Intraand Interspecific Competition Research Articles

Reintroduction to the edge of its range: quenda (Isoodon fusciventer) to Wadderin Sanctuary in the eastern wheatbelt of Western Australia

Context Quenda (bandicoots, Isoodon fusciventer) have shown a major decline in range since European settlement, contracting to the more mesic coastal and forest zones in south-west Western Australia. Key actions to recover this species include broad-scale fox control, cat control and reintroductions. Most reintroductions have been to coastal and forest habitats. Aims To monitor the reintroduction of quenda to fox-free habitat of Wadderin Sanctuary in the wheatbelt of Western Australia, close to the eastern and drier margin of the species’ former range. Methods Relative abundance of the population was monitored over a 12-year period by regular standardised trapping throughout the sanctuary. Key results Quenda were reintroduced in 2010 and have persisted for >12 years. They were protected from fox predation by an exclusion fence, but were subject to a low level of cat predation for the first 8 years. Quenda showed both a ~20% drop in mean body condition over time and a trend of decreasing number of pouch young per female over time, likely a result of a succession of dry years and intra-and inter-specific competition for food resources. However, despite this, the index of abundance suggests that quenda numbers substantially increased, aided by high annual recruitment, in years following removal of the feral cat. Conclusions Quenda appear resilient at this site despite consecutive years of very low rainfall and apparent competition for food resources. Implications Quenda seem able to persist on the drier margin of their former range when protected from high levels of predation.

Intra-and interspecific competition of endangered plant Tetracentron sinense Oliv.

Intra-and interspecific competition of endangered plant Tetracentron sinense Oliv.

Intra-and inter-specific competition effects on survival and growth of juvenile Procambarus acutus acutus and Procambarus clarkii

Four similar sizes eastern white river crayfish (Procambarus acutus acutus) and red swamp crayfish (Procambarus clarkii) were stocked separately to determine intra and inter-specific-competition. Three treatment levels were used three treatment levels, with six replicates tanks each with stand green rice (representing a stocking density of approximately 21 individuals per m2). This study was carried out during 90 days to determine growth and survival rate. Results showed that the growth of P. acutus acutus in the interspecific treatment tank was found higher than those grown in the intraspecific-treatment tanks. For P. clarkii, no significant differences in growth (estimated from the mean Total length, TL) were detected between treatments. The survival of the two species was the same up to the first 60 days of the experiment, while the difference in survival was only noticeable at 90 days. The survival rate of P. clarkii in the intraspecific-treatment tanks (55.0%) was higher than in the interspecific tanks (26.7%) treatment, while the survival of P. acutus acutus was found similar in two treatments. It was achieved higher survival, faster growth and larger size in P. a. acutus than P. clarkii when grown in the tank study. Size of body was important in determining competitive interactions between the two species.

Understanding how environmental factors influence reproductive aspects of wild myomorphic and hystricomorphic rodents.

Myomorphic and hystricomorphic rodents are vital for maintaining various ecosystems around the planet. This review enables a better understanding of how these rodents respond to environmental factors and adapt to climate adversities. Innumerable factors, such as photoperiod, rainfall, and temperature, can impair or contribute to the quality of rodent reproductive parameters. Prolonged animal exposure to high ambient temperatures alters thermoregulation mechanisms and causes testicular and ovarian tissue degeneration and hormonal deregulation. Photoperiod influences the biological circannual rhythm and reproductive cycles of rodents because it strongly regulates melatonin secretion by the pineal gland, which modulates gonadotropic hormone secretion. Rainfall quantity directly regulates the abundance of fruits in an ecosystem, which modulates the reproductive seasonality of species which are most dependent on a seasonal fruit-based diet. Species with a more diversified fruit diet have smaller reproductive seasonality. As such, habitats are chosen by animals for various reasons, including the availability of food, sexual partners, intra-and inter-specific competition, and predation. This knowledge allows us to monitor and establish management plans to aid in conservation strategies for wild rodent species.

