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1.
Outi Ala-Honkola Laura Tuominen Kai Lindström 《Behavioral ecology and sociobiology》2010,64(9):1403-1414
Polyandry is hypothesized to give females an opportunity to avoid inbreeding through postcopulatory selection mechanisms if
precopulatory inbreeding avoidance is not possible, for example, because of forced matings. Here, we report a postcopulatory,
prefertilization, inbreeding avoidance mechanism in the least killifish, Heterandria formosa, a species in which males can force matings. Females had 50% less sperm in their oviducts and ovarian cavities after mating
with a sibling compared to a mating with a nonsibling male. Neither sex showed inbreeding avoidance in a dichotomous precopulatory
mate choice test or during mating trials. Females in this species invest substantially in each offspring after fertilization
(matrotrophy), whereas males invest little more than sperm. Based on theory, females should therefore be more likely than
males to avoid inbreeding in this species. We suggest that females do this by reducing the amount of sibling sperm in their
reproductive system. However, the possibility that males invested more sperm to nonsiblings could not be ruled out. In a fertilization
success experiment, the first male to mate with a female sired all the offspring in most cases, even if it was a sibling.
However, large females were more likely to carry offspring of multiple males. Possibly female sperm storage sites were filled
by the first male, and only large females had space for the second male's sperm. 相似文献
2.
J. Scott Keogh Kate D. L. Umbers Eleanor Wilson Jessica Stapley Martin J. Whiting 《Behavioral ecology and sociobiology》2013,67(4):629-638
Sexual selection theory predicts different optima for multiple mating in males and females. We used mating experiments and genetic paternity testing to disentangle pre- and postcopulatory mechanisms of sexual selection and alternate reproductive tactics in the highly promiscuous lizard Eulamprus heatwolei. Both sexes mated multiply: 30–60 % of clutches were sired by two to four fathers, depending on the experiment. Larger males sired more offspring when we allowed male contest competition: 52 % of large males but only 14 % of small males sired at least one offspring. In the absence of male contest competition, females mated promiscuously and there was no large male advantage: 80 % of large males and 90 % of small males sired at least one offspring, and there was no evidence for last-male precedence. Multiple mating did not yield obvious direct or indirect benefits to females. E. heatwolei represents a complex system in which males attempt to improve their fertility success by limiting rivals from access to females and through adopting alternate reproductive tactics. Conversely, females exhibit no obvious precopulatory mate choice but may influence fitness through postcopulatory means by either promoting sperm competition or through cryptic female choice. Our results support the hypothesis that female multiple mating in nonavian reptiles is best explained by the combined effect of mate encounter frequency and high benefits to males but low costs to females. 相似文献
3.
Daniela Canestrari Marta Vila José M. Marcos Vittorio Baglione 《Behavioral ecology and sociobiology》2012,66(9):1225-1235
In cooperatively breeding species, parents should bias offspring sex ratio towards the philopatric sex to obtain new helpers (helper repayment hypothesis). However, philopatric offspring might increase within-group competition for resources (local resource competition hypothesis), diluting the benefits of helper acquisition. Furthermore, benefits of offspring sex bias on parents’ fitness may depend on different costs of production and/or different breeding opportunities of sons and daughters. Because of these counteracting factors, strategies of offspring sex allocation in cooperative species are often difficult to investigate. In carrion crows Corvus corone corone in northern Spain, sons are more philopatric and more helpful at the nest than daughters, which disperse earlier and have higher chances to find a breeding vacancy. Consistent with the helper repayment hypothesis, we found that crows fledged more sons in groups short of subordinate males than in groups with sufficient helper contingent, where daughters were preferred. Crow females also proved able to bias primary sex ratio, allocating offspring sex along the hatching sequence in a way that provided the highest fledging probability to sons in the first breeding attempt and to daughters in the following ones. The higher cost of producing male offspring may explain this pattern, with breeding females shifting to the cheapest sex (female) as a response to the costs generated by previous reproductive attempts. Our results suggest complex adjustments of offspring sex ratio that allowed crows to maximize the value of daughters and sons. 相似文献
4.
