共查询到20条相似文献,搜索用时 15 毫秒
1.
K. Tanaka T. Watanabe H. Higuchi K. Miyamoto Y. Yusa T. Kiyonaga H. Kiyota Y. Suzuki T. Wada 《Researches on Population Ecology》1999,41(3):253-262
To examine density dependence in the survival, growth, and reproduction of Pomacea canaliculata, we conducted an experiment in which snail densities were manipulated in a paddy field. We released paint-marked snails of
15–20 mm shell height into 12 enclosures (pens) of 16 m2 at one of five densities – 8, 16, 32, 64, or 128 snails per pen. The survival rate of released snails was 95% and was independent
of snail density. The snail density had a significant effect on the growth and egg production of individual snails. This density
dependence may have been caused by reduced food availability. The females at high density deposited fewer and smaller egg
masses than those at low density, and consequently produced fewer eggs. The females at densities 8 and 16 deposited more than
3000 eggs per female, while the females at density 128 oviposited only 414 eggs. The total egg production per pen was, however,
higher at higher snail density. The survival rates of juvenile snails were 21%–37% and were independent of adult density.
The juvenile density was positively correlated with the total egg production per pen and hence was higher at higher adult
density. However, the density of juveniles larger than 5 mm in shell height, i.e., juveniles that can survive an overwintering
period, was not significantly different among density treatments. These results suggest that snail density after the overwintering
period is independent of the density in the previous year. Thus, density dependence in growth and reproduction might regulate
the population of P. canaliculata in paddies.
Received: October 23, 1998 / Accepted: July 16, 1999 相似文献
2.
Osamu Imura 《Researches on Population Ecology》1986,28(2):281-293
Summary The population fitness in terms of the intrinsic rate of increaser
m was measured in eight pure (homogenic) strains ofEphestia kühniella
Zeller with different larva color at an optimal temperature of 25°C, and in three strains at unfavorble temperatures of 15, 17,
28, and 30°C, to understand a mechanism of maintenance of a larval color variation found in wild populations. The survival
rate, hatchability, and gross rate of reproduction were poorly correlated with the fitness but the mean generation time and
net reproduction rate were correlated with the fitness significantly at 25°C. Intermediate color (pink) strain(s) grew faster,
initiated reproduction earlier and had shorter longevities than other strain(s) under the range of 15 and 28°C; the fitness
was highest in the intermediate larval color strains except at 30°C in which all strains had a negative rate of increase.
The results were discussed with reference to the relationship between the larval color and fitness along with a maintenance
mechanism of the variation. 相似文献
3.
Kazuhiko Sakai 《Researches on Population Ecology》1998,40(3):287-292
The present study examines (1) the cost of reproduction on colony growth, and (2) relationships among sexual maturity, whole-colony
mortality rate and colony growth rate inGoniastrea aspera free from external influences by macrobenthos. Survival of colonies in permanent plots was followed for two years. Egg production
by polyps in colonies collected just before the first spawning of a year was estimated by dissecting the polyps. Growth of
the colonies (increase in number of polyps) was followed over one annual reproductive cycle. The cost of egg production on
colony growth was apparent through colony ontogeny: (1) immature colonies had a greater annual growth rate than mature colonies,
but produced almost no eggs; (2) in mature colonies, growth rate was negatively correlated with NE/PV (number of eggs per
polyp volume mm-3). Annual whole-colony mortality was high in colonies with fewer than11 polyps in initial colony size, while mortality was extremely low once a colony grew beyond this size. This critical size
for low whole-colony mortality was much smaller than the colony size (40 polyps) which would attain maturity one year later.
Age at maturity was estimated as six years. While survival to maturity may be a selective force for the evolution of delayed
maturation, the present data suggest that high colony fecundity, achieved after a long growth period as an immature colony,
and an abrupt decrease of colony growth rate after maturation are the crucial forces. 相似文献
4.
Frank J. Sonleitner 《Researches on Population Ecology》1977,19(1):10-32
Summary A model is described for investigating the interactions of age-specific birth and death rates, age distribution and density-governing
factors determining the growth form of single-species populations. It employs Monte Carlo techniques to simulate the births
and deaths of individuals while density-governing factors are represented by simple algebraic equations relating survival
and fecundity to population density. In all respects the model’s behavior agrees with the results of more conventional mathematical
approaches, including the logistic model andLotka’s Law, which predicts a relationship betwen age-specific rates, rate of increase and age distribution.
