Latitudinal effects on treehopper species richness (Hornoptera: Membracidae)

Abstract. 1. Membracid species richness declines with increasing latitude in the Western hemisphere but begins to increase again in temperate regions. In northern latitudes this transition occurs in the highlands of Mexico and is the result of the emergence of a new tribe and greater host specialization.
2. The relationship between number of species per genus and latitude is parabolic.
3. We suggest the low number of species per genus in tropical regions may be due to the lack of host specialization and reduced coordination of life history with host phenology.     

次生林不同类型森林边缘的鸟类物种丰富度及个体多度比较

边缘效应对动物的分布及行为会产生一定的影响,在鸟类生态学研究中已证实某些鸟类在森林内部和森林边缘区域存在着物种丰富度和个体多度的差异。于1999至2001年的春夏季,在吉林省左家自然保护区对阔叶林/农田边缘、阔叶林/灌丛边缘及阔叶林/针叶林边缘3种不同类型边缘地带的鸟类物种丰富度及个体多度进行了比较研究。结果表明,不同年间鸟类物种丰富度无显著变化,但个体多度存在着一定的波动。不同类型森林边缘的鸟类物种丰富度存在着一定的差异,阔叶林/灌丛边缘的鸟类物种丰富度最高,而阔叶林/针叶林边缘的鸟类物种丰富度最低。鸟类个体多度的总体趋势在3种不同类型的边缘差异不显著,但存在种间差异,灰椋鸟、灰头啄木鸟和喜鹊在阔叶林/农田边缘的个体多度最高,斑啄木鸟、黄胸、三道眉草和日本树莺在阔叶林/灌丛边缘的个体多度最高,而沼泽山雀、冕柳莺和山在阔叶林/针叶林边缘的个体多度最高。     

不同更新方式对林地植物群落特种多样性的影响

本文就人工林经营中的三种更新方式对植物群落中物种多样性的影响进行研究。结果表明,1200m^2样地物种丰富度为：天然更新159种,人促更新130种,人工造林94种;多样性指数（Dsh）分别为4.3004、3.9283、3.5048;多样性均匀度指数(Jsh)分别为0.8484、0.8070、0.7714。人工造林的营林干扰是物种丧失和林分物种多样性下降的主要原因。     

The effect of the taxon and geographic range size of host eucalypt species on the species richness of gall-forming insects

Abstract This field study was designed to test whether the taxonomic group and geographic range size of a host plant species, usually found to influence insect species richness in other parts of the world, affected the number of gall species on Australian eucalypts. We assessed the local and regional species richness of gall-forming insects on five pairs of closely related eucalypt species. One pair belonged to the subgenus Corymbia, one to Monocalyptus, and three to different sections of Symphyomyrtus. Each eucalypt pair comprised a large and a small geographic range species. Species pairs were from coastal or inland regions of eastern Australia. The total number of gall species on eucalypt species with large geographic ranges was greater than on eucalypt species with small ranges, but only after the strong effect of eucalypt taxonomic grouping was taken into account. There was no relationship between the geographic range size of eucalypt species and the size of local assemblages of gall species, but the variation in insect species composition between local sites was higher on eucalypt species with large ranges than on those with small ranges. Thus the effect of host plant range size on insect species richness was due to greater differentiation between more widespread locations, rather than to greater local species richness. This study confirms the role of the geographic range size of a host plant in the determination of insect species richness and provides evidence for the importance of the taxon of a host plant.     

