食虫蝙蝠与昆虫之间的相互作用和协同进化关系

食虫蝙蝠与昆虫之间是捕食和被捕食的关系,夜行性昆虫是食虫蝙蝠主要的食物来源。在漫长的协同进化中,蝙蝠施加的捕食压力导致夜行性昆虫一系列特征的进化,其中一部分昆虫进化出能听到蝙蝠的超声波信号并采取逃跑行为或者能通过其它方式躲避蝙蝠,同时昆虫的适应性特征同样影响着蝙蝠的回声定位和捕食策略。本文从蝙蝠捕食昆虫的种类、昆虫对蝙蝠捕食的反应和食虫性蝙蝠对昆虫防卫的适应对策等三个方面对食虫蝙蝠与昆虫之间的相互关系进行了概述。     

三种共栖蝙蝠的回声定位信号特征及其夏季食性的比较

2005年6至9月,对桂林市郊区两个山洞中高颅鼠耳蝠(Myotissiligorensis)、菲菊头蝠(Rhinolo-phuspusillus)和黑髯墓蝠(Taphozousmelanopogon)的回声定位叫声特征和食性进行分析,并结合其形态特征与野外观察,推断其捕食生境和捕食策略。研究结果发现:黑髯墓蝠体型最大,声音特征属短调频型多谐波,一般为4个谐波,能量主要集中在第二谐波上,主频率为(32·84±1·17)kHz,选择鞘翅目和双翅目昆虫为主要食物;高颅鼠耳蝠(长调频型)和菲菊头蝠(长恒频-调频型),体型都较小,主频率分别是(84·44±8·13)kHz和(110·78±1·65)kHz,以双翅目昆虫为主要食物;而菲菊头蝠则以鞘翅目和双翅目昆虫为主要食物。上述结果证明,高颅鼠耳蝠、菲菊头蝠和黑髯墓蝠在声音和食物组成等方面出现了明显分化。     

Genomic Characterization of Novel Circular ssDNA Viruses from Insectivorous Bats in Southern Brazil

Circoviruses are highly prevalent porcine and avian pathogens. In recent years, novel circular ssDNA genomes have recently been detected in a variety of fecal and environmental samples using deep sequencing approaches. In this study the identification of genomes of novel circoviruses and cycloviruses in feces of insectivorous bats is reported. Pan-reactive primers were used targeting the conserved rep region of circoviruses and cycloviruses to screen DNA bat fecal samples. Using this approach, partial rep sequences were detected which formed five phylogenetic groups distributed among the Circovirus and the recently proposed Cyclovirus genera of the Circoviridae. Further analysis using inverse PCR and Sanger sequencing led to the characterization of four new putative members of the family Circoviridae with genome size ranging from 1,608 to 1,790 nt, two inversely arranged ORFs, and canonical nonamer sequences atop a stem loop.     

Of Trees and People: The Changing Entanglement in the Israeli Desert

This article portrays the shift experienced in the role of acacia trees during environmental–political struggles as the entanglement of trees and people. Drawing on a four-year ethnographic study around Israel’s Arava desert valley, the article narrates human interactions with these trees amid an environmental conflict fraught with personal and political conflict, opposing perspectives on natural preservation and scientific debate, as well as disputes among environmental organisations. Contrary to current approaches in anthropology that –theoretically at least – confer agency on the non-human, I refocus on the human practices that weave the non-human into the social fabric. In this article, I argue that the trees – not actors in their own right, yet inhabiting a tapestry of people and other elements – are essential to understanding a variety of social processes.     

