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1.
The host size model, an adaptive model for maternal manipulation of offspring sex ratio, was examined for the parasitoid
wasp Spalangia endius. In a Florida strain, as the model predicts, daughters emerged from larger hosts than sons, but only when mothers received
both small and large hosts simultaneously. The pattern appeared to result from the mother's ovipositional choice and not from
differential mortality of the sexes during development. If sex ratio manipulation is adaptive in the Florida strain, it appears
to be through a benefit to daughters of developing on large hosts rather than through a benefit to sons of developing on small
hosts. Both female and male parasitoids were larger when they developed on larger hosts. For females, developing on a larger
host (1) increased offspring production, except for the largest hosts, (2) increased longevity, (3) lengthened development,
and (4) had no effect on wing loading. For males, development on a larger host had no effect on any measure of male fitness
– mating success, longevity, development duration, or wing loading. In contrast, a strain from India showed no difference
in the size of hosts from which daughters versus sons emerged, although both female and male parasitoids were larger when
they developed on larger hosts. These results together with previous studies of Spalangia reveal no consistent connection between host-size-dependent sex ratio and host-size-dependent parasitoid size among strains
of S. endius or among species of Spalangia.
Received: 28 October 1998 / Received in revised form: 20 May 1999 / Accepted: 30 May 1999 相似文献
2.
B. H. King K. B. Saporito J. H. Ellison R. M. Bratzke 《Behavioral ecology and sociobiology》2005,57(4):350-356
Despite common stereotypes, males are not always indiscriminate and eager when it comes to mating. In the parasitoid wasp Spalangia endius, the initial response of males to females was almost always one of apparent excitement; however, this was followed by a clear preference for virgin females over mated females in both no-choice and choice situations. The no-choice data were collected from videotapes of male-female pairs of all possible combinations of mated and virgin individuals. Neither female nor male mating status had a significant effect on likelihood of, or time until, contact or male courtship fanning. However, a males first retreat was sooner when the female was mated than when she was virgin; mated males exhibited their first retreat sooner than did virgin males; and mated females were less likely to be mounted than were virgin females. In addition to the videotapes, male-choice experiments were performed. When given a choice of a virgin and a mated female, both virgin and mated males were more likely to mount and copulate with the virgin. The difference in response to virgin versus mated females seemed to be less in virgin males than in mated males, perhaps due to virgin males greater eagerness to mate: when a virgin male and a mated male were presented with a dead virgin female, the virgin male was usually the first to respond to the female. That males preferentially retreated from and avoided mounting mated females appears to be adaptive given that mated females rarely copulated.Communicated by N. Wedell 相似文献
3.
In behavioral ecology it is generally assumed that behavior is adaptive. This assumption is tested here for sex ratio manipulation in response to host size in the parasitoid wasp Spalangia cameroni. Females produce a greater proportion of daughters on larger hosts. If this behavior is adaptive, it is not through a positive effect of host size on the fitness of daughters, as theory suggests and as found for other species. Females that developed on larger hosts were not more successful at drilling into hosts, were not more successful at interspecific competition for hosts, and did not have greater dispersal ability as measured by wing loading (weight/area of wing and thorax). The possibility that S. cameroni's sex ratio manipulation may be adaptive through a negative effect of host size on the fitness of sons cannot be ruled out. Relative to males from larger hosts, males from smaller hosts had lower wing loading and thus potentially greater dispersal ability. The actual effect of wing loading on fitness remains to be tested. 相似文献
4.