Performance variation of common ragweed (Ambrosia artemisiifolia L.) across invasion levels in Western Europe

The occurrence of an invasive plant across a continent is generally not homogeneous; typically, some areas are highly invaded whereas others show moderate or low invasion levels. This situation might be a snapshot of an ongoing spread, but it could also remain stable under the pressure of factors that constrain the invasion. Among those factors, plant performance variation among invasion levels can explain an invasion slowdown. However, few studies have investigated the large-scale variation of invasive plant performance in the field. Ambrosia artemisiifolia L. in Western Europe represents a good opportunity to address this issue, with areas of high, moderate and low invasion levels being documented across a ca. 1000km transect. In this study, we compared in situ plant performance-related traits in 12 populations from areas of contrasting invasion levels. We also tested whether performance-related traits were influenced by the intra-and inter-specific competition, by the local climatic conditions or by latitude (a proxy for growing season length). Overall, we did not find differences in performance-related traits across invasion levels, and intra-and inter-specific competition had low effects on plant performance. This study highlights the fact that A. artemisiifolia individuals express similar performance across invasion levels, even beyond what can be considered the present invasion front. Further research has to expand this study northwards, and assess other factors that could constrain the invasion in order to highlight if the species invasion northward is constrained or if it has the potential to invade new areas.

AM真菌在草原生态系统中的功能

PDF HTML阅读 XML下载 导出引用 引用提醒 AM真菌在草原生态系统中的功能 DOI: 10.5846/stxb201404230807 作者: 作者单位: 兰州大学 草地农业生态系统国家重点实验室 草地农业科技学院,兰州大学 草地农业生态系统国家重点实验室 草地农业科技学院,云南农业大学 植物保护学院,兰州大学 草地农业生态系统国家重点实验室 草地农业科技学院,兰州大学 草地农业生态系统国家重点实验室 草地农业科技学院,兰州大学 草地农业生态系统国家重点实验室 草地农业科技学院,兰州大学 草地农业生态系统国家重点实验室 草地农业科技学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31270558); 国家公益性行业(农业)科研专项经费(201203041); 兰州大学中央高校基本科研业务费专项资金(lzujbky-2013-86) Functions of arbuscular mycorrhizas in grassland ecosystems Author: Affiliation: State Key Laboratory of Grassland Agro-Ecosystem, School of Pastoral Agriculture Science and Technology, Lanzhou University,,,,,,State Key Laboratory of Grassland Agro-ecosystems,School of Pastoral Agriculture Science and Technology,Lanzhou University,P.O. Box 61 Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:AM真菌是土壤生态系统中重要的微生物类群,能与陆地生态系统中80%以上的高等植物建立共生体系。目前,AM真菌在维持草原生态系统稳定性中的功能已经成为生态学研究的热点问题之一。基于此,从植物个体、种群、群落和生态系统等不同层次探究AM真菌在维持植物群落多样性和草原生态系统稳定性中的功能。分析发现在个体水平上,AM真菌对宿主植物具有促生效应、抑制效应或中性效应。在种群水平上,分析AM真菌对不同宿主植物吸收土壤矿质营养的分配和调控策略,围绕构成草原植被的两大组成成分:牧草和有毒植物,论述AM真菌对植物种群增长和衰败的调控机制,并从草原植物群落的物种多样性和稳定性角度,探讨AM真菌与植物群落之间的相关性。在生态系统水平上,围绕AM真菌对草原生态系统的演替和退化草原的修复等展开论述,以期为利用AM真菌开展草原生态系统保护和恢复治理提供理论依据,并对草原菌根生态学领域未来的研究进行展望。 Abstract:Arbuscular mycorrhizal (AM) fungi are important soil microorganisms, which can form symbioses with more than 80% of vascular plants in terrestrial ecosystems. It has been demonstrated that AM fungi could improve the growth of host plants through regulation of their physiological and biochemical characteristics. In light of this, AM fungi could regulate plant intra-and inter-specific competition in natural habitats. Recently, using AM fungi to protect plant biodiversity and maintain plant community stability in grassland ecosystems has generated much interest. Here, the functions of AM fungi are discussed at the autecology, population, community and ecosystem levels in order to discover the relationship between AM fungi and host plants. There are three different responses of individual host plants to AM fungi symbiosis, including positive, negative and neutral effects. At the population and community levels, AM fungi could regulate intra- and inter-specific competition by influencing the transportation of nutrients and water among individuals, such as to regulate herbaceous and poisonous plant populations. AM fungi also could maintain plant community structures and plant diversity in grasslands by regulating the plant competition. At the ecosystem level, AM fungi could promote the process of community succession, and thus could be used in bioremediation of damaged ecosystems. This review aims to provide theories and methods for the protection of grassland ecosystems by integrating the uses of AM fungi. 参考文献 相似文献 引证文献

