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1.
Summary Dispersions and resource utilization of primary and secondary parasitoids developing in non-depletable primary host populations
were determined for an aphid-parasitoid community occurring on strawberries. Analyses of dispersions based onGreen's coefficient andLloyd's Patchiness Index indicated parasitized aphids were highly aggregated initially, became less aggregated as density increased,
and remained aggregated following collapse of the aphid populations. The “index of aggregation” values calculated usingTaylor's Power Law concurred with results from the other indices, and the similarity of the regression coefficients from both seasons
suggests that the index of aggregation may be characteristic for communities as well as species. Analysis withIwao's regression of mean crowding on the mean generated similar results when population data were stratified temporally, and
also indicated that the individual was the basic unit of the population.
In a non-depletable environment, oviposition of individuals exhibiting an aggregated dispersion pattern within clumps of hosts
provides primary parasitoids with a suitable trade-off between energy utilization or genetic potential, and losses associated
with hyperparasitism. 相似文献
2.
Summary Time-specific life tables were constructed for three pea aphid,Acyrthosiphon pisum (Harris) (Homoptera: Aphididae), populations using a modification ofHughes' analytical procedure. All populations were studied on second-growth alfalfa (mid-June to mid-July) in south central Wisconsin;
data for two populations were collected during 1980, and data for the third population were collected during 1982. The intrinsic
rate of increase (r
m) estimated on a physiological time (day-degree) scale under field conditions but in the absence of natural enemies, provided
a reliable estimate of potential population growth rate and was used in preference toHughes' approach of estimating potential population growth rates directly from stage structure data. Emigration by adult alatae and
fungal disease were the major sources ofA. pisum mortality in each of the three populations studied. These factors were most important because of their impact on reducing
birth rates within the local population. Parasitism was never greater than 9 percent. Mortality attributable to predation
ranged from 0.0 to about 30.0%; however, even at the highest predator densitiesA. pisum populations increased exponentially. 相似文献
3.
Indirect interactions between populations of different species can be important in structuring natural communities. Indirect
effects are either mediated by changes in population densities (trophic or density-mediated effects) or by changes in the
behavior of species that are not trophically connected (behavioral or trait-mediated effects). We reviewed the literature
on aphids and their parasitoids to explore the various possible indirect interactions that can occur in such communities.
The review was motivated by our study of a particular aphid–parasitoid community in a natural (i.e., nonagricultural) habitat,
and by the wealth of information that exists about aphid–parasitoid systems in agricultural settings. We focused our review
on aphid–parasitoid interactions, but considered how these were influenced by the other aphid natural enemies and also by
aphid mutualists and host plants. We conclude that indirect effects are likely to have a major effect in structuring aphid–parasitoid
communities, and that the latter are a valuable model system for testing ideas about community interactions.
Received: December 20, 1998 / Accepted: January 12, 1999 相似文献
4.
Eizi Kuno 《Researches on Population Ecology》1988,30(1):69-82
Summary The influence of spatial distribution pattern on the outcomes of intra- and interspecific competition is studied theoretically.
The models developed are the generalized logistic andVolterra equations, whereLloyd’s indices of intra- and interspecies mean crowding were incorporated with their assumed linear relationship to mean density
in order to express the intensity of crowding which is really effective to the existing individuals. It is shown that while
the increasing patchiness of distribution has a pronounced effect of promoting the intraspecific competition and lowering
the equilibrium density for individual populations, it generally relaxes the interspecific competition, making it easy for
different species sharing the same niche, which would otherwise be incompatible, to coexist stably. These models thus provide
a simplest theoretical basis to explain why many insect populations in nature are kept relatively rare in number and why a
number of allied species often coexist freely sharing the same resource, against the “competitive exclusion principle” deduced
from the originalVolterra equations. 相似文献
5.
Maternal age as a source of variation in the ability of an aphid to produce dispersing forms 总被引:2,自引:0,他引:2
Summary Apterous parthenogentic females of the pea aphid,Acyrthosiphon pisum (Harris), begin to produce alate offspring soon after they have been subjected to crowding.
Females which were born early in their own parent's reproductive period respond most strongly to crowding, producing much
larger numbers of alatae than their late-born sisters.
In contrast, the early-born daughters of most alate females do not produce winged offspring after being crowded. Some of their
later-born sisters may produce a few winged individuals, resembling in this respect the late-born daughters of the apterous
females.
