Pupation-temperature range in 12Drosophila species from different ecological backgrounds

Summary A comparison of pupation-temperature range was made in the laboratory on a temperature gradient (3–38°C) using 12 species ofDrosophila representing four species groups and four different ecological backgrounds (temperate-montane forest:virilis group; desert;repleta group; cosmopolitan:melanogaster group; tropical forest:willistoni group). Within groups, differences are found which usually reflect species' distributions. Comparisons of species' mating-, oviposition- and pupation-temperature ranges reveal that pupation most-often occurs at temperatures beyond those for mating and oviposition. Each species reflects a different combination of temperature effects. Individual species have different temperature-limits for mating, oviposition and pupation. Temperatures permissive for one response are not predictive of limits on other responses. Among species, temperature can affect a particular response differently. Within groups, species differences can be at high and/or low temperatures for any response, and temperature effects among closely related species can manifest themselves in one, or any combination of responses. One cannot predict which responses will be most and least limited, or at which end of the temperature scale a response will be most limited. Among groups,common, but notabsolute temperature ranges generally correspond to the geographic distributions and ecological backgrounds of the species triads. The evaluation of temperature effects on species, based on a single activity, may not be adequate for predicting adaptive strategies.     

What distinguishes cosmopolitan and endemicDrosophila species?

Summary CosmopolitanDrosophila species can survive wide ecological tolerances measured by resistance to desiccation/temperature extremes compared with endemic rain forest species. This, rather than any genetic features, is important in helping to explain the widespread distributions of cosmopolitan species.We thank Dr Lee Ehrman for cultures ofD. paulistorum, and the Australian Research Grants Committee for financial support.     

升高CO2浓度和温度对针叶林的影响以及在川西亚高山针叶林研究中的展望

以CO2浓度和温度升高为主要特征的全球气候变化受到了世界各国科学家们的普遍关注。目前已经有大量关于森林生态系统对全球变化响应的研究报道和综述性文章,涉及分子、生理生态、种群和群落生态以及区域和全球尺度等微观和宏观领域的研究内容,因而要想对森林生态系统对全球变化的响应研究进行全面的综述是相当困难的。因此,本文只简要评述了森林生态系统对升高CO2浓度和温度响应研究中的诸如CO2浓度和温度升高对森林生长和生产力的影响、森林生态系统物种组成和多样性对升高CO2浓度和温度的响应、植被变化与全球碳循环的互动以及气候变化与森林生态系统生物地球化学循环的关系等几个热点问题。川西亚高山针叶林区为我国的第二大林区,地处高山峡谷地带,是全球变化的敏感地带。相对简单的植物群落结构、较低的物种丰富度和多样性、巨大的冷冻土壤碳库、不同演替阶段和功能的植物群落组合以及分布于林线附近的邻接效应等为研究针叶林系统对升高CO2浓度和温度的响应提供了良好的天然实验室。针叶林生产力、植物群落物种组成和多样性以及土壤碳氮过程等对升高CO2浓度和温度的响应对于预测未来气候变化下针叶林系统的生态过程具有重要意义。     

Invaders,weeds and the risk from genetically manipulated organisms

Invaders, weeds and colonizers comprise different but overlapping sets of species. The probability of successful invasion is low. The 10:10 rule state that 10% of introduced speices (those with feral individuals) become established, 10% of established species (those with self-sustaining populations) become pests. The rule gives an adequate fit to British plant data. The rule predicts that invaders will be rarer than natives. This is shown for British Anatidae. There is a continuous spectrum of perceived weediness. Although this spectrum is significantly related to Baker characters, neither those characters or any others can usefully predict which species will be weeds over a wide range of species. Characters tuned to sets of closely related species shown more promise. A study of BritishImpatiens shows that the characters responsible for critical ecological behaviour are still obscure. Small genetic changes can cause large ecological changes. GMOs will have characters entirely new to that species' evolutionary history. While most will have little ecological effect, a few may be ecologically and economically damaging. A sensible programme of field trials and monitoring is justified to minimize the risk.     

