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1.
Takao Itino 《Researches on Population Ecology》1986,28(2):185-199
Summary I compared life tables between the solitary eumenid waspAnterhynchium flavomarginatum
Smith and the subsocial eumenid waspOrancistrocerus drewseni
Saussure in Kyoto, Japan, during 1980–1983. The subsocial eumenid is parthenogenetic in this study area. There were 9 identified mortality
factors in the solitary eumenid and 7 in the subsocial eumenid, 6 of which were common to the two eumenids. The important
differences of mortality between the two eumenids were seen in the egg, larval, and prepupal stages. In the egg stage, mortality
by the phorid flyMegaselia sp. was much lower in the subsocial eumenid (1.4%) than in the solitary eumenid (15.0%) likely because of the matenal care
of the subsocial eumenid (progressive provisioning and other related behavior), which reduced predation pressure. In the larval
stage, mortality by the miltogrammine flyAmobia distorta was also lower in the subsocial eumenid (8.1%) than in the solitary eumenid (23.8%) also probably because of the maternal
care of the subsocial eumenid. A comparison of mortality in the two eumenids between the stable, long continuing natural nest
sites and the additional temporal ones showed that the phorid fly remained near its birth place and parasitized stable nest
sites. The miltogrammine fly followed returning eumenid wasps and parasitized those nest sites that have a high host density.
In the prepupal stage, mortality by endogenous death was higher in the subsocial eumenid than in the solitary eumenid. Mortality
due to the rhipiphorid beetle was also higher in the subsocial eumenid probably due to more frequent flower-visits by the
subsocial eumenid.
The defense mechanism of the subsocial eumenid was discussed in relation to the evolution of subsociality.
Contribution to the ecological studies of the eumenid wasps. I. 相似文献
2.
Masakazu Shimada 《Researches on Population Ecology》1985,27(2):203-216
Summary Effects of niche shift in ecological time scale on the population dynamics of competing species were studied in the experimental
populations of two parasitoid wasp species,Anisopteromalus calandrae andHeterospilus prosopidis (both are solitary parasites), on a host, the azuki bean weevil,Callosobruchus chinensis. Four resource conditions were set up with combination of kind of bean (azuki or black eye), and host distribution (uniform
or clumped). In each resource condition, four developmental stages of hosts were provided as a resource spectrum for parasitoid
wasps.
Population dynamics of the two wasp populations were investigated in each resource condition in Multi-Generation Competitive
Systems (MGCS), in which fresh hosts of four developmental stages were periodically introduced and were parasitized competitively
by the two wasp species. Competitive coexistence of both wasps occurred in the azuki-clumped condition, where the peaks of
the resource utilization curves separated in the two species; pupae inA. calandrae and the early or late fourth instar inH. prosopidis, A. calandrae was eliminated in the azuki-uniform condition andH. prosopidis went extinct in two black eye conditions irrespective of host distributions. The degrees of overlap of the resource utilization
patterns of the two wasp species during population dynamics were not significantly different among resource conditions irrespective
of the results of coexistence or extinction. Even in the azuki-clumped condition, however, extinction ofA. calandrae was observed when resource partitioning could not be realized with only the late fourth instar larvae available to wasps.
Further analytical experiments showed that parasitizing ability ofA. calandrae increased with host density per bean with azuki beans, butA. calandrae could express higher parasitizing ability with black eye beans thanH. prosopidis irrespective of host density per bean.
The flexibility in parasitizing ability byA. calandrae for various host stages under different resource conditions was thought to be the major factor in determining the competitive
coexistence or the extinction of either species under different resource conditions. The present experiments also suggested
that different second-best host stages between competitors could be a major contributing factor to competitive coexistence. 相似文献
3.
