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1.
Since genital morphology can influence the outcome of post-copulatory sexual selection, differences in the genitalia of dominant
and subordinate males could be a factor contributing to the fertilisation advantage of dominant males under sperm competition.
Here we investigate for the first time if penile morphology differs according to male social status in a promiscuous mammal,
the bank vole (Myodes glareolus). In this species, dominant males typically achieve higher reproductive success than subordinates in post-copulatory sexual
selection, and male genital morphology is complex, including both a baculum (os penis) and penile spines. Our results show
that despite no difference in body size associated with male social status, baculum width is significantly larger in dominant
male bank voles than in subordinates. We also found evidence of positive allometry and a relatively high coefficient of phenotypic
variation in the baculum width of male bank voles, consistent with an influence of sexual selection. By contrast, baculum
length and three measures of penile spinosity did not differ according to male social status or show evidence of positive
allometry. We conclude that dominant male bank voles may benefit from an enlarged baculum under sperm competition and/or cryptic
female choice and that differences in penile morphology according to male social status might be important but as yet largely
unexplored source of variation in male reproductive success. 相似文献
2.
Parker's seminal work brought attention to the possibility of postmating sexual selection by non-random fertilization success.
Mechanisms for these processes are still only partly understood and there is clearly a need for more studies of intraspecific
variation in sperm precedence. Here, we report results from an experimental study of the variation in fertilization success
between males of the water strider Gerris lacustris. Genital morphology, male body size, and copulation duration were examined as possible correlates of paternity. The significance
of guarding duration was also analysed. Only male genital morphology was correlated to fertilization success. This is one
of the first studies showing a relationship between male genital traits and fertilization success, supporting the view that
sexual selection may be responsible for the rapid and divergent evolution of genital structures in animals with internal fertilization.
The fertilization success of last males varied considerably after double matings with a short mating interval (10 min). Last-male
priority ranged from 0 to 100% and usually one of the males involved fertilized almost all the eggs. After double matings
with a short mating interval, the proportion of eggs fertilized by the last male averaged 0.68 and was greater than 0.5. In
contrast, the average fertilization success was biased towards the first male when the matings were more spread out over time
(24 h). These results do not support earlier suggestions of a widespread last-male sperm priority in water striders.
Received: 28 July 1998 / Received in revised form: 15 March 1999 / Accepted: 28 March 1999 相似文献
3.
Stefan H. Nessler Gabriele Uhl Jutta M. Schneider 《Behavioral ecology and sociobiology》2009,63(3):355-362
Sperm competition is a potent driving force in evolution leading to a remarkable variety of male adaptations that prevent
or reduce fertilization by rivals. An extraordinary defensive strategy against sperm competition has evolved in a number of
web spiders where males break off parts of their paired genitalia in order to obstruct the copulatory openings of females
(mating plug). A recent comparative analysis on the family level reports that genital damage is most frequent in species with
sexual cannibalism although, as yet, a functional association between sexual cannibalism and genital damage has not been found.
Using the moderately sexually cannibalistic orb-web spider Argiope lobata, we show for the first time that males cannibalized during their first copulation damaged their pedipalps with significantly
higher probability (74%) than males that escaped (15%). Of all males that damaged their genitalia, 44% were able to place
a genital fragment inside the copulatory opening of the female, resulting in a relatively low total plugging rate of 14%.
Successful obstruction of the female copulatory opening reduced the share of paternity of subsequent males (P
2 = 0.06%), thus, indicating that genital damage may have evolved as a response to sperm competition in this species as well.
However, the low incidence of successful plugging and the strong relationship between sexual cannibalism and genital damage
suggest that apart from paternity protection, the nature of genital damage in A. lobata is further shaped by sexual conflict or cryptic female choice. 相似文献
4.
Oddmund Kleven Frode Jacobsen Rasa Izadnegahdar Raleigh J. Robertson Jan T. Lifjeld 《Behavioral ecology and sociobiology》2006,59(3):412-418
In socially monogamous species, extra-pair paternity has the potential to increase the variance in male reproductive success,
thereby affecting the opportunity for sexual selection on male extravagant ornamentation. In the European barn swallow (Hirundo rustica rustica), the tail streamer length is a sexually selected male ornament and an honest indicator of viability. The North American
barn swallow (Hirundo rustica erythrogaster) also shows sexual dimorphism in tail streamer length, but whether this trait holds the same signalling function in this
subspecies is a controversial issue, and the available literature is presently scarce. Here, we present data on paternity
in the North American barn swallow, including a complete sampling of extra-pair sires in four colonies. We analysed how extra-pair
paternity affected the variance in male fertilization success and examined whether male tail streamer (i.e. the outermost
tail feather) length correlated with fertilization success (n=86 males). Extra-pair paternity constituted 31% of all offspring and significantly increased the variance in male fertilization
success. The number of offspring sired by extra-pair males accounted for almost half of the total variance in male fertilization
success. Males with naturally long tail streamers had a higher fertilization success than males with shorter tail streamers,
and this pattern was mainly caused by a higher extra-pair success for males with long tail streamers. Males with long tail
streamers also paired with early breeding females in prime body condition. These results are consistent with the idea that
there is directional sexual selection on male tail streamer length, possibly mediated through male extra-pair mating success
or the timing of breeding onset. 相似文献
5.
