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1.
Summary This paper analyzes the flexibility of maternal care in wild house mice (Mus domesticus) under different reproductive conditions in the laboratory. All maternal activities were both qualitatively and quantitatively analyzed over a period of 28 days after birth of a litter. The standard behavior of a lactating house mouse with 7–8 young can be described as follows: During days 1–16 the offspring fully depend on the mother for nutrition. Due to rapid growth of the litter, the energetic demands of lactation reach a peak for the female during days 13–16. During days 17–22, the weaning period, the young begin to eat solid food. This period is characterized by behaviors that indicate different interests of the mother and offspring, and thus the existence of a parent-offspring conflict sensu Trivers (1974). Resting alone and remaining far from the litter indicate the female's interest in avoiding the offspring's demands, which are expressed in frequent attempts to initiate sucking. There is no aggression towards the young during weaning. House mice are weaned at 23 days. The relationship between mother and young appears free of conflict after weaning. Nursing is replaced by resting with body contact, but the offspring do not try to suck. The following results suggest that during the weaning period the offspring do not get more milk than corresponds to the maternal optimum—despite their frequent sucking attempts:(a) When the mother is simultaneously lactating and pregnant, offspring are smaller at weaning than under standard conditions. (b) Small litters are weaned earlier than large ones. Despite a longer nursing period, offspring from large litters are lighter at weaning than those from small ones. (c) Under high energy demand, as after postpartum mating and with large litters, females wean their young at a body weight which corresponds to the earliest physiologically possible state of independence.Parity of the female has no effect on maternal activities, nor has the presence of the father. In the latter case, however, offspring are less often left alone and unprotected.Females seem to adjust their investment according to the body weight of the progeny by delaying or advancing the date of weaning (Table 2). This behavior allows the production of the largest possible number of offspring that can be raised to a minimal physiological threshold corresponding to a body weight of approximately 9 g. Such flexibility in parental care may enhance maternal fitness under different and unpredictable environmental conditions. 相似文献
2.
Adam Dušek Luděk Bartoš František Sedláček 《Behavioral ecology and sociobiology》2011,65(12):2209-2217
The issue of adaptive adjustment of offspring sex ratio (proportion of male births) in polytocous mammals, producing several
offspring per litter, is controversial because females of these species can maximize their fitness mainly by adjusting offspring
number. To address this issue, we examined the effect of maternal condition at mating, experimentally decreased by pre-mating
food restriction, on the sex ratio variation in 137 female mice. We tested two basic sex allocation hypotheses plausible for
polytocous mammals: (1) the Myers hypothesis, predicting that cheaper sex should be favored in poor environmental conditions
to maximize offspring number; and (2) the Williams hypothesis, predicting maximum fitness returns by adjusting size- and sex-specific
composition of the litter according to the maternal condition. The food-restricted mothers produced larger litters with a
higher proportion of cheaper daughters than the control mothers. By contrast, the control mothers optimized size and sex composition
of the litter according to their weight at mating. In addition, the offspring of the food-restricted mothers suffered less
from pre-weaning mortality than those of the control mothers. Therefore, when comparing the groups, the Myers hypothesis had
a general significance while the Williams hypothesis was plausible only for the control mothers. Furthermore, some of the
food-restricted mothers partly coped with the pre-mating food restriction and increased the proportion of sons in the litter
with the increasing maternal weight loss (during the period of food restriction). The sex ratio variation was thus a result
of three sex allocation strategies depending on the maternal condition at mating. 相似文献
3.