Control of the production of alatae thus begins in the grandparental generation. Risk-spreading by means of differential dispersal
becomes a less uncertain venture when local populations can modify their responses to environmental changes by utilizing past
as well as present signals from their surroundings. 相似文献
6.
John T. Trumble 《Researches on Population Ecology》1985,27(2):277-285
Summary The influence of pesticide application on the within-field distribution of arthropods was investigated forTetranychus urticae, the twospotted spider mite, on strawberries. Analyses of dispersions based onGreen's coefficient,Iwao's regression of mean crowding on the mean, andTaylor's power law all indicated that mite populations were highly aggregated initially. As densities increased, more of the avialable
niches were filled, leading to a less clumped dispersion. However, pesticide applications causing greater than 99.9% mortality
acted in a nearly density independant fashion and, although the originating populations were similar in number, did not produce
dispersions equivalent to the initial migrants. As a result, ignoring these changes by developing sampling plans based on
dispersion indices which generated a single slope for an entire data set, led to statistical errors that invalidated the sampling
programs. In order to accurately reflect the field biology of the spidermites, sampling plans for pre and post-treatment populations
were substantially different.
The impact of such changes in dispersion were graphically demonstrated using both sequential and binomial sampling techniques.
Both methods showed that fewer samples were necessary to estimate densities at a given precision level for post-treatment
populations. Also, these techniques indicated that post-treatment populations had similar, but significantly different, dispersions.
The implications of changes in pre and post-treatment dispersions, as well as problems associated with inconsistant dispersions
following pesticide use, are discussed. 相似文献
7.
Summary AsMatsumoto andHuffaker (1973) concluded that their initial universe size was too small for the proper separation of the effects of host density
and dispersion on parasite performance, a larger universe of 38 1/2″ (length) ×38 1/2″ (width) ×3″ (height) was used.
When individual parasites were exposed to fixed densities and dispersion patterns of host, they displayed an overall decrease
in the parasitization rate when compared to the small universe. In all cases aHolling-type response resulted.
When a group of 10 parasites per test was employed a Nicholsonian type of response resulted.
In an experimentally confined space, the parasites displayed a mutual behavioral interference resulting in emigration which
accelerated as the parasite density increased.
These studies were conducted as a partial fulfillment in the Ph. D. program of one of us (B. M. Matsumoto) and is a part of a broad investigation into the processes operating in the dynamics of arthropod populations under grants
toC. B. Huffaker from the U. S. Public Health Service, National Institutes of Health and the U. S. Department of Agriculture. 相似文献
8.
E. G. White 《Researches on Population Ecology》1975,16(2):153-187
Summary Population units which are homogeneous with respect to capture-recapture assumptions are identified by applying 11 contingency
table tests to grasshopper data according to various site, species, growth stage and sex groupings. The results of 2337 contingency
table analyses have permitted a definition of the biological, spatial and temporal characteristics of those groupings which
were found to be homogeneous. The same analyses suggest that dispersal rates and dispersal patterns pose the greatest single
difficulty in defining population homogeneity within an open community. The effects of failures in capture-recapture assumptions
are discussed in relation toJolly’s 1965 stochastic model.
A more detailed presentation of the study is available from the author on request. 相似文献
9.
Makoto Kato 《Researches on Population Ecology》1996,38(1):27-40
Population dynamics of a leafminer,Chromatomyia suikazurae (Agromyzidae, Diptera) and its parasitoid community were studied for ten years at seven natural populations along an altitudinal
gradient in Japan. This species which mines leaves of a forest shrub,Lonicera gracilipes (Caprifoliaceae), was attacked by 25 hymenopterous parasitoid species. Annually, the parasitoid community structure varied
less within a population than among populations. The seven parasitoid communities were clustered into three groups corresponding
to the altitudinal gradient: (a) lowland communities dominated by late-attacking, generalist pupal idiobiont eulophids and
with highest species diversity, (b) hillside communities dominated by an early-attacking, specialist larval-pupal koinobiont
braconid and (c) highland communities dominated by an early-attacking, generalist larval idiobiont eulophid. Annual changes
of the host larval densities among the local populations were largely synchronous rather than cyclic. Among these populations,
host density levels and mortality patterns greatly varied. By analyzing these inter-populational differences of host mortality
patterns, the following conclusions were drawn: (1) The host mortality patterns were determined by the host utilization patterns
of the locally dominant species. (2) The host pupal mortality but not larval mortality was related to species diversity but
not to species richness itself of each parasitoid community. (3) Density dependence was detected only in pupal mortality at
a lowland population dominated by late-attacking pupal parasitoids. These results suggest that interspecific interactions
of parasitoids add additive effects to host population dynamics dissimilarly among local populations with different parasitoid
communities. 相似文献
10.
