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101.
The ecology of ruffe,Gymnocephalus cernuus (Pisces: Percidae) introduced to Mildevatn,western Norway 总被引:2,自引:0,他引:2
Steinar Kålås 《Environmental Biology of Fishes》1995,42(3):219-232
Synopsis Diet, habitat use, diel and seasonal activity and a number of population parameters were studied on ruffe,Gymnocephalus cernuus, introduced to Mildevatn, western Norway. This lake is sited outside the natural range of the ruffe and has a lower fish
diversity and a different fish species composition than within its native range. From June through September the ruffe was
planktivorous and mainly caught at 4 to 6 m depth in the benthic zone. At other times of year ruffe was feeding on zoobenthos
and caught deeper in the benthic zone. Ruffe was mainly day active. Zooplankton feeding during summer is the clearest difference
compared to ruffe populations living within its natural range. Presence of large zooplankton organisms available for ruffe
is suggested as the main reason for the difference found in food choice. The availability of large zooplankton is probably
due to community structure caused by a predator and lack of interspecific competition for zooplankton in the deeper parts
of the lake. Piscivorous brown trout.Salmo trutta, restrict the habitat of threespined stickleback,Gasterosteus aculeatus, to the zone of littoral vegetation, allowing high densities of larger zooplankton species likeBythotrephes longimanus to be present in the lake. Brown trout is present only in the upper light and well oxygenated parts of the lake, leaving
a refuge for the ruffe, where they can feed on the rich zooplankton community. 相似文献
102.
Dennis M. Allen William S. Johnson Virginia Ogburn-Matthews 《Environmental Biology of Fishes》1995,42(1):37-50
Synopsis In a high salinity estuary at North Inlet, South Carolina, co-occurrence and possible competition among adults of four dominant zooplanktivorous fishes were minimized by seasonal adjustments in lateral and vertical distributions as well as in dietary preferences. In winter, Atlantic silversides, Menidia menidia, occupied the entire water column while other planktivores were rare or absent from the estuary, and they consumed large prey such as mysid shrimps and fish larvae. An immigration of bay anchovies, Anchoa mitchilli, in the spring resulted in a redistribution of species with Atlantic silversides shifting to the surface waters and bay anchovies dominating the lower half of the water column. Both fishes consumed mostly copepods in the spring, but each favored a different species. There was little similarity in the large prey items consumed by the two fishes. Striped anchovies, Anchoa hepsetus, arrived in mid-summer and were most abundant at the surface while bay anchovies continued to dominate the bottom waters. Atlantic silversides were rare in all summer collections. The diets of the two anchovies were similar, but vertical separation during the period of maximum zooplankton abundance probably minimized competition. Rough silversides, Membras martinica, which were obligate surface dwellers, shared the upper water column with striped anchovies, but the two species had very different diets during their period of co-occurrence. Although seasonal changes in fish diets reflected shifts in zooplankton composition and all fishes consumed a variety of prey types, preferences for some prey taxa and total avoidance of others were indicated. Electivity indices indicated an especially strong selection for fiddler crab megalopae by all fishes in the summer and fall. All fishes, except rough silversides, which fed almost exclusively on copepods and crab zoeae, consumed large prey items when they were available. Fine scale partitioning of the food resources was apparent in the selection of different copepod and insect species by the fishes. Spatial and temporal separation in the distribution and/or dietary preferences of the zooplanktivores fishes probably reduces the potential for resource competition. Given the high abundances and selectivity of the planktivores, significant impacts on some zooplankton populations probably result. 相似文献
103.
Peter B. Pearman 《Oecologia》1995,102(1):1-8
Experimental ponds were used as a model system of habitat patches to study the effect of habitat size on the relative growth performance of tadpoles of Bufo americanus and Pseudacris triseriata, and on colonization by predatory insects. Three pond depths and surface areas were habitat size treatments in a replicated, factorial experiment. Tadpoles of both species were astablished together at a single density and ponds were left open to natural colonization by aquatic insects. Pond area had a significant effect on the multivariate response of P. triseriata larval period, survival, and metamorphic mass. P. triseriata survived better relative to B. americanus in larger ponds. However, increasing pond area led to greater incidence of predacious beetle larvae (Dytiscus, Coleoptera: Dytiscidae). Dytiscus larvae had a significant negative effect on the survival of P. triseriata and led to reduced P. triseriata survival relative to B. americanus in colonized ponds. The results suggest that habitat size can influence community structure by altering the distribution of predation among habitat patches. 相似文献
104.
应用 二次正交旋转组合设计方法,对稻田生态系统中3种捕食性天敌(三突花蛛Misumenops tricuspidata(Tabricius)、草间钻头蛛Hylyphantes graminicora(Sundevall)、真水狼蛛Pirata piraticus(Clerk)和1种害虫(白背飞虱Sogatella furcifera(Horvath)的共存系统进行研究,获得了天敌对害虫控制作用的数 相似文献
105.