Since the mating of the parasitoid wasp Melittobia australica occurs on their eclosed hosts, the sex ratio is predicted to follow the local mate competition (LMC) theory. However, while LMC models predict that the sex ratio will increase from female-biased toward a 1:1 ratio with an increase in the number of foundresses, the observed female-biased sex ratios (1–5% males) show little increase in response to an increased foundress number. Lethal combat among adult males may serve as an explanation for this observed phenomenon. Using a microsatellite DNA marker, we first examined the individual sex ratio of two foundresses who had sequentially parasitized the same host. Both foundresses produced an extremely female-biased clutch and the sex ratios of the second foundress were only slightly less biased than that of the first. A small number of sons from both foundresses emerged at a constantly low rate over a prolonged period, resulting in a temporal mixture of emerging males derived from both the foundresses. Second, we conducted a one-on-one arena experiment to examine the combat level in relation to the relatedness of the opponents. Almost all the later-emerging males were killed by previously eclosed males irrespective of whether they were sibs or non-sibs. These results suggest that each foundress should not produce males in a single burst, but continue to produce male eggs at a constantly low rate in order to avoid the high mortality of her own sons by lethal male-male combat. This combat may be one of factors in explaining the extremely female-biased sex ratio even with an increasing foundress number.Communicated by R.F.A. Moritz 相似文献
5.
José L. Tella Manuela G. Forero José A. Donázar Juan J. Negro Fernando Hiraldo 《Behavioral ecology and sociobiology》1997,40(4):253-260
We examined the causes, costs and benefits of adoption in the altricial lesser kestrel Falco naumanni. Specifically, we tested the intergenerational conflict hypothesis, proposed to explain adoption in some birds. Adoptions
involved 76% of the nests and 51% of the nestlings at a mean age of 25 days (12 days before fledging). Nest-switching nestlings
were not in poorer body condition, more parasitized or younger than their siblings, and body condition and prey delivery rates
of their parents did not differ from those of other parents. In the foster nest, adopted nestlings did not benefit from higher
feeding rates or a prolongation of the nestling period. They did not have fewer nest-mates or achieve higher rank within the
new brood. Thus, adopted nestlings did not improve their body condition and survival. Adult lesser kestrels seemed unable
to finely discriminate beween their own and alien chicks. Foster parents bore the cost of an increase of prey delivery rates,
although it did not affect their survival or subsequent reproductive performance. Therefore, our results do not support the
intergenerational conflict hypothesis, and suggest that adoption in this species is non-adaptive. Traditionally, the lesser
kestrel bred in cliffs where movement among nest-sites was restricted. Nowadays, about half of the colonies are in tiled roofs
which facilitate nest-switching by nestlings. The high rate of adoptions may thus be explained as reproductive errors associated
with the recent occupation of a new breeding habitat.
Received: 3 May 1996 / Accepted after revision: 19 January 1997 相似文献
6.
Maternal investment in rhesus macaques (Macaca mulatta): reproductive costs and consequences of raising sons 总被引:1,自引:0,他引:1
Maternal investment in offspring is expected to vary according to offspring sex when the reproductive success of the progeny
is a function of differential levels of parental expenditure. We conducted a longitudinal investigation of rhesus macaques
to determine whether variation in male progeny production, measured with both DNA fingerprinting and short tandem repeat marker
typing, could be traced back to patterns of maternal investment. Males weigh significantly more than females at birth, despite
an absence of sex differences in gestation length. Size dimorphism increases during infancy, with maternal rank associated
with son’s, but not daughter’s, weight at the end of the period of maternal investment. Son’s, but not daughter’s, weight
at 1 year of age is significantly correlated with adult weight, and male, but not female, weight accounts for a portion of
the variance in reproductive success. Variance in annual offspring output was three- to fourfold higher in males than in females.
We suggest that energetic costs of rearing sons could be buffered by fetal delivery of testosterone to the mother, which is
aromatized to estrogen and fosters fat accumulation during gestation. We conclude that maternal investment is only slightly
greater in sons than in daughters, with mothers endowing sons with extra resources because son, but not daughter, mass has
ramifications for offspring sirehood. However, male reproductive tactics supersede maternal investment patterns as fundamental
regulators of male fitness.
Received: 23 July 1999 / Received in revised form: 23 February 2000 / Accepted: 13 March 2000 相似文献
7.
