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1.
Takashi Saitoh 《Researches on Population Ecology》1990,32(2):391-406
Summary A population of the grey red-backed vole,Clethrionomys rufocanus bedfordiae, was investigated on a 1 ha control grid and a 1 ha grid on which the voles were fed within a 2.1 ha outdoor enclosure in
Hokkaido, Japan by live trapping from 1984 to 1986, for testing the Reproductive Suppression Model of Wasser and Barash (1983)-females
can optimize their lifetime reproductive success by suppressing reproduction when future conditions for the survival of offspring
are likely to be sufficiently better than present ones as to exceed the costs of the suppression itself. Age at the first
pregnancy more varied in a higher density population on the experimental grid and females could be classified into the early
and the late reproductive type in two generations (A: females born from February to June 1985; B: females born from September
to November 1985). Lifetime reproductive success (the number of pregnancies, the number of successful litters, and the number
of offspring) was not different between the early and the late reproducing females. The late reproducing females lived for
longer periods than the early reproducing females, so that the loss by delayed start of reproduction was compensated for by
a longer life span. Life span was not different between offspring of the early and the late reproducing females. These facts
supported the Reproductive Suppression Model. 相似文献
2.
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
3.
Takashi Saitoh 《Researches on Population Ecology》1991,33(2):367-386
Summary The effects of breeding territoriality on the stability of grey red-backed vole (Clethrionomys rufocanus bedfordiae) populations were investigated on a control grid and a grid on which the voles were fed, in an outdoor enclosure in Hokkaido,
Japan. Vole populations were monitored by live trapping from 1984 to 1986: (1) Population density was 2–7 times greater on
the experimental grid to which food was added than on the control grid. Reproductive output was more closely associated with
the difference in density between grids than survival or dispersal (immigration and emigration) rates. (2) The number of adult
females and pregnancy rate of the experimental population were significantly greater than those of the control one. The difference
in the number of adult females between the populations was greater than that in pregnancy rate. (3) The proportion of successful
litters and the number of weanlings per litter were not significantly different between the control and experimental population.
(4) Adult females held territories on both the control and experimental grid; they were spaced out more than would be expected
from random occupation. The territories overlapped more on the experimental grid than on the control grid. (5) Mean territory
size of adult females on the experimental grid was about half of that on the control grid. The territory size was correlated
negatively with population density. (6) The proportion of trap sites that were used by adult females was significantly greater
on the experimental grid than on the control grid. This suggests that adult females on the experimental grid used the area
more extensively. This factor, in association with territory size and overlapping of territory, was also important in causing
the difference in the number of adult females between the grids. (7) These results call into question the hypothesis that
territoriality stabilizes the density in populations ofClethrionomys. 相似文献
4.
Takashi Saitoh 《Researches on Population Ecology》1995,37(1):49-57
The natal dispersal distance of the grey-sided vole,Clethrionomys rufocanus (Sundevall), was measured in a large outdoor enclosure (2.1 ha) in Hokkaido, Japan. Voles in about half of the enclosure
(1 ha) were fed. Distance from the natal site to the site of reproduction was significantly greater in males (64.9 m) than
in females (35.3 m). In males, 24.8% settled within one home range length of their natal site and 49.6% settled further than
two range lengths from their natal site. In femles, the respective percentages were reversed: 51.2% and 22.0%. The timing
of large movements (≥50 m) was related to body mass in both sexes. The population density was always higher on the fed grid
than on the control grid, which resulted in the frequency of large movements being greater on the fed grid that on the control
grid. Thus, the percentage of voles performing a large movement was not different between the grids in both sexes. 相似文献
5.
Yasuyuki Ishibashi Takashi Saitoh Syuiti Abe Michihiro C. Yoshida 《Researches on Population Ecology》1998,40(1):51-59
Kinship amongClethrionomys rufocanus was investigated during the winter of 1992/93 in a 3-ha enclosure using both molecular and catch-mark-release techniques.
