蜘蛛与蜘蛛、蜘蛛与猎物之间的信息联系机制

作为农林生态系统中首要的捕食性节肢动物的蜘蛛,只有单眼和听毛,并没有复眼和听器。因而在一定的距离之外,蜘蛛要高效、成功寻觅其理想的猎物,仅仅凭视觉、触觉、听觉均无法实现和完成这一功能。因此,蜘蛛的嗅觉即化学通信于蜘蛛种间和种内的信息联系中扮演着举足轻重的角色,现已有大量的研究用行为学的方法证明蜘蛛与猎物之间,蜘蛛与蜘蛛之间能够通过信息化学物质进行信息联系,但蜘蛛的嗅觉即化学信息素的释放与接收机制以及信息素的结构成份等方面的研究甚少,有待进一步深人。对蜘蛛与猎物之间,蜘蛛与蜘蛛之间的信息化学联系机制的研究进展做一综述。     

The Relation Between Unpalatable Species, Nutrients and Plant Species Richness in Swiss Montane Pastures

In agriculturally marginal areas, the control of unpalatable weeds on species rich pastures may become problematic due to agricultural and socio-economic developments. It is unclear how increased dominance of unpalatable species would affect the botanical diversity of these grasslands. We investigated whether there was any relationship between plant species diversity and the abundance of unpalatable species and whether soil conditions affected this relationship. In three species-rich montane pastures in western Switzerland, we related plant species richness to soil attributes, the relative cover of all unpalatable species and the relative cover of the locally dominant, toxic Veratrum album in 25 plots of 4 m². We furthermore determined species richness in small transects through patches of V. album. Species richness was significantly lower in and near (≤ 0.3 m) patches of V. album. At the field scale, plant species richness was best described by total soil N:P ratio (positive relation) in one site and the relative abundance of unpalatable species (negative relation) and soil N:P ratio (positive relation) in a second site. In the third site, species richness was not significantly related to any measured variable. Vegetation diversity (Simpson's D) was negatively related to the relative abundance of unpalatable species in one site and positively related to pH in another site. The results suggest that no single factor can explain plant species richness and diversity in montane pastures. At very high densities unpalatable species can have adverse effects but soil nutrient status appears to be a more general determinant of plant species richness. Conservation efforts should give priority to the prevention of intensification of these pastures.     

小麦幼苗光呼吸与活性氧累积的关系

用Na2 S处理小麦幼苗 ,提高了光呼吸速率 ,减少了O- ·2 的含量 ;用草酸处理 ,降低了光呼吸速率 ,增加了O- ·2 的含量。光呼吸速率的变化与H2 O2 含量无关 ,却与膜脂过氧化水平呈负相关。体外试验表明 :Na2 S和草酸对O- ·2 和H2 O2 没有作用。小麦幼苗中 ,过氧化氢酶活性比乙醇酸氧化酶活性高 3个数量级 ,Na2 S和草酸对乙醇酸氧化酶活性分别有促进和抑制作用 ,却对过氧化氢酶活性没有影响。这些结果表明光呼吸是植物体内防止活性氧积累和伤害的一道防线。     

子午岭植被自然演替中植物多样性变化及其与土壤理化性质的关系

在野外样方调查和室内实验分析的基础上,采用相关性分析和多元逐步回归方法,分析了黄土高原子午岭地区不同演替阶段群落物种多样性、土壤理化特性以及二者的相互关系.结果表明:群落物种多样性随演替进展呈增长趋势,但其增长并非完全线性,主要表现为草本群落演替阶段物种多样性指数高于灌木演替阶段.0~20 cm和20~40 cm土层土壤的全氮、有效氮和有机质等土壤养分指标随着植被演替不断增大.在演替过程中,土壤含水量变化虽有波动,但总体上升,土壤容重波动下降,说明演替过程中土壤环境在不断得到改善.40~60 cm土层土壤理化性质变化未表现出一定规律,说明其与植被演替没有必然联系.物种多样性指数与土壤因子的相关性分析表明,群落演替过程中物种多样性变化与土壤因子存在一定相关性,其中0~20 cm土层土壤的全氮和有机质与物种的多样性指数呈显著正相关.随着土层加深,物种多样性对土壤理化性质影响表现出减弱趋势.     