Bottom-up effects of host-plant species diversity and top-down effects of ants interactively increase plant performance

While plant diversity is well known to increase primary productivity, whether these bottom-up effects are enhanced by reciprocal top-down effects from the third trophic level is unknown. We studied whether pine tree species diversity, aphid-tending ants and their interaction determined plant performance and arthropod community structure. Plant diversity had a positive effect on aphids, but only in the presence of mutualistic ants, leading to a threefold greater number of both groups in the tri-specific cultures than in monocultures. Plant diversity increased ant abundance not only by increasing aphid number, but also by increasing ant recruitment per aphid. The positive effect of diversity on ants in turn cascaded down to increase plant performance; diversity increased plant growth (but not biomass), and this effect was stronger in the presence of ants. Consequently, bottom-up effects of diversity within the same genus and guild of plants, and top-down effects from the third trophic level (predatory ants), interactively increased plant performance.     

大明山云贵山茉莉群落物种多度分布的Weibull模型

物种多度分布的分析对于了解群落物种多样性具有重要意义。Weibull模型是拟合物种多度分布的重要模型之一。在采用倍程对物种多度分组的基础上,用Weibull模型分别拟合广西大明山保护区云贵山茉莉群落乔木层、灌木层以及乔木+灌木物种的多度分布,结果三者均符合Weibull分布。由此表明所提出的方法应用于物种多度分布研究是理想的,从而完善了Weibull模型在物种多度分布上的应用。     

Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plants

SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 μm (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants.     

Polychaete community structure of the northwestern coast of Mexico: patterns of abundance and distribution

In August 1998, 72 benthic stations were sampled off the northwestern coast of Mexico. A baseline survey of the polychaete macrofauna was carried out for the southernmost portion of the Southern California Bight (SCB) region. Spatial patterns of polychaete assemblages were characterized to determine evidence of environmental impact from point sources of wastewater discharge near the study area, and to define a standard against which to detect future change. A total of 4231 polychaetous annelids representing 38 families and 210 species were identified, which constituted 53% of the total macrofauna. Families with highest species richness were Spionidae (18 spp.), Onuphidae (15 spp.), and Terebellidae (14 spp.). Species with greatest abundances were Spiophanes duplex (490 ind.), Spiophanes fimbriata (330 ind.), Lanassa sp. D (209 ind.), Pectinaria californiensis (138 ind.), and Euclymeninae sp. A (124 ind.). Based on polychaete assemblages, communities for the southernmost SCB were found to be composed primarily of non-opportunistic species, and no numerically dominant species were found. High values of polychaete diversity (H) indicated the majority of the area of study could be considered an undisturbed environment. Principal Components Analysis (PCA) applied to environmental and faunistic parameters indicated depth, organic carbon, and sediment grain size as the main influences determining the polychaete faunal communities.     

The distribution of aphids in response to variation among individual host plants: Uroleucon rudbeckiae (Homoptera: Aphididae) andRudbeckia laciniata (Asteraceae)

Abstract. 1. An investigation was conducted to determine the effects of variation among individual plants of Rudbeckia laciniata L. on the distribution and abundance of the aphid Uroleucon rudbeckiae (Fitch).
2. Wild plants were examined repeatedly for up to 2¹/₂ years to obtain information about plant growth and flowering, and about aphid densities on individual plants.
3. Aphid densities on individual plants were positively associated with several measures of plant vigour, including height, growth since previous year, and occurrence of flowers.
4. The colonization of plants by alate aphids was more highly correlated with plant height than with plant exposure. Aphid densities on individual plants were more strongly associated with plant height than with number of colonists.
5. In all years there were many hosts which were never colonized by aphids. Some of these plants produced shoots but did not flower. Experimental infestation of these plants showed that they were unsuitable for aphid growth and reproduction. Some plants which did flower and which escaped aphid infestation were nevertheless suitable hosts. Previously unsuitable host individuals were able to support aphids when grown under glass-house conditions.     