Summary The present paper dealt with the sequential changes of the distribution pattern of apterous females aphid populations, that
were artificially settled at the beginning on the experimental barley ‘field’. The aphids were settled at random or even with
a fixed denisty per plant. For five or six days after the settling, the number of individuals followed the negative binomial
distributions in all cases while the parametersk andp were varying. The estimated values ofk were rather small for the first one week after the settling, which may suggest that the number of moving aphids between plants
was relatively small and the degree of concentration expressing the intrinsic increase was high. After that, as the number
of individuals increased, the number of moving aphids between plants would be considered to be increased. It was found that
with the lapse of time the degree of concentration decreased ork became larger.
The distribution of aphids per blade in a plant was also described briefly. 相似文献
11.
Syun'iti Iwao 《Researches on Population Ecology》1977,18(2):243-260
Summary and Conclusion The measurement of spatial association between two species is considered on the basis of interspecies mean crowding. Two indices
of overlapping, γ andC
p, are derived as geometric and weighted arithmetic means of the same component ratios related to inter-and intraspecies mean
crowdings. Both indices behave in a similar way, ranging from 1 when the distributions of two species are completely overlapped
to 0 when they are completely exclusive with each other. The former is essentially identical with indices proposed byKuno (1968) andPianka (1973), and the latter is a modified form ofMorisita's (1959)C
σ index. Indices to measure the degree of spatial correlation between species, Ω andR
μ, are then derived for both kinds of overlapping indices, which vary from 1 in complete overlapping, through 0 in independent
occurrence, to −1 in complete exclusion.
Various kinds of interspecies association are analyzed using these indices and an extended form of the
regression graph which provides a convenient way of indicating the spatial interrelation between two species as well as distribution
patterns of respective species.
The method presented in this paper may also be applicable to compare temporal distribution patterns between species, similarity
between communities, etc. For such a wider application which includes continuous as well as discrete distributions, the interpretation
of intra-and interspecies mean crowdings is not necessarily appropriate, and hence the concept of mean concentration with
the symbols
and
for intraspecies relation and
and
for interspecies relation is suggested.
This study was supported by Science Research Fund (No. 148041) from the Ministry of Education. 相似文献
12.
Kazuyuki Fujita 《Researches on Population Ecology》1984,26(2):379-388
Summary I propose a new method for anlysing predatorprey interactive systems in discontinuous environments. The basic index used here
is a generalized version ofLloyd's (1967) “interspecies mean crowding”, which is defined as the number of individuals of one species existing in a given patch
per that of the other species in either the same or different patches at either the same or different times. Four indices
are derived from different combinations of the numbers of the prey and the predator in habitat patches. Then, the correlation
coefficients between the numbers of individuals in patches in both different locations and times are derived by modifying
the above new indices. Using this technique, dynamical changes of the joint distributions of the numbers of predators and
prey which reflect variation in local conditions, can readily be described. As an example, this method was applied to an analysis
of the outcomes of a multi-patch version of theLotka-Volterra model of predator-prey interactions. 相似文献
13.
Summary The dynamics of Angoumois grain moth,Sitotroga cerealella (Olivier), and maize weevil,Sitophilus zeamais
Motschulsky, populations breeding in a small bulk (initially 5.36 t) of shelled corn were studied over an 8-year period by monthly sampling.
The weevil population showed wide fluctuations in density superimposed on a general decline with time. The moth population
showed no upward or downward trend for the first 60 months, although it fluctuated widely. Following a decline that occurred
between 56 and 60 months, the moth population fluctuated within a much narrower range, and there was a general decrease in
density with time. The decline of the weevil population paralleled deterioration of the corn as did that of the moth population
after ca 60 months, and the decline of both species probably resulted from increasing scarcity of suitable breeding sites.