Plant Functional Diversity and Species Diversity in the Mongolian Steppe

Background

The Mongolian steppe is one of the most important grasslands in the world but suffers from aridization and damage from anthropogenic activities. Understanding structure and function of this community is important for the ecological conservation, but has seldom been investigated.

Methodology/Principal Findings

In this study, a total of 324 quadrats located on the three main types of Mongolian steppes were surveyed. Early-season perennial forbs (37% of total importance value), late-season annual forbs (33%) and late-season perennial forbs (44%) were dominant in meadow, typical and desert steppes, respectively. Species richness, diversity and plant functional type (PFT) richness decreased from the meadow, via typical to desert steppes, but evenness increased; PFT diversity in the desert and meadow steppes was higher than that in typical steppe. However, above-ground net primary productivity (ANPP) was far lower in desert steppe than in the other two steppes. In addition, the slope of the relationship between species richness and PFT richness increased from the meadow, via typical to desert steppes. Similarly, with an increase in species diversity, PFT diversity increased more quickly in both the desert and typical steppes than that in meadow steppe. Random resampling suggested that this coordination was partly due to a sampling effect of diversity.

Conclusions/Significance

These results indicate that desert steppe should be strictly protected because of its limited functional redundancy, which its ecological functioning is sensitive to species loss. In contrast, despite high potential forage production shared by the meadow and typical steppes, management of these two types of steppes should be different: meadow steppe should be preserved due to its higher conservation value characterized by more species redundancy and higher spatial heterogeneity, while typical steppe could be utilized moderately because its dominant grass genus Stipa is resistant to herbivory and drought.     

Recombination, Diversity and Allele Sharing of Infectivity Proteins Between Bartonella Species from Rodents

The alpha-Proteobacterium Bartonella is a common parasite of voles and mice, giving rise to short-lived (4 weeks to 2 months) infections. Here, we report high sequence diversity in genes of the VirB/VirD type IV secretion system (T4SS), amongst Bartonella from natural rodent populations in NE Poland. The VirB5 protein is predicted to consist of three conserved alpha helices separated by loops of variable length which include numerous indels. The C-terminal domain includes repeat stretches of KEK residues, reflecting underlying homopolymeric stretches of adenine residues. A total of 16 variants of VirB5, associated with host identity, but not bacterial taxon, were identified from 22 Bartonella isolates. One was clearly a recombinant from two others, another included an insertion of two KEK repeats. The virB5 gene appears to evolve via both mutation and recombination, as well as slippage mediated insertion/deletion events. The recombinational units are thought to be relatively short, as there was no evidence of linkage disequilibrium between virB5 and the bepA locus only 5.5 kb distant. The diversity of virB5 is assumed to be related to immunological role of this protein in Bartonella infections; diversity of virB5 may assist persistence of Bartonella in the rodent population, despite the relatively short (3-4 weeks) duration of individual infections. It is clear from the distribution of virB5 and bepA alleles that recombination within and between clades is widespread, and frequently crosses the boundaries of conventionally recognised Bartonella species.     

Species Diversity and Biomass Stability

With the current accelerating rate of biodiversity extinction, there is great interest in how species diversity influences ecosystem properties. In this article, we investigate the relationship between species diversity and the stability of community biomass in the face of stochastic perturbations of species' abundances. The model explicitly includes species' interactions. We show that the pattern of species' interactions affects whether the relationship between diversity and biomass stability is positive or negative. In particular, assumptions about community structure influence the relationship between species diversity and community biomass, which in turn influences the diversity-stability relationship. We also discuss the relationship between diversity and another type of stability, the proportional change in community biomass with the extinction or introduction of a species. Regardless of community type, diversity buffers the change in biomass when a species is added or removed.     