Contradictory findings in studies of sex ratio variation in roe deer (Capreolus capreolus) 总被引:3,自引:0,他引:3
A. J. Mark Hewison Reidar Andersen Jean-Michel Gaillard John D. C. Linnell Daniel Delorme 《Behavioral ecology and sociobiology》1999,45(5):339-348
Patterns of sex ratio variation and maternal investment reported in the literature are often inconsistent. This could be
due to intra- and inter-specific variation in social systems, but may also be a result of the a posteriori nature of much
of this type of analysis or the testing of models which are inappropriate. Two recent papers reported directly opposed results
concerning variation in offspring sex ratios in relation to maternal condition in roe deer, interpreting the results as support
for the Trivers and Willard model and for the local resource competition hypothesis, respectively. In this paper, we present
data on offspring sex ratios and early juvenile body weight from two long-term studies of this species to test predictions
arising from these two models concerning sex biases in litter composition and maternal care. First, we observed no consistent
pattern of sex differences in an index of weaning weight or body weight at 1 month old in either population, indicating a
lack of sex bias in maternal care. However, in one population, higher maternal body weight was associated with higher juvenile
body weight of daughters, but not of sons. Secondly, we found a negative, but not statistically significant, relationship
between maternal body weight and litter sex ratio such that heavier females tended to produce more daughters and lighter females
to produce more sons. These results indicate that roe females which have additional investment potential available do not
invest it in sons, as predicted by the Trivers and Willard model. Our results may provide some support that roe deer are subject
to local resource competition acting at the level of the individual mother; however, the fact that particular trends in sex
ratio data can be explained in functional terms provides no indication that they are actually adaptive.
Received: 9 December 1997 / Accepted after revision: 11 November 1998 相似文献
4.
Luc A. Wauters Simon A. de Crombrugghe Nadia Nour Erik Matthysen 《Behavioral ecology and sociobiology》1995,37(3):189-193
In polygynous roe deer Capreolus capreolus, males are only slightly heavier than females and the overall sex ratio at birth is close to unity. We studied offspring sex ratio and litter size (range 1–4, n = 74) of culled females, in utero, which provided an opportunity to examine responses of sex ratio to maternal condition. Male embryos were heavier than their sisters, and male fawns (9 months old) heavier than female fawns, suggesting a higher growth rate in males. There was no evidence for differential mortality between the sexes from birth to 9 months old. Heavier adult females produced larger embryos than lighter, or primiparous females. The overall sex ratio of embryos did not differ from unity, but adult does had more male embryos (55%) than primiparous does (32%), and the proportion of male embryos in a litter increased with the mother's body mass. Litter size also tended to increase with maternal age and body mass. We argue that this pattern reflects adaptive variation in offspring sex ratio. 相似文献
5.
E. C. Pariser L. Gilbert N. Hazon K. E. Arnold J. A. Graves 《Behavioral ecology and sociobiology》2012,66(4):519-527
Females are expected to partition resources between offspring in a context-dependent way to maximise total fitness returns
from a reproductive attempt. Female zebra finches (Taeniopygia guttata) vary the allocation of yolk androgens and antioxidants among offspring. Importantly, the balance between androgens and antioxidants
in yolks may be more important than their independent absolute amounts in terms of fitness consequences for developing young.
Therefore, we tested whether the relative allocation of these two resources in yolks varies according to either the Trivers–Willard,
positive or compensatory maternal investment hypothesis. We manipulated male attractiveness using coloured leg bands (red-banded
males appear attractive; green-banded males, unattractive) and measured yolk androgens and antioxidants in each egg, egg sex,
clutch sex ratio and female condition. While female zebra finches manipulated the balance of androgens and antioxidants within
and between clutches in response to mate attractiveness, offspring sex and their own condition, they did not do so in a way
that consistently followed any of the hypotheses. Mothers paired with unattractive males allocated a larger antioxidant/androgen
ratio to daughters than sons. This pattern was reversed when paired to an attractive male; sons received a larger antioxidant/androgen
ratio than daughters. We also found offspring sex ratio decreased with increasing female condition for unattractive males,
but not for attractive males. However, without knowing the fitness consequences of the balance of different egg constituents,
it is difficult to interpret the patterns consistently in terms of the Trivers–Willard, compensatory and positive investment
hypotheses. 相似文献
6.
S. L. Wright C. B. Crawford Judith L. Anderson 《Behavioral ecology and sociobiology》1988,23(6):357-365
Summary Female mammals in good condition can maximize their inclusive fitness by investing more in male offspring than in female offspring during periods of poor environmental quality. To test this hypothesis, we measured the effects of undernutrition and crowding before and during gestation on the sex ratio and weight of offspring at parturition and at weaning in Mus domesticus. Sex ratio was not significantly affected by density. Dams altered the sex ratio of their offspring in response to food availability, but only if variance in competitive success within the experimental subpopulation was evident. Thus ad lib fed females produced litters with an unbiased sex ratio, competitively successful females under moderate food availability produced a male-biased sex ratio, and severely food deprived females produced litters with a female-biased sex ratio. In groups that experienced competition for food, successful dams favoured male offspring during lactation. These results are consistent with the predictions of Trivers and Willard (1973). Analysis of within-cell variance and covariance suggests that the interaction of social structure and food availability provides specific cues for the dams' tactical reproductive choices. 相似文献
7.
