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1.
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
2.
T. S. Bellows Jr. 《Researches on Population Ecology》1985,27(1):55-64
Summary The effects of host age on parasitoid reproductive capacity are studied using the pteromalid parasitoidLariophagus distinguendus
F?rster and its bruchid hosts,Callosobruchus chinensis (L.) andC. maculatus (F.). A series of experiments were performed to investigate relationships between age and size of host parasitized and the
developmental period of pre-imaginal progeny, sex ratio, female size, longevity, fecundity and oviposition rate. There was
no effect of host size on preimaginal parasitoid developmental period. Sex ratio varied from less than 5% females from young
(small) hosts to 60% females from mature (large) hosts. Adult size, female longevity, fecundity, and oviposition rate were
also positively related to host age. Females provided mature hosts lived longer than those provided either young hosts or
no hosts, possibly because of an increased ability to host-feed from the larger hosts. The implications of these findings
to parasitoid population reproductive capacity and host-parasitoid synchrony are discussed. 相似文献
3.
Koh-ichi Takakura 《Researches on Population Ecology》1999,41(3):269-273
Mating behavior and the male's contribution to female fecundity were studied in the bean weevil Bruchidius dorsalis (Fahraeus) (Coleoptera: Bruchidae) in comparison with two other species, Callosobruchus chinensis (which infests stored beans) and Kytorhinus sharpianus (which feeds on wild legumes). Only females of B. dorsalis showed multiple mating and characteristic precopulatory behavior that appeared to solicit the male's nutritious secretion.
In contrast, all females of the other two species did not copulate multiply and did not show such precopulatory behavior.
In B. dorsalis, the decrement of male body weight just after copulation indicated that seminal fluid weighing as much as approximately 7%
of the male's body weight was transferred to the female. Fecundity was more than eight times higher in females that had copulated
ten times than in females that had copulated only once, indicating that males paid most of the nutritional cost of egg production.
These facts suggest that the sex role is reversed in B. dorsalis.
Received: May 22, 1998 / Accepted: July 19, 1999 相似文献
4.
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
5.
Takayoshi Nishida 《Researches on Population Ecology》1993,35(1):45-56
Summary Spatial relationships of mate acquisition probability for individuals of both sexes of a gregariously-mating coreid bug,Colpula lativentris, were studied in relation to aggregation size. Operational sex ratio was always strongly male biased. Mate acquisition probability
of females was rather constant and independent of aggregation size, as predicted by an ideal free distribution. Moreover laboratory
experiments showed that both multiple mating and rearing density little affected female fecundity, suggesting ideal free distribution
of females in terms of reproductive success. On the other hand, mate acquisition probability of males was higher in larger
aggregations, where more receptive females were available. This male discrepancy from an ideal free distribution was similar
to the patterns predicted by an ideal free distribution under perceptual constraints (Abrahams, 1986), but not by that under
unequal competitive ability. 相似文献
6.
Takayoshi Nishida 《Researches on Population Ecology》1989,31(2):211-224
Summary The mating system of the coreid bug,Colpula lativentris, was studied, and compared with those in other hemipteran bugs. Copulating pairs formed a compact aggregation on a shoot
of the Japanese knotweed,Polygonum cuspidatum, and there continued copulation and feeding for more than one day. This aggregation was defined as “a shoot aggregation”.
Other than this aggregation composed of copulating pairs, there were loose aggregations on the ground composed of males and
females not in copula. This loose aggregation was defined as “a ground aggregation”. Males searched for receptive females
mostly in a ground aggregation.
Sex ratio was constant and variance of sex ratio was also very small in any shoot aggregations and in large ground aggregations.
However, in small ground aggregations, sex ratio was strongly male biased and variance of sex ratio was fairly large. This
was because receptive females tended to leave a small ground aggregation and join a large one. These results suggest that
a male can attain higher mating success in a larger ground aggregation. 相似文献
7.
Motoaki Kinoshita Eiiti Kasuya Tetsukazu Yahara 《Researches on Population Ecology》1998,40(2):239-242
The sex ratio of the pollinator fig wasp,Blastophaga nipponica Grandi (Agaonidae), was examined in an experiment manipulating the number of foundresses. The sex ratio ofB. nipponica was conditional on the number of foundresses and corresponded to the qualitative prediction of the local mate competition
(LMC) theory that the proportion of males increases as foundress number increases. However, the sex ratio ofB. nipponica was consistently more female-biased than predicted by extended LMC theories that incorporated effects of inbreeding, and
these deviations were statistically significant. Plausible factors that would make predictions more female-biased are discussed. 相似文献
8.