Gregory I. Holwell Claire Winnick Tom Tregenza Marie E. Herberstein 《Behavioral ecology and sociobiology》2010,64(4):617-625
The rapid divergence of male genitalia is a widely observed evolutionary phenomenon. Although sexual selection is currently
regarded as providing the most likely driving force behind genital diversification, the mechanisms responsible are still debated.
Here, we investigate the relationship between male genital morphology and sperm transfer in the praying mantid Ciulfina klassi using geometric morphometrics. The shape of male genitalia in C. klassi influenced sperm transfer duration and the number and proportion of sperm transferred, suggesting that genital morphology
is under sexual selection in this species. Genital size however was not correlated with any aspect of sperm transfer. Intriguingly,
two of the major genital shape components correlated positively with the number of sperm transferred, but negatively with
sperm transfer duration. Hence, males that most effectively transfer sperm to the female spermatheca do so in a relatively
short period of time. A direct negative relationship was also found between sperm transfer duration and sperm transfer success.
Overall, our study suggests that the variable genital shape of Ciulfina may have been selected for more efficient sperm transfer. 相似文献
6.
Antje Engelhardt Michael Heistermann J. Keith Hodges Peter Nürnberg Carsten Niemitz 《Behavioral ecology and sociobiology》2006,59(6):740-752
One of the basic principles of sexual selection is that male reproductive success should be skewed towards strong males in
species with anisogamous sex. Studies on primate multi-male groups, however, suggest that other factors than male fighting
ability might also affect male reproductive success. The proximate mechanisms leading to paternity in multi-male primate groups
still remain largely unknown since in most primate studies mating rather than reproductive success is measured. Furthermore,
little research focuses on a female’s fertile phase. The aim of this study was to investigate the relative importance of male
monopolisation and female direct mate choice for paternity determination. We also investigated the extent to which paternity
was decided post-copulatory, i.e. within the female reproductive tract. We used a combined approach of behavioural observations
with faecal hormone and genetic analysis for assessment of female cycle stage and paternity, respectively. The study was carried
out on a group of wild long-tailed macaques living around the Ketambe Research Station, Gunung Leuser National Park, Indonesia.
Our results suggest that both male monopolisation and post-copulatory mechanisms are the main determinants of male reproductive
success, whereas female direct mate choice and alternative male reproductive strategies appear to be of little importance
in this respect. Female cooperation may, however, have facilitated male monopolisation. Since paternity was restricted to
alpha and beta males even when females mated with several males during the fertile phase, it seems that not only male monopolisation
but also post-copulatory mechanisms may operate in favour of high-ranking males in long-tailed macaques, thus reinforcing
the reproductive skew in this species. 相似文献
7.
Determinants of paternity success in the spider Pholcus phalangioides (Pholcidae: Araneae): the role of male and female mating behaviour 总被引:1,自引:0,他引:1
In double mating experiments, we examined whether and to what extent various male and female behavioural traits influence
the course of mating and fertilization success in the cellar spider. In males, we focussed on pre-copulatory behaviour and
on the rhythmic twisting movements that the male performs with his pedipalps during copulation. In females, we investigated
remating decisions and the effect of female termination of copulation. Second males fertilized a high proportion of the eggs
(P
2: median 89%) despite much shorter second matings, with high variation in relative paternity success. The number of pedipalp
movements (PPMs) of either male was a better predictor of paternity than copulation duration. Our results suggest that in
second matings, PPMs help to remove sperm from previous males, whereas in first matings a high number of PPMs enhances fertilization
success, either due to numerical sperm competition or cryptic female choice. Furthermore, we found a negative male age effect
on paternity in second matings, implying that age-related deterioration of spermatozoa may promote variation in fertilization
success. Female receptivity decreased significantly in second matings; only 70% of the females remated. Females that accepted
a second copulation were found to terminate these much earlier and with higher probability than first matings. This suggests
that the intensity of conflict between the sexes is higher in second matings. Increased intensity of sexual conflict may be
responsible for stronger selection on male traits, as pre-copulatory behaviour and age only affected male copulatory performance
and paternity in second matings.