Sjouke A. Kingma Michelle L. Hall Anne Peters 《Behavioral ecology and sociobiology》2011,65(6):1203-1213
When fitness returns or production costs vary between male and female offspring, selection is expected to favor females that
adjust offspring sex ratio accordingly. However, to what extent vertebrates can do so is the subject of ongoing debate. Here,
we explore primary sex ratios in 125 broods of cooperatively breeding purple-crowned fairy-wrens Malurus coronatus. We expected that females might adjust offspring sex ratio because this passerine species experiences considerable variation
in social and environmental conditions. (1) However, although helpers substantially increase parental fitness, females (particularly
in pairs and small groups) did not overproduce philopatric males (helper-repayment hypothesis). (2) Sex-ratio adjustment based on competition among individuals (helper-competition hypothesis) did not conceal helper-repayment effects or drive sex allocation on its own: while high-quality territories can accommodate
more birds, brood sex ratios were independent of territory quality, alone or in interaction with group size. (3) Additionally,
males are larger than females and are possibly more costly to produce (costly sex hypothesis), and (4) female offspring may benefit more from long-term effects of favorable conditions early in life (Trivers–Willard hypothesis). Nonetheless, large seasonal variation in food abundance was not associated with a consistent skew in primary sex ratios.
Thus, overall, our results did not support the main hypotheses of adaptive sex-ratio adjustment in M. coronatus. We discuss that long-term differential costs and benefits may be insufficient to drive evolution of primary sex-ratio manipulation
by M. coronatus females. More investigation is therefore needed to determine the general required sex differences in long-term fitness returns
for mechanisms of primary sex-ratio manipulation to evolve. 相似文献
8.
Kelly M. Proffitt Robert A. Garrott Jay J. Rotella 《Behavioral ecology and sociobiology》2008,62(10):1679-1687
The Trivers–Willard model predicts that in polygynous species, superior-quality females will maximize their fitness by producing
male offspring. Using a sample of 1,780 Weddell seal (Leptonychotes weddellii) pups recorded over 31 years, we investigated relationships between offspring sex ratio and maternal age, reproductive experience,
an index of maternal lifetime reproductive output, and annual environmental variations. We found evidence that females with
higher index of lifetime reproductive output were more likely to produce male than female offspring but found only weak evidence
that large-scale environmental variations influenced sex ratios. Our results suggest that mothers manipulate offspring sex
to maximize their own fitness, and inherent maternal quality may influence offspring sex. These findings support the Trivers–Willard
sex-allocation model.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
K. Reinhold 《Behavioral ecology and sociobiology》1996,39(3):189-194
Offspring sex ratio at hatching was examined in the bushcricket Poecilimon veluchianus. Offspring sex ratios varied significantly between females (Fig. 1). Low mortality prior to sex determination established
that this heterogeneity was already present in the primary offspring sex ratio. Sperm age and female age had no influence
on offspring sex ratio (Fig. 2). Male age at copulation, however, correlated significantly with offspring sex ratio (Fig. 3).
There were two types of males: one type produced predominantly daughters when young and an increasing proportion of sons with
age. The other type produced, independent of age, 1:1 offspring sex ratios (Fig. 4). The two types of males seem to occur
in approximately equal numbers. Sex ratio variation (1) may adaptively compensate for local sex ratio biases caused by sex-specific
motility, or (2) it may be adaptive if there is a sex-differential effect of laying date on offspring fitness.
Received: 14 March 1996/Accepted after revision: 24 June 1996 相似文献
10.
