Acclimation to changing light conditions of long-term shade-grown beech (Fagus sylvatica L.) seedlings of different geographic origins

 Effects of changing light conditions on the ecophysiological condition behind survival were examined on beech from two different populations. Plants were grown in a greenhouse under simulated understorey and canopy gap light conditions. Upon exposure to high light maximum photosynthesis of shade-acclimated leaves increased followed by a reduction over several days to between high- and low-light control rates. In the reciprocal transfer, the decrease in maximum photosynthesis was rapid during the first 2–3 days and then levelled off to values comparable to low-light controls. Seedlings from Sicily (Madonie) showed generally higher maximum photosynthetic rates than those from Abetone. Leaf conductance varied in the same direction as photosynthesis in high- to low-light seedlings but to a lesser degree. Leaves grown under low light and exposed to high light experienced photoinhibition. The Abetone population was more susceptible to photoinhibitory damage than the seedlings from Sicily. Exposure to high light of shade-acclimated seedlings resulted in intermediate chlorophyll concentrations between levels of the high-light and low-light seedlings. Carotenoid concentration was unaffected by treatments. Seedlings grew more in high light, but had a lower leaf area ratio. Light-limited seedlings showed a shift in carbon allocation to foliage. Leaves formed in the new light regime maintained the same anatomy that had been developed before transfer. Seedlings from Sicily had thicker leaves than those of seedlings from Abetone. Seedlings from Abetone were found to be more susceptible to changing light conditions than seedlings from Sicily. We conclude that small forest gaps may represent a favorable environment for photosynthesis and growth of beech regeneration as a result of the limited ability of seedlings to acclimate to sudden increases in high irradiance and because of the moderate levels of light stress in small gaps. Received: 11 April 1997 / Accepted: 11 December 1997     

海南南湾猕猴种群增长的研究

对海南南湾猕猴１９６５～１９９４年间的种群动态和雌性猴生命表的研究表明,该种群年均增长率为９．７％,１９８７年后种群增长率和繁殖率有所下降,猴群中非成年猴比例已不足５０％。半驯化雌性猴的逐年存活率到１７岁仍达０．５８,通过对存活曲线和寿命期望曲线的分析,南湾雌猴寿命可达３３～３８岁。婴猴死亡率较低、成年猴死亡率较高,存活曲线属Ⅰ形即凸形。研究表明静态生命表编制方法不适于灵长类,在建立标准化存活曲线时应考虑种群综合死亡系数。猕猴通过存活率、繁殖率、群体结构变化等社群调节机制达到种群平衡。对南湾猕猴近年内每年可捕捉利用１００～１５０只左右,１０岁以上的猴应占５０％以上,在不影响种群遗传多样性水平上,可适当多捕一些成年雄猴。     

Isozyme variation and species relationships in the genus Lolium L. (ryegrasses,Graminaceae)

Thirty-two natural populations belonging to the eight species of the genus Lolium (ryegrass) or to Festuca pratensis (meadow fescue) were recorded for allelic frequencies at 13 isozyme loci. Cultivated ryegrass (L. perenne and L. multiflorum), meadow fescue, and the annual L. rigidum, are true outbreeders. The other species are true inbreeders, except for L. canariense, which shows a moderate level of cross fertilisation (20%). Hierarchical clustering from Nei's unbiased distance leads to four groups. The three self-pollinating, weed species, L. temulentum, L. remotum and L. persicum, belong to the first cluster, which is the most differentiated one. The second cluster comprises L. multiflorum, L. subulatum and most populations of L. rigidum. All L. perenne populations belong to the third cluster, as do two of L. rigidum. The average genetic distance within the L. perenne group is very low. Surprisingly, the fourth cluster groups together L. canariense and Festuca pratensis. The data suggest that L. rigidum is the species with the greatest diversity, and could be a common ancestor of the genus. Knowledge of historical processes of domestication could help to calibrate the molecular clock.     