Clare C. Rittschof Swetapadma Pattanaik Laura Johnson Luis F. Matos Jérémie Brusini Marta L. Wayne 《Behavioral ecology and sociobiology》2013,67(4):529-540
The risk of disease transmission can affect female mating rate, and thus sexual conflict. Furthermore, the interests of a sexually transmitted organism may align or diverge with those of either sex, potentially making the disease agent a third participant in the sexual arms race. In Drosophila melanogaster, where sexual conflict over female mating rate is well established, we investigated how a common, non-lethal virus (sigma virus) might affect this conflict. We gave uninfected females the opportunity to copulate twice in no-choice trials: either with two uninfected males, or with one male infected with sigma virus followed by an uninfected male. We assessed whether females respond behaviorally to male infection, determined whether male infection affects either female or male reproductive success, and measured offspring infection rates. Male infection status did not influence time to copulation, or time to re-mating. However, male infection did affect male reproductive success: first males sired a significantly greater proportion of offspring, as well as more total offspring, when they were infected with sigma virus. Thus viral infection may provide males an advantage in sperm competition, or, possibly, females may preferentially use infected sperm. We found no clear costs of infection in terms of offspring survival. Viral reproductive success (the number of infected offspring) was strongly correlated with male reproductive success. Further studies are needed to demonstrate whether virus-induced changes in reproductive success affect male and female lifetime fitness, and whether virus-induced changes are under male, female, or viral control. 相似文献
5.
Dara H. Wilber 《Behavioral ecology and sociobiology》1989,24(6):445-451
Summary Postcopulatory mate guarding in crustaceans traditionally has been viewed as a behavioral mechanism that prevents predation on the soft post-molt female. This study tests the effects of sexual selection and predation on the postcopulatory guarding durations of male stone crabs, Menippe mercenaria, M. adina, and their hybrid. Male stone crabs were held with a pre-molt female, and either another adult male stone crab, an intermolt female, or a male blue crab, which corresponded to intermale competition, control, and predation treatments, respectively. The mating behavior of the heterosexual pair was recorded with a time lapse video system and the durations of copulation and postcopulatory guarding were measured. Males guarded longer in the intermale competition treatment than either the control or predation treatments. In the competition treatment, agonistic encounters occurred between the males at the den containing the female and several mate takeovers occurred. Females survived the predation treatment in trials in which the guarding durations were the longest, whereas females were eaten by the blue crab in trials with the shortest guarding durations. Sexual selection appears to be important in maintaining postcopulatory mate guarding in stone crabs. 相似文献
6.
Mixed reproductive strategy and mate guarding in a semi-colonial passerine,the swallow Hirundo rustica 总被引:6,自引:0,他引:6
Anders Pape Møller 《Behavioral ecology and sociobiology》1985,17(4):401-408
Summary Both male and female swallows Hirundo rustica have a mixed reproductive strategy (parental care for offspring and extra-pair couplations). Mate guarding protects females from male harassment and male swallows from being cuckolded. Females hide their fertile period by copulating successfully with their mates for an extended period during first clutches. Males guard in the pre-fertile period, when many unpaired males are present. Early breeding swallows guard more than late breeders since more sexual chases of females by non-mate males take place in the early period. Solitarily breeding females experience few chases by strange males; copulation frequency, length of copulation period and mate guarding is adjusted to a lower level than among colonial birds. Male guarding activity is more intense in the fertile than in the pre-fertile period. Guarding reduces success of extra-pair copulation attempts.Three female swallows each paired and copulated with a single male and later changed to a new male before starting to breed. Extra-pair copulations most often take place between neighbouring swallows in the fertile period of the female. Many old, early breeding males and many young, late breeding females participate in extra-pair couplations. Successful extra-pair copulations peak in the fertile period contrary to success of pair copulations which does not change during the copulation period. 相似文献
7.