Offspring sex ratios in mammals vary in potentially adaptive yet unpredictable ways. An integrative approach that simultaneously examines proximate and ultimate explanations of mammalian sex ratios would greatly advance the field. We examined the importance of maternal glucose and stress hormones for offspring sex (male or female) as mechanisms associated with the Trivers–Willard and the local resource competition hypotheses of sex allocation. We tested this framework in a marsupial mammal, the tammar wallaby (Macropus eugenii). Mothers that were better able to maintain body condition over the driest part of the year, a presumptive proxy for local resource availability, were more likely to produce daughters (the philopatric sex), consistent with local resource competition. Maternal glucose was correlated with offspring sex, but in the opposite direction than we predicted—higher maternal glucose was associated with female pouch young. These patterns, however, were not consistent across the 2 years of our study. Maternal stress hormone metabolites measured from fecal samples did not predict glucose or offspring sex. A causative glucose mechanism may underlie an adaptive strategy for mothers with high local resources (high glucose) to produce philopatric daughters that will benefit from inheriting resource access. Examining species-specific relationships between glucose and offspring sex across mammals could provide crucial insight into the disparate ecological and selective pressures faced by mammals with respect to offspring sex ratio. 相似文献
11.
Birth sex ratios in toque macaques and other mammals: integrating the effects of maternal condition and competition 总被引:2,自引:0,他引:2
Wolfgang P. J. Dittus 《Behavioral ecology and sociobiology》1998,44(3):149-160
Mammalian life histories suggest that maternal body condition and social dominance (a measure of resource-holding potential)
influence the physical and social development of offspring, and thereby their reproductive success. Predictably, a mother
should produce that sex of offspring which contributes most to her fitness (as measured by the number of her grandchildren)
and that she is best able to raise within the constraints imposed by her condition, social rank, and environment. Such combined
effects were investigated by monitoring variations in body condition (weight) and behavior of female toque macaques, Macaca sinica of Sri Lanka, in a changing forest environment over 18 years. Maternal rank, by itself, had no influence on offspring sex,
but did affect maternal body condition. The combined effects of rank and condition indicated the following: mothers in robust
condition bore more sons, whereas those in moderate condition bore more daughters, but both effects were expressed most strongly
among mothers of high rank. Where the consequences of low rank were felt most acutely, as shown by poor condition, mothers
underproduced daughters. Environmental quality directly influenced rank and condition interactions, and thus sex ratios. These
relationships, and data from other mammals suggest an empirically and theoretically consistent pattern of sex allocation in
mammals. New predictions integrate effects, proposed by Trivers and Willard, that are rooted in male mate competition, which
is universal among polygynous mammals, with those of local resource competition (and/or female reproductive competition),
which are not universal and differ in intensity between the socioecologies and local environments of different species.
Received: 30 May 1998 / Accepted after revision: 29 August 1998 相似文献
12.
Summary In polygynous mammals, it may be adaptive for mothers to invest more in sons and/or to adjust the sex ratio of offspring in relation to body condition. Calving patterns were examined over an 8-year period (1982–1989) for a population of Bison bison in which barren females are not selectively culled. From these data, we tested predictions of the sex ratio adjustment hypothesis as well as two assumptions: (1) that offspring weight at the end of the period of parental investment (PI) is correlated with later condition, and (2) that maternal and offspring condition during the period of PI are correlated. In contrast to predictions, there was little evidence that mothers in better condition bear more sons. Short- and long-term measures of maternal condition (previous reproductive status, age, dominance status, pre-pubertal body weight, age at first reproduction, birth date, and the duration of the mother's own suckling period) were little related to offspring sex ratio, although the last calves of old females were nearly always female. Similarly, there was little evidence for sex-biased PI. Weights at about 7 months of age were greater for males than females; males also had somewhat later birth dates, suggesting either longer gestation or later conception. However, maternal reproductive costs, as measured by subsequent fecundity, weight loss, and interbirth intervals, did not vary with calf sex. Both assumptions of the model received some support. However, while maternal condition was correlated with offspring condition, there may be sex differences in investment patterns. Mothers appear better able to influence the condition of daughters than of sons. This sex difference may negate any benefit from male-biased investment. 相似文献
13.