Competitive exclusion through reproductive interference 总被引:6,自引:0,他引:6
Eizi Kuno 《Researches on Population Ecology》1992,34(2):275-284
Summary A simple differential equation model was developed to describe the competitive interaction that may occur between species
through reproductive interference. The model has the form comparable to Volterra's competition equations, and the graphical
analysis of the outcome of the two-species interaction based on its zero-growth isoclines proved that: (1) The possible outcome
in this model, as in usual models of resource competition, is either stable coexistence of both species or gradual exclusion
of one species by the other, depending critically upon the values of the activity overlapping coefficientc
ij
; (2) but, for the samec
ij
-values, competitive exclusion is much more ready to occur here than in resource competition; (3) and moreover, the final
result of the competition is always dependent on the initial-condition due to its non-linear isoclines, i.e., even under the
parameter condition that generally allows both species to coexist, an extreme bias in intial density to one species can readily
cause subsequent complete exclusion of its counterparts. Thus, it may follow that the reproductive interference is likely
to be working in nature as an efficient mechanism to bring about habitat partitioning in either time or space between some
closely related species in insect communities, even though they inhabit heterogeneous habitats where resource competition
rarely occurs so that they could otherwise attain steady coexistence. 相似文献
4.
Hiroshi Inoue 《Researches on Population Ecology》1985,27(2):255-264
Summary Nymphs ofAgriosphodrus dohrni
Signoret (Reduviidae) have a strong gregariousness and show group predatory behavior. This study was conducted to clarify adaptive
significance of group predation of this species, including laboratory observations and 6-year field surveys.
In the laboratory, observations on both solitary and group attacking against armyworms were made at varying prey size classes
to compare the capture success rate by solitary predators with that by groups. The efficiency in capturing the prey was significantly
higher in group attacking at any prey size class compared.
Data obtained from the field surveys indicated the tnedency for searching nymphs to feed in group and to increase the number
of predators feeding per prey item with increasing prey size. Average sizes of prey captured were also larger in group feeding
throughout the nymphal stage. In particular, it was remarkable that, when prey were “creeping” types, the upper size limit
of prey eaten was dramatically increased. 相似文献
5.
Shiro Kobayashi 《Researches on Population Ecology》1991,33(2):345-360
Summary In six different environments of the Towada-Hachimantai National Park, the forest floor coleopterons were sampled by means
of pitfall traps with five different baits. Their niche breadths and niche overlaps were assessed for the electivity of habitat,
bait, and habitat × bait, and compared with those expected from neutral models constructed randomly. The niche breadths in
the observed assemblages were smaller than those expected from the neutral model, while the niche overlaps were more widely
distributed than those expected from the neutral model. Mean overlaps between species neighbors in niche space, cluster analyses,
and ordinations of species revealed a guild for habitat, bait and habitat × bait. Lawlor’s (1979) gamma matrices concerning
the habitat electivity show that the rates of mutualism resulted from indirect interspecific competitions are significantly
smaller in the guild than in the whole assemblage. This suggests that the interspecific competition among the guild members
is mitigated or even converted into mutualism by joining of the species which do not belong to the guild. The rates of mutualism
were also significantly larger in the resource state of two dimensions (habitat × bait) than in that of either one. Therefore,
if niche overlaps are measured on the basis of resource state of multi-dimensions, the rates of mutualism may increase further. 相似文献
6.
Summary The biology of the veliid bugM. d. atrolineata, its predatory behavior, and the effects of plural hunting were studied to evaluate its role as a predator of the brown planthopperNilaparvata lugens in the Philippines. The probability of planthoppers falling onto the water surface and provision of habitat continuity was
measured by a sticky trap placed at the base of rice hills in a greenhouse and in paddy fields.
The developmental period of immature stages combined was 21 days. If given prey, females laid 25 eggs on the average during
an adult life span of 18 days. Starved adults could survive for only 3–5 days.
The functional response to prey density was sigmoid, and the maximum number of prey killed was 7 per day. Prey feeding was
completed in 12–36 min. The percentage of successful prey attacks averaged 5–8%, decreasing with higher (and larger) developmental.
stages of prey, but adult prey were found the soonest. Plural hunting increased the probability of capturing prey by as much
as 2.5 times that by individual hunting.
Late-instar nymphs, which may be more active, fell from rice hills in a greenhouse more than early-instar nymphs, and the
number falling increased with density. In the field the percentage of planthoppers falling to the water in 1 day varied considerably,
from 1% for nymphs in one field to 67% for adults in another field.