The Importance of Large-Diameter Trees to Forest Structural Heterogeneity

Large-diameter trees dominate the structure, dynamics and function of many temperate and tropical forests. However, their attendant contributions to forest heterogeneity are rarely addressed. We established the Wind River Forest Dynamics Plot, a 25.6 ha permanent plot within which we tagged and mapped all 30,973 woody stems ≥1 cm dbh, all 1,966 snags ≥10 cm dbh, and all shrub patches ≥2 m². Basal area of the 26 woody species was 62.18 m²/ha, of which 61.60 m²/ha was trees and 0.58 m²/ha was tall shrubs. Large-diameter trees (≥100 cm dbh) comprised 1.5% of stems, 31.8% of basal area, and 17.6% of the heterogeneity of basal area, with basal area dominated by Tsuga heterophylla and Pseudotsuga menziesii. Small-diameter subpopulations of Pseudotsuga menziesii, Tsuga heterophylla and Thuja plicata, as well as all tree species combined, exhibited significant aggregation relative to the null model of complete spatial randomness (CSR) up to 9 m (P≤0.001). Patterns of large-diameter trees were either not different from CSR (Tsuga heterophylla), or exhibited slight aggregation (Pseudotsuga menziesii and Thuja plicata). Significant spatial repulsion between large-diameter and small-diameter Tsuga heterophylla suggests that large-diameter Tsuga heterophylla function as organizers of tree demography over decadal timescales through competitive interactions. Comparison among two forest dynamics plots suggests that forest structural diversity responds to intermediate-scale environmental heterogeneity and disturbances, similar to hypotheses about patterns of species richness, and richness- ecosystem function. Large mapped plots with detailed within-plot environmental spatial covariates will be required to test these hypotheses.     

The Importance of Ficus (Moraceae) Trees for Tropical Forest Restoration

Forest restoration is an increasingly important tool to offset and indeed reverse global deforestation rates. One low cost strategy to accelerate forest recovery is conserving scattered native trees that persist across disturbed landscapes and which may act as seedling recruitment foci. Ficus trees, which are considered to be critically important components of tropical ecosystems, may be particularly attractive to seed dispersers in that they produce large and nutritionally rewarding fruit crops. Here, we evaluate the effectiveness of remnant Ficus trees in inducing forest recovery compared to other common trees. We studied the sapling communities growing under 207 scattered trees, and collected data on seed rain for 55 trees in a modified landscape in Assam, India. We found that Ficus trees have more sapling species around them (species richness = 140.1 ± 9.9) than non‐Ficus trees (79.5 ± 12.9), and significantly more saplings of shrub and large tree species. Sapling densities were twice as high under Ficus trees (median = 0.06/m²) compared to non‐Ficus (0.03/m²), and seed rain densities of non‐parent trees were significantly higher under Ficus trees (mean = 12.73 ± 3/m²/wk) than other fruit or non‐zoochorous trees (2.19 ± 0.97/m²/wk). However, our regression model found that canopy area, used as a proxy for tree size, was the primary predictor of sapling density, followed by remnant tree type. These results suggest that large trees, and in particular large Ficus trees, may be more effective forest restoration agents than other remnant trees in disturbed landscapes, and therefore the conservation of these trees should be prioritized.     

Importance of Terrestrial Arthropods as Subsidies in Lowland Neotropical Rain Forest Stream Ecosystems

The importance of terrestrial arthropods has been documented in temperate stream ecosystems, but little is known about the magnitude of these inputs in tropical streams. Terrestrial arthropods falling from the canopy of tropical forests may be an important subsidy to tropical stream food webs and could also represent an important flux of nitrogen (N) and phosphorus (P) in nutrient‐poor headwater streams. We quantified input rates of terrestrial insects in eight streams draining lowland tropical wet forest in Costa Rica. In two focal headwater streams, we also measured capture efficiency by the fish assemblage and quantified terrestrially derived N‐ and P‐excretion relative to stream nutrient uptake rates. Average input rates of terrestrial insects ranged from 5 to 41 mg dry mass/m²/d, exceeding previous measurements of aquatic invertebrate secondary production in these study streams, and were relatively consistent year‐round, in contrast to values reported in temperate streams. Terrestrial insects accounted for half of the diet of the dominant fish species, Priapicthys annectens. Although terrestrially derived fish excretion was found to be a small flux relative to measured nutrient uptake rates in the focal streams, the efficient capture and processing of terrestrial arthropods by fish made these nutrients available to the local stream ecosystem. This aquatic‐terrestrial linkage is likely being decoupled by deforestation in many tropical regions, with largely unknown but potentially important ecological consequences.     

