Temporal dynamics in non-additive responses of arthropods to host-plant genotypic diversity

Genotypic diversity within host‐plant populations has been linked to the diversity of associated arthropod communities, but the temporal dynamics of this relationship, along with the underlying mechanisms, are not well understood. In this study, we employed a common garden experiment that manipulated the number of genotypes within patches of Solidago altissima, tall goldenrod, to contain 1, 3, 6 or 12 genotypes m^?2 and measured both host‐plant and arthropod responses to genotypic diversity throughout an entire growing season. Despite substantial phenological changes in host plants and in the composition of the arthropod community, we detected consistent positive responses of arthropod diversity to host‐plant genotypic diversity throughout all but the end of the growing season. Arthropod richness and abundance increased with genotypic diversity by up to～65%. Furthermore, arthropod responses were non‐additive for most of the growing season, with up to 52% more species occurring in mixtures than the number predicted by summing the number of arthropods associated with component genotypes in monoculture. Non‐additive arthropod responses were likely driven by concurrent non‐additive increases in host‐plant aboveground biomass. Qualitative differences among host‐plant genotypes were also important early in the season, when specialist herbivores dominated the arthropod community. Neither arthropod diversity nor flower number was associated with genotypic diversity at the end of the growing season, when generalist floral‐associated herbivores dominated. Taken together, these results show that focusing on the temporal dynamics in the quantity and quality of co‐occurring host‐plant genotypes and associated community composition can help uncover the mechanisms that link intraspecific host‐plant diversity to the structure of arthropod communities. Furthermore, consistent non‐additive effects in genotypically diverse plots may limit the predictability of the arthropod community based solely on the genetic make‐up of a host‐plant patch.     

Estimates of damage by herbivorous insects on Eucalyptus trees

High levels of insect damage on Eucalyptus have been noted but not quantified in previous literature. We present estimates of leaf damage for 44 Eucalyptus species from a variety of habitats. Overall, an average of 15% of expanded leaf area was missing. While some species were generally lightly grazed, others, especially those in more mesic. higher altitude communities, usually sustained much heavier leaf damage. In the age and size classes, communities and years that we sampled, the overall levels of damage to eucalypts were higher than chronic damage levels reported for north temperate communities. We also suggest a simple method for rapidly estimating the proportion of leaf area missing from trees.     

Community dynamics of carrion-attendant arthropods in tropical african woodland

Summary Carcasses are temporary resources which are unbredictable and inconsistent in their availability and locality. A recognisable community of interacting user arthrocods comprising sarcophages, coprophages, dermatophages, keratophages, detritivores, predators and parasites has evolved to exploit the carcass habitat. The large number of arthropods, close confinement, and limited duration of resources necessitates aggressive utilisation. The trophic relations, competition and successionary pattern of these arthropods is discussed. Several pathways to reduce competitive conflict are described. Succession at carcasses is viewed as being inherently different from the traditional concept as the habitat is non-replenishing and does not lead to a climax community.     

Seasonal variation of natural products in European trees

The present review gives an overview about the status of research on seasonal variation of natural products in European trees. Due to their different life forms, gymnosperms, deciduous angiosperms, and evergreen angiosperms are reviewed separately. Besides trying to give an overview about the existing newer literature, the review tries to define some repetitively found trends and discusses some possible explanations for these trends. Moreover, open research questions are highlighted and some suggestions for future studies are given. These suggestions encompass both subjects and desirable quality standards with regards to experimental designs. The reviewed publications are mainly focused on leaves, some on fruits, and some on barks and twigs. Phenolics, including phenolic acids and flavonoids of different types as well as tannins, are the most often studied compound class; additionally, some papers assess seasonal variation of alkaloids, diterpenes, essential oils, lignans, simple organic acid, secoiridoids, and stilbenoids.     

Population dynamics and life history tactics of arthropods from Mediterranean-type ecosystems