Both populations exhibited seasonal variation in density with minima in late summer and early fall, following periods of adversely
high temperatures in the storage shed. The populations increased during the fall, leveled off or declined slightly during
the winter months, and then increased to maximum levels in late spring or early summer. It thus appears that high temperatures
had a greater adverse effect on the populations than low temperatures. The grain moth and the maize weevil both tended to
be randomly dispersed at low population levels and moderately aggregated at intermediate and high levels, although the degree
of aggregation was not correlated with population density when low population levels were considered separately, and the maize
weevil showed a greater tendency for aggregation than did the grain moth. Analysis of individual samples at fixed points in
time showed a conspicuous bias for negative correlation between numbers of the two species within sampling quadrats, suggesting
a tendency for the two species to segregate within the grain mass. This process could have resulted from behavioral differences
or from the destruction of one species by the other. Competitive displacement of the grain moth by the maize weevil has been
demonstrated in laboratory experiments but has rarely been observed under natural conditions, and in our study the two species
coexisted for 8 years in a relatively small grain bulk. 相似文献
14.
The thimbleberry aphid,Masonaphis maxima (Mason) lives on patches of plants that support 3,4 or 5 generations depending on site and weather. The life cycle requires
sexual females and males to produce overwintering eggs. The eggs hatch in the spring to produce the first ’fundatrix’ generation;
subsequent generations are produced parthenogenically. Males and other morphs are produced by wingless virginoparae, but sexual
females are produced by ’gynoparae’, a winged morph that is specialized to produce only sexual females. The fundatrices have
no indication of the number of generations that the plants will support in the current year. There are two fundatrix types
that coexist in different ratios depending on the number of generations supported by the patch the previous year. One type
produces sexual females in generations 3 and 5, and males in generations 4 and 5; the other type produces sexual females in
generations 4 and 5, and males in generations 3, 4 and 5. The dimorphism adapts the aphid to its heterogeneous and somewhat
unpredictable environment. The role of sex in the maintenance of the dimorphism is discussed. This is the first report of
fundatrix polymorphism and consequent differential sex expression in aphids. 相似文献
15.
T. H. Chua 《Researches on Population Ecology》1977,19(1):125-139
Summary Studies on populations ofBrevicoryne brassicae (L.), its parasites and hyperparasites were carried out by actual counting in the sprouts field and by sticky and water traps.B. brassicae was found to be attacked by one primary parasite,Diaretiella rapae (McIntosh), which in turn is parasitized byAlloxysta brassicae (Ashm.),Asaphes vulgaris
Walker,A. suspensus (Nees),Pachyneuron minutissimum (F?rster) andDendrocerus carpenterii (Curtis). The aphid population in the field was started by immigrant alates which were found flying too early to be synchronized
with the sprouts plants. SimilarlyD. rapae was not synchronized with the aphids although many individuals could have been carried into a plot through parasitized immigrant
alates, of which less than 30% were found parasitized. Because of high hyperparasitism (especially byA. brassicae)D. rapae was not able to maintain a high rate of parasitism to curb the aphid population growth. The maximum percentage mummies being
27.8%, while the maximum, percentage parasitism being 56.6% recorded only during the early 1974 season (mean=12.9%). The decline
of aphid population from September onwards was largely due to the cold weather, Syrphid predation and occasionally fungal
attack. The high rate of hyperparasitism byA. brassicae is attributed to its better synchronization withD. rapae. The mean percentage of parasite that emerged from mummies collected during 1973–74 wereD. rapae 31.3%,A. brassicae 64.3%,A. vulgaris andA. suspensus 4.3%,D. carpenterii 0.2% andP. minutissimum 0.1%. 相似文献
16.
How an ant decides to prey on or to attend aphids 总被引:3,自引:0,他引:3
Hiroshi Sakata 《Researches on Population Ecology》1994,36(1):45-51
The following results on the behavior decision making of the antLasius niger toward two species of myrmecophilous aphidsLachnus tropicalis andMyzocallis kuricola on chestnut trees have been found. (1) An individual worker consistently attended only one aphid species, even if her nestmates
attended other aphid species on the same tree. (2) The ants preyed less on the aphid species which they attended than on other
myrmecophilous aphid species. (3) The ants preyed less on the aphids which had been attended by their nestmates, even if both
aphids were the same species. (4) The ants preyed less on aphids which had provided honeydew to their nestmates. (5) The increased
aphid density per ant led to an increase in the rate of predation on the introduced aphids by the ants. These results suggest
that each worker ofL. niger chooses aphid species to attend from her experience. In addition, the workers can recognize whether an aphid has been attended
by their nestmates and whether an aphid has given their nestmates honeydew. Through these processes, each worker decides to
attend or to prey on the aphid. As a result, they may realize efficient collective foraging dependent on aphid density per
worker. 相似文献
17.
