湖北咸丰长穗桑的生境与种群结构初探

初步调查了湖北咸丰长穗桑种群 1 7株个体 ,主要结果表明 :咸丰长穗桑种群个体一般生长在人类频繁的干扰区内 ,遭到人们的大肆砍伐和破坏。其种群结构为倒金字塔形 ,缺乏幼苗和幼树 ,为衰老型种群 ;种群雌雄性比为 1 .83∶ 1 ,种群的生殖力和自我更新降低。必须大力加强对咸丰长穗桑的就地和迁地保护的研究和实施。     

Open ground individuals and population structure in Drosophila subobscura Collin

The distribution of Drosophila subobscura adults within, and their movement through, open ground habitats has been investigated, along with the status of such individuals within populations as a whole. Movement occurs between open ground and woodland, to some extent as a result of passive transport by air currents, but flies can remain in open ground for at least several days at a time. There are no detectable differences in either the reproductive age-structure or the body-size distributions of flies collected from woodland and open ground habitats, although a significantly higher proportion of females are found in open ground than in woodland. The large number of gravid females in open ground provide the potential for breeding there, but circumstantial evidence suggests that this is unlikely to occur. Rather, their presence appears to reflect the foraging strategy adopted by females in response to their high nutritional requirements. The flux of flies through open ground between woodlands suggests that previous estimates of the genetically-important parameter, effective population size, have been seriously underestimated for natural D. subobscura populations.     

太白山巴山冷杉林主要树种与开花秦岭箭竹的空间点格局分析

采用单变量和双变量O-ring函数对太白山大熊猫栖息地巴山冷杉林主要树种的空间分布格局、种间关联性及其与林下开花箭竹的空间关联性进行了多尺度分析.结果表明: 巴山冷杉林中,巴山冷杉数量最多,但种群结构衰退,白桦种群相对年轻,种群结构稳定,红桦种群也呈衰退趋势;3个主要树种在小尺度上呈聚集分布,随尺度增加,逐渐表现为随机分布.3个树种的空间关联性主要表现在小尺度范围内,随尺度增加,空间分布格局逐渐表现为不关联;巴山冷杉和白桦与开花秦岭箭竹在大、中尺度内呈现正相关,而红桦与开花秦岭箭竹在大、中尺度上表现出负相关.大熊猫栖息地内乔木和林下秦岭箭竹共同推动森林的动态演替和发展,进而影响秦岭大熊猫栖息地的环境变化.     

Bathymetric barriers promoting genetic structure in the deepwater demersal fish tusk (Brosme brosme)

Population structuring in the North Atlantic deepwater demersal fish tusk ( Brosme brosme ) was studied with microsatellite DNA analyses. Screening eight samples from across the range of the species for seven loci revealed low but significant genetic heterogeneity ( F _ST = 0.0014). Spatial genetic variability was only weakly related to geographical (Euclidean) distance between study sites or separation of study sites along the path of major ocean currents. Instead, we found a significant effect of habitat, indicated by significant differentiation between relatively closely spaced sites: Rockall, which is surrounded by very deep water (>1000 m), and the Mid-Atlantic Ridge, which is separated from the European slope by a deep ocean basin, were differentiated from relatively homogeneous sites across the Nordic Seas. Limited adult migration across bathymetric barriers in combination with limited intersite exchange of pelagic eggs and larvae due to site-specific circulatory retention or poor survival during drift phases across deep basins may be reducing gene flow. We regard these limitations to gene flow as the most likely mechanisms for the observed population structure in this demersal species. The results underscore the importance of habitat boundaries in marine species.     

Population dynamics of a phytophagous lady-beetle,Epilachna vigintioctopunctata (Fabricius), living in spatio-temporally heterogeneous habitats. III. Effects of habitat structure on population dynamics

Temporal changes in the population size of a phytophagous lady-beetle were analyzed to identify mechanisms affecting lady-beetle population dynamics at different spatial scales. The study area (15 ha) included 18 habitat patches. The major host plants were potato for first generation larvae and eggplant for second generation larvae. The habitat patches were classified into three groups according to the major host plants in each patch: P-E patches (both host plants available), P patches (potato only), and E patches (eggplant only). The winter disappearance of adults in the whole study area, and larval mortality in E patches were apparently the most important factors disturbing the overall population density. Density-dependent movement of females appeared to have the greatest stabilizing effect on the yearly fluctuation of population density. Rate of increase of female adults from the first to the second generation,R, was generally higher on eggplants in E patches than in P-E patches because the adult density of the first generation was much higher in P-E patches. The yearly fluctuation of adult density in each generation tended to be less in patches with all habitat components necessary for the full life cycle (P-E patches). However, such patches were not favorable for first generation females, as indicated by the lower rate of increase from the first to the second generation. The density and stability of lady-beetle populations is discussed in relation to habitat structure.     