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
8.
Engelhardt A Fischer J Neumann C Pfeifer JB Heistermann M 《Behavioral ecology and sociobiology》2012,66(1):121-134
Primates are unusual in that many females display sexual signals, such as sex skin swellings/colorations and copulation calls,
without any sex role reversal. The adaptive function of these signals remains largely unclear, although it has been suggested
that they provide males with information on female reproductive status. For sex skin swellings, there is increasing evidence
that they represent a graded signal indicating the probability of ovulation. Data on the functional significance of copulation
calls are much scarcer. To clarify the information content of such calls, we recorded copulation calls in wild long-tailed
macaques (Macaca fascicularis) and analysed the structure of these calls during the ovarian cycle. Specifically, we correlated selected call parameters
with the female oestrogen to progestogen ratio (obtained from faecal samples), which are known to be elevated during the female's
fertile phase. In addition, we ran a general linear mixed model for these call parameters, testing factors (cycle phase, occurrence/absence
of ejaculation, male dominance status, occurrence/absence of mate guarding) which potentially influence female copulation
calls in primates. Our results show that copulation calls of female long-tailed macaques signal mating outcome and rank of
the mating partner, but not female reproductive status. They also show for the first time on primates that copulation calls
can convey information on whether a female is mate guarded or not. We suspect that the function of these calls is manipulation
of male mating and mate-guarding behaviour and that in this way the degree of sperm competition and ultimately male reproductive
success is influenced. 相似文献
9.
Polyandry and enhanced reproductive success in the harlequin-beetle-riding pseudoscorpion 总被引:1,自引:0,他引:1
J. A. Zeh 《Behavioral ecology and sociobiology》1997,40(2):111-118
The growing molecular evidence that females of many species mate with several males calls for a critical reassessment of
the selective forces which act to shape female mating tactics. In natural populations of the harlequin-beetle-riding pseudoscorpion,
Cordylochernes scorpioides, females are polyandrous and typically produce mixed-paternity broods. Laboratory behavioral analyses and breeding experiments
indicate that polyandry in this pseudoscorpion is an active strategy which increases female reproductive success. Females
restricted to mating with a single male experienced a higher rate of embryo failure and produced significantly fewer offspring
than either females mated to more than one male in the laboratory or females naturally inseminated in the field. Forced copulation,
insufficient sperm from a single mating, male nutrient donations and variation in inherent male genetic quality cannot explain
the greater number of nymphs hatched by polyandrous females in this study. Evidence suggests that, by mating with several
males, C. scorpioides females may exploit postcopulatory mechanisms for reducing the risk and/or cost of embryo failure resulting from fertilization
by genetically incompatible sperm.
Received: 5 May 1996 / Accepted after revision: 16 October 1996 相似文献
10.
Kooji Hayashi 《Behavioral ecology and sociobiology》1985,16(4):301-306
Summary Males of the water strider Gerris elongatus established territories which included copulation and oviposition sites (small pieces of fallen bamboo). Males were aggressive and competition for territory and females was observed frequently. Male midlegs were more developed than female midlegs and were used as weapons. Reproductive behaviour changed as the breeding season advanced. Early in the season immature females were attracted by male surface wave courtship signals, then copulated white floating on the water surface without ovipositing (type 1). In midseason, males established territories, produced calling signals and attracted females which copulated and oviposited there with male postcopulatory guarding (type 2). In late season, many females oviposited without postcopulatory guarding on pondweed mats near fallen bamboo. Non-territorial males waiter for the arrival of these females and copulated without courtship, but mating success was low (type 3). These alternative mating strategies appeared to depend on differences in male size. Larger males were superior to smaller males in many ways (establishing territory, fighting, mating etc.). The largest males defended territories and had higher mating success than small non-territorial males. Medium sized males used all three strategies according to the number of empty territories and seasonal femald distribution. 相似文献
11.