塔克拉玛干沙漠南缘3种果树幼苗光合及抗逆性研究

于2010年7~8月份,以塔克拉玛干沙漠南缘绿洲-荒漠过渡带人工种植的桑树(Morus albaL.)、沙枣(Elaeagnus angustifoliaL.)和杏树(Prunus armeniacaL.)幼苗为材料,研究了它们在相同生境条件下光合响应特征、水势、脯氨酸和可溶性糖含量等生理指标的变化,并用隶属函数值法对3种果树幼苗的抗旱性进行综合评价。结果表明:(1)3种果树幼苗光响应曲线具有相同的变化规律,当光合有效辐射(PAR)在0~200μmol.m-2.s-1之间变化时,净光合速率(A)随着PAR的增大呈直线增大,当PAR>200μmol.m-2.s-1时,A随PAR的变化呈二次曲线变化;(2)3种果树幼苗的光响应参数最大光合速率(Amax)、曲角(K)、表观量子效率(φ)、暗呼吸速率(Rday)、光饱和点(LSP)、光补偿点(LCP)以及光合色素的变化趋势并不完全一致,其中桑树具有最大的Amax、φ、Rday和叶绿素含量,而杏树的LSP最高,LCP最低,因此桑树具有最大的光能利用效率,而杏树能更有效地利用强光进行光合作用;(3)3种果树幼苗脯氨酸(Pro)、可溶性糖以及丙二醛(MDA)含量,除沙枣和杏树之间可溶性糖含量差异不显著外,其他指标含量差异在3种果树之间均达到显著水平(P<0.05);(4)在本研究期间3种果树的抗逆性表现为沙枣>桑树>杏树。研究发现,塔克拉玛干沙漠南缘绿洲-荒漠过渡带的3种果树幼苗光响应曲线变化趋势基本一致,体现了植物对环境条件适应的一致性,但是各个生理指标的变化趋势并不完全一致,这可能是由于植物种对环境条件的适应差异所导致。     

Facilitative-Competitive Interactions in an Old-Growth Forest: The Importance of Large-Diameter Trees as Benefactors and Stimulators for Forest Community Assembly

The role of competition in tree communities is increasingly well understood, while little is known about the patterns and mechanisms of the interplay between above- and belowground competition in tree communities. This knowledge, however, is crucial for a better understanding of community dynamics and developing adaptive near-natural management strategies. We assessed neighbourhood interactions in an unmanaged old-growth European beech (Fagus sylvatica) forest by quantifying variation in the intensity of above- (shading) and belowground competition (crowding) among dominant and co-dominant canopy beech trees during tree maturation. Shading had on average a much larger impact on radial growth than crowding and the sensitivity to changes in competitive conditions was lowest for crowding effects. We found that each mode of competition reduced the effect of the other. Increasing crowding reduced the negative effect of shading, and at high levels of shading, crowding actually had a facilitative effect and increased growth. Our study demonstrates that complementarity in above- and belowground processes enable F. sylvatica to alter resource acquisition strategies, thus optimising tree radial growth. As a result, competition seemed to become less important in stands with a high growing stock and tree communities with a long continuity of anthropogenic undisturbed population dynamics. We suggest that growth rates do not exclusively depend on the density of potential competitors at the intraspecific level, but on the conspecific aggregation of large-diameter trees and their functional role for regulating biotic filtering processes. This finding highlights the potential importance of the rarely examined relationship between the spatial aggregation pattern of large-diameter trees and the outcome of neighbourhood interactions, which may be central to community dynamics and the related forest ecosystem services.     