川西亚高山针叶林土壤生态过程的研究

土壤生态过程是川西亚高山针叶林生态系统过程研究中最具挑战性的研究领域，也是森林生态系统功能和过程研究中不可或缺的研究重点。土壤生态过程研究将有助于深入了解森林生态系统功能。目前。有关土壤生态过程的研究主要集中在土壤生物对土壤物理、化学和生物过程的影响以及人类活动干扰对土壤生态过程的影响等方面。但迄今为止，有关川西亚高山针叶林土壤生态过程的研究还处于空白。因此，建议在开展川西针叶林生态过程研究时，应加强以下研究领域的工作：土壤生物多样性的功能重要性及其对土壤过程的影响、土壤与植被的互动、土壤生态过程对气候变化的响应、土壤生态过程中土壤酶系统分异以及土壤过程与针叶林生态系统地上过程的关系等。     

Extracellular proteins as enterobacterial thermometers

Biological thermometers are cellular components or structures which sense increasing temperatures, interaction of the thermometer and the thermal stress bringing about the switching-on of inducible responses, with gradually enhanced levels of response induction following gradually increasing temperatures. In enterobacteria, for studies of such thermometers, generally induction of heat shock protein (HSP) synthesis has been examined, with experimental studies aiming to establish (often indirectly) how the temperature changes which initiate HSP synthesis are sensed; numerous other processes and responses show graded induction as temperature is increased, and how the temperature changes which induce these are sensed is also of interest. Several classes of intracellular component and structure have been proposed as enterobacterial thermometers, with the ribosome and the DnaK chaperone being the most favoured, although for many of the proposed intracellular thermometers, most of the evidence for their functioning in this way is indirect. In contrast to the above, the studies reviewed here firmly establish that for four distinct stress responses, which are switched-on gradually as temperature increases, temperature changes are sensed by extracellular components (extracellular sensing components, ESCs) i.e. there is firm and direct evidence for the occurrence of extracellular thermometers. All four thermometers described here are proteins, which appear to be distinct and different from each other, and on sensing thermal stress are activated by it to four distinct extracellular induction components (EICs), which interact with receptors on the surface of organisms to induce the appropriate responses. It is predicted that many other temperature-induced processes, including the synthesis of HSPs, will be switched-on following the activation of similar extracellular thermometers by thermal stimuli.     

Evolutionary and ecological consequences of interspecific hybridization in cladocerans

The evolutionary process of interspecific hybridization in cladocerans is reviewed based on ecological and population genetic data. The evolutionary consequences of hybridization, biogeographic patterns and fitness comparisons are analyzed within the conceptual framework of theories on hybridization. Among species of theD. longispina complex no interpopulational transition zones (hybrid zones) have been detected, but rather patchy distributions of hybrids and parentals have been found. Hybrids occur across broad geographic ranges and can be more abundant than parental species. Due to asexual reproduction (ameiotic parthenogenesis), hybrid breakdown can be avoided, and hybrids can even (temporarily) combine advantageous traits of both parental species. Evolutionary consequences may arise from repeated backcrossing, which in some cases results in introgression and patterns of reticulate evolution.Those forms which possess in some considerable degree the character of species, but which are so closely similar to some other forms, or are so closely linked to them by intermediate gradations, that naturalists do not like to rank them as distinct species, are in several respects the most important to us (Charles Robert Darwin 1859)     

Biochemical ecology of deep-sea animals.

Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.     

Biochemical ecology of deep-sea animals

Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.     

Role of visual and auditory cues in mating behavior of two desert species ofDrosophila

Summary The effects of visual and auditory cues on mating behavior was examined for 2 members of theDrosophila nannoptera species group. Results indicate that visual and auditory signals do not play a significant role in mating success inDrosophila acanthoptera andD. species W.Acknowledgments. This study was supported by a Division of Research Resources-National Institute of Health, Minority Biomedical Support grant (RR 07152-04) awarded to M.C.J. The grant provides a stipend for E.S.G. who is completing requirements for her Master of Science degree in Biology. Send reprint requests to M.C.J.     