用DNA指纹法研究野生天鹅种群的遗传分化

DNA指纹技术自问世以来,已被广泛地用于法医学上个体识别和亲缘关系的鉴定。此外,人源DNA指纹探针(即多位点型小卫星探针)还被用于动植物等的研究,特别是在研究动物的繁育规律方面成效显著。近一两年来,DNA指纹技术也在分子水平上用来研究种群分化,为物种起源研究开辟了新的途径。本文利用人源多位点型小卫星探针,对分布在英国和美国的四种天鹅(小天鹅、疣鼻天鹅、大天鹅和喇叭天鹅)的种群结构和天鹅小卫星的分化初步进行了研究。用酶HaeIII和探针pSPT19.6分析了分布在英国的疣鼻天鹅种的两个群体(洛锡安群体和阿伯茨伯里群体)的DNA指纹图,结果表明两群体之间的遗传变异性大于群体内的遗传变异性;洛锡安群体内小卫星的变异程度较高。虽然小卫星在基因组中的作用尚不清楚,但某些天鹅小卫星在种间发生了分化,因而同一个种内不同个体的DNA指纹图有一些共同的特征,导致DNA指纹图的物种特异性。DNA指纹分析表明:小天鹅、大天鹅和喇叭天鹅在遗传上比较接近,而疣鼻天鹅与它们在遗传上相距较远,这与原来对天鹅种下分类情况是一致的。就遗传变异程度而言,在英国仕林布里奇的小天鹅为最高,英国卡拉乌尔洛克的大天鹅次之,英国阿伯茨伯里的疣鼻天鹅居第三,美国蒙大拿的喇叭天鹅最低。我们认为,基因迁移和遗传漂变对     

达乌尔黄鼠种群年龄结构的研究

1987—1989年,作者捕获达乌尔黄鼠2487只,用晶体干重法,将其中的1885只划分为5个年龄组,分析不同年龄阶段臼齿的生长、更换、磨损特点以及体重、体长、胴体重及头骨生长的年龄变化。结果表明随着年龄增长,臼齿磨损明显,而体重、体长等5项指标趋于恒定。达乌尔黄鼠种群年龄结构的季节变化非常显著,不同地区间亦有差别,但年间变动较小,种群增长比较稳定。     

中国和印度猕猴(Macaca mulatta)两个种群颅骨的比较

中国云南中南部和印度的猕猴(Macaca mulatta)两个种群的颅骨形态以及等位基因的比较研究结果表明:两者的面宽、颅的形态大小和等位基因频率均存在较大差异。这些差异也分别存在于印度种群(M.m.mulatta)与西藏亚种(M.m.vestita),川西亚种(M.m.lasiotis),泰国种群和越南种群之间。在20个血蛋白等位基因中,仅约8个是各亚种或种群共有的,代表共同的离征或祖征。因此,云南中南部标本既不是印度指名亚种,也不是泰国的siamica亚种,其亚种名应重新厘定。大陆型分布的猕猴区域性种群之间的遗传异质性大于同质性。上述差异可能是随机遗传漂变的产物。     

Evidence from genetic studies among rs2107538 variant in the CCL5 gene and Saudi patients diagnosed with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a chronic and metabolic disorder that affects the adult population. Chemokines are proinflammatory cytokines that play a role in the development of chronic diseases such as obesity, gestational diabetes, and T2DM. The C-C Motif Chemokine Ligand 5 (CCL5) gene plays a role in antiviral immunity, tumor development, obesity, impaired glucose tolerance, and T2DM. This study aimed to investigate the genetic role of the rs2107538 variant in the CCL5 gene in Saudi patients with T2DM. Sixty subjects with T2DM patients and 60 healthy controls participated in this prospective case-control study. Prior to Sanger sequencing, genomic DNA was extracted and amplified with Polymerase chain reaction (PCR), after which the PCR products were purified. The collected data were used to conduct various statistical analyses to determine the relationship between T2DM and control subjects. The findings of the current study revealed a positive association for most parameters between T2DM and control subjects (p < 0.05). The frequency of genotypes (p = 0.002, AA vs.GG: p = 0.008, GA + AA vs. GG: p = 0.0002) and alleles (A vs. G: p = 0.0007) revealed a strong risk association. Multiple logistic regression with individual effects revealed a link between SBP and HDLc levels (p = 0.03). In patients with T2DM, waist (p = 0.001), TG (p = 0.0007), and LDLc (p = 0.0004) levels were all associated with the ANOVA. Finally, the rs2107538 variant was linked to an increased risk of T2DM in the Saudi Population. The GA and AA genotypes were strongly connected to the T2DM subjects. In order to rule out disease-causing variants in the global population, future research should use a large sample size.     