Gauri R. Pradhan Antje Engelhardt Carel P. van Schaik Dario Maestripieri 《Behavioral ecology and sociobiology》2006,59(3):333-343
Female copulation calls are mating-associated vocalizations that occur in some species of Old World monkeys and apes. We argue
that copulation calls have two immediate functions: to encourage mating attempts by other males and to increase mate guarding
by the consort male. We hypothesize that female copulation calls have evolved under the selective pressures of risk of infanticide
and sperm competition. When male mate guarding is effective, copulation calls allow females to concentrate paternity in dominant
males and benefit from their protection against the risk of infanticide. When mate guarding is ineffective, copulation calls
may bring genetic benefits to females through facilitation of sperm competition. We present a quantitative model in which
interspecific variation in females' promiscuity predicts their tendency to use copulation calls in conjunction with mating.
The model predicts that in species with little female promiscuity, copulation calls should be rare and exhibited only in association
with mating with dominant males. In species in which females are highly promiscuous, copulation calls should be frequent and
unrelated to male dominance rank. The limited data available to test the model support its main predictions as well as the
predicted relation between copulation calls and male dominance rank.
相似文献
Dario MaestripieriEmail: |
12.
Summary Copulation in Ischnura graellsii may be divided into three stages, according to the movements and position of the male's abdomen. We measured sperm volumes in males and females interrupted at different phases of copulation in laboratory-reared and field specimens. The results showed that males remove sperm from the female during stage I, and do not transfer sperm until stage Il of the copulation. In the field females interrupted during stage I of copulation had less sperm than postcopula females, and the volume of sperm in laboratory females mated once or twice was similar. These results suggest that males can remove most of the sperm during stage I of copulation. Preparations of in-copula specimens showed the horns of the penis (used to remove sperm) inside the bursa copulatoox and the spermatheca. Therefore males can remove sperm from both organs, in contrast to the other Ischnura species so far studied, where males can empty only the bursa. The length of these horns is positively correlated with male body length, and there are significant differences in length between the left and right horns of individual males. This suggests great variability in the male's ability to remove sperm. On the other hand, ejaculate volume is positively related to male and female size, and negatively to male age. Males are likely to be able to detect the presence of sperm in females: if the effect of population density and time of start of copulation are taken into account, copulations are longer with mated than with virgin females. Using genetic markers, sperm precedence was studied by rearing the female offspring of 6 females mated with two males of different genotype. In 5 out of 6 crosses, the second male fertilized all the eggs laid by the female in her first clutch. On average, the following clutches were progressively more fertilized by the first male, but there were striking differences between crosses. These differences are probably due to the variability in the amount of sperm transferred and/or removed.
Offprint requests to: A. Cordero 相似文献
13.
Christian Luis Rodriguez-Enriquez Eduardo Tadeo Juan Rull 《Behavioral ecology and sociobiology》2013,67(6):937-946
Postcopulatory processes can influence male reproductive success in several animal species. Females can use different mechanisms to bias male paternity after copulation. One of such mechanisms consists in expelling all or part of the ejaculate after copulation. Euxesta bilimeki is an Ulidiid fly whose females not only frequently expel ejaculates after mating but also consume the ejaculate after expulsion. In order to understand the significance of these behaviors we examined video recordings of courtship, copulatory, and postcopulatory behaviours. The presence of sperm in female storage organs was confirmed after mating with males of different sizes and was correlated with duration of courtship, copulation, and the period from the end of copulation to ejaculate expulsion. The effect of ejaculate consumption on female fitness (fecundity and longevity) was compared among females held under different dietary treatments: a rich diet consisting of protein, sugar and water, an intermediate diet composed of sugar and water, a poor diet of only water and females that were completely deprived of food and water. All of the observed females expelled ejaculates after mating. The probability of storing sperm in the two spermathecae and the ventral receptacle was correlated with interactions between the duration of all behaviours examined and male size. Except for starved females, who lived longer when allowed to consume ejaculates, ejaculate consumption had no effect on fitness. Results suggest that females can bias sperm storage according to male mating effort, while the consumed ejaculate had some nutritional value only evident when females were completely starved. 相似文献
14.