Verena Dietrich-Bischoff Tim Schmoll Wolfgang Winkel Sven Krackow Thomas Lubjuhn 《Behavioral ecology and sociobiology》2006,60(4):563-571
Females of many socially monogamous bird species commonly engage in extra-pair copulations. Assuming that extra-pair males are more attractive than the females’ social partners and that attractiveness has a heritable component, sex allocation theory predicts facultative overproduction of sons among extra-pair offspring (EPO) as sons benefit more than daughters from inheriting their father’s attractiveness traits. Here, we present a large-scale, three-year study on sex ratio variation in a passerine bird, the coal tit (Parus ater). Molecular sexing in combination with paternity analysis revealed no evidence for a male-bias in EPO sex ratios compared to their within-pair maternal half-siblings. Our main conclusion, therefore, is that facultative sex allocation to EPO is absent in the coal tit, in accordance with findings in several other species. Either there is no net selection for a deviation from random sex ratio variation (e.g. because extra-pair mating may serve goals different from striving for ‘attractiveness genes’) or evolutionary constraints preclude the evolution of precise maternal sex ratio adjustment. It is interesting to note that, however, we found broods without EPO as well as broods without mortality to be relatively female-biased compared to broods with EPO and mortality, respectively. We were unable to identify any environmental or parental variable to co-vary with brood sex ratios. There was no significant repeatability of sex ratios in consecutive broods of individual females that would hint at some idiosyncratic maternal sex ratio adjustment. Further research is needed to resolve the biological significance of the correlation between brood sex ratios and extra-pair paternity and mortality incidence, respectively. 相似文献
8.
Jorge E. Rabinovich Martín Torres Jordá C. Bernstein 《Behavioral ecology and sociobiology》2000,48(4):308-315
Telenomus fariai is a gregarious endoparasitoid of the eggs of several species of Triatominae (Hemiptera) with a high degree of sibmating:
males fertilize their sisters inside the host egg before emergence or emerge first and copulate with their sisters as these
emerge. Our results show that, when laying alone, T. fariai behaves adaptively, minimizing offspring mortality and conforming to the prediction of local mate competition (LMC) theory
by laying a single male, which is sufficient to fertilize all the sisters. When more than one wasp was placed with one host,
sex ratios still conformed to LMC predictions but, despite the decreasing number of eggs laid per wasp, clutch size could
not be completely adjusted to avoid mortality. This is not surprising, as superparasitism is rare in the field. Offspring
production was independent of the contacts between conspecifics but was affected by the number of mothers laying on a single
host egg. The sex of the progeny was precisely determined: a female produced one male per clutch when laying on both unparasitized
or previously parasitized hosts. On the other hand, a mother produced less daughters when superparasitizing. Under crowded
conditions, the number of eggs laid per female wasp and per host decreased as the number of mothers increased. Developmental
mortality also increased with the number of T. fariai eggs per host, determining a maximum of approximately 14 emerged adults. Host resources per individual affected male and
female adult size with similar intensity, and male adult mortality was slightly higher than that for females. These results,
and previous findings, suggest that T. fariai attains Hamiltonian sex ratios by laying one male and a variable number of females, and that the detection of chemical marks
left by conspecifics provides information on the number of foundresses sharing a patch.
Received: 4 February 2000 / Received in revised form: 19 April 2000 / Accepted: 20 May 2000 相似文献
9.
