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1.
Summary We studied the stopping rule obeyed by the female parasitoid,Chrysocharis pentheus, in deciding when to leave the leaflet on which she is searching for larvae ofPhytomyza ranunculi. She seemed not to employ some stopping rules that have been suggested; i.e., a fixed-number rule and a fixed-time rule and
others. The stopping model formulated forDapsilarthra rufiventris parasitic on the same host species fitted well to the results. The model assumes that the searching female will deposit a
marking pheromone on the leaflet at a rate proportional to the search speed and will leave the leaflet when the amount of
the pheromone that has accumulated on the leaflet reaches the threshold,L. In this model,L denotes the amount of search effort spent on the leaflet. A comparison of the observed results with the predictions from
the model suggested thatL increased markedly at the first encounter with the mine (host), but less at later encounters.C. pentheus appears to employ a mixed strategy of a fixed search-effort and an area-concentrated search. This would confer an adaptive
advantage in foraging forP. ranunculi larvae, which are distributed in clumps among leaflets in the field. 相似文献
2.
Summary
Luehdorfia butterflies lay eggs in clusters. Clones of their host plants (Asiasarum andHeterotropa) are distributed pacthily among the understory of deciduous forests. Groups ofLuehdorfia larvae often exhaust the clones and may wander over the forest floor seeking new clones. The highest mortality observed is
during this wandering period. To elucidate whyLuehdorfia butterflies lay eggs in clusters, a simulation experiment was made for hypothetical populations which lay eggs in clusters
or singly. Field data on larval mortality, consumption, density of host clones and leaf weight forLuehdorfia japonica were incorporated into the model. The predictions of the simulation were: (1) When the egg density is low, the single egg
type could leave many more pupae than the egg clustering type, but when the egg density is high, the former might leave smaller
number of pupae than the latter; and (2) There are optimal sizes of egg clusters for different egg densities and the optimal
size becomes larger as the egg density increased.
This work was supported in part by Grant-in-Aid No. 439017 and No. 56480039 from the Ministry of Education, Science and Culture,
Japan. 相似文献
3.
Summary The present study investigated the way a wild bruchid,Kytorhinus sharpianus, distributes its eggs on host pods. First, we counted the number of eggs per pod on the host plant (Sophola flavescens) in the field. The egg-distributions by the overwintered-generation adults in July and by the second-generation adults in
mid October did not deviate from Poisson distribution because of small numbers of eggs laid. However, the egg-distribution
in late August when many first-generation adults emerged was significantly contagious.
The deposition of eggs was determined for three types of pods: (A) clean pods, (B) pods with eggs, and (C) those which eggs
had been laid on but were removed from later. The numbers of eggs laid newly on three types of pods were significantly different;
A>C>B, suggesting that an oviposition marker pheromone (O.M.P.) caused females to avoid pods on which eggs were deposited.
Egg-shells reinforced that response.
Monte Carlo simulations for the egg-distribution on pods predicted that even if females avoid pods with heavy egg-load through
O.M.P., the egg-distribution becomes contagious when there is a large heterogeneity in quality of the pods. 相似文献
4.
B. Leroi 《Researches on Population Ecology》1973,15(1):163-182
Summary The leaf-mining larvae of the celery fly,P. heraclei, have the ability to leave their primary mine to bore a secondary mine in another leaflet or leaf. This phenomenon is always
numerically significant under natural conditions (depending on the plots and the years, 38 to 97% of the larvae observed made
such a change), although it is not an obligatory behavior.
The distribution of the secondary mines on the leaflets and on the leaves varies with the importance of the migrations, with
the total unoccupied and healthy leaf area and with the relative position of different leaves on the plant. These migrations
are due to the insufficiency of healthy food available for the larvae: either because the quantity of parenchyma offered by
a leaflet is too small for a larva, or because there is intraspecific competition following multiple egg-layings on the same
leaflet, or because there is a deterioration of the quality of the parenchyma, particularly following the development of celery
leaf-spot.
The possibility for the larvae ofP. heraclei to bore secondary mines appears to be an extremely important factor in the population dynamics of this species. This permits
the reduction of the negative effects of intraspecific competition and celery leaf-spot, and permits the colonization by the
larvae of young leaves not used by the females at the time of egg-laying. 相似文献
5.