Species Delimitation and Analysis of Cryptic Species Diversity in the XXI Century

The potentials and limitations of different approaches to revealing species boundaries and describing cryptic species are discussed. Both the traditional methods of species delimitation, mostly based on morphological analysis, and the approaches using molecular markers are considered. Besides, the prospects of species identification using digital image recognition and machine learning are briefly considered. It is concluded that molecular markers provide very important material for species delimitation; the value of these data increases manifold if they can be compared with information on morphology, geographic distribution, and ecological preferences of the studied taxa. In many cases, only a practicing taxonomist who knows his or her group thoroughly can correctly interpret the molecular data and incorporate them into the existing knowledge system in order to make a taxonomic decision.

     

Patterns of Tree Species Diversity in Relation to Climatic Factors on the Sierra Madre Occidental,Mexico

Biological diversity can be defined as variability among living organisms from all sources, including terrestrial organisms, marine and other aquatic ecosystems, and the ecological complexes which they are part of. This includes diversity within species, between species, and of ecosystems. Numerous diversity indices combine richness and evenness in a single expression, and several climate-based explanations have been proposed to explain broad-scale diversity patterns. However, climate-based water-energy dynamics appears to be an essential factor that determines patterns of diversity. The Mexican Sierra Madre Occidental occupies an area of about 29 million hectares and is located between the Neotropical and Holarctic ecozones. It shelters a high diversity of flora, including 24 different species of Pinus (ca. 22% on the whole), 54 species of Quercus (ca. 9–14%), 7 species of Arbutus (ca. 50%) and many other trees species. The objectives of this study were to model how tree species diversity is related to climatic and geographic factors and stand density and to test the Metabolic Theory, Productivity-Diversity Hypothesis, Physiological Tolerance Hypothesis, Mid-Domain Effect, and the Water-Energy Dynamic Theory on the Sierra Madre Occidental, Durango. The results supported the Productivity-Diversity Hypothesis, Physiological Tolerance Hypothesis and Water-Energy Dynamic Theory, but not the Mid-Domain Effect or Metabolic Theory. The annual aridity index was the variable most closely related to the diversity indices analyzed. Contemporary climate was found to have moderate to strong effects on the minimum, median and maximum tree species diversity. Because water-energy dynamics provided a satisfactory explanation for the patterns of minimum, median and maximum diversity, an understanding of this factor is critical to future biodiversity research. Quantile regression of the data showed that the three diversity parameters of tree species are generally higher in cold, humid temperate climates than in dry, hot climates.     

A Reciprocal Relationship Between the Genetic Diversity at Two Metabolically-linked Isozyme Loci in Several Conifer Species

In the context of a general survey on genetic variation of isozyme-gene systems which function in the carbohydrate degradation and conversion, we detected a reciprocal relationship between genetic diversity at the hexokinase (HEK-A) and phosphoglucose isomerase (PGI-B) loci in Scots pine populations. Further studies on Norway spruce, Douglas-fir and Siberian stone pine revealed that this relationship appears to be a more general phenomenon in conifers such that increasing diversity at one locus is correlated with a decrease in diversity at the other locus. Since the two gene loci are not structurally linked but are encoding enzymes of two sucessive metabolic steps in the glucose conversion towards glycolysis, it is assumed that some sort of selection, especially during germination and early embryo development, may be the causal explanation. A metabolically-based model incorporating selective advantage and disadvantage of alternate two-locus genotypes at HEK-A/PGI-B was presented in order to elucidate the possible adaptive nature of this reciprocal relationship. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic Diversity and the Reintroduction of Meadow Species