Vertical distribution and seasonal numerical abundance of the Calanidae in oceanic waters to the south-west of the British Isles

The vertical distribution and seasonal abundance of the copepodite and adult stages of Calanus finmarchicus, C. helgolandicus, C. tenuicornis, Neocalanus gracilis, Nannocalanus minor and Calanoides carinatus from a series of Longhurst Hardy Plankton Recorder hauls taken in the oceanic waters, off the continental shelf, to the south-west of the British Isles are described. The sampling area was selected because the geographical distributions of the major Calanidae copepods of the north-east Atlantic Ocean are shown to overlap in this region. It marks the southern boundary of the distribution of C. finmarchicus, the central area of C. helgolandicus and the approximate northern limit of distribution of C. tenuicornis, N. gracilis, N. minor and C. carinatus. These four southern species occasionally penetrate further north (60° N) in the open ocean but do not breed at these northern latitudes. In autumn and winter, when C. finmarchicus and C. helgolandicus were overwintering below 400 m primarily as Stage V copepodites, N. gracilis occurred in the upper 200 m of the water column in a breeding condition; all copepodite stages were present. This copepod reproduced throughout the year in this regions while C. tenuicornis was observed to breed primarily in spring and summer. The geographical and vertical distributions of the Calanidae are related to the observed seasonal temperatures of the North Atlantic and the breeding strategies of species are compared.     

Effects of plant species richness on invasion dynamics, disease outbreaks, insect abundances and diversity

Declining biodiversity represents one of the most dramatic and irreversible aspects of anthropogenic global change, yet the ecological implications of this change are poorly understood. Recent studies have shown that biodiversity loss of basal species, such as autotrophs or plants, affects fundamental ecosystem processes such as nutrient dynamics and autotrophic production. Ecological theory predicts that changes induced by the loss of biodiversity at the base of an ecosystem should impact the entire system. Here we show that experimental reductions in grassland plant richness increase ecosystem vulnerability to invasions by plant species, enhance the spread of plant fungal diseases, and alter the richness and structure of insect communities. These results suggest that the loss of basal species may have profound effects on the integrity and functioning of ecosystems.     

Nematode species abundance patterns and their use in the detection of environmental perturbations

If the concepts of biological indices and biomonitoring at the multi-species level are to prove viable, then meiofauna and marine nematodes in particular should be an ideal group with which to test the hypothesis. Many attempts to assess the structure of species assemblages, such as the use of diversity indices, nematode: copepod ratios and the graphical method of log normal plots, have been shown to be theoretically unsound and/or impractical, especially for routine use by extension workers. A method of assessing shifts in dominance patterns which involves all the proportional species abundances is suggested as a better means of comparing diversity. A modified method of rapidly assessing Simpson's dominance-weighted diversity index is also advocated as being of practical use. In combination, they should enable the diversity aspect of the multi-species approach to biomonitoring to be rigorously and exhaustively evaluated.     

云南高黎贡山北段植物物种多样性的垂直分布格局

在高黎贡山北段沿海拔梯度设置17个样地,采用数量分类,对高黎贡山北段植物群落类型、物种组成和多样性的垂直格局进行了研究.结果表明:(1)随着海拔的升高,森林群落类型由常绿阔叶林(2 000～2 300 m)依次过渡为以阔叶树为主的针阔混交林(2 300～2 600 m)、以针叶树为主的针阔混交林(2 600～3 000 m)和针叶林(3 000～3 100 m);(2)木本植物的物种丰富度随着海拔高度的增加显著下降,而草本植物的物种丰富度则随着海拔高度的增加先下降,然后在林线以上显著上升;(3)木本植物β多样性随着海拔的上升呈单调下降趋势,而草本植物β多样性在中海拔附近区域较低;(4)在植物区系方面,热带亚热带成分所占比例随海拔上升而下降,温带成分、世界分布成分则随着海拔的升高而增加.中国特有分布成分所占比重较小,主要分布在中海拔区域.总体上,温带成分占主导地位.区系平衡点在海拔2100～2200 m.     