Carl O. Mohr 《Researches on Population Ecology》1967,9(2):95-107
Summary Home areas of hosts are, in effect the gardens in which parasite populations grow. The parasites flourish in response to the
kind and amount of host activity modified, of course, by the habitat, and become microcommunities supported by their host
and its artifacts. When scatter diagrams of points at which hosts have been observed are divided by median major and minor
axes, and when the resulting four quarters, designated A, B, C, D, corresponding to concentration of points in the quarters,
the relative concentration usually is: A>B>C>D. The concentration of observed points also is generally greatest nearest the
major axis and frequently, but not always, near the median center. Nests of hosts, hence nest-parasites, appear generally
to be near the center. For the host examined in detail here, the New Guinea coarse-haired rat, mostLeptotrombidium deliensis appear to have been acquired in the AB sector of the host's home areas but a greater diversity of chiggers is acquired in
the CD sector. It is postulated that, ifL. akamushi had been present, it would have occurred in the CD sector where, though the observed concentration of host activity was least,
the mixed grassforb and shrub habitat would have been more suitable than in the AB sector.Gahrliepia pingue, C. ewingi, Schoengastia blestowei andS. schueffneri, appear also to be more abundant in the CD sector than in the AB sector. The chiggers themselves have home clusters, or lairs,
and adjacent areas of activity (home areas) somewhat resembling those of the hosts.
This analysis of sectors of home areas was begun in 1965 under provision of a research grant (AI-03653) by the National Institutes
of Health to the Division of Parasitology, University of California at Berkeley. It was completed during 1967. 相似文献
6.
Karin Amit 《Social indicators research》2018,139(3):1219-1235
Recent studies examining immigrant intentions to leave the host country have focused on return migration to the origin country (De Haas and Fokkema in Demogr Res 25:755–782, 2011; De Haas et al. in J Int Migr Integr 16(2):415–429, 2015). The current study examines immigrant intentions to leave the host country, but not necessarily to return to the homeland. The predictive model, which focuses on immigrant subjective identity, was tested through a survey of 338 first and 1.5 generation Former Soviet Union (FSU) immigrants in Israel, who applied to a prominent NGO to obtain proof of their Jewishness. These individuals are from the largest recent immigrant group in Israel, and are highly represented among the young adult (aged 25–40) immigrants leaving Israel. The findings indicate that contrary to our expectations, Israeli local identity did not have a significant effect on the immigrants’ intentions to leave Israel. By contrast, Jewish identity and level of religiosity did play a significant role in attenuating the immigrant’s tendency to leave. This paper highlights the complex relationship between ethnic identities and religiosity among immigrants in general, and in Israel in particular. 相似文献
7.
Takatoshi Ueno 《Researches on Population Ecology》1999,41(1):47-57
Charnov's host-size model explains parasitoid host-size-dependent sex ratio as an adaptive consequence when there is a differential
effect of host size on the offspring fitness of parasitoid males versus females. This article tests the predictions and the
assumptions of the host-size model. The parasitoid wasp Pimpla nipponica Uchida (Hymenoptera: Ichneumonidae) laid more female eggs in larger or fresher host pupae when choice among hosts of different
sizes or ages was allowed. Then, whether an asymmetrical effect of host size and age on the fitness of females versus males
existed in P. nipponica was examined. Larger or fresher host pupae yielded larger wasps. Larger females lived longer, whereas male size did not influence
male longevity. Large males mated successfully with relatively large females but failed with small females, whereas small
males could mate successfully either with small or with large females. Thus, small-male advantages were found, and this held
true even under male–male competition. Ovariole and egg numbers at any one time did not differ among females of different
sizes. Larger females attained higher oviposition success and spent less time and energy for oviposition in hosts. Larger
females produced more eggs from a single host meal. Taken together, females gained more, and males lost more, by being large.
Host size and age thus asymmetrically affected the fitness of offspring males versus females through the relationships between
host size or hast age and wasp size, which means the basic assumption of the host-size model was satisfied. Therefore, sex
ratio control by P. nipponica in response to host size and age is adaptive.
Received: November 13, 1998 / Accepted: January 18, 1999 相似文献
8.