Effect of climate and intra- and inter-specific competition on diameter increment in beech and oak stands

Differences between intra- and inter-specific competition strategies in mixed stands account for higher productivity. The mechanisms of competition as they relate to stand structure remain poorly explored. Climatic effects have also been overlooked in most approaches aimed at studying tree growth. These effects were investigated through the case study of beech-oak mixtures in France. A single-tree diameter-increment mixed model was fitted to data gathered from the Laboratoire d'Etude des Ressources Foret-Bois (LERFoB) network of permanent plots. In order to take stand structure into account, the model was able to distinguish between inter-and intra-specific competition at tree level. Differences in intra-and inter-specific competition are mainly detected in the understorey of oak-dominated stands, where suppressed beech trees performed better than suppressed oak trees. From a climatic point of view, diameter increment was sensitive to the mean temperature of the vegetative period. Concerning competition, our results demonstrate that optimal growth induced by mixtures is not only a matter of species proportion but also depends on stand structure. Regarding climatic effects, they need to be considered in growth predictions, especially given the future climatic conditions predicted for continental Europe. These findings could serve as guidelines for designing strategies to alleviate stress in oak-beech stands.

Effect of European Union BSE-Related Enactments on Fledgling Eurasian GriffonsGyps fulvus

The effects of supplemental feeding on Eurasian Griffon range from increased survival and reproduction to population recoveries. In 2000, the appearance of Bovine Spongiform Encephalopathy (BSE) in Europe resulted in the implementation of the 1774/2002 regulation that required carcass removal and incineration at processing plants within the European Union and resulted in an immediate reduction of food availability for scavengers. We wished to evaluate the effect of the implementation of the reduced food availability on the scavenging Eurasian Griffon population. The study was conducted in La Rioja province (northern Spain). Eurasian Griffon fledglings are regularly brought to a rehabilitation center and can help evaluate the changes in nutritional condition before and after the enactment of the BSE regulations. A total of 47 first year griffons were sampled. Ptilochronology was applied to the rectrices, growth bars that are grown during the fledgling period were counted among nestlings before and after implementation of the EU-BSE directives. We found that the width of the growth bars, that represent the nutritional condition of the bird, showed significant differences over time. The growth bars before the implementation of the BSE EU-directives were significantly narrower than the subsequent period wherein carcasses were greatly reduced. The frequency of fault bars showed trends opposite to those of growth bars and there were significantly more fault bars in the pre-removal implementation period than the post-removal period. In conclusion, we consider this to be a result wherein the local adults with fidelity to their breeding colonies remained in the area while the non-breeding sub-adults and floaters have strayed in search of food. This has resulted in reduced inter-and intra-specific competition and only adults in good body condition breed resulting in healthier fledglings.

Caracterización preliminar de los sitios de cría de Aedes (Stegomyia) albopictus (Skuse, 1894) (Diptera: Culicidae) en el municipio de Leticia, Amazonas, Colombia

Because the role of Aedes albopictus as an incriminated vector of several viral pathogens, its control is important to human health. To establish appropriate control methods, characterization of the larval habitats is a necessary first step. Habitats of the immature stages of Ae. albopictus were characterized with respect to physical-chemical parameters and by floral and faunal arrays present. Leticia is located at the southernmost tip of Colombia on the banks of the Amazon River. In the urban area, 154 houses were inspected in December 2002 and January 2003. Physical-chemical data were collected, including exposure to sunlight, location, container size and material, water conductivity, and dissolved oxygen. Macroinvertebrates and plankton samples were taken at each positive larval site. The results were compared using descriptive analysis, principal component analysis, classification dendrograms, and diversity indexes. Twenty-one habitats were found positive for Diptera, and 13 were positive for Ae. albopictus larvae. Most of the positive habitats (92%) were located near the houses--they were small or medium size receptacles located in the shade. This water generally had low conductivity and low turbidity, although high values of these parameters were also identified. The habitats had low diversity indexes for macroinvertebrates and high diversity indexes for plankton. In the principal component analysis, significant correlation was found with mites, oligochaetes and hemipterans (the macroinvertebrates) and with bacilarophyceaes, clorophyceaes and cianophyceas (the algal forms). In Leticia, females of Ae. albopictus were found in newly established habitats with sufficient availability of resources, low conductivity, and turbidity, lower intra-and interspecific competition.