Forty-six adult voles (22 males and 24 females) having high heterozygosities, which were collected from several natural populations,
were released into the enclosure on 29 September 1992. Most fall-born individuals of both sexes stayed in their natal site
during the non-breeding period (December–March), although reproductively active females dispersed during the fall breeding
season (October–November). These philopatric individuals aggregated and formed an maternal family in the winter. Several females
which failed to reproduce were solitary during this season. Some individuals which were derived from several families also
aggregated into a mixed lineage group. Survival rate of fall-born voles from earlier litters was higher than that from later
ones. Maternal families broke up soon after the onset of spring reproduction. Most females established a territory near the
wintering site and made a kincluster, in which close relatives neighbored each other. Maternal families in winter bring about
female kin-clusters in spring, which may influence reproductive output in the breeding season. 相似文献
6.
Kohji Hirano 《Researches on Population Ecology》1995,37(2):185-195
Temporal changes in the population size of a phytophagous lady-beetle were analyzed to identify mechanisms affecting lady-beetle
population dynamics at different spatial scales. The study area (15 ha) included 18 habitat patches. The major host plants
were potato for first generation larvae and eggplant for second generation larvae. The habitat patches were classified into
three groups according to the major host plants in each patch: P-E patches (both host plants available), P patches (potato
only), and E patches (eggplant only). The winter disappearance of adults in the whole study area, and larval mortality in
E patches were apparently the most important factors disturbing the overall population density. Density-dependent movement
of females appeared to have the greatest stabilizing effect on the yearly fluctuation of population density. Rate of increase
of female adults from the first to the second generation,R, was generally higher on eggplants in E patches than in P-E patches because the adult density of the first generation was
much higher in P-E patches. The yearly fluctuation of adult density in each generation tended to be less in patches with all
habitat components necessary for the full life cycle (P-E patches). However, such patches were not favorable for first generation
females, as indicated by the lower rate of increase from the first to the second generation. The density and stability of
lady-beetle populations is discussed in relation to habitat structure. 相似文献
7.
Kenichi Ozaki 《Researches on Population Ecology》1993,35(2):273-284
Summary The number of larvae reaching maturity within the gall ofAdelges japonicus was positively related to gall volume, and the relationship between the number of mature larvae and gall volume did not change
with different densities of colonized larvae.
The population changes in the bud galls ofA. japonicus were surveyed by collecting the galls, which did not suffer predation or parasitism within the galls, from young artificial
plantations ofPicea jezoensis over two years. In the year when the density of colonized larvae was high, they suffered a 42% mortality within the galls,
whereas mortality was nearly zero in the low density year. The numbers of larvae per gall were positively correlated with
gall volume. The regression lines of the number of colonized larvae on gall volume did not differ significantly in the regression
coefficients between the two years, whereas the intercept was significantly higher in the year when the density of colonized
larvae was higher. However, different within-gall mortality nullified this difference, and the regression lines of the number
of mature larvae on gall volume had no significant difference both in the regression coefficients and the intercepts. This
suggests that the number of mature larvae per gall was limited by available resources within the gall which were positively
related to gall volume. In 25% of the galls in which mature larvae inhabited, the space within the galls were completely filled
by the larvae, indicating that space was one of the limiting resources. Gall volume also affected the number of adults that
emerged from the gall and the potential number of their progeny. 相似文献
8.
Summary The population growth of the green rice leafhopper,Nephotettix cincticeps, in the paddy field was analyzed based on the life table data accumulated for six years.
The paddy field population, which stems from the invading adults of the first generation (G-I), repeats two complete generations,
and the hatchlings of the fourth generation (G-IV) enter diapause and overwinter as the fourth instar nymphs in fallow paddy
fields. It was clarified that the density dependent reduction in the mean longevity and oviposition rate of adult females
in G-II and III played a primary role in stabilizing the annual population densities. The annual average of the mean longevity
of G-II females (3.9 days) was much shorter than that of G-III ones (7.7 days) and thus the density dependent reduction in
the mean longevity induced a more prompt regulatory effect on the oviposition of G-II females compared with G-III ones. As
the result, two equilibrium densities of eggs were obtained,e.g., ca 100 and 700 eggs per hill in G-III and IV, respectively. Density dependent decrease in the proportion of mature females in
the adult population was especially conspicuous in G-II, and this was closely associated with the density dependent reduction
in the mean longevity and fecundity. Thus, the density dependent dispersal (emigration) of the adult females by flight in
G-II and III was the most convincing factor in the process of population regulation. The density dependent dispersal of the
adult females is effective in avoiding the deleterious effects of nymphal crowding in a breeding habitat unit (a paddy field),
and may result in a more even distribution of the population over a continuous habitat units in a locality than otherwise. 相似文献
9.
