limnocharis flava has sympodial growth and produces evicted branch primordia solely by meristematic bifurcation. Only certain leaves of the axis are associated with evicted branch primordia and each such primordium gives rise to an inflorescence. The flowers of L. flava are borne in a cincinnus and, although the inflorescence is simpler than that of Butomus umbellatus, the two inflorescences appear to conform to a fundamental body plan. The ultimate bud on the inflorescence of Limnocharis flava always forms a vegetative shoot, and the inflorescence may also produce supernumerary vegetative buds. Butomus umbellatus and Limnocharis flava exhibit a high degree of mirror image symmetry.     

锡金小家鼠种群年龄结构和繁殖研究

锡金小家鼠(Mus pahari)为东南亚及南亚的热带和亚热带山地常见农田害鼠,在我国主要分布于西藏、四川、广西和贵州等省区。本文是我们在黔西北地区对锡金小家鼠种群年龄结构和繁殖情况的调查结果。     

COMPARATIVE POPULATION GENETIC STRUCTURE OF A PARASITE (FASCIOLOIDES MAGNA) AND ITS DEFINITIVE HOST

The population genetic structure of the American liver fluke, Fascioloides magna, and its definitive host the white-tailed deer, Odocoileus virginianus, was examined in South Carolina. Flukes were significantly more common in deer from river-swamp habitat than upland areas and prevalence increased with host age. The distribution of flukes among deer occurred as a negative binomial with the mean dispersion parameter, k, equal to 0.17 and the range from 0.10 to 1.11 within local areas. Significant spatial genetic differentiation was observed for flukes and deer. Patterns of genetic distance in flukes were not concordant with those of the definitive host nor were they related to geographic distance between sample locations. Spatial genetic differentiation among flukes reflected the tendency for individual hosts to harbor multiple individuals from a limited number of parasite clones. The large population size of the parasite and movements of the definitive host tend to counteract factors that lead to spatial differentiation.     

Studies on the breeding system of Limnocharis flava (Butomaceae)

Limnocharis flava ( Linn. ) Buch. normally produced 2 ～ 13 bisexual flowers in a cincinnus (seorpioid cyme). The anthesis of each flower lasted 5 ～ 13 hours. In natural populations, two species of beetles were observed visiting the flowers in bloom. Several whorls of staminodes outside of the stamens limited the pollen to disperse outward, and made the pollen deposit only on the stigma of the same flower. After the perianth closed, the inner perianth changed into liquid which created a suitable environment for pollen germination. The pollen-ovule ratio, which ranged from 650 to 1120( 930±180) reflects an economical self-pollination system. As the fruits maturied, the inflorescence fell to ground or mud, and the vegetative buds (i.e. vegetative components ), developed at the apex of the inflorescence, grew into new vegetative shoots. One mother plant usually could produce 6 ～ 20 new vegetative shoots in a life cycle. One fruit of L. flava contained 470 ～ 640 seeds, with an average seed-set rate of about 80%. The seeds of Limnocharis flava could disperse a long distance and occupy new suitable habitats to establish new populations. The vegetative buds, however, predominantly could only spread to nearby places and thus enlarge the size of the population. Results from some artificial treatments, such as emasculating and netting, emasculating and bagging, hand-pollinating, netting, and bagging, indicate that L. flava is selfing in general but also cross-compatible. Based on the above results, it is considered that the breeding system of L. flava is predominantly selfing, but mixed with outcrossing, and the likely evolutionary tendencyis from outcrossing to selfing.     

高山红景天（Rhodiola sachalinensis）遗传变异及其濒危机制的探讨

采用淀粉凝胶电泳手段,等位酶分析技术对分布于黑龙江大海林林业局高山红景天天然分布区内３个亚种群及吉林长白山１个亚种群的９种酶系统１８个位点进行了遗传分析,结果表明种群内存在一定的遗传变异（从态位点百分比为３０．５５％,等位基因平均数为１．３３３）但不是很丰富,主要是该种类狭窄的分布区致使生境单一及人为破坏其本身的生物学特性长期的进化过程中相互适应相互选择的结果。在黑龙江的分布区内各亚种群之间一致度     