The null hypothesis of this paper is that survival of arthropods under the severe Mediterranean conditions involves specific combinations of conservative and conformist traits. To test this hypothesis a modeling approach employing a Leslie-type matrix model and a fuzzy systems technique for parameter estimation is developed and applied to a model species. The general conclusion is that the results of this paper add support to the null hypothesis, whereas specific conclusions are as follows: 1) matrix models merging demographic and physiological parameters are suitable tools for the simulation of population dynamics of arthropods and further for the discussion of the interplay among life history traits; 2) employing linguistic instead of arithmetic variables, fuzzy approaches allow for the formalization of incomplete and/or missing data exploiting expertise concerning related species; 3) in general, population dynamics of arthropods follow the seasonality of the Mediterranean climate; 4) the basic mechanism underlying skewing phenologies and stochastic equilibrium is identified with the type of temperature dependence of arthropod metabolic activity; 5) under optimal conditions an exponential trend is superimposed on seasonal population dynamics; 6) more realistic conditions involving large-scale random oscillation in temperature in autumn and spring coupled with small-scale temperature oscillation in summer and winter result in stochastic equilibrium; 7) moderate contamination of soil and medium-scale oscillation in temperature result in stable temporal patterns; 8) a sensitivity analysis shows disproportional effect of different demographic parameters on population growth rate. Fecundity of young and middle-aged adults is most important for the rate of population growth, whereas elder animals are considered an important pool for maintenance of the population.     

小蠹虫对针叶类寄主树木的选择危害机制

小蠹虫对寄主植物的选择是一个非常复杂的过程,也是近年来小蠹虫生态学研究的一个热门话题。文章对国内外小蠹虫寄主搜寻、寄主识别,以及适宜寄主选择等机制等方面的最新研究成果进行了系统报道。     

桃园捕食性节肢动物群落结构及动态研究

【目的】探讨桃园捕食性节肢动物群落特征、结构组成及动态规律,为桃园害虫防治提供依据。【方法】在西北农林科技大学实验站选择树龄5~6年的桃园为调查对象,系统调查园内节肢动物群落的种类和数量,测定群落的相对丰富度、多样性指数(H')、均匀度指数(E)及优势集中性指数(C)等指标,研究园内捕食性节肢动物群落的变化规律。【结果】桃园捕食性节肢动物群落的多样性指数和均匀度指数表现为高-低-高-低的趋势;群落优势度(B)与优势集中性指数呈现低-高-低趋势。食蚜蝇、蜘蛛、瓢虫、步甲和草蛉是桃园主要捕食性节肢动物亚群落。大灰食蚜蝇Metasyrphus corollae和黑带食蚜蝇Episyrphus balteata是食蚜蝇亚群落的优势种群,5月中旬至6月下旬是其发生高峰期;龟纹瓢虫Propylaea japonica是瓢虫亚群落的优势种群,5月中旬至7月下旬是其发生高峰期,随后数量维持在较低水平;龟纹瓢虫鼎斑变型和锚斑变型是桃园最常见的色斑变型,分别占49.6%和29%;蜘蛛亚群落主要包括皿蛛、蟹蛛和球蛛类群,5月上中旬、8月中下旬和10月中旬是其发生高峰期;步甲亚群落的发生高峰期为5月上旬至6月下旬,随后维持在较低的水平;中华草蛉Chrysoperla sinica为草蛉亚群落的优势种群,6月上旬至8月上旬是其发生高峰期。【结论】桃园捕食性节肢动物主要包括捕食性蜘蛛、食蚜蝇、捕食性瓢虫、步甲和草蛉5个亚群落,不同天敌亚群落的结构特征随着季节和气温的变化而相互演替,共同发挥控制害虫的作用。     

丛枝菌根真菌种群的孢子季相动态研究

以草坪为研究对象,研究草坪土壤中丛枝菌根真菌种群的孢子组成、孢子密度、物种丰富度、多样性及其季相变化规律。结果表明,丛枝菌根真菌孢子密度、物种丰富度和多样性指数在一年内随季节变化表现出一定的季相变化规律,三者均在冬季达到最高,在时间节律上与植物群落季相变化不同步;同时分析了气候因素(平均温度、降雨量和日照时间等)对丛枝菌根真菌的影响。结果表明,气候因素对孢子密度、物种丰富度和多样性指数均有显著影响。     

Augmentation of beneficial arthropods by strip-management

Summary A 5-year-field experiment was performed in a meadow to test the effect of strip-management (small unmown strips alternating with broad mown strips, Fig. 1) on the abundance and composition of arthropods. The species number and density of most predator groups increased from year to year. The succession (parallel to the development of the unmown strips) favoured more specialized species, so that the initial pioneer species become less abundant in consecutive years. In spiders, this succession leads from a dominance of Linyphiidae to a dominance of Lycosidae; the spider biomass increases and probably predator pressure by spiders is augmented. The stability of the predator community (measured as the variance of their frequency in successive years) is higher than that of the phytophagous groups. Under strip-managed conditions the abundance (activity density) of most arthropod groups decreases by an average of ca. 12%. The trophic levels, however, are affected to different extents and strong species-specific preferences were found as well. These combined effects lead to constant increase in the ratio of predacious and parasitic to phytophagous insects in the strip-managed area and probably lead also to an increase of the predator pressure facing phytophagous insects. Strip-management is discussed as an important technique among integrated methods for the biological control of pests.     