Tadashi Miyashita 《Researches on Population Ecology》1992,34(1):143-153
Summary Field studies were conducted to clarify whether variation in food availability among habitats influences population density,
and whether population density has a negative effect on foraging success in the orb-web spider,Nephila clavata.
Lifetime food consumption per individual (i.e., foraging success) strongly correlated with mean body size of adult females
and mean fecundity in populations. Also, there was a positive correlation between foraging success and population density.
Since foraging success reflected potential prey availability in the habitat, food resource appeared to be a limiting factor
for populations in this spider. Mean fecundity per individual correlated with population density of the following year, suggesting
that decreased reproduction is a major component of food limitation on population density. Consistent defferences in mean
body size between particular sites were observed over years, while such difference was less obvious in density. Thus, ranking
of food abundance among habitats seems to be predictable between years. A field experiment revealed that an artificial increase
in population density had no negative effect on the feeding rate of individuals, suggesting that intraspecific competition
for food is not important in this species. 相似文献
10.
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
11.
Summary Male and female prairie deermice housed singly from weaning (21 days) until 40 days of age had urine from one of the following
sources applied daily to their nostrils: sexually mature laboratory population males or females, and sexually mature breeder
males or females from our laboratory colony. Other males and females were treated with water. Records were obtained of the
weights of the tests, seminal vesicles and bacula of males and the ovaries and uteri of females at 40 days of age.
The major results of this study were as follow: Female urine from sexually mature and inhibited population or isolated mice
stimulated the development of the male reproductive organs significantly more than water or male urine. Male urine applied
to young males did not differentially affect the weights of their reproductive organs compared with water and thus showed
no inhibition effects.
The reproductive organs of females treated with male urine did not differ significantly in weight from those of females treated
with female urine. Females treated with water developed significantly larger uteri than those treated with urine from sexually
mature population females (P≤0.02), inhibited population females (P<0.001) and inhibited population males (P<0.007). 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.
Summary A field work with two plots of grid, a snap trap being set on each station spaced 5 m apart, was executed in the summer of
1968 to evaluate prebaiting in census trapping by comparing the result in one plot, prebaited for three days, with that in
the other not prebaited. Since the population was as high as some 230 per acre on the average in density and formed of the
vole,Microtus montebelli, alone, sufficient samples were gathered irrespective of the plot size as small as 50×50 m.
Owning to the circumstances, multiple collisions inflicted so intense influence on sampling especially in the prebaited plot
thatz-equation for census adjusted to the effect was well applicable to the data in either plot. In sampling, the fact that small
voles are apt to be caught later than large voles was statistically evidenced in either sex, and yet any proof that males
tend to be caught prior to females was not offered. It was ascertained in either plot that the daily catch was realized according
to the same rule through the whole period of trapping in both external belt and internal square within the plot; hence it
follows that no considerable immigration occurred.
One of the beneficial effects of prebaiting is sure to be that the probability of capture was markedly enhanced in the prebaited
plot, and a second is supposed, though inconclusively, to be that a good sampling could be executed consistently through the
census period giving rise to no inordinate catches perhaps due to heterogeneous sampling as was seen in earlier days in the
not prebaited plot. The supposition has derived from the condition that most of the whole population is trappable, which is
established by interrelation among population density, size of home range and trap spacing. It was suggested that the effect
of prebaiting should be evaluated from the view-point of the interrelation, because the basic utility of prebaiting consists
in that it may help to our utlimate purpose to estimate the whole population.
Contribution from JIBP-PT No. 55, carried out by the grant from the expenditure of Education Department to the specific study
on “Dynamics of Biosphere” 相似文献
14.
Ryo Tanaka 《Researches on Population Ecology》1972,13(2):127-151
Summary A substantial explication of the edge effect has been attempted by use of capture-recapture data for a vole population (Microtus montebelli), gathered intwo plots of 100×100 m or less during 12 days, cheked twice daily, in August 1970; the sample was quite sufficient
for the aim.
