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1.
Thomas W. Pike 《Behavioral ecology and sociobiology》2005,58(4):407-413
A number of recent reports have documented offspring sex ratio biases in birds. However, to date the potential mechanisms that have been put forward to explain the proximate basis for these deviations are entirely speculative. Using a captive population of domestic pigeons (Columba livia domestica), I tested the hypothesis that mothers in relatively poor physical condition should overproduce daughters by manipulating maternal body condition around the time of egg laying by continuous egg removal and differing feeding regimes. During treatment, females were fed a controlled quantity of food. This, combined with the high energetic costs of repeated egg production caused a significant reduction in maternal body weight. In contrast, during control when food was available ad libitum, maternal body weight did not decline, despite repeated egg production. No significant deviation from parity was evident in the sex ratio of either the first or second eggs during control, whereas during treatment a significant female bias was evident in not only the first egg, but also in the second egg. The absence of single-egg clutches, the rarity of infertile eggs and the lack of laying delays between eggs strongly suggests that the mechanism of sex ratio adjustment in pigeons occurs prior to ovulation. The highly skewed sex-distribution within the two-egg clutches and the unexpectedly large amount of variation in the yolk weight of eggs produced during treatment (but not control) are consistent with the expectations of pre-ovulatory selective resorption of wrong sex ovarian follicles. 相似文献
2.
Vivian C. Goerlich Cor Dijkstra Ton G. G. Groothuis 《Behavioral ecology and sociobiology》2010,64(4):599-606
Primary sex ratio adjustment in birds has been extensively studied, yet the underlying physiological mechanisms are far from
understood. Avian females are the heterogametic sex (ZW), and the future sex of the offspring is determined at chromosome
segregation during meiosis I, shortly before the oocyte is ovulated. Assuming that the mother can detect the sex of the developing
oocyte before ovulation, it has been suggested that a follicle of the un-preferred sex could selectively be induced to become
atretic and regress instead of being ovulated (selective follicle abortion). This potential mechanism has been proposed to
underlie biased primary sex ratios in birds, including the homing pigeon (Columba livia domestica), which produces a modal clutch size of two eggs. However, without replacement by an additional, already mature follicle,
abortion of a preovulatory follicle would most likely result in either reduced clutch sizes or laying gaps, since a not-yet-recruited
follicle still needed to undergo the whole maturation phase. In the current study we killed female pigeons, which were adjusting
embryo sex of first eggs according to change in body mass. We examined ovaries for signs of follicle abortion but did not
find any supporting evidence. All females produced one or two mature follicles but only two out of the 56 experimental birds
produced an additional third mature follicle. Therefore, our results do not corroborate the hypothesis that pigeon mothers
manipulate primary offspring sex by selectively aborting follicles of the un-preferred sex. 相似文献
3.
Vedder O Magrath MJ Niehoff DL van der Velde M Komdeur J 《Behavioral ecology and sociobiology》2012,66(4):603-612
Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little
is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies
indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation
by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental
inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair
paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase
and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted
how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring
among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental
treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order
was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that
female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire
extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size
may be a general pattern within bird species. 相似文献
4.
Willow B. English Douglas Schamel Diane M. Tracy David F. Westneat David B. Lank 《Behavioral ecology and sociobiology》2014,68(12):1939-1949
Fisher’s sex ratio theory predicts that on average parents should allocate resources equally to the production of males and females. However, when the cost/benefit ratio for producing males versus females differs, the theory predicts that parents may bias production, typically through underproduction of the sex with greater variation in fitness. We tested theoretical predictions in the red-necked phalarope, a polyandrous shorebird with sex-role reversal. Since females are larger and therefore potentially more expensive to produce and may have greater variation in reproductive success, we predicted from Fisher’s hypothesis a male bias in population embryonic sex ratio, and from sex allocation theory, female biases in the clutches of females allocating more resources to reproduction. We measured eggs and chicks and sexed 535 offspring from 163 clutches laid over 6 years at two sites in Alaska. The embryonic sex ratio of 51.1 M:48.9 F did not vary from parity. Clutch sex ratio (% male) was positively correlated with clutch mean egg size, opposite to our prediction. Within clutches, however, egg size did not differ by sex. Male phalarope fitness may be more variable than previously thought, and/or differential investment in eggs may affect the within-sex fitness of males more than females. Eggs producing males were less dense than those producing females, possibly indicating they contained more yolk relative to albumen. Albumen contributes to chick structural size, while yolk supports survivorship after hatch. Sex-specific chick growth strategies may affect egg size and allocation patterns by female phalaropes and other birds. 相似文献
5.