California ground squirrels (Spermophilus beecheyi) and northern Pacific rattlesnakes (Crotalus viridus oreganus) have an adversarial relationship. Adults are partially protected by venom resistance and harass rattlesnakes in part to defend their more vulnerable offspring. Larger, warmer snakes are more dangerous than smaller colder snakes, and in escalated conflict squirrels could benefit from risk assessment strategies. Rattlesnakes often rattle at harassing squirrels and rattling sounds produce cues related to body size and temperature. In study 1 we played back rattling sounds from snakes that varied in dangerousness and evaluated the roles of sex and parity in squirrel risk assessment strategies. In general, squirrels tail flagged and stood bipedally more, and were slower to reapproach the playback speaker following playbacks of rattling sounds from more dangerous snakes. In comparison with males and nonmothers, mothers were most responsive to rattling sounds and more sensitive to variation in snake dangerousness. Mothers tail flagged more than males and nonmothers, and this behavior tracked variation in snake dangerousness most closely, perhaps reflecting the effects of snake size and temperature on pup vulnerability. These findings suggest that many aspects of squirrel antisnake behavior are governed by their effects on descendant kin. In study 2 we tested the effects of offspring age on mothers responses to live rattlesnakes and rattling sounds. According to the offspring value hypothesis, mothers should take more risks in defense of older offspring because they are more likely to survive to reproductive age. By contrast, under the offspring vulnerability hypothesis, older offspring are less vulnerable to predators and thus mothers should take fewer risks. Risk-taking, as measured by behaviors that bring the squirrel close to the snakes strike range, was either unaffected by or negatively correlated with offspring age. Thus, our findings suggest that whereas offspring value is unimportant in squirrel antisnake behavior, offspring vulnerability may affect maternal defense. We suggest that offspring vulnerability in mammals, in comparison with birds, may play a larger role in parental defense against predators.Communicated by P.A. BednekoffAn erratum to this article can be found at 相似文献
10.
Fisher’s 1930 theory of sex allocation predicts a population-wide 1:1 ratio of parental investment. We tested this prediction in the European beewolf, a sphecid wasp that hunts for honeybees as larval food. Because the method to quantify parental investment is of crucial importance, we compared the suitability of several different investment measures. Female/male cost ratios were determined from a sample and the total investment in sons and daughters was calculated. In addition, the actual number of prey items for sons and daughters was directly determined by excavating nests and counting the cuticle remains of the prey. Though mortality was high (70%), it had only a weak effect on the estimate of the investment ratio. Based on commonly used measures like fresh and dry weight of emerged adults, the investment ratio did not deviate from Fisher’s prediction of equal investment. However, progeny weight considerably underestimates investment in males and investment in large progeny. Measures that reflect the allocation of resources more directly (amount of provisions, brood cell volume) revealed a significant male bias and thus contradicted Fisher’s theory. Three kinds of explanation are discussed. First, non-adaptive explanations are unlikely. Second, from the spectrum of alternative adaptive theories, only models that assume a non-linear relationship between amount of investment and progeny fitness seem to be relevant for the study species. Third, though the number of prey in a brood cell seems to be a rather good measure of parental investment in European beewolves, some problems in measuring parental investment remain. These problems are of broad significance. Received: 17 June 1999 / Received in revised form: 6 July 1999 / Accepted: 11 July 1999 相似文献
11.