Sex allocation theory predicts that female birds with high-quality mates will benefit from producing more sons, since sons
will inherit their father’s superior traits and enjoy a great reproductive success, whereas females with low-quality mates
will benefit from producing more daughters, since the variance in reproductive success among daughters is typically lower.
The male attractiveness hypothesis may apply to extra-pair paternity (EPP) because socially monogamous females routinely mate
with higher quality males outside the pair bond. We test these predictions using the Tibetan ground tit (Pseudopodoces humilis), a sexually monomorphic, socially monogamous, facultatively cooperative breeder. There was greater variation in actual reproductive
success among males than females due to EPP. An excess of sons was detected for bi-parental (i.e., non-cooperative) broods
wherein EPP was mainly sired by bi-parental males. The pattern was attributed to male-biased sex ratios produced for both
EPP and within-pair offspring within the same broods. The reason for the latter case might be a random allocation of more
offspring to sons by the potentially EPP-exposed females that have an inability to control fertilization by specific males.
In cooperative broods where EPP mostly resulted from within-group helpers of presumed low-quality, as indicated by their failure
in acquiring a social mate, there was a non-significant tendency for EPP offspring to be daughters and for within-pair offspring
in the same broods to be unbiased. These results support the EPP-related male attractiveness hypothesis especially in terms
of the overproduction of sons. Offspring produced through quasi-parasitism was unbiased towards either sex, suggesting a weak
female choiceness with respect to the quality of host males. 相似文献
15.
We report a long-term study of offspring sex ratios in the cooperatively breeding superb fairy-wren Malurus cyaneus. Detailed study of this species had revealed a suite of potentially strong selection pressures on the sex ratio. First, females
gain substantial fitness benefits from the presence of helpers; so females without male helpers would benefit from any strategy
that increased the probability of recruiting help, such as overproduction of sons (local resource enhancement hypothesis),
but large numbers of helper males compete among themselves, favouring the production of daughters (local resource competition).
Second, daughters fledged early in the season have far greater chances of recruitment to the breeding population than late-fledged
daughters, so mothers would benefit from production of daughters early in the breeding season (early bird hypothesis). Third,
extra-group mate choice imposes strong sexual selection on males, suggesting that females mating with attractive sires could
benefit from investing in sons (sexual selection hypothesis). However, the predictions from these and other sex ratio hypotheses
were rejected. The only convincing evidence for manipulation of the sex ratio was a slight bias towards sons (11 sons to 10
daughters) that occurred regardless of context. This result does not support current theory. 相似文献
16.
Non-aggressive mate guarding by the blue-footed booby: a balance of female and male control 总被引:3,自引:1,他引:2
Thirteen pairs of blue-footed boobies (Sula nebouxii) were observed on their colony. Pairs courted frequently and, on average, copulated 24 times during the 30 days before laying,
with 38% of those copulations occurring in the last 5 days (presumed fertile period). Males and females increased attendance
at the nest site as laying approached. Seven females performed an average seven extra-pair copulations, with 1–2 paired male
neighbors, but these were less concentrated in the presumed fertile period than within-pair copulations, and the last two
copulations of all 7 females were with their social mates. Rates of female extra-pair copulations were six times lower when
their social mate was present, and during the presumed fertile period, no female performed an extra-pair copulation in the
presence of her mate. Males did not respond to infidelity of social mates with aggression, prompt copulation, retaliatory
copulation, or increase in copulation. Seven of 13 males performed an average of five extra-pair copulations, with 1–3 paired
female neighbors, before their own mates began egg-laying. The males' extra-pair copulations represented only 4% of their
total copulations during their own mates' presumed fertile periods. Females, the larger sex, apparently control sexual access
and copulate with extra males to achieve extra-pair fertilization. Males pursue a mixed strategy: they copulate with extra
females, mostly outside their own mate's presumed fertile period, and they copulate increasingly with their social mate as
laying approaches, probably assuring some paternity by mate guarding, involving attendance and courtship. Behavior of males
and females is also consistent with other hypotheses for extensive joint nest site attendance: pairbonding, copulation access,
and territory acquisition.
