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1.
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
2.
Nils Chr Stenseth Ottar N. Bj?rnstad Takashi Saitoh 《Researches on Population Ecology》1998,40(1):85-95
We interpret gradients in population dynamics of the gray-sided vole from the southwestern part of the island of Hokkaido
to its northeastern part within the framework of a phenomenological model involving the relative length of summer and winter.
In Hokkaido, as in other northern regions, both spring and fall is considered as short transition periods between the two
main seasons — summer (the primary breeding season) and winter (the non-reproductive or secondary breeding season). We show
that the geographic transition in dynamics may be understood as the combined consequence of different patterns of density-dependence
during summer and winter, and geographically varying season lengths. Differences are shown to exist between summer and winter
with respect to strength of density-dependence. Direct density-dependence, in particular, is stronger during winter than during
summer. A model is presented to show how relative lengths of seasons can induce both stable and periodically fluctuating population
dynamics. The results are compared and contrasted with what is otherwise known about the gradient in rodent dynamics in Fennoscandia. 相似文献
3.
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
4.
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
5.
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
6.
Eiichiro Urano 《Researches on Population Ecology》1985,27(2):393-412
Summary Settlement date, mating status, and breeding success of individually marked great reed warblers,Acrocephalus arundinaceus, were studied during the 1980–84 breeding seasons in Kahokugata, Ishikawa Prefecture, Japan. Twenty-five per cent of the
territorial males were polygynous, of which the majority were bigamous. The settling periods of both sexes were long, extending
for 65 days in males and 49 days in females. About 80% of males and females settled in the first half of the settling period,
and the settlement date of 28–54% males overlapped with that of females. Many of the late settlers were bachelors and the
males which mated earlier tended to be polygynous. The timing of a male's settlement is important in acquiring mates. Fifty-five
per cent of eggs laid were lost before fledging, mainly due to predation. The mean number of fledglings was 3.19 per primary
female, 2.41 per secondary female, and 2.80 per monogamous female. Comparison of the number of fledglings of females which
mated during the same period showed that the presence of another female in the same territory did not adversely affect the
breeding success of either of the polygynous females. Polygynous males have the advantage of decreasing the risk of breeding
failure under high predation pressure. 相似文献
7.
Yukibumi Kaneko Keisuke Nakata Takashi Saitoh Nils Chr Stenseth Ottar N. Bj?rnstad 《Researches on Population Ecology》1998,40(1):21-37
The biology of the gray-sided voleClethrionomys rufocanus in Hokkaido, concerning taxonomy, morphology, phylogeny, distribution, and natural history, is reviewed. Applied issues in
forest management (damage, control and census) are also mentioned. AlthoughClethrionomys rufocanus of Hokkaido was originally identified as a distinct species,Evotomys (=nowClethrionomys) bedfordiae Thomas, 1905, current literature generally refers to the gray-sided vole of Hokkaido asClethrionomys rufocanus or asC. rufocanus bedfordiae (vernacular name, the Bedford’s red-backed vole). The gray-sided vole is the most common small mammal in Hokkaido. It inhabits
open areas as well as forests, and mainly feeds on green plants. The gray-sided vole has a high reproductive potential; litter
size: 4–7; gestation period: 18–19 days; maturation age: 30–60 days old. Although spring-born individuals usually attain sexual
maturity in their summer/fall of birth, their maturation is sometimes suppressed under high densities. The breeding season
is generally from April to October, but with some regional variation.Clethrionomys rufocanus has a rather specialized diet (folivorous), particularly during winter when it feeds on bamboo grass. Many predators specialize
on the grey-sided vole in Hokkaido; even the red fox, which is a typical generalist predator, selectively feeds on this vole.
Damage by voles’ eating bark used to be sever on forest plantations in Hokkaido. Censuses of small rodents have been carried
out for management purpose since 1954. 相似文献
8.
Takaki Kondo 《Researches on Population Ecology》1982,24(1):85-96
Summary The role of social behavior on the population regulation of the Japanese wood mouse,Apodemus speciosus, was studied in the Ashu Experimental Forest of Kyoto University by monthly trapping and direct observation on the social
behavior at the artificial feeding site. The census was carried out from May to October in 1974 and 1975, and the direct observation
in June, August and October, 1975.
In the study area, the Japanese wood mouse has two breeding seasons in a year: in spring and in autumn. Minimum survival rate
was high in the non-breeding season and low in the breeding season. It was negatively correlated to the number of sexually
active adults in both sexes.
Home ranges of females tended to be mutually exclusive, and female residents prevented the settlement of female immigrants.
On the other hand, home ranges of males overlapped largely and males had a straight social hierarchy. Subordinate males tended
to disappear more often than dominant males did, but male residents did not hinder the settlement of male immigrants. Males
may regulate their number by driving out the subordinate males, while females by spacing behavior.