On the basis of work described above and given the high density of veliid predators in flooded paddy fields of tropical Asia,M. d. atrolineata is considered one of the most important natural enemies of the brown planthopper. 相似文献
7.
Summary Simulation model for niche shift in ecological time scale was constructed on the basis of the optimal foraging theory. In
accordance with the previous experimental study (Shimada andFujii, 1985), the model competitive system consisted of 2 parasitoid wasp species utilizing 4 host stages. Wasps were assumed to
choose host stages in the manner that they realized the maximal gain/cost values, where gain was represented by body weight
of a wasp progeny emerging from each host stage and cost was expressed by time required to search for and detect an unparasitized
host. The number of parasitized hosts in each host stage was calculated numerically by usingArditt's (1983) model for avoidance of superparasitism.
The model simulated well the experimental results ofShimada andFujii (1985) andShimada (1985). Sensitivity analysis of the model showed that the experimentally derived criterion for competitive coexistence (different
second-best host stages between competing species even with the common best) was not necessarily the indispensable condition
for niche shift and separation, but that if the criterion was not satisfied, stable competitive coexistence occurred only
in the narrow range of the parametric values. Further, niche shift in ecological time scale made the competitive coexistence
more stable than fixed niche on which the current niche theory stands. 相似文献
8.
Habitat stability and the larval mosquito community in treeholes and other containers on a temperate Island 总被引:3,自引:0,他引:3
The temporal fluctuation of water levels and the presence of mosquito larvae were investigated for four types of small container
habitats (treeholes, bamboo stumps, cemetery stone vases, and cemetery stone vessels) on Kabeshima Island in Kyushu, southwestern
Japan. The probability that containers held water was positively correlated with the quantity of the preceding rainfall and
with the depth and volume of the containers. It was estimated that dehydration occurred more regularly in autumn and winter
than in summer. The probability that mosquito larvae were present in each type of container was positively correlated with
habitat stability in terms of the probability of the existence of standing water and the coefficient of variation of the water
level. Twelve species of mosquito larvae, including two rare predators, were found. Species composition differed between the
different types of container. Although 4 to 10 species used each type of container, the median number of species per container
was two for treeholes and bamboo stumps, and one for the others. The dominant species wasTripteroides bambusa in treeholes and bamboo stumps,Aedes albopictus in stone vases, andA. japonicus in stone vessels. The larval mosquito community, which lacked major predators, possessed the following features that may
facilitate the coexistence of many species: (1) niche segregation amongst species in terms of their selection of container
types; (2) an aggregated distribution of the individual species among containers of the same type; (3) high intraspecific
mean crowding (and hence probably intense intraspecific competition) in the dominant species in each type of container; (4)
independent species associations within the same type of container; and (5) low interspecific mean crowding (and hence probablynot intense interspecific competition) between species in the same type of container. 相似文献
9.
Mechanisms allowing the persistence of an aquatic predator-prey system in tiny pools (the mean ca. 0.5 ml) held by taro axils
were analyzed from the viewpoint of temporal and spatial patterns of habitat use. Predatory larvae of a mosquitoTopomyia tipuliformis concentrated in young axils, while 9 other taxa utilized both young and old axils or concentrated more in older axils. The
total prey density was lower in axils with the predator but the density of each prey taxon (except for a few cases) and the
number of prey taxa did not differ between axils with and without predators. This indicates thatT. tipuliformis is a general predator and does not influence prey community organization through selective removal of particular prey taxa.
Inter-axil distribution ofT. tipuliformis was aggregated in the first instar but uniform in the third and fourth instars due to intraspecific cannibalism, which assures
the survival of a single individual under short food supply. Distributions of prey taxa were mostly aggregated, fitting the
negative binomial distribution. Thirty seven out of 45 associations of 10 taxa were independent with 3 negative (between the
predator and some late-colonizing prey) and 5 positive (between some prey taxa) associations. Probabilistic refuges (produced
by independent aggregated distributions) reduced interspecific encounters which may result in competition and predation, and
thus probably facilitated prey coexistence. There was no evidence for the importance of predation in structuring the prey
community. This system may be prey-dominated in that predator persistence depends on prey community existence but prey community
structure depends less on predation. 相似文献
10.