The edge effect as guessed by increased catch per trap is usually suspected to ensue from range-settlers in the outside boundary
strip of a plot and immigrants. But by a theoretical analysis I could attain a tentative conclusion that no increased catch
per trap will occur unless any invasion takes place. Then it follows that, apart from the effect of invasion, the role of
the adjoining outside settlers in the edge effect is essentially required to be studied in the light of knowledge on the truth
of size and shift in home range.
The variation in range behavior for 183 adult voles, captured 6 times or more, could be grouped into eight types, of which
the range-conservative type possessed 52% of the sample and the group of the type was justly utilized for giving averages
of range size. Besides, it was seen from the observed frequency of types that a considerable number of immigrants onto the
census plot were induced perhaps being allured by trap baits, but the majority of them proved to be assigned to the voles
that have their ranges inside the assessment line ofDice; the rest referable to effective immigrants was only a few (7%). I could perceive no reason such as disproves the idea ofDice’s additional boundary strip.
Viewed from maps of ingress shift of ranges, the effect of ingress must have been greater in the outer trap rows than in the
inner within the plot, so that it might well be called edge effect in general; such effect, however, is seen gradually diminishing
toward the center, and hence it is almost unlikely that one should find any clear-cut intra-plot assessment lines demarcating
such an inner square as quite free from edge effects.
Averages of observed range length and width (ORL and ORW), as reliable measures for the true range size, were determined from
the above group of specimens; as a result, the remarkable concept of elliptic range shape was established by regarding ORL
as long axis and ORW as short one, and, directly from these averages, the mean range sizes worked out at 0.04 for females
and 0.09 for males in acreage which proved to be surprisingly well agreeable with those of isotope-revealed ranges for voles
given byGodfrey (1954) andAmbrose (1969).
The catchability for marked voles (
) was estimated by the maximum likelihood method by use ofJolly’s formulae (1965), but that for unmarked ones (
) was made by the regression census formula; as a result it was shown that the population was clearly of π>p type and that the trap-experience that voles underwent one month or more ago can make them retain as high catchability as
π.
Contribution from JIBP-PT No. 110, carried out by the grant from the expenditure of Education Department to the specific study
on “Dynamics of Biosphere”. 相似文献
15.
Masaya Matsumura 《Researches on Population Ecology》1996,38(1):19-25
A population census was conducted to describe the effects of the growth stage of rice on the population dynamics ofS. furcifera, in particular, on immigration, seasonal abundance, population growth rate, and wing-form expression. The number of immigrants
was highest on rice plants 17 to 30 days after transplanting (DAT), which suggested that immigrants prefer to settle or remain
more on rice plants at the tillering stage (approximately 20–30 DAT). Population growth rate from immigration to the 1st generation
decreased with an increase in rice plant age. In contrast, population growth rate from the 1st to 2nd generation was not influenced
by rice plant age and was negatively density-dependent. The percentage of macropters (flyers) was positively related to the
growth stage of rice when rice was in the vegetative or early part of the reproductive stage, and reached 100% at about 10
days before heading (booting stage). Threafter, most adult females molted into macropters regardless of population density.
The roles of host plant age and crowding effect on the population dynamics ofS. furcifera are discussed. 相似文献
16.
Body masses of wild-caught habu,Trimeresurus flavoviridis, were measured with known error range. Habu larger than mature female size had steeper slope in length-mass regression than
smaller individuals. Females outweighed males in most snout-ventlength classes and in early summer. Gravid females outweighed
non-gravid ones by about 20% on the average, but the body mass ranges of the two groups overlapped. Through the body mass
change in mature females, the proportion of gravid females was estimated to be about 0.5. 相似文献
17.
Hiroyuki Matsuda Yasuto Takenaka Tetsukazu Yahara Yuji Uozumi 《Researches on Population Ecology》1998,40(3):271-278
We estimate the extinction probability of a large and decreasing population, the southern bluefin tuna. This tuna was listed
as critically endangered by the World Conservation Union (IUCN) in 1996. However, the absolute population size is still large
and the extinction probability within the next half century is negligible if the recent population decline rate does not increase
in the future. IUCN’s criterion with respect to the population decline rate should be linked to the absolute population size,
if this is estimated. Several methods estimating the probability of extinction conclude that the southern bluefin tuna population
will be below 500 mature individuals within the next 100 years and may be listed as vulnerable. These analyses suggest that
extinction risk assessment is useful for management action for taxa that still have large population and are rapidly decreasing. 相似文献
18.