GENETIC POPULATION STRUCTURE AND MATING SYSTEM IN CHONDRUS CRISPUS (RHODOPHYTA)1

Chondrus crispus Stackh. has been intensely studied, yet no study to date has elucidated its population structure or mating system despite many populations in which there was a haploid bias and lack of male gametophytes. Therefore, 12 nuclear microsatellite loci were identified in this red alga. Microsatellite markers were developed and tested against a panel of specimens collected from two shore levels at two sites in Brittany, France: Pointe de Primel and Pointe de la Jument, Concarneau. Single locus genetic determinism was verified at eight polymorphic loci, as only one band was observed for haploid genotypes, whereas one or two bands were observed for diploids. These markers enabled the detection of unique genotypes within sampled populations, indicating that very few fronds shared the same multilocus genotype. This finding suggests that asexual reproduction was not the prevailing mode of reproduction. In addition, we explored the hierarchical population structure showing that gene flow is restricted at small spatial scales (<50 m) between upper and lower Chondrus‐range populations within a shore. Sexual reproduction predominated in the populations of C. crispus studied, but probably due to fine‐scale spatial substructuring, inbreeding was also significant. In conclusion, this study reveals that fine‐scale genetic variation is of major importance in C. crispus, suggesting that differences between microhabitats should be essential in understanding evolutionary processes in this species.     

花鼠种群年龄和繁殖的初步研究

1991年3-10月在山西省中条山区猎获花鼠202只。以眼晶体干重为指标划分出4个年龄组,分析了种群年龄组成的季节变化。该鼠每年繁殖1次, 3月下旬-1月中旬怀孕,产仔期在4月中旬-5月中旬,胎仔数5.08±0.16只, 6月上旬幼鼠出现。幼鼠于翌年春季出蛰后参加繁殖。此外,还将晶体干重、齿高指数和臼齿磨损程度3种年龄指标所划分的结果作了比较,也证实体重、体长和尾长不能用于该鼠的年龄鉴定。     

BREEDING STRUCTURE OF A YUCCA FILAMENTOSA (AGAVACEAE) POPULATION

Yucca filamentosa and its species-specific pollinator, the yucca moth, Tegeticula yuccasella (Lepidoptera: Prodoxidae), form a relationship that is often cited as a classic example of a coevolved plant-pollinator mutualism. Observations of the moth's behavior have led to predictions that moth dispersal is relatively limited and that, as a consequence, the self-compatible Y. filamentosa should experience relatively high rates of self-fertilization. In contrast, analyses of its mating system indicated that Y. filamentosa was predominantly outcrossed. To better understand effective breeding patterns in Y. filamentosa populations, 10 polymorphic allozyme loci were investigated to analyze the breeding structure of a natural Y. filamentosa population. Analyses revealed that Y. filamentosa is predominantly outcrossed, has multiply sired fruits, and that each fruit was sired by a different set of pollen donors. The effective number of pollen donors per fruit ranged from 1.56 to 3.13, indicating that some correlated mating exists within fruits. Paternity analyses revealed that pollen moved from 6 m to 293 m (mean = 118 m) within the study population and that a minimum of 10% of the progeny were sired by pollen originating outside of the population. These results are discussed in the context of the yucca–yucca moth mutualism.     

BREEDING SYSTEM AND GENETIC VARIANCE IN THE MONOGAMOUS,SEMI-SOCIAL SHREW,CROCIDURA RUSSULA

The population-genetic consequences of monogamy and male philopatry (a rare breeding system in mammals) were investigated using microsatellite markers in the semisocial and anthropophilic shrew Crocidura russula. A hierarchical sampling design over a 16-km geographical transect revealed a large genetic diversity (h = 0.813) with significant differentiation among subpopulations (F_ST = 5–6%), which suggests an exchange of 4.4 migrants per generation. Demic effective-size estimates were very high, due both to this limited gene inflow and to the inner structure of subpopulations. These were made of 13–20 smaller units (breeding groups), comprising an estimate of four breeding pairs each. Members of the same breeding groups displayed significant coancestries (F_LS = 9–10%), which was essentially due to strong male kinship: syntopic males were on average related at the half-sib level. Female dispersal among breeding groups was not complete (~39%), and insufficient to prevent inbreeding. From our results, the breeding strategy of C. russula seems less efficient than classical mammalian systems (polygyny and male dispersal) in disentangling coancestry from inbreeding, but more so in retaining genetic variance.