Among many stabilizing factors for community dynamics, nonlinear biological interactions such as type III functional response
have been widely considered to be major characteristics. However, most experimental biological communities employed so far
had quite simple structures. Therefore, the possibility that the conclusions in earlier studies were dependent on simple community
structure is undeniable. In this study, using a multiple-species experimental community, we evaluated which combinations of
component species and what kinds of interspecific interactions allow communities to persist and how these contribute to community
persistence. We conducted experimental communities using two species of beans, the adzuki bean (Vigna angularis) and the red kidney bean (Phaseolus vulgaris), two species of bean weevils, the Mexican bean weevil (Zabrotes subfasciatus, Coleoptera: Bruchidae) and adzuki bean weevil (Callosobruchus chinensis, Coleoptera: Bruchidae), and two species of parasitic wasp, Heterospilus prosopidis (Hymenoptera: Braconidae) and Anisopteromalus calandrae (Hymenoptera: Pteromalidae). The outcome of multiple-generation experimental communities was explained by the characteristics
of component species obtained from short-term experiments. In our two resources–two herbivores–one carnivore system, the strong
density-dependent attack ability of one parasitic wasp species (A. calandrae) led to the extinction of C. chinensis. On the other hand, the weak density-dependent attack ability of the other parasitic wasp species (H. prosopidis) led to system persistence. Our overall results show that, in a multiple-species community, the combination of species itself
is more important for community persistence than are the characteristics of the particular species.
Received: September 29, 1997 / Accepted: October 5, 1998 相似文献
11.
The mathematical model presented here aims to elucidate the essential mechanisms of coexistence of species, especially those
of closely related forms, as a result of competition in the same environment. It describes a system where the fate of the
competitors or mutants is observed at the initial stage of evolution. The model encompasses both the external variables and
the internal state of the competitors, which differ only in one of the metabolic rate constants. Results of simulations, even
with the simplified form of the model, show that stable coexistence of closely related forms in a uniform environment is possible.
In addition, the model allows the analysis of the limitations on the level of differences and similarities among the competitors
for achieving a state of coexistence. The essential mechanisms for the coexistence of closely related competitors are proposed
to be the involvement of the metabolic network in allowing the same growth rate of competitors which have different internal
states, and the interplay between the internal states of the competitors and the external variables of their environment. 相似文献
12.
We modelled the population dynamics of two types of plants with limited dispersal living in a lattice structured habitat.
Each site of the square lattice model was either occupied by an individual or vacant. Each individual reproduced to its neighbors.
We derived a criterion for the invasion of a rare type into a population composed of a resident type based on a pair-approximation
method, in which the dynamics of both average densities and the nearest neighbor correlations were considered. Based on this
invasibility criterion, we showed that, when there is a tradeoff between birth and death rates, the evolutionarily stable
type is the one that has the highest ratio of birth rate to mortality. If these types are different species, they form segregated
spatial patterns in the lattice model in which intraspecific competitive interactions occur more frequently than interspecific
interactions. However, stable coexistence is not possible in the lattice model contrary to results from completely mixed population
models. This clearly shows that the casual conclusion, based on traditional well mixed population models, that different species
can coexist if intraspecific competition is stronger than interspecific competition, does not hold for spatially structured
population models. 相似文献
13.
Yutaka Sait 《Researches on Population Ecology》1990,32(2):263-278
Summary The mating system of a subsocial spider mite,Schizotetranychus miscanthi Saitō, which is closely related toSchizotetranychus longus Saitō (the long seta form ofSchizotetranychus celarius (Banks) is a synonym of the latter) was studied in comparison with that ofS. longus.