N. A. C. Kidd 《Researches on Population Ecology》1990,32(2):189-208
Summary The large pine aphid,Cinara pinea lives exclusively onPinus species, where it feeds on the foliated shoots of the current and previous year. The paper describes the development of a
computer model designed to simulate the aphid’s population dynamics on saplings in the controlled environment of the laboratory,
i.e. in the absence of natural enemies. The model was able to account for about 80% of the variation in aphid numbers within
and between trees over a three month period. Sensitivity analysis revealed that the number of pine aphids is limited primarily
by nymphal emigration, the operation of which is sensitive both to density and to plant quality as reflected in aphid growth
rates. Of secondary importance are changes in reproduction acting through increased reproductive delay, again a result of
altered growth rates and adult size. Development, too, has an important secondary influence. Contrary to expectation and conventional
belief, however, alate production proved to be of negligible importance, either in limiting or regulating population numbers.
Alatae are produced in too few numbers and for too short a period to significantly alter the pattern of population change. 相似文献
18.
Summary Population dynamics ofHeliothis virescens (F.) andHeliothis zea (Boddie) (Lepidoptera: Noctuidae) eggs and larvae were studied for two years in a small plot of cotton,Gossypium hirsutum (L.). Due to morphological and ecological similarities, the pooledHeliothis population was considered for most of the analyses. Two generations ofHeliothis eggs and larvae were completed during each year. Stage recruitment was estimated for the eggs and larval instars 2–6, and
recruitment variances were estimated by a Monte Carlo method. A modified form of the Weibull distribution was developed and
used as a model to characterize survivorship curves for each of the fourHeliothis generations. A Type I survivorship curve (mortality rate increasing with age) was inferred for both Generation 1 (early season)
data sets, whereas a Type II survivorship curve (mortality rate constant and thus independent of age) was inferred for both
Generation 2 (late season) data sets. The shapes of the survivorship curves for the individualH. virescens andH. zea populations were inferred to be the same as those for the pooled populations. Analysis of the contributions of various factors
toHeliothis stage-specific mortality indicated that natural enemies (predators and parasites) and the availability of food for larvae
were responsible for between-generation differences in survivorship patterns. 相似文献
19.
Summary The abundance of moths was monitored with light-traps in two sites in southern Bohemia, České Budějovice for 22 years and
in Černiš for 9 years. In these sites, that are vastly different in environmental stability and predictability, stability
of insect populations was studied. The amplitude of fluctuations in abundance of the insect populations, as measured by the
coefficient of variation (CV), varied a great deal between species so that there was a large overlap between the two sites.
Nevertheless there was a highly significant tendency for species at Černiš, the more stable site, to have smaller values of
CV, i.e., to be less fluctuating. Also in species co-occurring in the two sites, the CV at Černiš tended to be smaller. Trends
in abundance of individual species over time, both increases and decreases, were common in both sites and did not differ between
habitats. Environmental stability begets insect population stability in terms of the amplitude of the fluctuations, but trends
in time occur irrespective of stability of the habitat. 相似文献
20.
Tom M. Spight 《Researches on Population Ecology》1981,23(2):245-261
Summary Competition theory poses a major problem when several species coexist on what appears to be one resource. ThreeThais species living on the Pacific Northwest Coast provide an example: at many sites, all three depend primarily on one barnacle
species. Growth rates of three species were measured for 3 years and these provide an indirect means to assess how these snails
use their common food resource. Major temporal differences were observed:T. lamellosa grew 0–1 mm/mo during the spring and 2–3 mm/mo during the summer, whileT. emarginata andT. canaliculata grew 2–3 mm/mo during the spring and 0–1 mm/mo during the summer. However, all species are opportunists when food is available,
and seasonal and interspecific differences disappeared when all three species were kept well fed together in the laboratory.
Therefore, temporal differences arise from spatial segregation rather than from intrinsic differences in activity, and must
arise because barnacle abundance patterns differe consistently from one area of the shore to another. Species-specific activity
patterns lead each species to a food intake that is independent of the food supply on the shore as a whole and is also independent
of food intake by the other two species. Where two snail species depend upon a single food species, their use of the food
supply appears to make it function as two different resources. This resource use is possible because prey quality is markedly
dependent on shore level. 相似文献