Wolbachia bacteria are obligatory intracellular parasites of arthropods and have been detected in about 70 species of parasitic wasps
and three parasitoid flies. Wolbachia are transmitted cytoplasmically (maternally) and modify host reproduction in different ways to enhance their own transmission:
parthenogenesis induction (PI), cytoplasmic incompatibility (CI), or feminization (F) of genetic males. Only PI and CI are
known in parasitoids. PI-Wolbachia cause thelytoky in otherwise arrhenotokous parasitoids by generating diploid (rather than haploid) unfertilized wasp eggs.
CI-Wolbachia cause incompatibility of crosses between infected males and uninfected females because the paternally derived chromosomes
fail to decondense and are destroyed after syngamy. More complex situations arise when hosts harbor multiple infections, which
can lead to bidirectional incompatibility and may be involved in parasitoid speciation. The relative fitness of infected and
uninfected hosts is important to the population dynamics of Wolbachia, and more data are needed. Evolutionary conflict should be common between host genes, Wolbachia genes, and other "selfish" genetic elements. Wolbachia-specific PCR primers are now available for several genes with different rates of evolution. These primers will permit rapid
screening in future studies of spatial and temporal patterns of single and multiple infection. Molecular phylogenies show
that CI- and PI-Wolbachia do not form discrete clades. In combination with experimental transfection data, this result suggests that host reproductive
alterations depend on the interaction between attributes of both Wolbachia and host. Moreover, Wolbachia isolates from closely related hosts do not usually cluster together, and phylogenies suggest that Wolbachia may have radiated after their arthropod hosts. Both results support considerable horizontal transmission of Wolbachia between host species over evolutionary time. Natural horizontal transmisson between parasitoids and their hosts, or with
entomoparasitic nematodes or ectoparasitic mites, remains a tantalizing but equivocal possibility.
Received: November 27, 1998 / Accepted: January 15, 1999 相似文献
9.
Intra- and interspecific larval interactions that take place in a host body were investigated for two tachnid fliesEpicampocera succincta andCompsilura concinnata (Diptera: Tachinidae) parasitizingPieris butterfly larvae.E. succincta, a specialist onPieris butterflies, showed contest-type intraspecific competition, eliminating all the other conspecific larvae. On the other hand,
an extreme generalist parasitoidC. concinnata exhibited scramble-type competition, sharing the host with other conspecifics and suffering reduced body size as a result.
However, when these two species occurred together in a single host,C. concinnata had a much higher chance of survival. Moreover,C. concinnata could often survive in the presence of a parasitoid waspCotesia glomerata (Hymenoptera: Braconidae) whileE. succincta could not. The high tolerance ofC. concinnata could be attributable to its being an extreme generalist: To attack and survive on many different hosts, one has to be able
to deal with various competitors. The competitive inferiority of the specialistE. succincta, on the other hand, may be a result of relatively recent encounter with, those competitors. 相似文献
10.
Summary The virgin female introduced pine sawfly,Diprion similis (Hartig), produces a powerful sex pheromone capable of attracting males. Pending chemical identification of the substance, a pilot
study in male annihilation is under consideration. A mathematical model was developed to assess the feasibility of population
suppression using pheromone-baited traps. Departure from preexisting population models resulted chiefly from the arrhenotokous
nature of the sawfly. The model predicts alternating sawfly generations which undergo first a large shift in the sex ratio
but no population reduction, followed by a large decrease in population size with a moderating sex ratio. Four generations
of intensive trapping would theoretically be sufficient to eliminate the sawfly from an isolated area. 相似文献
11.
Combining pheromone-baited and food-baited traps for insect pest control: Effects of additional control by parasitoids 总被引:1,自引:0,他引:1
Hugh J. Barclay 《Researches on Population Ecology》1991,33(2):287-306
Summary Two age-structured population dynamic models are analyzed in which pheromone-baited trapping and food-baited trapping are
used simultaneously to eradicate an insect pest. The pest species is assumed to be under partial control by a host-specific
parasitoid species. The two models assume that density-dependent population regulation is accomplished either by host larval
competition or by means of oviposition interference among the parasitoids. The two trap types interact in a positive synergistic
manner and this combination appears to be very promising as a useful combination of pest control methods. Several features
of the system are examined; the feature which appears to cause the greatest problem is the possibility of the parasitoids
being attracted to the pheromone or the food traps. In either case, the degree of attraction does not have to be very great
to undermine the control effort. It is seen that food trapping becomes indispensible if host pheromone is used by the parasitoids
as a host-locating kairomone. If odor in the food traps is used by the parasitoids as kairomone, then the situation appears
more optimistic, as the reduction in efficiency of the food traps appears much less than with the pheromone traps when pheromone
acts as kairomone. 相似文献
12.