Comparisons between nesting patterns of the two related species,S. miscanthi andS. longus revealed a difference in distribution of males among nests. Although more than one male sometimes occurred in the large nests
ofS. miscanthi, most nests were occupied only by a single male. On the other hand, many nests ofS. longus included several males.
Behavioral experiments revealed that the male and females ofS. miscanthi which cohabited in a nest defended their offspring from phytoseiid predators. Observations and a census of the nesting pattern
in a wild population indicate that this is the second example of biparental defense and of a subsocial life-pattern in spider
mites.
Differences in mating systems were experimentally demonstrated in the two species. Only a single male ofS. miscanthi survived in a nest, as a result of highly aggressive male-male combat, while two males ofS. longus cohabited in a nest. The mating system of the former species is thus considered as harem polygyny, while that of the latter
as scramble type polygyny. Furthermore, observations by video recording and scanning electron microscopy showed that the winning
male in the male-male combat inS. miscanthi often preyed on the loser, suggesting cannibalism among them. 相似文献
14.
Parasitoid-mediated effects: apparent competition and the persistence of host–parasitoid assemblages 总被引:3,自引:0,他引:3
Indirect effects such as apparent competition (in which two hosts that do not compete for resources interact via a shared
natural enemy) are increasingly being shown to be prevalent in the structure and function of ecological assemblages. Here,
we review the empirical and theoretical evidence for these enemy-mediated effects in host–parasitoid assemblages. We first
address questions about the design of experiments to test for apparent competition. Second, we consider factors likely to
affect the coexistence of host species that share a parasitoid and are involved in apparent competition. We show that parasitoid
aggregation, and the switching effect that this can generate when hosts occur in separate patches, not only promotes persistence
but is also strongly stabilizing. The broader consequences of these effects are discussed.
Received: November 6, 1998 / Accepted: January 13, 1999 相似文献
15.
Masayoshi Suwa 《Researches on Population Ecology》1986,28(2):231-252
Summary There are 4 species belonging to the wolf spiderPardosa amentata species group in Hokkaido. The 4 species have separately occurred in Hokkaido in general, but a few species have sometimes
occurred together at the same sites. Their biology at the coexisting sites, with special reference to partitioning of space
was studied.P. agraria mainly inhabited fields and occurred widely in Hokkaido.P. hokkaido, P. brebivulva andP. lugubris inhabited the vicinity of forests and occurred in southern Hokkaido and on the side of the Sea of Japan in Hokkaido, all
over Hokkaido excent the side of the Sea of Japan in central Hokkaido, and the lowlands and highlands in northern and eastern
Hokkaido and mainly the highlands in other regions, respectively. In eastern Hokkaido whereP. brevivulva andP. lugubris have coexisted, as the number of spiders detected and the number of localities of the former were less than those of the
latter, it was concluded that the former occurred mainly in southern Hokkaido and the Hidaka region. In southern Hokkaido
whereP. hokkaido andP. brevivulva have coexisted, few individuals of both species were collected together at the same sites, and they were distributed allotopically.
In short, the partitioning of space among theP. amentata species group occurring in Hokkaido was clear. From investigations on the coexisting sites and some other reports, it was
considered that food, life cycle and diel activity periodicity amongPardosa occurring in Hokkaido were similar to one another. This may be one of the causes of the clear space partitioning amongPardosa. SincePardosa is a raptorial predator that does not weave but wanders on the ground and uses space horizontally, available prey resource
forPardosa would be limited. It was therefore conjectured that the spider would be prone to space segregation, even if the spider could
segregate the other niche dimensions. The partitioning of space betweenP. agraria andP. hokkaido inhabiting distinct habitats was loose when it was compared with that between species inhabiting similar habitats. As most
of the spiders observed in the overlapping areas were females with egg cocoons, which required little food, the reduced feeding
was considered to have allowed the loose partitioning. 相似文献
16.
An individual-based model forDrosophila is formulated, based on competition amongst larvae consuming the same batch of food. The predictions of the model are supported
by data for single speciesDrosophila populations reared in the laboratory. The model is used to build a simple discrete model for the dynamics ofDrosophila populations that are kept over a number of generations. The dynamics of a single species is shown to give either a stable
equilibrium or fluctuations which can be periodic or chaotic. When the dynamics of a species in the absence of the other is
periodic or chaotic, we found coexistence or two alternative states, on neither of which the species can coexist. 相似文献
17.