青藏高原东部暗针叶林采伐迹地小气候及植被演替

暗针叶林主要分布在青藏高原东部的多条大江大河的上游和源头地区,具有重要的生态屏障功能,对于维护区域生态安全、促进经济可持续发展具有十分重要的作用。但自20世纪40年代以来,原始林被大规模采伐,形成大面积采伐迹地灌丛和草丛,其生态屏障功能逐步减弱,引起一系列生态环境因子变化。本文综述目前暗针叶林采伐迹地小气候、植被演替的研究现状,指出森林采伐后引起迹地小气候发生剧烈变化,导致迹地植被物种组成、盖度、生物量、生理生态因子等随着人为对其的不同干预也发生着相应的变化。指出今后应加强：（1）暗针叶林采伐迹地植被演替规律的研究;（2）加强人工造林树种的筛选;（3）采伐迹地0～1．5m下垫面小气候立体综合定位监测。     

亚高山针叶林群落系统的生态学过程和持续性机制

森林生态系统由于其复杂的物质循环与能量转化通道，直接参与地图一生物圈问的生物地球化学循环。因此，对森林生态系统结构与功能的研究一直是研究全球生态环境问题的核心。目前在这个研究领域的共识是：对生态系统功能的了解首先是基于对系统组分过程结构和动态的理解，而生态系统多功能的持续性机制在于确保组成系统的各组分过程结构的维持和良好的协调。在森林群落生态系统中，最基本的植物、生态学过程是能流传输(transfer)和分配(partitioning)过程，碳、养分和水循环过程，生态位的相对稳定和分化过程以及植物的生长，死亡和更新过程。川西亚高山针叶林是我国西部目前唯一保存良好的天然森林。除了它重要的、不可替代的生态、经济和社会地位外，从生态系统本身以及与全球气候变化的联系上，地处高寒环境下的川西亚高山针叶林生态系统有其独特之处：相对简单的层次结构和种丰富度，清晰的更新和演替规律，有意义的地质、气候和区系历史，巨大的土壤冷冻碳库，更加分化的结构和功能类型，复杂的地形、地貌组合以及生态位的多样性等。这些特征一方面给系统生态过程研究带来许多挑战性的问题，另一方面为研究植被动态过程以及植被与气候变化相互作用提供了一个天然实验室。     

Population genetic structure and mating system evolution in freshwater pulmonates

Freshwater gastropods (Basommatophora and Prosobranchia) harbor a variety of mating systems. In particular, apomictic parthenogenesis in prosobranchs and self-fertilization in the hermaphrodite pulmonates may be viable alternatives to outcrossing sexuality in a number of species. The coexistence of different mating systems in extant populations provides opportunities to examine the forces directing their evolution. We review the models analyzing and predicting genetic variability in subdivided populations, with an emphasis on the effects of inbreeding. Population genetic data on freshwater pulmonates are examined in the context of selfing rates and the loss of variability under selfing. Furthermore, the genetic and demographic factors thought to influence mating system evolution are considered, and we highlight the different approaches available to estimate mating system parameters, in particular the selfing rate. Recent population biological studies on polyploid species (Bulinus truncatus, Ancylus fluviatilis) indicate that selfing is the predominant mating system. These studies have contributed to a deeper understanding of conceptual issues in the evolution of selfing rates. Throughout, we emphasize the need for further carefully designed studies.     

Alkaloidal oviposition stimulants for a danaid butterfly,Ideopsis similis L., from a host plant,Tylophora tanakae (Asclepiadaceae)

Chemicals releasing oviposition by an Asclepiadaceae feeder,Ideopsis similis, were identified from a host plant,Tylophora tanakae. A strong positive response was evoked by a methanolic extract of the plant, which proved to contain multiple stimulants. A mixture of two phenanthroindolizidine alkaloids, (+)-isotylocrebrine and (–)-7-demethyltylophorine, isolated from organic fractions, elicited significant ovipositional responses from females.     

外来物种水葫芦的生态环境效应

任何外来物种均是“双刃剑”，其带来的生态环境效应有利有弊。在当前全面否定外来物种的形势下，如何正确客观评估水葫芦这样的外来种的生态环境效应成为一项迫切工作。本文从辩证的角度出发，论述水葫芦的生态环境效应(正、负)。水葫芦二十世纪初引入中国后作为家禽饲料推广养植，带来了牲畜饲料、改良水质、抑制藻类、供作绿肥、沤制沼气、栽培草菇等积极的生态环境效应，也带来了阻塞航道、影响水产养殖产量和质量、降低水体物种丰富度，破坏水体生物多样性、污染水体、加剧富营养化、使用后的二次污染等生态环境负效应。引种前缺乏对外来物种理性而全面的认识是水葫芦危害的根源，而引种后缺乏有效监控与管理则是水葫芦危害及其扩大化的根本，强化水葫芦的生态效应特别是负效应与生态控制技术开发的深入研究是目前有效规避水葫芦危害的关键。生物控制、水体生态系统调控、人为干预以及合理利用等综合措施应是水葫芦生态控制的重点。     