Leaf surface waxbloom in Pisum sativum influences predation and intra-guild interactions involving two predator species 总被引:2,自引:0,他引:2
Suppression of shared prey populations by insect predators can be influenced by interactions among these predators (intra-guild
interactions). Intra-guild interactions among predators attacking herbivores may be influenced by plant characteristics, but
this possibility has not been examined. Plant surface waxes are a ubiquitous and variable morphological feature that are known
to affect insect predator behavior, and potentially in- fluence inter-predator interactions. To test this possibility we measured
the effectiveness of individual and multiple predators on Pisum sativum L. lines with either wild-type crystalline waxes (normal waxbloom) or with reduced waxbloom resulting from a genetic mutation.
On caged five-node plants of each line, reduction in populations of Acyrthosiphon pisum (Harris) (Homoptera: Aphidae) by individuals or pairs of second-instar Hippodamia con- vergens Guerin de Meneville (Coleoptera: Coccinellidae), and second-instar Chrysoperla plorabunda (Fitch) (Neuroptera: Chrysopidae), was significantly greater on the reduced waxbloom plants. Intra-specific interference
by H. convergens depended on plant waxbloom type. Pairs of H. convergens larvae were no more effective than individuals of this species at reducing aphid populations on normal waxbloom plants, indicating
interference, but were additive in their reduction of aphids on reduced waxbloom plants, indicating no interference. In contrast,
pairs of C. plorabunda apparently interfered regardless of plant waxbloom type; pairs were no more effective at reducing aphids than individuals
of this species. Heterospecific pairs of H. convergens and C. plorabunda were more effective on reduced waxbloom plants and showed no evidence of interference on either waxbloom type. Differences
in behavior of the two predator species provided a partial explanation for the asymmetrical effect on intraspecific interactions
in the two species. H. conver- gens spent significantly more time walking and less time ”scrambling” (ineffective locomotion) on reduced waxbloom plants than
on normal waxbloom plants, and distributed these activities differently among plant parts on the two waxbloom types. In contrast, C. plorabunda spent the same amount of time walking and scrambling on each waxbloom type, although they distributed this walking and scrambling
differently among plant parts of the two waxbloom types. The stronger influence of plant waxbloom on H. convergens behavior is consistent with the difference in intra-specific interference for this species on the two waxbloom types. The
mechanisms of intra-specific interference by H. convergens on normal waxbloom plants and by C. plorabunda on both waxbloom types were not determined.
Received: 14 July 1999 / Accepted: 10 January 2000 相似文献
106.
Constraints on body size distributions: an experimental approach using a small-scale system 总被引:6,自引:0,他引:6
Holling’s (1992) proposition that discontinuities in biotic and abiotic processes generate structure in ecological systems
is examined experimentally by imposing size-specific perturbations on marine sediment assemblages. Two kinds of perturbations
were applied: organic enrichment and predation, each at two levels. Perturbations significantly affected the densities and
relative abundance of the main invertebrate taxa and these effects were consistent with the known effects of enrichment and
predation. However, there was little evidence of significant treatment effects on the overall benthic biomass or abundance
size spectrum, supporting the contention that the spectrum is conservative and is probably constrained by habitat architecture.
Received: 28 June 1999 / Accepted: 24 September 1999 相似文献
107.
异色瓢虫若虫对麦三叉蚜的捕食作用 总被引:5,自引:4,他引:1
研究表明,异色瓢虫高龄若虫捕食麦二叉蚜的功能反应为HollingⅡ型反应,喜好捕食低龄若蚜;在40℃下捕食率最低,10℃次之,25℃最高.在10~25℃内捕食率y与温度x的关系为y=28.1303+2.6665x,在25~40℃内为y=199.9275-3.642x;在种内干扰条件下,其捕食作用率E与开敌密度P的关系为E=0.6897P-0.7930,搜索常数Q为0.6897,干扰系数m为0.7930;其分摊竞争强度I与异色瓢虫密度P的关系为I=0.0400+1.0383logP. 相似文献
108.