Yoshinari Tanaka 《Researches on Population Ecology》1990,32(2):329-335
Summary Age-specific effects of inbreeding on fecundity were assayed for adzuki bean weevilCallosobruchus chinensis by comparing inbred lines and their cross. Four consecutive full-sib matings reduced only 10.3 percent in total fecundity,
and did not decrease early fecundity at all until third day from the onset of reproduction. It is suggested that recessive
detrimental genes have been eliminated from the early period of adult life span when reproductive value is high. There was
a slight tendency that inbreeding depression increased as age proceeded though not statistically significant. 相似文献
9.
Summary Lifetime mating success of males in a natural population of the papilionid butterfly,Atrophaneura alcinous, was investigated and causes of the variation were examined. The most successful males mated with 5 females, whereas about
73% of the males failed to mate. Body size of males was not correlated with their eclosion date, longevity and lifetime mating
success. There was no trade-off between mating success and longevity, and long-lived males had a disproportionately high mating
success. Although number of available females per male per day was not variable among males with different longevities, long-lived
males had higher mating efficiency. Time interval between matings by non-virgin males was shorter than that from eclosion
to the first mating. High lifetime mating success of long-lived males was strongly related to their mating experience, not
to their ageper se. 相似文献
10.
Yoshinari Tanaka 《Researches on Population Ecology》1997,39(1):57-66
The process of population extinction due to inbreeding depression with constant demographic disturbances every generation
is analysed using a population genetic and demographic model. The demographic disturbances introduced into the model represent
loss of population size that is induced by any kind of human activities, e.g. through hunting and destruction of habitats.
The genetic heterozygosity among recessive deleterious genes and the population size are assumed to be in equilibrium before
the demographic disturbances start. The effects of deleterious mutations are represented by decreases in the growth rate and
carrying capacity of a population. Numerical simulations indicate rapid extinction due to synergistic interaction between
inbreeding depression and declining population size for realistic ranges of per-locus mutation rate, equilibrium population
size, intrinsic rate of population growth, and strength of demographic disturbances. Large populations at equilibrium are
more liable to extinction when disturbed due to inbreeding depression than small populations. This is a consequence of the
fact that large populations maintain more recessive deleterious mutations than small populations. The rapid extinction predicted
in the present study indicates the importance of the demographic history of a population in relation to extinction due to
inbreeding depression. 相似文献
11.
J. P. Spradbery R. S. Tozer J. M. Robb P. Cassells 《Researches on Population Ecology》1989,31(2):353-366
Summary The feasibility of the sterile insect release method (SIRM) was tested against natural populations of the Old World screw-worm
fly,Chrysomya bezziana in the Musa Valley, Papua New Guinea. Sterile mating frequencies were determined from egg masses laid by native females on
wounded, sentinel cattle. The aerial release of sterilised puparia resulted in low frequencies of sterile matings and few
trap recaptures of released material. The release of chilled adult flies resulted in higher frequencies of sterile matings
and many trap recaptures. The mean density of males released was 230 males per km2 per week over a target area of 361 km2 (48% of the valley). Sterile masses were first detected 2 weeks after the release of chill flies commenced, reaching a weekly
peak of 33% after 5 weeks of releases with 15% of egg masses found to be sterile during the final month. The levels of sterile
matings achieved in this trial were similar to comparable SIRM studies made in the USA, Mexico and Guatemala to control the
New World screw-worm fly,Cochliomyia hominivorax. 相似文献
12.
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
13.
Kenji Fujisaki 《Researches on Population Ecology》1981,23(2):262-279
Summary The mating system of the winter cherry bug,Acanthocoris sordidus, was analyzed precisely. As a result, it was found that male adults of this species establish a small territory for mating
on the stem of host plant which harbors females. These males abandoned their territories soon after the disappearance of monopolized
females. Thus it was confirned that the cue for the territorial establishment of males is the presence of females per se on
the host plant. Moreover, most aggregations of adults observed on the host plant contained only a single male. This one-male
unit in the mating was named a harem. Harem holding males were usually big in body-size and had a high chance of copulations.
The defence behaviors of harem holding males, the mating disparity among males, and the oviposition habit of females in relation
to the mating system, were observed. The results obtained were discussed in relation to the sexual selection theories. 相似文献
14.
The lifetime mating frequency of female butterflies is believed tobe dependent on the reproductive status of the males which
they have mated. This report assesses those status usingPieris rapae L. Multiple mating females mated males with a short time interval after the last mating or males with many mating records.