Abstract: Restoration of formerly nutrient‐poor and species‐rich grasslands generally leads to an increase in species diversity. However, species without a persistent seed bank and with poor dispersal ability often do not re‐establish spontaneously. Here, reintroduction is an option. If existing populations are comparable in their genetic composition, any population will do. This is not the case if populations have local adaptations. Unfortunately, whether populations are adapted locally is not easily determined, in contrast to assessing differentiation using neutral genetic markers. We used AFLP to study genetic diversity of Cirsium dissectum and Succisa pratensis within and among several Junco‐Molinion plant communities in the Netherlands (up to 200 km apart) that were potential source populations, and followed the reintroduction using seeds from these populations. Also, vegetative growth phase characteristics of three populations of C. dissectum were analyzed under controlled conditions. Most of the genetic variation in these cross‐fertilizing species was found within populations. Small but significant genetic differences in band frequencies were found among populations (F_st 0.100 ‐ 0.135). The first generation of reintroduced plants contained less polymorphic bands than the source populations. The genetic differences caused by reintroduction using a limited number of seeds (founder effects) were significant in all except one case (F_st 0.012 ‐ 0.101 between source and corresponding reintroduced population), but the magnitude was smaller than the source population differentiation. In assignment tests, reintroduced populations resembled their source population more than any other population, but all populations contained sizeable proportions of plants that were assigned to most similar plants from other populations, indicating that the populations are only marginally distinct. Calculations show that reintroduction from more than one source population introduces significantly more polymorphic bands into the new population, capitalizing on the existence of band frequency differences among populations.     

物种多样性研究的进展

物种多样性是生物多样性研究的一个重要层次。为适应资源与环境可发展的要求,物种多样性的研究受到了广泛的重视。文章阐述了物种多样性的概念、研究方法等,分析了当今物种多样性研究的几个热点问题。     

Distribution and Local Species Diversity of Freshwater Ostracoda in Relation to Habitat in the Kahramanmaraş Province of Turkey

To understand the relationship between local (alpha) diversity of ostracods and their distribution, 95 different locations were randomly sampled from southern Kahramanmaraş (Turkey) between 7 June and 31 July, 2010. Total of 46 ostracods were encountered from 68 sites. Four alpha diversity indices (Shannon‐Wiener, Menhinick, Brillouin, Margalef) individually quantified higher species diversity and evenness for three types of habitats (limnocrene springs, ponds, stream). Diversity partitioning analyses revealed a significant and substantial beta‐diversity among the sites. First axis of CCA exhibited about 71% of the correlations between species and environmental variables. Water temperature, having either a negative or positive correlation with individual species, was the most influential factor affecting diversity. Altitude did not significantly affect the numbers of species identified from the elevation ranges of 400–600 m and 800–1000 m. At least nine cosmopolitan species from 56 sites had an important contribution to local diversity. Hence, suitability of aquatic (ecological) conditions and habitat types provide better explanations for ostracod diversity than do other abiotic factors such as altitude, pH and salinity. The results may support the Habitat Diversity Hypothesis but the study needs to be expanded to different regions and cannot be generalized at the moment. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Chemical Diversity in Himalayan Elsholtzia Species

The terpenoid composition of essential oils from the leaves of five Elsholtzia species, viz., E. eriostachya Benth ., E. cristata Willd ., E. polystachya Benth ., E. flava Benth ., and E. pilosa Benth ., collected from the Himalayan region (India), was examined by GC, GC/MS, and NMR analyses. Comparison of the results with previous reports revealed new chemotypes. Cluster analysis was carried out in order to discern the similarities and differences within the essential‐oil compositions at their subspecies/chemotype level. Based on the major constituents of the essential oils, six chemical groups were obtained.     

Species Diversity, Biogeography, and the Evolution of Biotas

SYNOPSIS. A central scientific problem for ecologists and systematistshas been to explain spatiotemporal patterns of species diversity.One aspect of this question is how to understand the taxonomicassembly of biotas and their included ecosystems and communities.Four processes add or subtract species from a region: speciation,extinction, biotic dispersion, and long-distance dispersal.Speciation and biotic dispersion are postulated to result inhistorically structured (hierarchical) species assemblages,whereas long-distance dispersal results in assemblages thatwould be expected to be historically unstructured (nonhierarchical).Continental biotas, as exemplified by the Australian avifauna,are historically structured: they are segregated into areasof endemism having hierarchical relationships that presumablyarose as a result of their history being dominated by cyclesof biotic dispersion and vicariance. It is also proposed thatthese latter two processes are necessary, and in many casesprobably sufficient, to explain the taxonomic composition ofcommunities within these areas of endemism. Long-distance dispersalappears to play a much more minor role in the assembly of eithercontinental biotas or their communities than current ecologicaltheory would predict.