There is growing evidence that the sex ratios of wild vertebrate populations are determined by mechanisms that are directly
influenced by environmental characteristics. The Trivers–Willard (TWH) and extrinsic modification (EMH) hypotheses postulate
differing determinants of mammalian offspring sex ratios. TWH states that mothers allocate resources according to their current
condition and sex-specific offspring costs. EMH states that environmental forces that affect maternal condition determine
offspring sex ratios, independently of maternal tactics of sex-biased allocation. We statistically assessed support for each
of these hypotheses using long-term life histories of the allied rock-wallaby, Petrogale assimilis; a continuously breeding, polygynous, weakly dimorphic marsupial. We showed that birth sex ratios were equal and independent
of maternal and environmental conditions. However, secondary sex ratios were male-biased under good environmental conditions
and for high quality mothers or mothers in good condition. Sex differences in offspring survival contributed to these biases:
(1) environmental conditions strongly influenced survival to pouch emergence (in support of EMH) and (2) maternal quality
affected survival to the end of maternal care (in support of TWH). Environmental effects on survival were more important than
maternal factors over the entire period of maternal care and contributed most to male-biased sex ratios at pouch emergence.
In contrast, maternal mass was the best predictor of sex ratios at the end of maternal care—the life history stage where offspring
body mass differed between the sexes. 相似文献
14.
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
15.
Gabriele Gerlach 《Behavioral ecology and sociobiology》1996,39(3):159-170
Emigration in small mammals may be strongly related to social factors, but direct observations of emigrants are rare. Feral
house mice (Mus domesticus) were studied using a population cage system that allowed continuous observation of individually marked animals. Mice that
left their natal cage and took up residence in cages that could only be reached by crossing a water barrier were defined as
emigrants. Six pairs of house mice with their litters were placed in the system, and data on aggressive interactions, body
weight, reproduction, mortality and emigration were collected daily. Both sexes emigrated, but males did so twice as often
as females. Population density was not correlated with the frequency of aggression, and had no effect on the weight of emigrating
individuals. Male emigrants suffered more aggression before emigration than their non-emigrant brothers of the same age; they
were aggressively driven out by other males, predominantly by the father. Female emigration depended on the female’s chances
of reproduction. The probability of a female reproducing decreased with increasing birth order. Females born in a late litter,
who therefore had only a low chance of reproduction, dispersed earlier than those of early litters. Resident males were reproductively
suppressed. Male offspring had two different strategies for attaining top rank. They could develop rapidly and reach sexual
maturity early on, but face competition with the father, risking being forced to emigrate. Alternatively, they could develop
slowly, stay within their family and wait for a chance to take over the dominant position. It is concluded that emigration
in male and female feral house mice is caused by intrasexual competition.
Received: 13 July 1995/Accepted after revision: 8 June 1996 相似文献
16.
Kjell Einar Erikstad Jan Ove Bustnes Svein-Håkon Lorentsen Tone Kristin Reiertsen 《Behavioral ecology and sociobiology》2009,63(6):931-938
In birds, there is ample evidence that the mother can manipulate the sex of the young and produce more of the sex, which gives
the highest fitness return. This has previously been documented in gulls, Laridae. Gulls are sexually size dimorphic with
males larger than females, and there is good evidence that parents in poor body condition switch their investment to the smallest
sex. In the present study, we examined the primary sex ratio and the survival of male and female chicks of lesser black-backed
gull (Larus fuscus fuscus) in relation to their blood levels of organochlorines (OCs), perfluorinated compounds (PFCs) and polybrominated diphenyl
ethers (BDE-47). We show that females with high levels of OCs (but not PFCs and BDE-47) are likely to skew their sex ratio
at hatching towards female offspring. Few females had very high levels of OCs, and the many females with low levels of OCs
overproduced sons resulting in a male skew at hatching (59%). The survival of female offspring was lower than the survival
of male offspring, causing an even stronger male skew in sex ratio (71%). There is evidence to conclude that circulating levels
of OCs in the blood of females may have detrimental effect on the sex allocation strategy and could be of serious threat to
the population.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
Claire W. Varian-Ramos Jordan Karubian Vanessa Talbott Irma Tapia Michael S. Webster 《Behavioral ecology and sociobiology》2010,64(6):967-977
The repayment hypothesis posits that primary sex ratios in cooperative species should be biased towards the helping sex because
these offspring “repay” a portion of their cost through helping behavior and therefore are less expensive to produce. However,
many cooperatively breeding birds and mammals do not show the predicted bias in the primary sex ratio. Recent theoretical
work has suggested that the repayment hypothesis should only hold when females gain a large fitness advantage from the presence
of auxiliary adults in the group. When auxiliaries provide little or no fitness advantage, competition between relatives should
lead to sex ratios biased towards the dispersing (non-helping) sex. We examined the benefits auxiliaries provide to females
and corresponding offspring sex ratios in the red-backed fairy-wren (Malurus melanocephalus), a cooperatively breeding Australian bird with male auxiliary helpers. We found that auxiliaries provide little or no benefit
to female reproductive success or survival. As predicted, the population primary sex ratio was biased towards daughters, the
dispersing sex, and females with auxiliaries produced female-biased broods whereas females without auxiliaries produced unbiased
broods. Moreover, offspring sex ratios were more strongly biased toward females in years when auxiliaries were more common
in the population. These results suggest that offspring sex ratios are associated with competition among the non-dispersing
sex in this species, and also that females may use cues to assess local breeding opportunities for their offspring. 相似文献
18.