分布区西缘油松种群的生长特征

 在青海省互助北山林场和贵德东山林场的油松林内分别设置6个和5个样方,对分布区西缘的天然油松种群的生长特征进行了生态学研究。结果表明,两地的油松种群均为复层异龄结构;树高与胸径的关系揭示东山的油松种群其生长能力仅为北山的一半;种群内个体的树高直径比与个体的大小呈负相关,表明个体生长对被压的生态适应;两地个体的直径生长过程也差异很大,即东山油松的直径生长随年龄的增长呈下降趋势,而北山呈上升趋势或变化很小。上述差异导致两地的生产力差异很大：北山可望获得200t／ha的生物量,而东山仅约为100t/ha,但两地的生物量密度差异不大,为7一11t／ha．m,利用生物量密度与总胸高断面积之间的线性关系,可以建立良好的推算种群地上部生物量的方法。本文还对天然油松的种群密度与平均个体重之间的关系作了讨论。     

Population age structure of Pinus banksiana at the southern edge of the Canadian boreal forest

Abstract. To assess the effects of site type, forest initiation periods and fire regimes on the dynamics of Pinus banksiana (Jack pine), the age structure of 69 populations of the species was analyzed. Two landscapes with different fire regimes were selected in the southern part of the Canadian boreal forest in Québec: the ‘mainland landscape’ is characterized by a fire regime of large lethal fires, the ‘island landscape’ is affected by a complex fire regime including lethal and non-lethal fires. Age structure was compared between forest initiation periods and site types (mesic mainland, xeric mainland and xeric island) using the Shannon regularity index. An even-aged population structure was found within the first 100 yr following a lethal fire, while after that period the population structure becomes more uneven-aged. Under mesic conditions, populations tend to have an even-aged structure, under xeric conditions an uneven-aged structure. Natural openings present in xeric sites allow for recruitment in the absence of fire. This permits the self-maintenance of Pinus banksiana. Xeric island populations show more uneven-aged structures than xeric mainland populations. The occurrence of non-lethal fires on the islands creates uneven-aged structures. Further, the results suggest that the selection pressure of the island fire regime, favouring non-serotinous and mixed P. banksiana individuals, is one of the factors responsible for a higher recruitment in the absence of fire on islands than on the mainland.     

RAPD variation within and among natural populations of outcrossing buffalograss [Buchloë dactyloides (Nutt.) Engelm.]

RAPD markers provide a powerful tool for the investigation of genetic variation in natural and domesticated populations. Recent studies of strain/cultivar identification have shown extensive RAPD divergence among, but little variation within, inbred species or cultivars. In contrast, little is known about the pattern and extent of RAPD variation in heterogeneous, outcrossing species. We describe the population genetic variation of RAPD markers in natural, diploid sources of dioecious buffalograss [Buchloë dactyloides (Nutt.) Engelm.]. Buffalograss is native to the semi-arid regions of the Great Plains of North America, where it is important for rangeland forage, soil conservation, and as turfgrass. Most sources of buffalograss germplasm are polyploid; diploid populations are previously known only from semi-arid Central Mexico. This is the first report of diploids from humid Gulf Coastal Texas. These two diploid sources represent divergent adaptive ecotypes. Seven 10-mer primers produced 98 polymorphic banding sites. Based on the presence/ absence of bands, a genetic distance matrix was calculated. The new Analysis of Molecular Variance (AMOVA) technique was used to apportion the variation among individuals within populations, among populations within adaptive regions, and among regions. There was considerable variation within each of the four populations, and every individual was genetically distinct. Even so, genetic divergence was found among local populations. Within-population variation was larger and among-population variation smaller in Mexico than in Texas. The largest observed genetic differences were those between the two regional ecotypes. These patterns of genetic variation were very different from those reported for inbred species and provide important baseline data for cultivar identification and continuing studies of the evolution of polyploid races in this species.