Tsukasa Sunose 《Researches on Population Ecology》1985,27(2):287-300
Summary Yearly population fluctuations ofM. pustulae were investigated at 19 sites in Kyushu. In sites where a platygastrid is the only parasitoid of the midge, the percentage
parasitism was very low in the incipient stage of the outbreak of the midge populations. After the number of midges reached
a peak, the midge populations declined as the percentage parasitism increased, and then the outbreak ceased. On the other
hand, in several populations no outbreak was found and the percentage parasitism was constantly at a high level. Therefore,
the immediate cause for the outbreak seemed to be a decline of the percentage parasitism. Like the midge, the platygastrid
has one generation each year, and its females also emerge in spring to deposit their eggs within host eggs. The decline of
the percentage parasitism seemed to be mainly affected by the time lag between emergence periods ofM. pustulae and the platygastrid.
In the midge populations parasitized by both the platygastrid and a eulophid (Chrysonotomyia sp.), an extinction of the population was observed, resulting from parasitism by the latter,Chrysonotomyia sp. is polyphagous and multivoltine, and is a late parasitoid, as discussed byAskew (1975). When the density of the midges is very low, the platygastrid may leave the host eggs unparasitized, whileChrysonotomyia sp. may not, because the mature galls are conspicuous. 相似文献
13.
Effects of population fluctuation of the gray-sided vole(Clethrionomys rufocanus) on the prevalence (infection rates) of the parasiteEchinococcus multilocularis in red fox(Vulpes vulpes) populations was investigated from 1985 to 1992 in eastern Hokkaido (Abashiri, Nemuro, and Kushiro area), Japan. This parasite
needs two hosts to complete its life cycle; the gray-sided vole as its intermediate host and the red fox as its final host.
We found that: (1) Infection rates in foxes depended on the current-year abundance of voles in all three study areas, particularly
in Abashiri. (2) In addition to this direct density-dependence, delayed density-dependence between the infection rate and
the prior-year abundance of voles was detected in Nemuro and in Kushiro. (3) The regional differences in density-dependence
pattern were related to regional differences in the winter food habits of red foxes: in Abashiri the proportion of voles in
the fox’s diet greatly decreases in winter, while the proportion remains high in winter in Nemuro and in Kushiro, probably
because of shallower snowpack. These results suggest that infection rates in foxes in Abashiri were less influenced by the
prior-year prevalence, since the infection cycle might be interrupted in winter, when voles became less important in fox’s
diet. In contrast, the state of the prevalence may carry over from year to year in Nemuro and in Kushiro, because red foxes
continue to eat a considerable amount of voles throughout year. The regionally contrasted results for the relationship between
infection rate in foxes and vole abundance were parallel to the regional difference in fluctuation pattern of vole populations,
which are highly variable in Abashiri area, but less variable in Kushiro-Nemuro area. Drastic change in vole populations appears
to affect the host-parasite system. 相似文献
14.
Stephan Grzeskowiak M. Joseph Sirgy Dong-Jin Lee C. B. Claiborne 《Social indicators research》2006,79(3):503-541
Housing well-being refers to the home resident’s cumulative positive and negative affect associated with the purchase, preparation,
ownership, use, and maintenance of the current home, and the selling of the previous home. Housing well-being is assumed to
occur when the home is bought with the least amount of effort (purchase), the home is prepared for use to meet the needs of the new occupants (preparation), ownership signals status and enhances the home owner’s financial portfolio (ownership), the home serves the housing needs of the residents (use), the maintenance, renovation, and repair in the home are minimal, least costly, and effortless (maintenance), and the sale of the home is transacted with the least amount of effort and most financial gain (selling). Based on this conceptualization of housing well-being, we conducted an exploratory study to identify the sources of satisfaction
related to the purchase, preparation, ownership, use, and maintenance of the current home, and the selling of the previous
home. The exploratory study also helped us articulate a theoretical model describing the interrelationships among the housing
well-being constructs and their consequence: the perceived quality-of-life (QOL) impact of the home. The exploratory study
helped us also to develop survey measures, which in turn were validated through two additional studies involving surveys of
home owners in the US and Korea. 相似文献
15.