The population density of herbivores depends on the spatial scale as well as the temporal scale. In a small-scale, short-term
experiment, the number of individuals entering from the surrounding area will be most influential in determining the herbivore
density. In large-scale, long-term experiments, however, the density of herbivores will rather be influenced by the survival
rate of individuals inside the field because most of the herbivorous population derives from the parents that developed inside
the field. If we want to predict the large-scale long-term density of herbivores, therefore, emphasis should be placed on
the estimation of survival rate. To elucidate the effects of plant density on the large-scale long-term abundance of cabbage
pests, we examined the survival rates of three lepidopterous pests, the small white butterfly Pieris rapae crucivora Boisduval (Pieridae), the beet semi-looper Autographa nigrisigna (Walker) (Noctuidae), and the diamondback moth Plutella xylostella (Linnaeus) (Yponomeutidae) under two levels of plant spacing (sparse plot, 2 m × 2 m interval; dense plot, 0.5 m × 0.5 m
interval). The experiment with four blocks was repeated in two seasons. The number of eggs per plant was larger in the sparse
plots than in the dense plots for all species. The survival rate of eggs and larvae, on the contrary, was lower in the sparse
plots than in the dense plots. The lower survival rate of eggs in the sparse plots was mainly caused by the density dependency,
while the lower survival rate of larvae in the sparse plots was mainly caused by the direct effects of plant density. It was
thus suggested that the density of herbivores may become lower in the sparsely planted field in the long run because of the
higher mortality of larvae.
Received: September 16, 1998 / Accepted: March 22, 1999 相似文献
19.
Summary The populations of native male adult oriental fruit flyDacus dorsalis (Hendel) and artocarpus fruit flyD. umbrosus (F.) in two selected site (BU and SD) were estimated weekly by the capture-recapture technique using live traps baited with
methyl eugenol. In BU where many varieties of fruit trees were grown, the estimated population densities ofD. dorsalis were between 980 and 3100 male flies per ha between May and July, 1984. During the same period, in SD where there were fewer
number and varieties of fruit trees, the estimated population densities were between 300 and 1000 flies per ha. The estimated
population densities ofD. umbrosus over the same period were between 570 and 1290 flies per ha in BU; and between 5 and 95 flies per ha in SD.
Of a total 6828 markedD. dorsalis flies released only one fly (released 6 weeks earlier in BU) was caught in a different site. 相似文献
20.
Hiroichi Sawada Ayi Kusmayadi S. W. Gaib Subroto Edi Suwardiwijaya Mustaghfirin 《Researches on Population Ecology》1993,35(1):113-137
Summary Population dynamics of the brown planthopper (BPH),Nilaparvata lugens St?l, were investigated in paddy fields in the coastal lowland of West Java, Indonesia, where rice is cultivated twice a
year, in the wet and dry cropping seasons. Distinct differences in the basic features of population dynamics were detected
between the two rice cropping seasons: (1) In the wet season, BPH populations multiplied rapidly in the period from initial
to peak generation, reaching quite often the destructive level despite the low density of initial immigrants. However, in
the dry season, the population growth rate and the peak population density were much lower than those in the wet season. The
abundance of natural enemies such as arthropod predators played a major role in determining such a difference in seasonal
population development. (2) The density at the peak generation or the occurrence of outbreaks in each field was predictable
in the wet season with fairly high accuracy on the basis of the density at the initial or previous seasonal generations. In
the dry season, however, the rate of population growth and the peak population density widely varied among the fields depending
on the water status in each field. (3) Density-dependent processes to regulate the population density were detected in both
cropping seasons. In the wet season, the regulatory processes were only detected in such high densities as cause the considerable
deterioration of host plants, which suggested that the processes were largely attributable to intra-specific competition.
In the dry season, however, the regulatory processes operated at a much lower density in the earlier stages of the crops.
The results of an analysis of adult longevity or residence period suggested that the density-dependent dispersal of macropterous
adults played an important role in stabilizing the population fluctuation among the fields in the early dry season. 相似文献