Kazuo Nakamura 《Researches on Population Ecology》1982,24(2):302-317
Summary The prey capture tactics of spiders was analyzed, considering the energy gained by the capture of prey and that required for
it. For the purpose of it, a growth model of spiders was constructed, expressing the flow rate of prey biomass to the spider's
body by differential equations. Solving these equations under the differing values of three parameters, growth curves of spiders
was obtained. These three parameters are the amount of prey biomass supplied daily to spiders,x
0, the rate of prey capture of spiders, α, and a coefficient of the respiration rate required for the capture of prey,k. When the value ofk increased, spiders could grow only at high value ofx
0. These results suggest that habitats with small prey biomass are preferred by spiders adopting a sit-and-wait tactics for
prey capture, which requires small values ofk. Wolf spiders are one of these spiders showing that tactics. On the other hand, web-builders which require large amount of
energy for spinning webs (namely, take large value ofk), are able to grow only in the habitats with large prey biomass. Each species of spiders are considered to locate in a certain
point between both extremes of these tactics for the capture of prey. 相似文献
18.
Asymmetric mating preferences occur in two closely related species, if females of one species are highly selective against
males of the second, while females of the second show less selection against males of the first species. It has been suggested
that such asymmetry is an indicator of common ancestry between the two species, but actual observations are contradictory
and inconclusive. We developed a scenario of speciation history and asymmetric mating preference, incorporating invasion dynamicsvia frequency-dependent interspecific sexual competition. A newly isolated (derived) species may form at the periphery of the
ancestral species’ distribution by invading a new range. Only a few closely related species would be expected in the new area,
while many related species are expected to coexist with the ancestral species. In a peripherally derived species, female mating
preferences should be relaxed through sexual character release, owing to a lack of sympatric species and a scarcity of intraspecific
mating opportunities. Secondary contacts may then happen as: 1. repeated invasions, i.e. subsequent invasion by the ancestral
species into the new range or, 2. backward invasions, i.e. derived species incursions into the ancestral range. Repeated invasions
could lead to the coexistence of both the derived species and the newly invading ancestor. Backward invasions by the derived
species can succeed only when the derived females develop a strict mating discrimination against the ancestral males. We then
expect strong character displacement in the derived species. Thus, peripheral isolation and repeated invasions lead to the
relaxed female mating preferences in the derived species and backward invasions lead to stronger female mating preferences
in the derived species. This agrees withDrosophila data from Hawaii and the continents. Experimental data of theDrosophila arizonaemojavensis species cluster also support the hypothesis. 相似文献
19.
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
20.
A quantitative risk assessment is needed for each quarantine pest insect to ensure quarantine security without sacrificing
the transparency of international trade. The probability of introduction, which is defined as the probability that one or
more reproductive individuals of a pest insect species pass the port, is one of the basic components determining the risk
of pest invasion. The probability depends on two biological characteristics of pests: mode of reproduction and spatial distribution
of insects per host plant. In this article, the probability of introduction was calculated for each of the following four
categories: (1) bisexual, gregarious pests; (2) bisexual, solitary pests; (3) parthenogenetic, gregarious pests; and (4) parthenogenetic,
solitary pests. Then, equations were derived to predict the effects of two prevention practices conducted before export: disinfestation
treatment and the subsequent export sampling inspection of consignments. These equations also enable estimation of the probability
of introduction under natural mortality, which thus can be used in place of the criterion of Maximum Pest Limit (MPL). The
method was applied to the Mexican fruit fly Anastrepha ludens (Loew), as an example. The contour graph of the probability of introduction indicated the optimal combination of the intensity
of two prevention practices that ensures a given security level. Existence of an antagonistic interaction was also indicated
between the disinfestation treatment and the subsequent sampling inspection.
Received: January 22, 1999 / Accepted: September 6, 1999 相似文献