The Role of Soil Arthropods in Community Energetics

Though the primary development of principles of energetics waspioneered in aquatic studies, considerable information has accruedfrom more recent investigations of terrestrial species. Studiesof soil organisms—particularly arthropods—have givenus some understanding of the applicability of principles ofenergetics to terrestrial communities. Data from soil communitieshave yielded an annual energy budget for oribatid mites, ecologicalefficiencies for two trophic levels, and a series of herbivore:carnivoreratios for a number of communities. Energy-flow analyses ofthe problems of species abundance in community organization,the relationship of population production and maintenance, andthe energy relationships of the soil to above-ground communitieshave also been attempted. As data accumulate, however, the inadequacyof the Lindeman model becomes apparent, and there are prospectsfor change in this conceptual scheme.     

Reproductive Trade-Offs and Direct Costs for Males in Arthropods

Until 30 years ago, the emphasis on reproductive costs for males was mainly on costs related to mate searching, courtship and fighting with rival males. However, costs for males are substantial and varied and often resemble the more thoroughly studied female reproductive costs. Costs can be referred to as trade-off costs, where investment in reproductive activity comes at the expense of another important activity or fitness component. Investment in reproduction at the expense of longevity and future reproduction is the ultimate cost, because it affects fitness directly. In contrast, flawed performance (e.g., of the immune system) is perceived as a mechanistic trade-off, because it affects fitness indirectly through a mediator (i.e., parasites). Finally, direct costs refer to direct measurements of the energy expenditure during involvement in reproduction-related activities. Both direct and mechanistic trade-off costs often result in decreased longevity compared to unmated males (an ultimate cost). Males incur costs during different reproductive phases: before copulation, when producing sperm, while searching for, courting and copulating with females, and subsequently when guarding females or taking care of offspring. This synthesis follows previous pioneering reviews addressing specific aspects of male costs, but strives to summarize all known male reproductive cost types more comprehensively, including their classification. We suggest several directions for targeted future research. While costs for males have been fairly well described, it is now necessary to uncover the ecological and evolutionary factors responsible for differences between closely related species and systems and to better link between directly-measured costs, mechanistic trade-off costs and ultimate trade-off costs.     

Relative Importance of Rootstock and Scion in Determining Growth and Fruiting in Young Apple Trees

Principal component analysis has been used on annual measuresof vegetative and reproductive activity of young apple trees.The trial consisted of four clones (M.2, M.4, M.9, and M.16)used as both rootstock and scion in all possible combinationsto give 16 tree types. The results have suggested that theseannual records can best be summarized by their sum and lineartrend with time. Further analyses using these new measures ofsum and trend have enabled the effects of rootstock and scionto be partitioned. Increase in stem dry weight is largely rootstock-controlledbut trend with time is mainly scion-controlled. The reverseoccurs with fruit number where total fruit is largely scion-controlledbut the trend is dominated by the rootstock. Measures of leadergrowth are intermediate between stem growth and fruiting intheir responses. Statistical interactions are greatest withfruiting records which suggests that this activity is less harmoniouslycontrolled by rootstock and scion than other activities. Use of sum and linear trend is recommended for future analysesof apple tree trials without recourse to further multivariateanalyses.     

Changes in water relations for Acacia ancistrocarpa on natural and mine-rehabilitation sites in response to an experimental wetting pulse in the Great Sandy Desert