Situations involving exponential growth, three different age-independent density functions affecting survival, three affecting
fecundity and their nine combinations were tested. The one function meeting the assumptions of the logistic model produced
a logistic growth curve embodying the correct values orr
m
andK. The others generated sigmoid curves to which arbitrary logistic curves could be fitted with varying success. Because of
populational time lags, two of the functions affecting fecundity produced overshoots and damped oscillations during the initial
approach to the steady state.
The general behavior of age-dependent density functions is briefly explored and a complex example is described that produces
population fluctuations by an egg cannibalism mechanism similar to that found in the flour beetleTribolium.
The model is free of inherent time lags found in other discrete time models yet these may be easily introduced. Because it
manipulates separate individuals, the model may be combined readily with the Monte Carlo simulation models of population genetics
to study eco-genetic phenomena. 相似文献
5.
Keisuke Nakata 《Researches on Population Ecology》1989,31(2):185-209
Summary Changes of the components of reproduction were analyzed quantitatively in a two-year cyclic population (which has two peaks
in alternate years during a five-year census) of the red-backed vole,Clethrionomys rufocanus bedfordiae, with reference to its regulatory mechanism: (1) Variation in sex ratios was not associated with population phase or density,
although a higher percentage of females in mature individuals was observed in the increase phase. (2) Females attained to
sexual maturity at younger age and at lighter body weight than did males. All the youngest mature individuals were found in
the low and the increase phases. Age and size at maturity became older and larger as the population went toward the peak phase.
(3) Maturation rate was strongly associated with population phase and density; this component is an important and good parameter
to predict population trend. Maturation rates were in the order, the low phase>the increase phase>the peak phase>the decline
phase; the differences in the rates among these phases were significant. Maturation rate was somewhat depressed when the population
density exceeded about 40 individuals/ha. Changes in age at maturity and in maturation rate are interpreted as derivative
phenomena related to the population density and the capacity of the number of mature voles per unit area. (4) The maximum
number of mature individuals were 26 males/ha and 29 females/ha; there was almost no increase of the number of mature voles
at higher population densities over about 40 individuals/ha. The number of exclusive home ranges per hectare calculated from
the observed range lengths did not differ much from the maximum number of mature voles of either sex. (5) Length of breeding
period was shorter in the high-density years than in the low-density years; the breeding started earlier and ended earlier
in the former than that in the latter. In the increase phase a few voles reproduced in winter. (6) The percentage of pregnant
females was significantly lower in the peak phase than those in the other phases. 相似文献
6.
Summary Population behaviour of adults and 5th-instar nymphs ofNezara viridula L. was analysed by means of the marking-and-recapture method in an early-planted paddy field. The field contained five varieties
of rice which differend in growth states. It was estimated that a total of more, than 7,000 adults of the first generation,
in which at least 3,000 were females, invaded the field from early July to middle August. Egg-mass census data, however, indicated
that only 10 per cent or less of the females participated in egg-laying. This was largely due to the, low rate of adult survival.
The adults preferred younger plants, for both feeding and oviposition.
The method described byIwao
et al. (1966) permitted estimate that 3,300–3,400 of the 5 th-instar nymphs and 1,100–1,200 of the adults of the second generation
were produced from 298 egg-masses (25, 700 eggs); while 95–6 per cent of the individuals were thought to have died before
reaching adulthood. Most of the 5 th-instar nymphs moved less than 4 m in three days as long as the condition of food plants
remained suitable, but they tended to move more towards younger plants when those on which they lived became too mature. The
apparent survival rate of the second generation adults was very low, probably due both to a rapid emigration and a high mortality
of newly-emerged adults. 相似文献
7.
Masami Hasegawa 《Researches on Population Ecology》1990,32(1):119-133
Summary The demography of the lizardEumeces okadae was studied for 4 years on Miyake-jima, in the Izu Islands, central Japan. Most males matured at 3 years of age with a mean
snout-vent length of 77.5 mm. Females matured at 3–4 years with a mean SVL of 77.8 mm, and reproduced biennially thereafter.
Growth continued after maturity with a decreasing rate. In females, annual growth was negligible in reproductive years, but
resumed markedly in non-reproductive years. Clutch size increased with SVL and was used to construct a fecundity schedule.
Population density (exclusive of hatchlings) was estimated to be ca. 4000 individuals/ha in August, an exceptionally high
density for lizards. Before introduction of the weasel onto Miyake-jima, low predation pressure had allowedE. okadae to maintain a high population density. Estimated annual survival rates were 36% for hatchlings, 56% for yearlings, 80% for
2-year-olds, 63% for adult males and 76% for adult females. The cohort generation time (6.95 years) was so long that theE. okadae population can be characterized by a combination of low natality and slow turnover. 相似文献
8.