In birds, the number of sperm trapped between the perivitelline membranes around the ovum is an estimate of sperm numbers
present at the time and place of fertilisation in the female reproductive tract. Sperm numbers may vary among species and
between eggs in a clutch and can provide information about sperm utilisation and mechanisms of sperm competition. Here, we
describe patterns of variation in sperm numbers through the egg-laying sequence in three passerines in which extra-pair paternity
is common, but copulation behaviour differs. Sperm numbers showed no systematic change across the laying sequence in blue
tits (Cyanistes caeruleus), but decreased significantly with laying order in bluethroat (Luscinia svecica) and tree swallow (Tachycineta bicolor) clutches. This is consistent with observations that blue tits regularly copulate throughout the laying sequence, while bluethroats
stop mate guarding and tree swallows reduce their copulation frequency once the first egg is laid. Nevertheless, cases of
a sudden increase in sperm numbers in clutches of bluethroats and tree swallows suggest that successful inseminations also
occurred after laying started. In blue tits and bluethroats, sperm numbers were not higher on extra-pair sired eggs than on
eggs sired by the social male, suggesting that extra-pair copulations are not timed to the period of peak fertility for each
egg. More extra-pair offspring originated from eggs laid early in the sequence in blue tits, while there was no systematic
bias in bluethroats. Our results suggest that copulations during the laying sequence are predominantly performed by within-pair
males in our study species. 相似文献
6.
Balázs Rosivall 《Behavioral ecology and sociobiology》2008,62(6):1037-1042
In avian sex ratio studies, results often differ between species and between populations within species. Some researchers
argued that positive results were simply statistical artefacts and that sex ratio adjustment did not exist. However, many
of the proposed mechanisms of sex ratio adjustment result in costly laying gaps. In these cases, females laying large clutches
may restrict the sex manipulation to the first egg of the clutch. Consequently, detectability of sex ratio adjustment on the
level of the clutch can be low. Though obvious, this fact is often neglected in the literature. Using simulations, I show
that the proportion of undetected sex manipulation can be surprisingly high when the manipulation is restricted to the first
egg. If the sample size is 50 broods, there is 47% and 71% chance in 6- and 12-egg clutches, respectively, that sex manipulation
is undetected. Even with large samples (n = 100), the figures are 15% and 46%. These data suggest that nonsignificant results for clutch sex ratios do not necessarily
mean that sex is not manipulated in a portion of the brood, e.g. in first-laid eggs. Hence, whenever possible, data on laying
order-specific sex manipulation should also be collected. Without such data, contradictory results on brood sex ratios should
be interpreted cautiously. 相似文献
7.
Diego Rubolini Maria Romano Roberta Martinelli Nicola Saino 《Behavioral ecology and sociobiology》2006,59(3):344-352
Androgen hormones of maternal origin contained in the eggs of avian species are considered to have positive effects on offspring
characteristics and performance. However, negative consequences have also been reported, suggesting that mothers may experience
a trade-off between beneficial and detrimental effects of egg androgens to offspring fitness. We studied the effects of elevated
yolk testosterone (T) concentration on survival, development and phenotype of male and female yellow-legged gull (Larus michahellis) chicks by injecting egg yolks with physiological doses of the hormone. Elevated yolk T resulted in a male-biased post-hatching
sex ratio, T-treated clutches producing a greater proportion of males compared to control ones at day 4 post-hatching, likely
resulting from a reduction of female embryonic survival, whereas no effect of hormone treatment on hatching success or short-term
chick survival was observed. In addition, T depressed post-hatching body mass in both sexes but had no effects on the intensity
of the cell-mediated immune response or skeletal growth. No sex differences in egg characteristics or chick phenotype were
detected. Time to hatching was not affected by T, but females originating from first laid eggs hatched earlier than males
of the same laying order, independently of hormone treatment. However, the implications of sex differences in hatching times
are unclear in the study species. Taken together, our results suggest that female yellow-legged gulls may be constrained in
transferring androgens to their eggs by negative consequences on the viability of female offspring and growth of chicks of
the two sexes. 相似文献
8.