Contribution from the Laboratory of Animal Ecology, Department of Zoology, Kyoto University, No. 445. 相似文献
9.
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
10.
In May 1971, 45 adults of an herbivorous lady beetleEpilachna niponica (Coleoptera: Coccinellidae) from Asiu Experimental Forest were introduced into a botanical garden of Kyoto University, where
is 10 km south of the southern limits of its distribution with being 3–5°C warmer than the original site. The introduced population
of the lady beetle was thus investigated from 1975 to 1981. Mark-release-recapture experiments were applied to individual
adult beetles, to estimate population size and daily survival rate. Overwintering adults emerged from hibernation around early
April, reaching peak numbers in late April to early May, then gradually declined to late June. No adults remained at the end
of June. Adult survival was maintained at a high level to early May, and declined consistently until late in the reproductive
season. New adults began to emerge in late June and quickly reached a peak in early July; thereafter they decreased in number
and had entered hibernation by late October. In spite of seasonally deteriorating food resources and heat stress in summer,
new adults showed moderately high survival during the inimical period. New adults which emerged later in the season tended
to be smaller in body size than those that emerged early. The proportion of females in the new adult population gradually
increased throughout the pre-hibernating period, suggesting that male-biased mortality occurred during this period. When compared
to the source population, the introduced population had a higher rate of population growth. Coupled with the improved population
growth, heavy leaf damage during the larval period suggested that intensive intraspecific competition was most likely to occur
among larvae in the introduced population. 相似文献
11.
Kenji Fujisaki 《Researches on Population Ecology》1992,34(1):173-183
Summary A male fitness advantage to wing reduction was investigated for the oriental chinch bug,Cavelerius saccharivorus, which is wing dimorphic. Field surveys for the frequency of matings between wing morphs showed that the mating probability
was much higher in brachypterous males than in macropterous males in the early breeding season. Brachypterous males copulated
with not only brachypterous females but also macropterous females in this season. This led to a considerable rate (30%) of
insemination of macropterous females just before emigration even in the early breeding season. A rearing experiment for the
pre-reproductive period of females revealed that females mated with brachypterous males copulated and oviposited earlier than
females mated with macropterous males. These results indicate that there is a fitness advantage to wing reduction in the males
ofC. saccharivorus in terms of the earlier sexual maturation. 相似文献
12.
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
13.
Seiji Arakaki Kazunori Yamahira Mutsunori Tokeshi 《Researches on Population Ecology》1999,41(3):235-242
The patterns of sex change and spatial distribution in an intertidal holothurian, Polycheira rufescens (Chiridotidae; Echinodermata), were investigated on a stony beach in Amakusa, western Kyushu. Field caging experiments revealed
that some individuals of P. rufescens underwent a sequential sex change from male to female via hermaphrodite stages and back to male again within a single reproductive
season. The sex ratio of the population gradually changed from male dominance at first to equal proportions of males and females
as the reproductive season progressed. Toward the end of the reproductive season, immature or spent individuals increased
in proportion. Stone size appeared to be an important factor affecting the occurrence of P. rufescens individuals on a stony beach. Analysis of spatial distribution by means of Morisita's index of dispersion and nearest neighbor
distances indicated that (i) males showed a slightly stronger tendency to aggregate than females, while females had a tendency
toward uniform distribution; (ii) females tended to attract males, as shown by relatively short female-to-male distances;
and (iii) there was a substantial variation in male-to-female distances, such that some males were positioned close to females
while others were not. It may be suggested that spatial distribution of P. rufescens individuals during the reproductive period is partly dictated by the differential needs of individuals of different sexual
states.
Received: January 25, 1999 / Accepted: June 10, 1999 相似文献
14.
Ottar N. Bj?rnstad Nils Chr Stenseth Takashi Saitoh Ole Chr Lingj?rde 《Researches on Population Ecology》1998,40(1):77-84
We study the regional transitions in dynamics of the gray-sided vole,Clethrionomys rufocanus, within Hokkaido, Japan. The data-set consists of 225 time series of varying length (most from 23 to 31 years long) collected
between 1962 and 1992 by the Forestry Agency of the Japanese Government. To see clearly how the periodic behavior changes
geographically, we estimate the spectral density functions of the growth rates of all populations using a log-spline method.
We subsequently apply functional data analysis to the estimated densities. The functional data analysis is, in this context,
analogous to a principal component analysis applied to curves. We plot the results of the analysis on the map of Hokkaido,
to reveal a clear transition from relatively stable populations in the southwest and west to populations undergoing 3–4 year
cycles in the northeast and east. The degree of seasonality in the vegetation and the rodent demography appear to be strongest
in the cyclic area. We briefly speculate that the destabilization of the rodent dynamics is linked to increased seasonalforcing
on the trophic interactions in which the gray-sided voles are involved. 相似文献
15.