Yoshio Tsuda 《Researches on Population Ecology》1982,24(2):388-404
Summary Diversity of oviposition curve observed in 125 insects was analysed using the ratio of the length of period for development
to that for reproduction. On the basis of this empirical data, two extreme reproductive patterns were selected: prolonged
reproduction with early maturity and concentrated reproduction with late maturity. Population growth of the species with each
reproductive pattern was calculated usingLeslie Matrix under some simulated fluctuating environments where the length of time during which the environments change is short
compared with the time required to stabilize age structure. These simulation studies show that there is an optimal ratio of
the length of period for development to that for reproduction in achieving high population densities and this ratio varies
depending on the favorableness of environment for reproductive success: as the environmental favorableness decreases, the
optimal ratio becomes larger. 相似文献
9.
Kazuhiko Kosuda 《Researches on Population Ecology》1981,23(2):379-386
Summary Competition experiments between a lac+ prototroph and a lac− auxotroph ofEscherichia coli were conducted by serial transfer procedure on four levels of sugar concentration. Changes of the relative frequencies of
both genotypes were followed and the relative fitness was estimated. Fitness was proved to be density-dependent. No explicit
dependence of fitness upon genotype frequencies could be detected by the simple method ofKosuda (1981). 相似文献
10.
Summary An increase in fish mortality due to fishing can theoretically change the growth and reproduction of fish populations from
the viewpoint of adaptation. We address the issue of how an iteroparous fish should convert surplus energy into somatic growth
and reproduction at each age under given conditions of mortality. A model of life history, which maximizes the net reproductive
rate using the discrete maximum principle, is improved employing a new relationship between body weight and surplus energy
which we have recently proposed. The model is applied to the North Sea plaicePleuronectes platessa, for which it has been reported that the average length of young fish had increased whereas that of old ones had decreased
for some decades. Although the model cannot directly explain the former phenomenon, the two phenomena can be interpreted as
a change in the optimal life history due mainly to an increase in mortality. 相似文献
11.
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
12.
Summary Stability of the stock-harvesting system regulated by a feedback control procedure of catch quota is examined. In the procedure
considered, catch quota is changed proportionally to the difference between current and the target stock level (with a proportionality
constanth) and to the annual stock growth rate (with a proportionality constantg). Condition for the local stability of the target equilibrium is obtained as a function of the stock-recruitment relation,
survival probability of adults, target stock level, time lag before implementation of regulation, age of sexual maturity of
the stock, and proportionality constantsg andh. It is shown that, (1) the procedure has the stabilizing effect; it can stabilize the target stock level that is unstable
under constant harvest, (2) lower target stock level favors largerg and smallerh, when the target is set around MSYL (the stock level that gives MSY), (3) the degree of stability, measured by the time required
to recover the target stock level, is an increasing function of the target stock level, (4) stability and sustainable yield
are in trade-off, (5) time delay caused by the time needed before sexual maturity does not affect the stability significantly,
but the effect of the time lag before implementation of regulation is significant. Comparison between harvest-control and
effort-control procedures is also made, and the advantage of the latter in terms of stability is shown. 相似文献
13.
The relation of the within-season and between-season patterns of shoot growth were compared in a clonal grass with long-lived
shoots,Festuca rubra, in a mown mountain grassland. The growth rate of shoot length from spring to summer in a year was almost constant for each
shoot irrespective of spring shoot length each year. The annual shoot growth rate from spring to spring was negatively correlated
with the shoot length in the first spring. Shoots of different length and age therefore tended to converge over time to a
population of identical shoot size, suggesting an equalizing effect of growth pattern on size structure. Shoot size (shoot
length and number of leaves) influenced the fates of shoots. Larger shoots showed an increased incidence of both flowering
and formation of intravaginal daughter shoots and a decreased incidence of death in the subsequent time period. The fates
of shoots were independent of their age. Although the negatively size-dependent springto-spring annual shoot growth rate acted
to decrease shoot size variation, the remaining variation within the shoot population was still sufficient to generate different
fates of shoots. These fates were not related to the previous life history of individual shoots. There was a significantly
positive effect of the shoot size at initiation on its life expectancy. This was mainly attributable to the positively size-dependent
survival rate of shoots in the early stage (<1 year old) of shoot life history. Later on (> 1 year old), shoot size had little
effect on the survival rate of shoots. Once small young shoots have survived this early stage (< 1 year old) in life history,
they can grow vigorously, little affected by competition regardless of shoot size, and converge to a stable size structure
of shoots of similar size. Only shoot size in the early stage ( < 1 year old) of life history is important for the persistence
of a shoot population. 相似文献
14.