Such males, like small ones, produced small spermatophores during copulation, which may have resulted in high mating frequency
of those females. The males with short time interval after the last mating or those with many mating records also showed a
long mating duration. Alternative interpretations of the adaptive significance of this behavior for males are discussed. 相似文献
15.
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
16.
Reproductive behaviors related to habitat utilization were studied in males of the damsefly,Mnais nawai, which has two male forms, territorial orange-winged males (nawai) and non-territorial pale-orange-winged males (sahoi), at the upper part of a mountain stream where they partiallycoexist with a related species,Mnais pruinosa, which also has two male forms, territorial orange-winged males (esakii) and non-territorial hyaline-winged males (strigata). These two species showed parapatric distribution; the lower part of the stream was occupied byM. nawai, and the upper part byM. pruinosa. In the present study, cross-matings occurred between bothMnais species, although normal intraspecific matings occurred more frequently than cross-matings. Territorial males of both species copulated
with conspecific females that entered their territory and guarded the ovipositing females, probably to avoid sperm displacement
resulting from subsequent copulations. Severe competition for oviposition sites by territorial males even occurred between
the two species. On the other hand, non-territorial males of both species have alternative mating strategies (including several
tactics such as sneaking, takeover and interception). The possible benefits from conflict among territorial males of both
species is discussed. 相似文献
17.
We examined the female-biased sex ratio of a trap-nesting wasp Trypoxylon malaisei considering the following factors: (1) local mate competition (LMC), (2) resource quality, (3) partial bivoltinism, and (4)
presence of constrained females. The sex ratio (expressed as male ratio) at emergence was strongly female biased, i.e., 0.30
and 0.19, in terms of the number and investment, respectively. To evaluate the primary sex ratio, we analyzed the data from
nests where all the offspring successfully emerged, excluding nests composed of single-sex offspring. The primary sex ratio
was also female biased, at 0.33 and 0.21, in terms of the number and investment, respectively. LMC was highly responsible
for the female-biased sex ratio because both the nonrandom oviposition sequence [females at inner cells and male(s) at outer
cells] and earlier emergence of males allowed sib-matings to occur. In contrast, the other three factors little affected the
female-biased sex ratio: the sex ratio was fairly constant when resource quality (nest size) varied, partial bivoltinism was
extremely rare or absent, and constrained females were absent or did not reproduce at all.
Received: June 19, 1998 / Accepted: January 18, 1999 相似文献
18.
Yutaka Sait 《Researches on Population Ecology》1990,32(2):263-278
Summary The mating system of a subsocial spider mite,Schizotetranychus miscanthi Saitō, which is closely related toSchizotetranychus longus Saitō (the long seta form ofSchizotetranychus celarius (Banks) is a synonym of the latter) was studied in comparison with that ofS. longus.
Comparisons between nesting patterns of the two related species,S. miscanthi andS. longus revealed a difference in distribution of males among nests. Although more than one male sometimes occurred in the large nests
ofS. miscanthi, most nests were occupied only by a single male. On the other hand, many nests ofS. longus included several males.
Behavioral experiments revealed that the male and females ofS. miscanthi which cohabited in a nest defended their offspring from phytoseiid predators. Observations and a census of the nesting pattern
in a wild population indicate that this is the second example of biparental defense and of a subsocial life-pattern in spider
mites.
Differences in mating systems were experimentally demonstrated in the two species. Only a single male ofS. miscanthi survived in a nest, as a result of highly aggressive male-male combat, while two males ofS. longus cohabited in a nest. The mating system of the former species is thus considered as harem polygyny, while that of the latter
as scramble type polygyny. Furthermore, observations by video recording and scanning electron microscopy showed that the winning
male in the male-male combat inS. miscanthi often preyed on the loser, suggesting cannibalism among them. 相似文献
19.
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
20.
We examined the age structure and sex ratio of a viperid snake,Trimeresurus flavoviridis, based on samples collected by hand by local inhabitants, habu hunters and by baited traps in the middle and south of Okinawa
Island, Japan. Small individuals had a low possibility of capture in all the collecting methods. The age structure was estimated
through summing up the age frequency in each snout-vent length (SVL) class in samples with a similar SVL structure. From the
age structures, annual survival rates of adult females and males were estimated to be 0.7 and 0.8, respectively. In most samples
the sex ratio was biased towards males, especially in March and August and in large individuals. However, the female proportion
increased in June. 相似文献