Tom M. Spight 《Researches on Population Ecology》1981,23(2):245-261
Summary Competition theory poses a major problem when several species coexist on what appears to be one resource. ThreeThais species living on the Pacific Northwest Coast provide an example: at many sites, all three depend primarily on one barnacle
species. Growth rates of three species were measured for 3 years and these provide an indirect means to assess how these snails
use their common food resource. Major temporal differences were observed:T. lamellosa grew 0–1 mm/mo during the spring and 2–3 mm/mo during the summer, whileT. emarginata andT. canaliculata grew 2–3 mm/mo during the spring and 0–1 mm/mo during the summer. However, all species are opportunists when food is available,
and seasonal and interspecific differences disappeared when all three species were kept well fed together in the laboratory.
Therefore, temporal differences arise from spatial segregation rather than from intrinsic differences in activity, and must
arise because barnacle abundance patterns differe consistently from one area of the shore to another. Species-specific activity
patterns lead each species to a food intake that is independent of the food supply on the shore as a whole and is also independent
of food intake by the other two species. Where two snail species depend upon a single food species, their use of the food
supply appears to make it function as two different resources. This resource use is possible because prey quality is markedly
dependent on shore level. 相似文献
16.
Takayuki Ohgushi 《Researches on Population Ecology》1987,29(1):147-154
Summary Size variation in newly-emerged adults was examined in two different local populations of an herbivorous lady beetle,Henosepilachna niponica, for 1976–80. Mean adult size of both sexes changed rather synchronously in the two populations over 5 years. Body size of
adult beetles apparently decreased with increasing leaf damage of the plants on which they developed. Adult beetles which
emerged late in the season, associated with increasing food deterioration, were smaller than those which emerged early. Ecological
consequences of adult size variation is discussed in terms of oviposition site selection. 相似文献
17.
18.
Festus A. Ukwuani Gretchen T. Cornwell Chirayath M. Suchindran 《Journal of Population Research》2002,19(2):155-171
Mortality risks under age five are estimated using data from the 1990 Nigerian Demographic and Health Survey for children
in monogamous and polygynous families. Integrating existing theories on polygyny’s relationship with infant and child mortality
and some demographic concepts, the study shows that polygyny has different effects on infant and child mortality at different
ages. The results indicate that polygyny does not have a significant effect on neonatal mortality (age less than one month).
In contrast to the results of previous research, polygyny is significantly associated with lower child mortality during the
post-neonatal period (1–11 months), but not during childhood (12–59 months). The study found socio-economic factors to be
important confounders of the relationship between polygyny and mortality during the neonatal and post-neonatal periods. The
protective effect of polygyny during the post-neonatal period suggests the need to further investigate circumstances that
may favour post-neonatal child survival in polygynous families including availability of childcare. 相似文献
19.
Katsuyuki Kohno 《Researches on Population Ecology》1997,39(1):11-16
The possible influences of life history and habitat characteristics on the evolution of semelparity and cannibalism in the
hump earwigAnechura harmandi were studied. This species is univoltine and overwinters as an adult. Females laid single egg-batches during winter in nests
under stones at a riverside in a valley. They took care of the eggs which hatched in early spring and the offspring ate their
mother before dispersing. The valley was sometimes flooded in summer. Nymphs emerged as adults and dispersed to elsewhere
before the rainy season arrived. They returned to the riverside after the rainy season. The flooding and/or summer heat seemed
to be the selective force for the evolution of dispersal behavior and semelparity in this species. The cannibalism of the
female parent by her offspring seemed to have readily evolved after the evolution of semelparity. The unfavorable environmental
conditions seemed to have a large effect on the evolution of semelparity and cannibalism in this species. 相似文献
20.
Yozo Koshiyama Hisaaki Tsumuki Kenji Fujisaki Fusao Nakasuji 《Researches on Population Ecology》1996,38(1):51-56
Menida scotti (Puton) males have been shown to transfer secretions from their bulbus ejaculatorius and reservoir of ectodermal accessory
gland to females by mating during hibernation. In the present study, the major components of the secretions were found to
be proteins and lipids. To specify the female organ incorporating the male secretions, a radiotracer experiment in which the
male secretions were labeled by [14C]valine was conducted in nine tissues of females collected in the fall and spring of the hibernation period. Relatively high
radioactivities were detected in the haemolymph and the residual carcass (head, legs, air-sacs, exoskeleton, etc.) in the
fall females, and in CO2 gas evolved and carcasses in the spring females. The radioactivities in the fat body were significantly higher in the fall
mating females than in the spring mating females, and vice versa in the ovary. The radioactivities in six fractions (lipids,
proteins, glycogen, sugars, free amino acids and the residues) were also assayed in the five organs of females that had a
relatively high radioactivity. The highest radioactivity was detected in the protein fraction of the haemolymph in fall and
spring females. There were significant differences in the radioactivities incorporated into the lipid fractions of the carcass
between fall and spring females. 相似文献