Parental condition, brood sex ratio and differential young survival: an experimental study in gulls (Larus fuscus) 总被引:6,自引:6,他引:0
R. G. Nager P. Monaghan D. C. Houston M. Genovart 《Behavioral ecology and sociobiology》2000,48(6):452-457
Empirical evidence is growing that the offspring sex ratio in birds can be biased in relation to the body condition of parents
during breeding. The sex ratio bias may come about because (1) the actual production of the two sexes may be skewed and/or
(2) there may be a sex bias in early nestling mortality contingent on parental condition. By manipulating parental condition
and giving them a control brood to rear, thereby eliminating effects operating via the eggs, we examined the extent to which
parental condition influences the post-hatching survival of male and female lesser black-backed gulls, Larus fuscus. We found that the pre-fledging survival of male chicks was strongly reduced in all-male broods reared by parents in poor
condition. Pre-fledging survival of female chicks was, however, unaffected by parental condition or brood sex composition.
Thus, independently of any production biases, sex differences in nestling mortality alone can bias the offspring sex ratio
at fledging in relation to the prevailing rearing conditions. In other studies on gulls we have, however, also shown that
females in poor condition at laying preferentially produce female eggs. Clearly a bias in fledging sex ratio can occur within
the same species due to a combination of differential production and differential post-laying mortality; the latter can involve
a differential effect of poor egg quality on male and female offspring, differential effects of brood sex composition on their
survival and a difference in the capacity of parents to rear males and females. All of these processes need to be taken into
account in attempting to understand offspring sex ratios.
Received: 15 February 2000 / Revised: 7 August 2000 / Accepted: 26 August 2000 相似文献
9.
When breeding diet is restricted, domesticated zebra finches,Taeniopygia guttata, produce male-biased primary and secondary sex ratios, but unexpectedly produce unbiased ratios when food is unrestricted. We investigated the primary sex ratios (at laying) of wild zebra finches in southeastern Australia in response to food supplementation and environmental factors predicted to enhance female breeding condition and to bias the primary sex ratio towards daughters. Molecular sexing of all nestlings in 54 complete broods where every egg hatched, failed to show any significant biases from random. Time of egg laying (month, season) and environmental conditions (rainfall, temperature) did not significantly predict variation in the primary sex ratio, but time of breeding did affect clutch size. Wild zebra finches at our colony did not bias their sex allocation as there were no differences in the primary sex ratio and no differences in the numbers and mass of sons and daughters at the end of parental care (day 35–40 post-hatch). Biases in primary sex ratio of our wild population are probably weak or non-existent possibly due to the unpredictable environment and/or multiple contrary selective forces acting on sex ratios. We also investigated the effects of photoperiod, biases in the adult sex ratio, and parental attractiveness on primary sex ratios of semi-domesticated, laboratory zebra finches. Molecular sexing of three-day old embryos from complete clutches, failed to reveal significant biases from random. In contrast to previous studies, sex of eggs did not correlate with laying order and egg mass declined with order, rather than increased. Domestication may be responsible for these differences. 相似文献
10.
Summary The parasitic wasp Nesolynx albiclavus maintains a very skewed offspring sex ratio (ca. 4% males). We studied proximate, causal factors of the son-daughter choice mechanism to obtain insight into the precision of the procedures and the underlying rules. We analyzed the number of males in clutches produced during sessions of 12 or 24 h. The results show that the timing of the next male egg depends on the time elapsed and the number of eggs laid since the previous one. The influence of the passage of time per se during non-laying periods was reduced in an experiment with 4-h periods. The data show that the first male egg is produced by a fairly rigid process: about the sixth egg in a run will be left unfertilized. No further male egg will appear in the next 10–20 eggs if they are laid in rapid succession. 相似文献
11.