Yutaka Sait 《Researches on Population Ecology》1987,29(1):57-71
Summary Experimental observations on the arrenotokous reproductive patterns of two spider mite species (Acari: Tetranychidae), the
long-seta form ofSchizotetranychus celarius (Banks) andTetranychus urticae
Koch, revealed that reproduction of unfertilized females of the former is very differnt from that of the latter. Unfertilized
females ofS. celarius, which has a subsocial life, laid a few eggs and then became inactive. In contrast, the fecundity of unfertilizedT. urticae females was only slightly reduced as compared with fertilized females. Mother-son matings may thus sometimes occur in naturalS. celarius populations.
A two-year field survey revealed that, in the absence of males, overwintering females ofS. celarius occasionally remain unfertilized until early spring. Furthermore, nest foundation observed in late spring indicated that
most of the season's first nests were founded by single females. These two sets of observations strongly suggest that motherson
mating takes places in nature, corresponding to the reproductive trait seen in the experiment.
Mother-son mating inevitably increases the relatedness between nest members. The estimated father's relatedness to its offspring
is extraordinarily high under such condition. The possibility that kin-selection in the long seta-form ofS. celarius led to subsociality, especially paternal care, is suggested.
This study was supported in part by Grant-in-Aid No. 61540468 from the Ministry of Education, Science and Culture, Japan. 相似文献
15.
Masahiro Nakaoka 《Researches on Population Ecology》1993,35(2):199-213
Summary Long-term variation in recruitment was estimated by constructing projection matrices for a marine bivalve,Yoldia notabilis, at two stations in Otsuchi Bay, northeastern Japan, and the effects of its variation on population dynamics were examined
using a simple matrix model. The matrix model was developed from the Leslie matrix, in which the population growth rate λ
was expressed as a function of recruitment rater
0. The equilibrium recruitment rater
s, or the recruitment rate required to maintain population at constant size (λ=1), was expressed by the reciprocal of the reproductive
value of a newly recruited individual. The estimates ofr
s for the field population were lower at the shallower station than at the deeper station, reflecting higher survivorship and
fecundity. Past recruitment rate estimated both by the field samplings for 3 years and by the back-calculation from the current
age structure for over 10 years showed large yearly variation, ranging between 0 and 58.6×10−4. The estimates were larger thanr
s, and hence, large enough to increase population size (λ>1) only in approximately one-third of the estimated years. This suggests
that the population has been maintained by occasional successful recruitment occurring once every few years. 相似文献
16.
Summary Difficulty arises in applying marking-and-recapture methods to insects when the probability of recapture of marked individuals
is changed with advancing age, either due to detachment of the mark by moulting (in the case of larvae) or to changes in their
survival rate or their behaviour. A modification of the re-recapture method (Leslie
et al., 1953) has been devised to analyze the capture-recapture data of the 5th-instar larvae and adults ofNezara viridula L. Estimation of the rate of moulting to the adult stage is made with the aid of additional information on larval survival.
Migration rates of the larvae between the two halves of the census field is estimated byIwao's (1963) method. Through these analyses, the dynamic feature of the population during transition from the 5th instar to, adult
is revealed. Several problems involved in the application of marking-and-recapture methods to insect populations are discussed.
Contribution from the Entomological Laboratory, Kyoto University No. 392. 相似文献
17.
Summary This paper theoretically analyses the relationship between surplus energy, which is available for either somatic growth or
reproduction, and body weight. From the data of metabolism and growth of the biwamasu,Oncorhynchus rhodurus, obtained by Miura et al., a Bernoulli's differential equation is induced to represent the relationship between body weight
and the sum of surplus energy and active metabolic rate. Solving this equation gives the amount of surplus energy,f(Wx), as follows:f(Wx) = (αW
x
1−γ
+β1−γ)1/(1−γ)−Wx, in which α, β and γ are constants andW
x is body weight at agex. The function is applied to ten fish populations and consequently it is found to be useful for a wider age range and a wider
variety of fishes than the conventional function. 相似文献
18.