The influence of agricultural land-use intensity on bryophyte species richness

This study is a quantitative approach to the estimation of bryophyte species richness in relation to land-use intensity at three spatial scales in highly cultivated areas. A total of 460 randomly selected habitats and their various substrates within 29 study sites were investigated with regard to their land-use intensity and their bryophyte species richness in an agricultural region of eastern Austria. On bare soils (substrate-scale), low but regular disturbance increases bryophyte diversity in comparison to lower land-use intensity. However, more frequent disturbance (e.g. ploughing more than two times a year) dramatically reduces species richness at these sites, with more than 50% of these sites showing no bryophytes. The production of reproductive units (sporophytes and vegetative units) is highest at an intermediate disturbance regime. On the habitat, as well as on the landscape-scale, there is a significant increase in total bryophyte species number as well as in the number of threatened species with decreasing land-use intensity. This is mainly due to habitat and structural diversity, which increases with decreasing land-use intensity. There are significant correlations between landuse intensity, structural diversity and species richness at the habitat as well as on the landscape scale.     

Floral preferences of hoverflies (Diptera: Syrphidae) in response to the abundance and species richness of flowering plants

For understanding the relationship between floral resources and the abundance of hoverflies, five meadows were selected at different elevations in a forested region. At each site the number of flowering herbaceous plants was assessed along a transect at 10-m intervals. To measure floral density, we counted the number of open flowers per species in each plot. Hoverflies visiting flowering plants were captured in each plot during 10 minutes. Path analysis showed that there was a negative correlation between plant species richness and syrphid abundance. Flower abundance had a strong positive direct effect on syrphid abundance but had indirect effects on the number of syrphid species. Only altitude had a strong positive direct effect on the number of syrphid species and this may be explained by the different climatic conditions. Some plant species attracted more syrphids than others. There were significantly fewer species of hoverfly per plot with increasing numbers of flowers. We interpret this to mean that plant species with a high density of flowers attracted more syrphids of the same species. Analysis of pollen grains extracted from two species of hoverflies showed that flower constancy occurred in three examined sites.     

北部湾海域浮游介形类物种组成、丰度分布及多样性

根据1998年1月～1999年5月北部湾海域4个航次生态环境综合调查资料,对北部湾海域浮游介形类进行分析研究。结果表明,北部湾渔场浮游介形类物种组成较为简单,记录有小型海萤（Cypridina nana）、齿形海萤（Cypridina dentata）、尖尾海萤（Cypridina acuminata）、纳米海萤（Cypridina nami）、针刺真浮萤（Euconchoecia aculeata）、细长真浮萤（Euconchoecia elongata）、后圆真浮萤（Euconchoecia maimai）等18种;隶属于2亚目、2科、4亚科、12属,其中有4种周年出现,9种只在特定的单一季节出现,其余5种季节性出现;夏季和冬季出现的物种数最多,达到11种;春季次之,为9种;秋季最少,只有6种。北部湾浮游介形类可以划分为3个生态类群,即低盐暖水类群、广温广盐类群和高温高盐类群,优势种群主要是近岸低盐暖水类群的针刺真浮萤和尖尾海萤。全海域栖息密度变化范围为0．02～51．58ind．／m^3,年平均1．22ind．／m^3,春季最高,达2．73ind．／m^3,在湾西北部密集有大量的针刺真浮萤;夏季此密集区逐渐向湾中部移动,纳米海萤为其密集种,栖息密度也有所降低;秋、冬季量少,但在湾南、北部各出现一个丰度相对较高的密集区,并由南北向湾中部递减。总生物量具有明显的季节性变化,平面分布趋势与栖息密度相似。生物多样性指数低,以湾口较高、湾顶较低,呈湾口向湾内西北方向递减趋势;全海域年平均多样性阈值为0．329,四季多样性水平皆为Ⅰ级,多样性程度低;多样性程度较高的区域,多出现于受外海水影响较大、水文状况变化较为复杂的海域。对浮游介形类的物种组成、丰度分布及多样性与北部湾的水系、水团、水温及盐度等环境因子的关系进行了探讨。