Vegetation plays an essential role in mine-site rehabilitation as it serves to reduce erosion and extract moisture from the soil cover, thus minimising deep drainage to potentially hazardous materials below. Plant water-use patterns and root development are likely to be impacted where subsoils are physically and/or chemically inhospitable and close to the surface, particularly in arid and semi-arid environments where pulses of rainfall are infrequent and interspersed with long dry periods. The aim of this investigation was to determine how plant water relations of the woody shrub species Acacia ancistrocarpa (Maiden and Blakely) were affected by a summer wetting pulse on a degraded mine-rehabilitation site and a pristine natural site in the Great Sandy Desert of north-western Australia. At both the natural and rehabilitation sites, 20 m³ of water was applied to emulate an 80-mm rainfall event comparable with cyclones that occur during the summer wet season. We found that plants responded with significant increases in stomatal conductance, leaf water potential and sap-flow in lateral roots within three days of irrigation at the natural site and two days at the rehabilitation site. At the rehabilitation site this response occurred despite the fact that sinker roots were stunted by impeding physical properties of the mine-waste material. Sap-flow velocity, using the heat ratio method, in lateral and primary sinker roots was close to zero at night and positive during the day for trees at both sites during the dry period before the irrigation. These data indicate hydraulic redistribution was not occurring between the primary sinker and lateral roots at night, and water was transported along the laterals towards the crown, despite the fact they were in dry soil. Excavations revealed that lateral roots extended up to 6 m and displayed secondary sinker roots accessing water from deeper soil layers, even from mine-waste material. These morphological traits likely improved the water relations and survival of A. ancistrocarpa at the rehabilitation site. Considering these traits and the rapid pulse responsiveness of this species, we recommend A. ancistrocarpa for future rehabilitation projects at this and other mine-sites in the region.     

Microbiology of Wetwood: Importance of Pectin Degradation and Clostridium Species in Living Trees

Wetwood samples from standing trees of eastern cottonwood (Populus deltoides), black poplar (Populus nigra), and American elm (Ulmus americana) contained high numbers of aerobic and anaerobic pectin-degrading bacteria (10⁴ to 10⁶ cells per g of wood). High activity of polygalacturonate lyase (≤0.5 U/ml) was also detected in the fetid liquid that spurted from wetwood zones in the lower trunk when the trees were bored. A prevalent pectin-degrading obligately anaerobic bacterium isolated from these wetwoods was identified as Clostridium butyricum. Pectin decomposition by C. butyricum strain 4P1 was associated with an inducible polygalacturonate lyase and pectin methylesterase, the same types of pectinolytic activity expressed in the wetwood of these trees. The pH optimum of the extracellular polygalacturonate lyase was alkaline (near pH 8.5). In vitro tests with sapwood samples from a conifer (Douglas fir, Pseudotsuga menziesii) showed that tori in membranes of bordered pits are degraded by pure cultures of strain 4P1, polygalacturonate lyase enzyme preparations of strain 4P1, and mixed methanogenic cultures from the tree samples of wetwood. These results provide evidence that pectin in xylem tissue is actively degraded by C. butyricum strain 4P1 via polygalacturonate lyase activity. The importance of pectin degradation by bacteria, including Clostridium species, appears paramount in the formation and maintenance of the wetwood syndrome in certain living trees.     

The Buzz of Drinking on the Wing in Echolocating Bats

Bats broadcast rapid sequences of echolocation calls, named ‘drinking buzzes’, when they approach water to drink on the wing. So far this phenomenon has received little attention. We recorded echolocation sequences of drinking bats for 12 species, for 11 of which we also recorded feeding buzzes. Based on the different sensorial tasks faced by feeding and drinking bats, we hypothesize that the drinking buzz structure will differ from that of feeding buzzes since unlike the latter drinking buzzes are not designed to detect and track mobile prey. We demonstrated that drinking buzzes are structurally different from feeding buzzes. We show that the buzz‐II phase common in feeding buzzes is absent in drinking buzzes; that is, call frequency is not lowered to broaden sonar beam since the task of drinking does not imply tracking fast‐moving targets. This finding indirectly confirms the role of buzz II in feeding buzzes. Pulse rate in drinking buzzes is also lower than in feeding buzzes, as predicted since the high pulse rate typical of feeding buzzes is important to update rapidly the relative location of moving targets. The most likely function of drinking buzzes is to guide a safe drinking manoeuvre, similar to ‘landing buzzes’ broadcast when bats land on the ground.