Summary. Domestic apple (Malus pumila)- and hawthorn (Crataegus sp.)-infesting races of Rhagoletis pomonella, Walsh (Diptera: Tephritidae) provide an excellent model to examine the role that host plant specificity plays during sympatric
speciation (i.e., divergence in the absence of geographic isolation). Previous work has shown that these races differ in their propensities
to accept apple and hawthorn fruits in behavioral choice assays, and that this discrimination translates into "host fidelity"
in the field (i.e., apple flies tend to mate on and oviposit into apples and hawthorn flies on hawthorns). ?We present the results of a study
examining possible physiological factors contributing to host choice differences in R. pomonella. We tested whether apple and hawthorn flies differ in their electroantennogram (EAG) responses to biologically relevant volatile
compounds emitted from apples and hawthorns. Significant differences were found in the relative EAG responses of apple and
hawthorn flies to host fruit compounds at five of six paired study sites across the eastern United States. The geographic
pattern of EAG variation was complex, however, with local populations of apple and hawthorn flies tending to be more similar
to one another than to flies of the same race at distant sites. This pattern was largely due to EAG responses for several
compounds showing longitudinal or latitudinal clines, the latitudinal clines being similar to those observed for allozyme
loci in the host races. We also found evidence for sex-related differences, as males tended to have higher mean EAG responses
to compounds than females. Host-associated differences were therefore nested within geographic and sex-related differentiation
in R. pomonella.?Further behavioral studies are needed to distinguish whether the EAG differences are responsible for, as opposed to being
a consequence of, host-plant fidelity and adaptation. Crosses are also required to establish a genetic basis for the EAG responses,
although we did find significant correlations between EAG scores for several compounds and the allozymes NADH-Diaphorase-2
and Hydroxyacid dehydrogenase at one of the study sites. Questions therefore remain concerning the evolutionary significance
of the EAG response differences between apple and hawthorn fly races. Nevertheless, these differences raise the possibility
that antennal responses to fruit-related volatile compounds contribute to host plant discrimination in R. pomonella. Regardless, the EAG responses represent another set of traits, in addition to diapause/eclosion time phenotypes and allozyme
frequencies, differing between apple and hawthorn host races of R. pomonella.
Received 17 March 1998; accepted 21 September 1989. 相似文献
12.
Brood sex ratios, female harem status and resources for nestling provisioning in the great reed warbler (Acrocephalus arundinaceus) 总被引:4,自引:0,他引:4
H. Westerdahl Staffan Bensch Bengt Hansson Dennis Hasselquist Torbjörn von Schantz 《Behavioral ecology and sociobiology》2000,47(5):312-318
The theory of parental investment and brood sex ratio manipulation predicts that parents should invest in the more costly
sex during conditions when resources are abundant. In the polygynous great reed warbler, Acrocephalus arundinaceus, females of primary harem status have more resources for nestling provisioning than secondary females, because polygynous
males predominantly assist the primary female whereas the secondary female has to feed her young alone. Sons weigh significantly
more than daughters, and are hence likely to be the more costly sex. In the present study, we measured the brood sex ratio
when the chicks were 9 days old, i.e. the fledging sex ratio. As expected from theory, we found that female great reed warblers
of primary status had a higher proportion of sons in their broods than females of lower (secondary) harem status. This pattern
is in accordance with the results from two other species of marsh-nesting polygynous birds, the oriental reed warbler, Acrocephalus orientalis, and the yellow-headed blackbird Xanthocephalus xanthocephalus. As in the oriental reed warbler, we found that great reed warbler males increased their share of parental care as the proportion
of sons in the brood increased. We did not find any difference in fitness of sons and daughters raised in primary and secondary
nests. The occurrence of adaptive sex ratio manipulations in birds has been questioned, and it is therefore important that
three studies of polygynous bird species, including our own, have demonstrated the same pattern of a male-biased offspring
sex ratio in primary compared with secondary nests.
Received: 1 June 1999 / Received in revised form: 10 January 2000 / Accepted: 12 February 2000 相似文献
13.
Jason H. Peterson Bernard D. Roitberg J. H. Peterson 《Behavioral ecology and sociobiology》2006,59(5):589-596
Fisher's theoretical prediction of equal investment in each sex for a panmictic population (The genetical theory of natural selection. Clarendon, Oxford, 1930) can be altered by a number of factors. For example, the sex ratio theory predicts variation in
equal investment in each sex when the maternal fitness gains from increased investment differ between sexes. Changing sex
allocation because of changing payoffs may result from different ecological situations, such as foraging conditions. We investigated
the impact of foraging travel cost on relative investment in sons vs daughters. Field studies were carried out with the central-place-foraging
leafcutter bee Megachile rotundata (Fabricius), which has smaller males than females. Therefore, less investment is required to produce a viable son compared
with a daughter. We found that with increased flight distance to resources, females produced a greater proportion of sons.
Females also invested fewer resources in individual sons and daughters and produced fewer offspring with increased flight
distance. 相似文献