Received: 14 November 1997 / Accepted after revision: 16 May 1998 相似文献
17.
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
18.
Katrin Brauch Keith Hodges Antje Engelhardt Kerstin Fuhrmann Eric Shaw Michael Heistermann 《Behavioral ecology and sociobiology》2008,62(9):1453-1466
In a wide variety of species, male reproductive success is determined by contest for access to females. Among multi-male primate
groups, however, factors in addition to male competitive ability may also influence paternity outcome, although their exact
nature and force is still largely unclear. Here, we have investigated in a group of free-ranging Barbary macaques whether
paternity is determined on the pre- or postcopulatory level and how male competitive ability and female direct mate choice
during the female fertile phase are related to male reproductive success. Behavioural observations were combined with faecal
hormone analysis for timing of the fertile phase (13 cycles, 8 females) and genetic paternity analysis (n = 12). During the fertile phase, complete monopolisation of females did not occur. Females were consorted for only 49% of
observation time, and all females had ejaculatory copulations with several males. Thus, in all cases, paternity was determined
on the postcopulatory level. More than 80% of infants were sired by high-ranking males, and this reproductive skew was related
to both, male competitive ability and female direct mate choice as high-ranking males spent more time in consort with females
than low-ranking males, and females solicited copulations mainly from dominant males. As most ejaculatory copulations were
female-initiated, female direct mate choice appeared to have the highest impact on male reproductive success. However, female
preference was not directly translated into paternity, as fathers were not preferred over non-fathers in terms of solicitation,
consortship and mating behaviour. Collectively, our data show that in the Barbary macaque, both sexes significantly influence
male mating success, but that sperm of several males generally compete within the female reproductive tract and that therefore
paternity is determined by mechanisms operating at the postcopulatory level. 相似文献
19.
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
20.
Sexual cannibalism particularly before mating is costly for the male victim but also for the female aggressor if she risks
remaining unmated. The aggressive spillover hypothesis explains the persistence of this behavior as a maladaptive side effect
of positive selection on aggressiveness in a foraging context. The hypothesis predicts that the occurrence of sexual cannibalism
is explained by female aggressiveness but is not related to male phenotype or behavioral type. An alternative hypothesis invokes
sexual selection and makes the opposite prediction namely that sexual cannibalism is an expression of female choice and should
hence mainly target males of low quality. We tested the above hypotheses on a sexually dimorphic nephilid spider Nephilengys livida, known for male monopolization of females via genital damage, female genital plugging, and mate guarding, by staging mating
trials during which we recorded mating behaviors and occurrences of pre- and postcopulatory cannibalism. We did not restrict
assessment of aggressiveness to the mating and foraging context but also included aggression against same sex conspecifics.
To assess female personalities, i.e., consistent individual differences in behavior including aggressiveness, we repeatedly
tested them for intra-sex aggression, voracity towards prey, locomotory activity, and boldness. Females exhibited consistent
differences in intra-sex aggressiveness, latency to attack prey, and boldness. Aggressive females had shorter latencies to
attack prey and were more active than non-aggressive ones. In contrast to the predictions of the aggressive spillover hypothesis,
females that were aggressive towards prey and towards other females were not more likely to attack a male than non-aggressive
females. In support of the mate choice hypothesis, less aggressive males were more likely attacked and cannibalized than more
aggressive ones. This hints at sexual selection for aggressiveness in males and raises the question of mechanisms that maintain
variation in male aggressiveness. 相似文献