Life history theory predicts that parents will have lower Darwinian fitness if they tend clutches that are above or below the size they naturally produce. We experimentally tested for relationships between fitness and clutch size in Tree Swallow (Tachycineta bicolor) offspring and parents. Over 130 trios of nests initiated on the same day were randomly divided among reduce (-3 eggs), control (3 eggs picked up and replaced), or add (+3 eggs) manipulations. Pre-manipulation modal clutch size was six eggs (range before manipulations was 1-10; afterwards, it was 1-11). Hatching took longer in larger clutches, but the proportion of eggs hatching and fledging was similar for clutches from 4 to 10, so that clutches of 10 produced the maximum number of fledgling. Parental feeding rates were higher for larger broods, but per capita feeds to nestlings were fewer, and nestlings were smaller. Nonetheless, survival of both young and adults, based on recaptures in subsequent years, was not significantly affected by manipulations. Manipulations also had no significant effect on subsequent reproduction, including the number of fledglings produced by either local recruits or returning breeders. Collectively, our results failed to detect fitness costs associated with tending larger clutches for either parents or the offspring reared and suggested directional selection for larger clutch size. However, because clutches that hatch later produce fewer recruits, the extra days required to lay more eggs and to fledge extra young may eliminate a large part of the advantage that would accrue to parents producing enlarged clutches. For example, our data suggest that there may be less than a 16% benefit to producing nine instead of six eggs, rather than 50%, as is suggested by experimentally manipulated egg numbers alone. Thus, time, rather than costs of reproduction, may be the crucial constraint selecting against Tree Swallows laying larger clutches. 相似文献
12.
R.F. Luck J.A.M. Janssen J.D. Pinto E.R. Oatman 《Behavioral ecology and sociobiology》2001,49(4):311-321
We determined the sex, order, and clutch size of eggs laid by the parasitoid wasp, Trichogramma pretiosum Riley, in the eggs of one of its natural hosts, Trichoplusia ni (Hübner). The parasitoid allocated sex non-randomly to hosts in the laboratory with a variance significantly less than that of a binomial (random) distribution, our null model. More clutches of two or more eggs contained a single male egg as the second or third egg laid than would be expected by chance and none contained two or more male eggs. T. pretiosum also increased the sex ratio (% male) of its offspring with increasing foundress numbers by increasing the frequency of male offspring as the second egg in a two-egg clutch allocated to unparasitized hosts and as the single egg allocated to previously parasitized hosts. These results indicate that T. pretiosum allocates the sex of its offspring precisely. Precise sex allocation is favored under local mate competition because it reduces variation in the number of sons per patch thus maximizing the number of inseminated daughters emigrating from the patch. Similar combinations of female and male offspring emerged from T. ni eggs parasitized by T. pretiosum in the field, again with a sex ratio variance less than that expected for a binomial distribution. These results strongly suggest that this parasitoid species manifests local mate competition. 相似文献
13.
In long-lived seabirds with low annual reproductive output, the renesting decision after breeding failure is critical, and
the parents have to weigh benefits of replacement clutches against possible future reproductive costs. In this study, we investigated
factors influencing renesting decisions in common terns (Sterna hirundo) and compared aspects of breeding biology and body mass between two breeding attempts by the same pairs in each of 4 years
of heavy losses due to predation. Renesting birds were characterized by early laying dates and by a high age. Among early
breeders, high egg mass reduced the probability of renesting. A long relaying interval coincided with low mass of replacement
eggs in one year, and short intervals with high egg mass in another. Further, egg mass decreased and relaying intervals increased
the later the predation events occurred. Evidence of high levels of parental care of replacement clutches came from body mass
data: female mass increase prior to egg laying was higher in the second attempt than in the first, whereas male mass was lower
during the second courtship period than during the first. Male mass also affected relaying intervals and mass of replacement
eggs. We conclude that common terns expend high levels of parental care of replacement clutches. Intrinsic factors related
to individual quality (age, body condition) seemed most important for renesting decisions and for the degree of parental care,
but foraging conditions seemed to have modifying effects.
Received: 13 August 1999 / Received in revised form: 5 February 2000 / Accepted: 13 March 2000 相似文献
14.
The theory of sex allocation suggests that if the reproductive value and the cost of producing/rearing offspring differ between
male and female offspring, parents should invest differently in sexes depending on environmental conditions. Female parents
could allocate more resources to eggs of one sex to compensate potential sex-dependent constraints later during the nestling
period. In this study, we tested the influence of environmental conditions on sexual dimorphism in eggs of Eurasian kestrels
(Falco tinnunculus) by experimentally manipulating food availability before laying. We found that an increase in food abundance before laying
did not increase egg mass but changed sex-dependent resource distribution in eggs. In food-supplemented pairs, but not in
control pairs, egg mass and hatchling mass were similar between males and females. In addition, we found, in the food-supplemented
group, that the latest hatched females showed shorter hatching times than in the control group. In control pairs, female eggs,
hatchlings and nestlings were heavier than males. In addition, male fledglings in the food-supplemented group gained less
mass than those in the control group. As that food abundance was only increased until the onset of laying, female kestrels
were expected to invest in eggs taking food abundance before egg formation as a predictor of future conditions during brood
rearing. Our study shows that environmental conditions before laying promote a subtle adjustment of the resources invested
in both sexes of offspring rather than in other breeding parameters. This adjustment resulted in a shortening of hatching
time of the last hatched females that possibly gives them advantages in their competitive capacity with respect to male nest-mates. 相似文献
15.