浙江古田山自然保护区甜槠种群结构与动态

应用“相邻格子法”对浙江古田山国家自然保护区的甜槠种群进行调查 ,将 2 5个样地分为不同演替阶段和不同生境的森林群落两大类型。对甜槠种群结构和动态进行分析 ,绘制甜槠种群大小结构图和存活曲线 ;并用泊松方差 /均值比率等 5个聚集度指标测定其种群分布格局。结果显示 :马尾松林→马尾松针阔叶混交林→次生常绿阔叶林→成熟山坡常绿阔叶林的演替过程中 ,马尾松林中甜槠个体极少 ,针阔叶混交林中种群结构为增长型 ;次生和成熟常绿阔叶林中其种群结构都比较稳定 ,但从群落外貌和结构仍可看出前者的次生性。不同生境的群落包括成熟沟谷常绿阔叶林、成熟山坡常绿阔叶林、黄山松林和黄山松针阔叶混交林 ,甜槠由沟谷地带的零星个体变为山坡上的稳定型种群 ,中山地带的黄山松林和黄山松针阔叶混交林中甜槠种群呈增长型 ,但不会取代黄山松的优势地位。种群空间格局大都为集群分布 ,并符合负二项式分布 ,仅两个次生群落的甜槠种群因缺 、 、 级幼苗而呈随机分布。此外 ,对成熟常绿阔叶林中不同大小级个体分布格局动态的研究表明 :甜槠在幼苗、幼树时为集群分布 ,随着甜槠个体进一步增大 ,其分布格局由集群分布变为随机分布。甜槠以其较强的更新能力 ,成为本区低海拔成熟常绿阔叶林中十分稳定的优势种     

The HK/LK polymorphism of erythrocyte cation content in two wild species of east African bovids: demonstrated in wildebeest but not in African buffalo

Concentrations of K and Na were determined in erythrocytes from wildebeest and African buffalo resident in Tanzania. The object was to determine if these species possess the HK/LK polymorphism which is typical of other bovid species, but not of other mammals. The polymorphism is characterized by individuals that are either of the HK phenotype (high K and low Na concentrations in red cells) or LK phenotype (low K and high Na concentrations in red cells). Wildebeest were shown to be polymorphic, with the distribution of phenotypes resembling that in domestic cattle. By contrast the polymorphism was not found in the African buffalo; all 59 individuals examined exhibited the HK phenotype. This was unexpected, since the polymorphism has been observed in five divergent bovid species, including two species (water buffalo and domestic cow) that are closely related to the African buffalo, and classified in the same subfamily (Bovinae). The most parsimonious interpretation of this pattern is that the trait was lost from the African buffalo after species in the Bovinae diverged. The biological significance of the HK/LK polymorphism, and reasons for its presence or absence among species in the Bovidae, remain obscure.     

Genetic differentiation of water buffalo (Bubalus bubalis) populations in China, Nepal and south-east Asia: inferences on the region of domestication of the swamp buffalo

Data from three published studies of genetic variation at 18 microsatellite loci in water buffalo populations in China (18 swamp type, two river type), Nepal (one wild, one domestic river, one hybrid) and south-east Asia (eight swamp, three river) were combined so as to gain a broader understanding of genetic relationships among the populations and their demographic history. Mean numbers of alleles and expected heterozygosities were significantly different among populations. Estimates of θ (a measure of population differentiation) were significant among the swamp populations for all loci and among the river populations for most loci. Differentiation among the Chinese swamp populations (which was due primarily to just one population) was much less than among the south-east Asian. The Nepal wild animals, phenotypically swamp type but genetically like river type, are significantly different from all the domestic river populations and presumably represent the ancestral Bubalus arnee (possibly with some river-type introgression). Relationships among the swamp populations (D(A) genetic distances, principal component analysis and structure analyses) show the south-east Asian populations separated into two groups by the Chinese populations. Given these relationships and the patterns of genetic variability, we postulate that the swamp buffalo was domesticated in the region of the far south of China, northern Thailand and Indochina. Following domestication, it spread south through peninsular Malaysia to Sumatra, Java and Sulawesi, and north through China, and then to Taiwan, the Philippines and Borneo.