Electronic Publication 相似文献
8.
Ståle Liljedal Geir Rudolfsen Ivar Folstad 《Behavioral ecology and sociobiology》2008,62(11):1805-1811
In postcopulatory sexual selection both sperm competition and cryptic female choice are considered to be important selective
agents, but their relative importance for male fertilization success has received little attention. We tested whether sperm
quality, male spawning coloration, male heterozygosity, and genetic overlap with the female explained a male’s fertilization
success in controlled in vitro fertilization competition trials between equal numbers of sperm from pairs of male Arctic charr
(Salvelinus alpinus), an external fertilizer. Offspring were genotyped to determine each males’ share of paternity. The velocity of a male’s
sperm relative to the velocity of the competing male’s sperm was the best predictor of male fertilization success. Yet, sperm
velocity was not related to spawning coloration or male heterozygosity. In fact, the most brightly colored male in a pair
had the lowest fertilization probability. This could result from cryptic female choice for pale males, but might rather be
a result of paler males producing more competitive sperm than more colored males. Furthermore, the more microsatellite alleles
a male shared with the female relative to the competing male, the higher fertilization success he had. We argue that this
latter may be an effect of assortative cryptic female choice, which might prevent hybridization with sympatric Arctic charr
morphs or one form of kin selection. 相似文献
9.
The number of eggs fertilized by a male at any given copulation (fertilization success) is affected by a large number of factors. Male insemination and sperm competition success and various female structures and/or processes that bias paternity in favor of some males over others (cryptic female choice) are all likely to affect fertilization success. We suggest that more comprehensive measures of male fertilization success can increase our understanding of postcopulatory sexual selection. To improve our understanding of the importance of various sources of variance in male fertilization success, we conducted a series of experiments using flour beetles. Different wild-type strains were used in reciprocal double mating experiments, against a phenotypic marker strain. We assessed the relative effects of female genotype, male genotype and mating order on independent and inclusive measures of male defense ability ( P 1), male offense ability ( P 2), and female remating behavior. Female genotype influenced both P 1 and P 2, and male genotype interacted strongly with female genotype in its effect on P 2. We also documented an interaction between female and male genotypes in the effects of mating on female remating behavior, such that females tended to remate most rapidly when mated to males of their own genotype. It is clear from our experiments that cryptic female choice influences the pattern of fertilization success in flour beetles, and we suggest that cryptic female choice may often be an important component of postcopulatory sexual selection. Future investigations would benefit from studying the multiple components of variance in male fertilization success. 相似文献
10.
A comprehensive understanding of sexual selection requires knowledge of the traits and mechanisms responsible for increasing a male’s paternity share (proportion of progeny sired) relative to that of other males mating with the same female. In this study we manipulated by starvation the expression of traits that might influence male paternity share in Tribolium castaneum. We then conducted experiments to examine how male starvation affects male performance during sequential episodes of sexual selection from mating to progeny production, and investigated female control over specific stages by using live vs dead females. Comparison of starved vs fed males revealed that T. castaneum females have control over spermatophore transfer during mating, as live females rejected inseminations by starved (“low quality”) males. None of the measured male copulatory behaviors (leg-rubbing frequency, asymmetry, and percent of time spent rubbing) affected the probability of successful insemination, but the last two were positively associated with male paternity share. Spermatophore positioning within the female reproductive tract was not affected by male treatment (starved/fed), by female treatment (live/dead), or by male copulatory behaviors. Starvation, however, had a dramatic effect on male reproductive physiology, decreasing both accessory gland size and total number of sperms transferred (but not sperm viability in seminal vesicles). In addition, females who mated to starved males stored fewer sperms in their spermathecae, which, together with decreased ejaculate size, may explain the reduced paternity share of starved males compared to fed males. This study elucidates some cryptic mechanisms influencing male reproductive success and aids our understanding of trait evolution through sexual selection. 相似文献
11.