Anton Antonov Bård G. Stokke Arne Moksnes Oddmund Kleven Marcel Honza Eivin Røskaft 《Behavioral ecology and sociobiology》2006,60(1):11-18
Eggs of several brood parasites have thicker and stronger shells than expected for their size. The present study evaluated
the puncture resistance hypothesis for the occurrence of thick-shelled eggs in common cuckoos Cuculus canorus by investigating costs of cuckoo egg ejection in four Acrocephalus warblers—the great reed warbler A. arundinaceus, reed warbler A. scirpaceus, marsh warbler A. palustris and sedge warbler A. schoenobaenus. The three latter species all suffered ejection costs, while ejection was not costly in the larger great reed warbler. The
occurrence of ejection costs was negatively related to host bill size. In the marsh warbler, we compared ejection costs in
naturally parasitized nests and two experimental treatments, in which broods were parasitized artificially with great reed
warbler and conspecific eggs. Hosts damaged their own eggs significantly more often when ejecting the thick-shelled cuckoo
eggs than when ejecting the similarly sized but thinner-shelled great reed warbler eggs, providing some support for the puncture
resistance hypothesis. Ejection of conspecific eggs did not involve any costs. Furthermore, contrary to predictions derived
from the laying damage hypothesis, there was no evidence that egg damage was associated with cuckoo egg laying. Hosts damaging
their own eggs during ejection were more likely to subsequently desert their clutches than those that did not. The frequency
of clutches smeared with the contents of the ejected egg were positively related to the hypothesized difficulty of foreign
egg puncturing. Potential advantages of thicker shells in common cuckoo eggs are discussed. 相似文献
16.
Keith W. Sockman Jack Weiss Michael S. Webster Vanessa Talbott Hubert Schwabl 《Behavioral ecology and sociobiology》2008,62(4):617-625
Maternally derived androgen hormones concentrate in avian egg yolks as the yolks grow on the female’s ovary, possibly forming
a basis for important maternal effects in birds. In the American kestrel (Falco sparverius), experimental elevation of yolk androgens in the first-laid egg of a clutch (a-egg) to the concentrations found naturally
in a clutch’s later-laid eggs reduces the growth rate of a-egg nestlings compared to controls. These findings, together with
discoveries from other species that the effects of yolk androgens on growth of female nestlings may differ from their effects
on growth of male nestlings, raise the hypothesis that natural changes in yolk-androgen concentrations with laying order are
ultimately due to a difference between the sexes in their yolk-androgen sensitivity and between early- and late-laid eggs
in their sex ratio. By re-analyzing previously published data and adding to the analysis data from previously unanalyzed blood
samples used for sex determination, we investigated possible sex-specific effects of yolk-androgens in the context of a potential
sex-biased laying order in free-living American kestrels. We used a multi-level, mixed model with a Gompertz function to analyze
growth of nestlings hatching from a-eggs that were control-treated or in which we experimentally elevated yolk-androgen concentrations
shortly after laying to the higher concentrations naturally found in later-laid eggs. We discovered that male nestlings were
more susceptible than female nestlings to growth inhibition by yolk-androgen elevation but did not find a bias in sex ratio
with respect to laying order. Together, these findings do not support the above hypothesis. However, they are consistent with
the hypothesis that sex differences in yolk-androgen sensitivity enable mothers to economically tune reproductive effort to
an individual offspring’s reproductive value, which can vary more for one sex than the other. 相似文献
17.