Patterns of activity cycles in juvenile California two-spot octopuses (Octopus bimaculoides)

Octopuses function as important prey and predators in many continental-shelf marine ecosystems. Understanding activity cycles of octopuses should help define their mode of foraging and potential resource utilization and, therefore, their niche within the marine community. Unfortunately, little is known concerning activity cycles of octopuses, especially during their juvenile life-history stages. Here, I present observations on juvenile activity in Octopus bimaculoides Pickford and McConnaughey, 1949 over three observational weeks in a semi-natural laboratory setting. Octopuses on average were nocturnal, but some individuals were active during daylight hours in all three observational weeks. Nocturnal activity cycles may decrease the risk of predation on juveniles by visual fish predators hunting during daylight hours. However, inter-and intraspecific competition with other octopuses in different life history stages, including adult O. bimaculoides and adult and juvenile Octopus bimaculatus Verrill, 1883 i...

ECOLOGY AND PHYSIOLOGY OF EN ROUTE NEARCTIC-NEOTROPICAL MIGRATORY BIRDS: A CALL FOR COLLABORATION

Ornithologists who regularly witness the breathtaking influx of songbirds at stopover sites during spring or fall migration know that birds are tremendously adaptable. Migration encompasses a range of actions distinct from permanent residency but includes altitudinal movements, sporadic irruptions, short-distance flights, as well as obligate long-distance movements (Able 1991). Migration can be acquired, abandoned, or prolonged by a species depending on conditions along their migratory routes (Able and Beltoff 1998). Previously nonmigratory populations may undertake migration where changing conditions become increasingly disadvantageous for the resident population or where interspecific competition becomes more severe. Regardless of the distance or motivation, migration is physiologically demanding and potentially risky. Nearctic-Neotropical migrants face both ecological and physiological challenges while en route from one location to another. Migrants require periodic stopovers to rest and refuel, and during these stopovers, they must cope with the uncertainties of resource abundance and availability, intraand interspecific competition, and predation pressures in unfamiliar environments (Moore et al. 1995). Physiologically, the size of many Nearctic-Neotropical migrants puts large constraints on fat storage, flight speed, and the ultimate distance a bird is able to travel in one migratory bout. Ecological and physiological hurdles associated with transand intercontinen-

Dispersal and persistence: Population processes and community dynamics

If we look at plant cover at a certain site, we can observe that it is made up of a number of species of different size and form, conferring a certain structure to the vegetation cover. If we compare two sites, we invariably see differences in structure and species composition. These differences are repeated across a hierarchy of scales: at the local scale, the regional scale and ultimately at the continental scale. By comparing structure and species compositions across a larger number of sites, a statistical pattern emerges from the data: some species are found together more frequently than expected and others seem to avoid each other. In fact, these positive and negative associations result in the observation that the species composition of a site is not just a random collection of species but is patterned, resulting in recognizable plant communities. In a spatial context we can fruitfully distinguish between within-site and among-site processes that influence the plant community. This distinction enables the description of species composition as a result of a dynamic process of within-community extinctions and colonizations from the outside. According to this view, community structure results from the differential performance of species as a function of biotic and abiotic environmental factors during the period between colonization and extinction. It now very much depends on the temporal scale of the dynamics of the system whether one puts emphasis on deterministic within-community processes, such as intraand interspecific competition, or on the stochastic processes of colonization and extinction. In fact there has been a long-standing debate about the relative importance of these two underlying assortative processes that are responsible for the perceived patterns in species composition (resulting in recognizable plant communities). This debate has its roots in the beginning of the last century and is conveniently summarized as the Clementsian versus the Gleasonian view on plant communities. The Clementsian view with its emphasis on the role of abiotic conditions and the regulative power of competitive processes has been dominant for a number of decades. In fact, a larger part of vegetation science is about finding the relationship between species composition and environmental factors. The fact that, given certain environmental conditions, we are able to