William K. Reisen Farida Mahmood Tauheeda Parveen 《Researches on Population Ecology》1979,21(1):12-29
Summary A mark-release-recapture experiment to estimate population survivorship and absolute size was performed with wild-caughtAn. subpictus adults at the village of Khano-Harni, Lahore District, Punjab Province, Pakistan during September 1978, the end of the monsoon
rainy season, when temporal population abundance was maximized. Daily survival rate estimated from the recapture sequence
of marked adults was low, males=0.192 and females=0.343. Survivorship for females estimated by several vertical age-grading
procedures ranged from 0.347 to 0.628. Both stage- and age-specific life tables were calculated from vertical age-grading
data determined by the dilatation method. Female and male population size was estimated byBailey’s modification of theLincoln Index and was found to average 4478.4 and 6106.8, respectively. The bionomics, survivorship and population size ofAn. subpictus in the Lahore are indicated that this species was probably not important in the transmission of human malaria. 相似文献
19.
Summary We studied settling-site selection and the resulting survival of two sessile scale insects,Ceroplastes rubens andC. ceriferus, in the citrus tree,Citrus unshiu, in central Japan.
C. rubens preferred 0-year-old twigs most as a settling-site; the density of nymphs settling on 0-year-old twigs was significantly
higher than those on ≥1-year-old twigs, and few nymphs settled on ≥3-year-old twigs. The mean survival rates from settling
until reproduction in the next year were significantly higher on more preferred twigs than on less preferred ones. InC. ceriferus, nymphs significantly preferred 1- and 2-year-old twigs to 0- and ≥3-year-old ones, and the mean survival rates on the more
preferred 1- and 2-year-old twigs were significantly higher than those on less preferred ≥3-year-old twigs. However, the survival
rate on less preferred 0-year-old twigs was slightly higher than those on 1- and 2-year-old ones. Thus, in both species of
scale, it was the preferred twigs which were more profitable sites for survival after settling, except for less preferred
0-year-old twigs forC. ceriferus.
In both scale species, most mortality was due to growth cessation, which is believed to be related to the twig quality as
a food source. Predators and parasitoids were minor mortality factors.
Both species showed constant survival rates until the density of settled nymphs exceeded double the “upper-limit” density,
whereupon they decreased drastically.
Nymphs ofC. rubens settling on twigs of high scale density showed a spacing-out distribution, those ofC. ceriferus did not. InC. rubens, an increase in preference for originally less profitable twigs at the later stage of the settling season was observed, but
not inC. ceriferus. Accordingly, individuals ofC. rubens showed a stronger tendency to avoid conspecifics than didC. ceriferus.
Although nymphs of the two scales clearly preferred more profitable sites, their settling-site selection did not agree with
the predictions from the ideal free distribution theory (Fretwell and Lucas, 1970). The discrepancies were (1) frequent settling
on less profitable sites at the early stage of the settling season, (2) insufficient utilization of the most profitable twigs,
and (3) virtually 100% mortality on overcrowded twigs under conditions where unoccupied profitable twigs still remained. These
discrepancies are thought due to the limited dispersal time of nymphs.
Contribution to the ecological studies of scale insects 2. 相似文献
20.
I Nyoman Widiarta Kenji Fujisaki Fusao Nakasuji 《Researches on Population Ecology》1991,33(2):257-267
Summary The three year (1988–1990) life tables ofNephotettix cincticeps were constructed, and the daily survival rate and longevity of female adults were estimated by Hokyo and Kiritani’s (1967)
method for the overwintering and the first-generations on the foxtail grass in Okayama, southwestern Japan. The life tables
and the population parameter values estimated were compared with those in the other generations on rice. The FARMCOP suction
sampler was employed to survey the population density.
The durations of pre-ovarial maturation of female adults of the 1st generation on foxtail grass and rice seedling were similar.
Longevity of adults of the overwintering and the first generations which emerged on the wild host was longer than that of
the other generations (2nd and 3rd generations) on the rice plants. Fecundity of females decreased successively as the generation
proceeded and it became lowest in the final 3rd generation.
Only about 3.5 percent of first-instar nymphs of the 1st generation emerged as adults in the fallow field. The survival rate
of nymphs on foxtail grass was always lower in comparison with that on rice plants. However, the survival rates of nymphs
on foxtail grass and rice seedling were not significantly different from each other under laboratory conditions. In the fields,
senescence of foxtail grass occurred in the midst of nymphal period of the 1st generation. The survival rate of nymphs on
foxtail grass decreased with the increasing in the nymphal density. Abundance of spiders during the 1st generation was higher
than that in the early stage of rice plants. 相似文献