We use data from the National Longitudinal Survey of Youth to examine the relationships between maternity leave coverage and U.S. womens post-birth leave taking and employment decisions from 1988 to 1996. We find that women who were employed before birth are working much more quickly post-birth than women who were not. We also find that, among mothers who were employed pre-birth, those in jobs that provided leave coverage are more likely to take a leave of up to 12 weeks, but return more quickly after 12 weeks. Our results suggest that maternity leave coverage is related to leave taking, as well as the length of time that a new mother stays home after a birth.All correspondence to: Jane Waldfogel. Funding for this project was provided by the National Institute of Child Health and Human Development and the William T. Grant Foundation. We are grateful to the editor and two anonymous referees for helpful comments. Responsible editor: Daniel S. Hamermesh. 相似文献
16.
K. L. Heong 《Researches on Population Ecology》1981,23(1):177-191
Summary The functional response parameters of the parasitoid,Anisopteromalus calandrae (Howard) to the third instar, the fourth instar and the pupae ofCallosobruchus maculatus (F.) were estimated from the Random Parasitoid Equation. By modifying this equation for a two host situation and using the
parameters estimated above, a no switch model could be obtained. This model was then used to test for switching. In the preference
experiments where two stages of the host were presented to the female parasitoid, a definite preference for the fourth instar
followed by the pupa and the third instar, respectively was shown. There was, however, no evidence of switching. There was
also no evidence that the data fitted the no switch models which suggests that when the parasitoid is searching in an environment
with two or more hosts, its searching behaviour is more complex. 相似文献
17.
Luca Maria Pesando Valentina Rotondi Manuela Stranges Ridhi Kashyap Francesco C. Billari 《Population and development review》2021,47(1):79-111
The Internet has revolutionized our economies, societies, and everyday lives. Many social phenomena are no longer the same as they were in the pre‐Internet era: they have been “Internetized.” We define the Internetization of international migration, and we investigate it by exploring the links between the Internet and migration outcomes all along the migration path, from migration intentions to actual migration. Our analyses leverage a number of sources, both at the micro‐ and the macro‐level, including the Gallup World Poll, the Arab Barometer, data from the International Telecommunication Union, the Italian population register, and unique register data from a migrant reception center in Southern Italy. We also distinguish between economic migrants—those who leave their country of origin with the aim of seeking better economic opportunities elsewhere—and political migrants—those who are forced to leave their countries of origin for political or conflict‐related reasons. Our findings point to a consistently positive relationship between the diffusion of the Internet, migration intentions, and migration behaviors, supporting the idea that the Internet is not necessarily a driving force of migration per se, but rather an enabling “supportive agent.” These associations are particularly relevant for economic migrants, at least for migration intentions. Further analyses underscore the importance of the Internet in providing a key informational channel which helps to define clearer migration trajectories. 相似文献
18.
Keizi Kiritani 《Researches on Population Ecology》1964,6(2):88-98
Summary Based on the results of five-year study on theNezara population, it was concluded that the level of abundance of the insect was determined partly by the combination and relative
adundance of the host plants and partly by the climatic factors. The endless increase of the population was checked by the
deleterious effects associated with the overpopulation which occurred locally. The degree of such overpopulation was determined
by the relative abundance of host plants to the current level of the population. Therefore, even when the general level ofNezara population seemed to be low, there still exists the possibility of overpopulation in some areas.
Winter was the critical period which threatened the persistence ofNezara population. The survival of the hibernating adults was partly dependent on the physiological state of adults which was determined
in the period of pre-hibernation. But when the severity of a winter exceeded the tolerance limit of the insect, the only safety-valve
which prevented the elimination ofNezara was the heterogeneity of hibernacula. Therefore,Milne's theory (1957) was closest to the known facts. 相似文献
19.
20.
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