Influence of Arbuscular Mycorrhizal Infection on Competition between Holcus Lanatus and Dactylis Glomerata

1 Holcus lanatus and Dactylis glomerata were grown in monocultures and mixtures to determine the influence of mycorrhizal fungi on intraand interspecific competition. 2 In monoculture, shoot biomass per plant of both species was increased over all densities by mycorrhizal infection. Increased tiller and leaf numbers per plant for H. lanatus, but not for D. glomerata, suggested that enhanced biomass was a result of greater tiller and leaf production in Holcus, but to increased tiller weight in Dactylis. Increased competition reduced shoot biomass, tiller number and leaf number in both species. 3 Although the response was variable, mycorrhizal infection generally enhanced shoot biomass of both species in mixed cultures. Tiller production in D. glomerata was generally unaffected by infection but reductions in leaf number were observed in mycorrhizal stands. In contrast to its effects on monocultures, infection had no effect on tiller production when H. lanatus was in mixture. 4 Relative yield totals (R YT) calculated for grasses grown in mixture suggest that, overall, mycorrhizal infection resulted in a reduction of resource complementarity, i.e. it increased the level of competition for the same resources. This was reflected in the relative yields which showed that the shoot biomass for each species in mixture was lower than that expected from growth in monoculture. 5 Aggressivity indices suggested that H. lanatus was more aggressive than D. glomerata when present in equal or greater numbers. Mycorrhizal infection altered the degree of aggressivity in favour of the already more aggressive plant within the combination, although, at very low densities, D. glomerata was more aggressive than H. lanatus when mycorrhizal.

Compétition intra-et interspécifique entre plantules d' Artemisia herba-alba Asso et Anthyllis henoniana Batt., chaméphytes de la Tunisie présaharienne

Intra-and interspecific competition between seedlings of two presaharian chamephytes was experimentally studied. For the two species raised separately we found an increase in interspecific competition with increasing density. In the mixed culture, Artemisia herba-alba competes better than Anthyllis henoniana for water, with an increase of mortality rate and a decrease of the biomass of Anthyllis henoniana being observed. Modelisation of changes in the mortality rate allow us to discern between three factors (date, treatment and density) those responsible of the mortality during soil drying. For Artemisia herba-alba the date and density effects explain the evolution of mortality rate, for Anthyllis henoniana the model includes interactions between the three factors.

Territory defense by the ant Azteca trigona: maintenance of an arboreal ant mosaic.

Mosaics of exclusive foraging territories, produced by intra-and interspecific competition, are commonly reported from arboreal ant communities throughout the tropics and appear to represent a recurring feature of community organization. This paper documents an ant mosaic within mangrove forests of Panama and examines the behavioral mechanisms by which one of the common species, Azteca trigona, maintains its territories. Most of the mangrove canopy is occupied by mutually exclusive territories of the ants A. trigona, A. velox, A. instabilis, and Crematogaster brevispinosa. When foraging workers of A. trigona detect workers of these territorial species, they organize an alarm recruitment response using pheromonal and tactile displays. Nestmates are attracted over short distances by an alarm pheromone originating in the pygidial gland and over longer distances by a trail pheromone produced by the Pavan's gland. Recruits are simultaneously alerted by a tactile display. No evidence was found for chemical marking of the territory. Major workers are proportionally more abundant at territory borders than on foraging trails in the interior of the colony. The mechanisms of territory defense in A. trigona are remarkably similar to those of ecologically analogous ants in the Old World tropics.

Avoidance of competition by spruce bark beetles,Ips typographus andPityogenes chalcographus

Bark beetles,Ips typographus andPityogenes chalcographus, attracted by synthetic or natural pheromone to Norway spruce logs,Picea abies, preferred to colonize uninfested logs rather than logs occupied by these beetles, probably as a means of avoiding intra-and interspecific competition. The aggregation pheromone components ofP. chalcographus, chalcogran and methyl (E, Z)-2,4-decadienoate, inhibited the attraction response ofI. typographus to its pheromone components (methyl butenol andcis-verbenol), while the converse was not true. However, verbenone released from colonized bark inhibited pheromonal response ofP. chalcographus.