In crested penguins (Eudyptes spp.), second-laid eggs typically hatch before first eggs. Amongst a variety of factors that have been considered as mechanisms underlying this reversal, has been the idea that crested penguins can adjust the degree of hatching asynchrony by manipulating egg positions (i.e. placing the smaller first egg in the supposedly thermally disadvantaged anterior position) during incubation (termed Preferential Incubation Hypothesis). We tested this in the Snares crested penguin (Eudyptes robustus) and the closely related, but synchronously-hatching, yellow-eyed penguin (Megadyptes antipodes). Snares crested penguins were more likely to place their first eggs, which are smaller than second eggs, in the anterior incubation position than were yellow-eyed penguins, which have a clutch of two similar-sized eggs. But when yellow-eyed penguins, a non-brood reducing species, were provided with an artificial size-dimorphic clutch, they also placed smaller eggs more frequently in the anterior position, suggesting that a general preference exists among penguins to place smaller eggs in the anterior position. Egg temperatures of small first eggs of Snares crested penguins were higher in the anterior than in the posterior position. Large first eggs in lesser size-dimorphic clutches experienced high temperature differences in relation to position, while small first eggs in greater size-dimorphic clutches were incubated at similar temperatures. In yellow-eyed penguins, large eggs within clutches generally had higher egg temperatures than small eggs. Incubation periods of second eggs declined with increasing egg size. Egg-size variation, rather than egg positioning behaviour, influenced hatching patterns in Snares crested penguins. In lesser size-dimorphic clutches, second eggs were more likely to hatch first while in greater size-dimorphic clutches, small first eggs were more likely to hatch at the same time or before the second eggs. This was similar in yellow-eyed penguins, where second eggs hatched earlier in clutches with large first eggs. Our data contradicts the Preferential Incubation Hypothesis and we conclude that this hypothesis is unlikely to explain the reversed hatching asynchrony in crested penguins.Communicated by C. Brown 相似文献
18.
Lynn Siefferman Kristen J. Navara Geoffrey E. Hill 《Behavioral ecology and sociobiology》2006,59(5):651-656
Egg coloration has been hypothesized to reflect female condition. Because of the proposed physiological costs associated with
deposition of biliverdin pigments and because of their conspicuousness, eggs with blue-green coloration may reliably convey
information about female or brood quality. We tested the hypothesis that expression of blue-green coloration of eastern bluebird
(Sialia sialis) eggs positively correlates to female condition. First, we documented the incidence of egg color polymorphism within the
population. We observed that 98% of females laid blue-green eggs while less than 2% laid white eggs and less than 1% laid
pink eggs. In a subset of clutches, we used full spectrum reflectance spectrometry (300–700 nm) to compare eggshell coloration
to measures of female condition. We found that the color of eggs within clutches was more similar than the color of eggs from
different clutches, and that the blue-green eggs have spectral peaks that are consistent with the characteristic absorbance
spectra of biliverdin pigmentation. Females in better body condition and older females laid more colorful eggs. Moreover,
individual females laid more colorful eggs later in the laying sequence. Overall, these data indicate that egg coloration
covaries with female condition, suggesting that egg coloration could function as a reliable signal of female quality or that
egg coloration may allow females to recognize eggs laid by conspecific brood parasites. 相似文献
19.
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
20.
János Török Rita Hargitai Gergely Hegyi Zoltán Matus Gábor Michl Péter Péczely Balázs Rosivall Gyula Tóth 《Behavioral ecology and sociobiology》2007,61(4):541-550
Birds may influence the fitness of their offspring by transmission of different amounts of carotenoids to their eggs. Carotenoids
play crucial roles in antioxidant protection and immune defence mechanisms, but they may be available to females in limiting
amounts. Therefore, their allocation to the eggs may be influenced by the female’s condition, age and environmental circumstances.
Furthermore, the quality of the male parent, which affects the reproductive value of the offspring, may also influence this
investment. In this correlational study, we investigated proximate and ultimate factors that may lead to variation in yolk
lutein, zeaxanthin and β-carotene concentrations among and within clutches of a wild passerine, the collared flycatcher (Ficedula albicollis). We found that carotenoid concentration was positively associated with caterpillar supply at the time of egg formation,
which suggests a proximate constraint of carotenoid availability on yolk composition. Neither female condition, body size,
age, nor male plumage ornamentation, age and body size correlated with carotenoid deposition. Yolk β-carotene concentration
was found to be positively linked to yolk testosterone concentration. We suggest that females allocated more β-carotene to
their eggs to mitigate the potentially detrimental effects of elevated steroid concentration. We found that concentration
of β-carotene increased with laying order. The possible function of this pattern may be to enhance the resistance to oxidative
stress and pathogens of the disadvantaged last-hatching nestling, suggesting that collared flycatchers pursue a compensatory,
“brood survival” strategy. 相似文献