松树皮下节肢动物种群动态研究初报

报道用环剥和砍伐模拟松树树势减弱和失水干枯的受害情况,同时观察松树皮下害虫侵入动态。环剥和砍伐对马尾松树皮下昆虫的入侵有完全不同的影响。松树失水,渐趋干枯是蛀干害虫得以入侵的主要原因。马尾松树皮下有多种蛀干害虫先后侵入、同时发生,其中松墨天牛为先锋虫种,依入侵先后顺序为松墨天牛、纵坑切梢小蠹、马尾松角胫象、小松角胫象、家白蚁。有多种捕食性和寄生性天敌跟随进入树干,虫种包括长线阎甲、根露尾甲、管氏肿腿蜂、黄隐翅虫、花绒穴甲、茧蜂、囊螨。     

广西南宁市园林树木白蚁发生种类及危害情况

2009年311月对南宁市园林树木白蚁为害情况进行了调查。结果表明,台湾乳白蚁Coptotermes formosanus Shiraki是危害园林树木的优势种;调查的57种树木中,45种树木受到了白蚁的侵害,占总数的78.95%,树木受害株率达13.11%,严重受害株率为1.66%。银桦、侧柏和樟树等树种受白蚁危害最为严重。     

Differential responses of ground dwelling arthropods to ski-piste restoration by hydroseeding

The construction of ski-pistes can cause serious damage to all the components of an ecosystem and may therefore be considered as one of the main causes of human-driven environmental changes in mountain habitats. This study was aimed at assessing the responses of different ground dwelling arthropod assemblages (i.e. ground beetles, spiders and grasshoppers) to ski-piste restoration through hydroseeding with commercial seed mixtures. The soil, vegetation and arthropods of restored and un-restored ski-pistes and the adjacent grassland have been sampled at two high altitude sites in the north-western Italian Alps. The ski-piste soil was characterized by a higher skeletal content and, consequently, a lower amount of fine earth and organic matter than that of the undisturbed adjacent grassland. The plant cover of the restored ski-pistes was very low above 2,500 m a.s.l.; the vegetation cover below this threshold was higher in the study area, mainly due to the seeded species. The unrestored ski-pistes showed very large proportions of bare ground. The responses of the three ground-dwelling arthropod groups to vegetation conditions were different. GLMMs and IndVal analyses showed that all three groups avoided the unrestored ski-pistes plots, which were characterized by a very scarce vegetation cover, irrespective of the altitude. The low altitude plots of the restored ski-pistes, which were characterized by a high vegetation cover, had a significantly larger number of grasshoppers on the ski-pistes than on the adjacent grassland plots. Moreover, these restored ski-piste plots were used in equal proportion to the adjacent grassland plots by ground beetles but avoided by spiders. When ski-pistes become sufficiently revegetated by hydroseeded plants, they are colonized by grasshoppers and, to a lesser extent, by ground-beetles. Spiders, instead, do not colonize the pistes, thus demonstrating that they are the most sensitive arthropods and may therefore represent the best indicators of human-driven environmental changes in high altitude alpine habitats.     

Seasonal dynamics of root system respiration inAtriplex confertifolia

Summary The seasonal dynamics of respiratory capacity in the root system ofAtriplex confertifolia was studied under field conditions. Respiratory capacity of the root system undergoes seasonal adjustments with peak capacity occurring in spring and minimum capacity occurring in late summer. At greater depths in the profile, the timing of peak and minimum capacities is progressively delayed.The timing of respiratory adjustments does not appear to be tightly correlated with soil moisture or soil temperature, and may reflect environmental pre-conditioning as well as an overall geneticallybased program to prolong the duration of root activity and minimize carbon requirements of the root system.     

Seasonal dynamics of adrenal mineralocorticoid function in rats

Seasonal peculiarities of adrenal mineralocorticoid function and some aspects of its regulation have been studied in experiments on male Wistar rats. It has been found that changes in aldosteronemia and aldosteronurea were maximum in spring and minimum in summer--autumn period. The highest indices of aldosterone metabolic clearance from plasma were observed in winter with the following progressing decrease and a small increase in autumn. The diagram of melatonin content in the epiphysis of experimental rats was the same. Hypokinesia attenuated aldosteronurea during all the investigation periods, preserving the character of aldosterone secretion year curve. PRA level changed irrespective of aldosterone levels in plasma and urea. It has been concluded that a certain stability of mineralocorticoid adrenal function seasonal rhythms has different regulating effects.