Increasing Gliricidia sepium and Cassia spectabilis biomass production

This paper examines the impact of spacing on biomass production of monocropped and mixed hedgerows of seedlings and cutting of Gliricidia sepium and Cassia spectabilis. The impact of lime on G. sepium biomass production was also evaluated. Seedlings survived better than cuttings; and no differences were observed between seedlings in either pattern at the highest density tested. Although spacing reduced inter-and intra-specific competition, total biomass production was greatest at higher densities. Mixing hedgerow species reduced intraspecific competition within C. spectabilis, resulting in increased biomass production. Six, 8 and 12 tons of lime per hectare significantly increased fresh G. sepium biomass production at all harvest dates except the first. Extrapolated to an alley cropping system, applying 6 t/ha of lime increased fresh cumulative G. sepium biomass production by almost 39 t/ha over the no lime treatment representing more than 200 kg N/ha.

Production Possibility Frontiers and Estimation of Competition Effects: The Use ofA PrioriInformation on Biological Processes in Intercropping

SummaryProduction possibility frontiers contribute much to an economic evaluation of yield advantages from intercropping. The difficulty with estimating a production frontier empirically from experimental data is one of ascertaining that the fitted curve corresponds with the frontier. This problem has been overcome by deriving the frontier froma prioriknowledge of the biological processes that determine the outcome in intercropping. The hyperbolic relationship between biomass yield and plant density, and the parameters that characterize the degree of intra-and inter-specific competition in intercropping are used in this paper to derive production possibility frontiers. The method is illustrated with data from three intercropping studies. A brief review of the two main methods used by researchers to evaluate the results of intercropping, and their limitations, is also presented.

Intra-Host Interactions between a Braconid Endoparasitoid, Apanteles glomeratus, and a Baculovirus for Larvae of Pieris brassicae

(1) This study explores within-host mechanisms of intraand interspecific competition involving the gregarious braconid endoparasitoid, Apanteles glomeratus, and the granulosis virus (GV) of Pieris brassicae. (2) Increasing doses of the GV resulted in increases in mortality and decreases in lifespan of the host. Susceptibility to the virus decreased markedly with host age. (3) High doses of the GV resulted in substantial reductions in production of pathogen progeny, consistent with intraspecific competition for a limited (but growing) resource. (4) Survival of the parasitoid brood within GV-infected hosts depended on the relative timing of parasitoid emergence (at the spinning of the host pupal mat) and host death due to the virus. (5) Interspecific competition between the natural enemies did not involve changes induced by the parasitoid in the pathogen's ability to infect the host. However, the expected life-span of hosts harbouring both competitors was significantly shorter than hosts infected with the virus alone. (6) Interspecific competition within the host was, on average, highly symmetrical. The presence of virus reduced the average weight of the parasitoid brood by 29 %, whereas the parasitoid brood reduced the potential reproductive output of the virus by 28%. However, when the size of the parasitoid brood was taken into account, the parasitoid individual was best off when in small broods, whereas the virus did best when competing with larger parasitoid broods.

Changes in Foraging Effort in Two Gerbil Species Correlate with Habitat Type and Intra- and Interspecific Activity

The effect of intraand interspecific competition on the foraging effort of two gerbil species, Gerbillus allenbyi and G. pyramidum, was studied in six 1-ha enclosures located in an area containing semistabilized dunes and stabilized sand fields in the Negev desert, Israel. It was found in both species that per capita foraging and non-foraging activity was negatively and significantly correlated with its own population density. When G. pyramidum was common, G. allenbyi limited most of its activity to the stabilized sand while most G. pyramidum activity occurred in the semistabilized dunes. However, with none or one G. pyramidum present, most G. allenbyi activity was shifted to the semistabilized dune. Per capita activity of both species declined significantly as a function of the increasing activity of the other. However, the decline in per capita activity of G. allenbyi in the presence of G. pyramidum was significantly greater than the decline in per capita activity of G. pyramidum in the presence of G. allenbyi. In the stabilized sand, per capita activity of each of the two species was also significantly correlated with the density of the other species. The density of G. allenbyi was positively correlated with per capita activity of G. pyramidum and the density of G. pyramidum was negatively correlated with per capita activity of G. allenbyi. Several possible mechanisms that might explain these interactions are discussed. We concluded that the asymmetric interspecific competition between G. allenbyi and G. pyramidum probably fits the shared preference habitat selection model.