Jan H. Mol 《Oecologia》1996,107(3):395-410
This study investigated the role of predators in preventing competitive exclusion among three closely related armoured catfishes (Callichthys callichthys, Hoplosternum littorale and H. thoracatum) that occur synthopically in multi-predator freshwater swamps of Suriname, South America. The potential impact of predation on armoured catfish was determined by combining laboratory measurements of predation rates on five early developmental stages of the armoured catfish H. thoracatum for 24 aquatic predators with field studies of the density of the predators in the swamps. The contribution of a particular predator to the total predation pressure on its prey was determined to a large extent by the density of the predator in the swamp. Seemingly innocuous predators with low or moderate predation rates in the laboratory may be extremely important in the swamps due to their high abundance. Small-sized omnivorous fishes and aquatic invertebrates were major predators of early developmental stages of armoured catfish. Both qualitative and quantitative ontogenetic changes in the predation pressure on armoured catfish were observed. Major predation on eggs, larvae and juveniles of H. thoracatum resulted from a different set of predators in each developmental stage of the prey. In all developmental stages of H. thoracatum the predation pressure involved several predator species and not a single, dominant predator. The potential predation pressure of the 24 predators taken together and the number of predators that were able to prey on H. thoracatum decreased sharply with increasing age (size) of the prey. Even if egg (nest) predation is prevented by the guarding male, the potential impact of the 24 predators on the populations of armoured catfish is large. Predation may account for the high mortality of H. thoracatum observed in the swamps. The high predation pressure on callichthyid catfishes may help to explain the coexistence of three closely related and morphologically quite similar armoured catfishes in Surinamese swamps. 相似文献
109.
Jill Lancaster 《Oecologia》1996,107(3):321-331
The effects of hydraulic disturbances on the impact of two predatory benthic invertebrates on their prey were examined in a stream at two distinct spatial scales. At the scale of small habitat patches (0.0625 m2), hydraulic patch type was an important determinant of the microdistribution of prey and predators. Prey abundances were similar across all patch types at baseflow, but local densities were higher in patches identified as low-flow refugia after periods of high and fluctuating flow. The microdistribution pattern of predatory larvae of a caddisfly, Plectrocnemia conspersa, was similar to that of its prey, whereas predatory larvae of an alderfly, Sialis fuliginosa, did not shift their microdistribution significantly with discharge and were always most abundant in lowflow refugia. There was little evidence of an aggregative response of predators with prey, even though both predators and prey are mobile. Both predator species showed similar patch-specific patterns of per capita consumption rates: uniform consumption rates across hydraulic patch types at low and moderate flows, but highest in flow refugia during high flows. Species-specific patterns, however, were apparent in the magnitude and direction of differences between consumption rates during disturbance events, and in comparable patches at base flow: At high flow, consumption rates for P. conspersa were exaggerated (3.9 times higher) in flow refugia but at par in other patches; for S. fuliginosa they were at par in flow refugia but reduced in other patches (up to 3.3. times lower). These differences may be related to species-specific foraging behaviours (search vs ambush predators) and the influence of prey movements on feeding success. Using the patch-scale results only, it is difficult to predict the effects of physical disturbance on predation intensity at the larger scales of whole habitats, populations or communities. At the large scale (>200 m2), net predator impacts were estimated over the stream reach, using a spatially explicit model that accounts, in an additive way, for habitat heterogeneity and patch-specific responses of predators and prey. The relationship between predator impact over the whole reach and hydraulic disturbance differed for the two predators. The predator impact of S. fuliginosa decreased with increasing hydraulic disturbance, as predicted by the harsh-benign hypothesis. There was no directional trend for P. conspersa, however, and maximum predator impact may occur at intermediate disturbance levels. For the prey community in this stream, predation pressure from S. fuliginosa appears to fluctuate directly with the discharge hydrograph, whereas predation from P. conspersa may be more persistent. Flow refugia may play a dual role in the sructure of stream communities by preventing catastrophic mortality of animals (predators and prey) from physical forces during disturbances, and by maintaining (or perhaps increasing) predation pressure. Summing the effects of species interactions in small habitat patches to the larger scale of a whole stream reach indicates that the scale of approach influences the observed patterns and their implied underlying process. 相似文献
110.
Effects of small mammals and vertebrate predators on vegetation in the Chilean semiarid zone 总被引:4,自引:0,他引:4
J. R. Gutiérrez P. L. Meserve S. Herrera L. C. Contreras F. M. Jaksic 《Oecologia》1997,109(3):398-406
We monitored the cover and seed bank response of shrubs, perennial herbs, and ephemeral plants to experimental exclusion
of both the principal rodent herbivore, Octodon degus, and its vertebrate predators from 1989 to 1994 in a semiarid Chilean mediterranean site. Although both richness and species
composition of the plant community at the study site were largely determined by abiotic factors (mainly rainfall and soil
nutrients), predator and herbivore exclusion had significant effects on the relative abundance of several plant species. Experimental
exclusion of herbivores was associated with increased cover of some shrubs and a perennial grass, and decreased cover and
seed densities of several ephemerals, especially those exotic or restricted to areas underneath shrubs. Herbivores apparently
reduced shrubs through browsing and indirectly affected herb cover and seed densities by opening up areas under shrubs and/or
modifying physical and chemical conditions of the soil. Plant responses to predator exclusion were less clear. Nevertheless,
higher cover of some shrubs and ephemerals in the presence of predators suggests tritrophic effects through changes in small
mammal densities and/or foraging behavior.
Received: 22 April 1996 / Accepted: 14 August 1996 相似文献