Jay B. Labov U. William Huck Prabha Vaswani Robert D. Lisk 《Behavioral ecology and sociobiology》1986,18(4):241-249
Summary The theory that female mammals in poor condition may increase individual fitness by skewing the sex ratio of their offspring toward daughters and by investing more resources in daughters than in sons was tested in hamsters. Newly mated experimental females were food-restricted during pregnancy and lactation (RR) or during lactation only (AR). Controls received food ad libitum. Maternal body weights were assessed daily from mating to 25 days postpartum. Litter survival (% litters with at least one pup surviving on any day), litter size, offspring sex ratios (=% males), and pup weights were monitored daily from birth (Day 1) to Day 25. All control and AR dams gave birth 16 days after mating. Gestation was extended by 1–3 days for 35.4% of RR dams. RR dams weighed significantly less at parturition than controls and AR females. During lactation, AR females showed the greatest weight loss and control females the least. AR weight loss exceeded that of RR females, possibly because the former maintained larger litters. Survival was highest for controls, intermediate for AR, and lowest for RR litters. Mean sex ratio at birth was significantly less for RR (40.7%) than for control (49.6%) and AR (48.8%) litters. RR sex ratio did not change significantly postnatally. Sex ratios of control and AR litters never differed statistically from 50%. Control male pups were significantly heavier than their sisters throughout the experiment. No significant gender differences were observed for AR pup weights after Day 2 postpartum. RR female offspring weighed more than their brothers throughout the experiment, and this difference was statistically significant immediately prior to the time that pups began to feed independently (Days 14–17). RR female pup weights were similar to, and sometimes significantly greater than, weights of control daughters during the period of postnatal maternal investment. Control males were always heavier than males from the other treatments. Patterns of weight gain by AR and RR males varied with age. We conclude that underfed female hamsters are able to adjust the sex ratio of offspring prenatally and parental investment postnatally to favor daughters. 相似文献
19.
When allocating investment among offspring, parents might maximize their fitness by biasing investment toward offspring with
the best direct fitness prospects. The observed preferences of avian parents for carotenoid-rich mouth colors that advertise
good condition has been interpreted as support for this hypothesis. However, because these condition-dependent visual signals
might also make offspring more visually conspicuous, active parental preferences for carotenoid-rich traits are difficult
to distinguish from passive responses to differences in detectability among offspring. Here, we used a visual model to examine
how mouth colors influence the visual conspicuousness of nestling house sparrows (Passer domesticus) to parents under a suite of realistic ambient light conditions. We found little evidence that mouths rich in carotenoids
provided more conspicuous targets to parents than mouths poor in carotenoids. While other features of mouth color may have
evolved to increase conspicuousness, our results suggest that carotenoid-based coloration is not a product of detectability
pressures and rather may serve as a signal of nestling quality. 相似文献
20.
Kapheim KM Bernal SP Smith AR Nonacs P Wcislo WT 《Behavioral ecology and sociobiology》2011,65(6):1179-1190
Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish
from other environmental factors. This is an important distinction within the context of social evolution, because if variation
in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as
those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which
might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary
nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive
helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores
provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content
varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content,
for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio
ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in
maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social
plasticity observed in M. genalis. 相似文献