Parental care in terrestrial gastropods

Parental care in terrestrial gastropods includes the of oviposition sites, production of large, heavily-yolked eggs supplied with calcium carbonate, provisioning of hatchings with eggs in specis with facultative sibling cannibalism, egg retention, and ovoviviparity. Evidence for true viviparity is scarce in terrestrial gastropods, as it is for postlaying care of eggs, though external egg carrying on the shell occurs in a few species. Care of young has not been observed in any terrestrial gastropod species. Provisioning of eggs with nutrients and calcium carbonate might be the most common form of parental investment. Ovoviviparity allows terrestrial gastropods to persist in habitats otherwise unsuitable for oviparous species (e.g. exposed rock walls). An interspecific comparison demonstrates that egg-retaining and ovoviviparous species produce smaller clutches than oviparous species and suggests a cost of parental care.     

Inter-specific avoidance of egg-associated semiochemicals in four tortricids

Oviposition of four tortricid pests of vineyards (the European grapevine moth and the grape berry moth) and fruit orchards (the codling moth and the oriental fruit moth) is deterred by a blend of straight chain fatty acids and esters of fatty acids that have been identified in the eggs of one of them: the European grapevine moth (EGVM)Lobesia botrana. This is the first evidence of inter-specific recognition of an egg-like signal in moths. We demonstrate that oviposition site selection is influenced by population density, avoidance of deterrent being most important when females are isolated. Inter-specific egg recognition might be an important phenomenon, especially in species competing for a common food resource. We propose the term oviposition regulating synomone for molecules and blends that affect the inter-specific spacing of eggs.     

The accessory gland proteins in maleDrosophila: structural,reproductive, and evolutionary aspects

Recent results from biochemical and molecular genetic studies of the accessory gland proteins in maleDrosophila are reviewed. The most prominent feature is the species-specific variability. However, the analysis of the sex peptide inD. melanogaster shows that there is a strong homology in the molecular structure to the closely related sibling species, and that divergence increases with increasing phylogenetic distance. For this reason the sex peptide, after being transferred to the female genital tract during copulation, reduces receptivity and increases oviposition only in virgin females belonging to the same species group and subgroup. Even though studies were hitherto limited to a small number of the secretory components, it is evident that the accessory gland proteins play a key role in reproductive success of the fruit fly by changing female sexual behavior, supporting sperm transfer, storage and displacement. Thus, genes encoding the accessory gland proteins are apparently under strong evolutionary selection.     

Correlated responses in lines of Drosophila melanogaster selected for different oviposition behaviors

D. melanogaster was subjected to selection for two different traits of oviposition behaviour in relation to oocyte retention in ovaries, i.e. the aptitude to stop laying in response to an unsuitable substrate, and the occurrence of a dusk peak in the circadian oviposition rhythm. Selection for high and low lines was rapidly successful for both characters. Each selected line was also tested for the non-selected trait. Results showed a genetic correlation between the two behaviours, suggesting a common mechanism for the control of oviposition, independently of the origin and the duration of oocyte retention.     

Response of the ampullae of Lorenzini to static combined electric and thermal stimuli in Scyliorhinus canicula.

The effect of long-lasting electric currents on the Lorenzinian ampullae at constant temperatures between and 25 degrees C was investigated in the dogfish (Scyliorhinus canicula). Steady state neural impulse patterns in single afferent units were analyzed by plotting interval length histograms and computing mean values and standard deviations for currents between -100 and +100 nA. The mean values depended on temperature and on current strength; the relative standard deviations remained almost constant (ca. 20--30%). Negative currents, inserted at the orifice of the ampullary canal led to higher, and positive currents to lower, steady impulse rates in the whole temperature range investigated here. This static component of electrosensitivity again disappeared at higher currents (of 50 nA and more; electric overstimulation). The maximum static response was two orders of magnitude less than the maximum dynamic component of electroreception. The electrosensitivity depended on temperature: the ampullae were most sensitive to electric currents between 13 and 19 degrees C. The maximal neural activity at 19 degrees C was not shifted to higher or lower temperatures by electric stimulation. A constant equivalent of electric and thermal stimulation throughout the tested temperature and current range could not be found.