Sperm competition and the level of polyandry in a bushcricket with large nuptial gifts 总被引:4,自引:0,他引:4
Variation in paternity due to sperm competition or post-copulatory female choice has a major influence on animal mating system evolution and on the levels of genetic variability in natural populations. However, there are relatively few studies comparing the outcome of sperm-competition experiments in the laboratory with natural variation in polyandry among families from the field. In the bushcricket Ephippiger ephippiger, females mate multiply, and the males provide them with a large, nutritious, and probably expensive, donation at mating. We examined paternity in a series of laboratory matings, where females mated with two males, and amongst a series of families collected from a natural population. In the laboratory, paternity was highly bimodally distributed: 24% of families had offspring fathered by the first male to mate, 68% by the second male (in only 8% was paternity shared). In the field, paternity was more mixed: only 27% of families had a single father, 14% had more than two fathers, whilst 59% had two fathers. While unsuccessful matings may contribute to the highly biased paternity in the laboratory, they cannot fully explain the high incidence of complete P2 families. Nonrandom sperm utilisation is therefore likely. Greater sperm mixing in the field probably results from females mating with more males, but the distribution of paternity also reflects an active process of nonrandom sperm utilisation. Confidence of paternity due to last male advantage may be relatively high in this species, and therefore may have facilitated the evolution of the large spermatophore in E. ephippiger.Communicated by D. Gwynne 相似文献
12.
Sperm competition and sexual selection: a meta-analysis of paternity studies of birds 总被引:8,自引:0,他引:8
Sperm competition (the competition among the sperm of different males for fertilization of the eggs of a female) has been
suggested to be an important component of sexual selection, but no general assessment has been made of this proposition. We
used a meta-analytic approach to assess the extensive literature on paternity (the proportion of offspring in a focal nest
sired by an attending male) in birds based on allozyme and molecular techniques. The relative variance in male mating success
was on average increased by a factor of 4.6 over the variance in apparent male success. Males with more extravagant secondary
sexual characters had higher paternity in their own nests than less adorned males. There was a weak effect of male age being
positively associated with paternity in own nests. Male body size measured as the length of wing and tarsus was weakly positively
associated with paternity in own nests. Male survival prospect was positively associated with paternity in own nests. Polygynous
males generally had decreased paternity of their broods compared to monogamous males. Paternity of the resident male decreased
with increasing population density and breeding asynchrony. The intensity of paternity guards such as within-pair copulation
rate and mate guarding were not significantly related to extra-pair paternity. Sperm competition was thus an important component
of sexual selection by increasing the variance in male mating success, and by being associated with the expression of secondary
sexual characters, in particular in dense and asynchronously breeding populations of birds.
Received: 12 February 1998 / Accepted after revision: 31 May 1998 相似文献
13.
Lifjeld JT Kleven O Jacobsen F McGraw KJ Safran RJ Robertson RJ 《Behavioral ecology and sociobiology》2011,65(9):1687-1697
When males become more ornamented and reproduce more successfully as they grow older, phenotypic correlations between ornament
exaggeration and reproductive success can be confounded with age effects in cross-sectional studies, and thus say relatively
little about sexual selection on these traits. This is exemplified here in a correlative study of male fertilization success
in a large colony of American barn swallows (Hirundo rustica erythrogaster). Previous studies of this species have indicated that two sexually dimorphic traits, tail length and ventral plumage coloration,
are positively correlated with male fertilization success, and a mechanism of sexual selection by female choice has been invoked.
However, these studies did not control for potential age-related variation in trait expression. Here, we show that male fertilization
success was positively correlated with male tail length but not with plumage coloration. We also show that 1-year-old males
had shorter tails and lower fertilization success than older males. This age effect accounted for much of the covariance between
tail length and fertilization success. Still, there was a positive relationship between tail length and fertilization success
among older males. But as this group consisted of males from different age classes, an age effect may be hidden in this relationship
as well. Our data also revealed a longitudinal increase in both tail length and fertilization success for individual males.
We argue that age-dependent ornament expression and reproductive performance in males complicate inferences about female preferences
and sexual selection. 相似文献
14.
Vedder O Komdeur J van der Velde M Schut E Magrath MJ 《Behavioral ecology and sociobiology》2011,65(4):741-752
Polygyny and extra-pair paternity are generally thought to enhance sexual selection. However, the extent to which these phenomena
increase variance in male reproductive success will depend on the covariance between success at these two strategies. We analysed
these patterns over four breeding seasons in facultatively polygynous blue tits Cyanistes caeruleus. We found that both polygyny and extra-pair paternity increased variance in male reproductive success and that standardised
variance in annual number of genetic fledglings was 2.6 times higher than standardised variance in apparent success when assuming
strict monogamy. Nevertheless, male success at securing within-pair paternity was unrelated to success at gaining extra-pair
paternity and, when considering the positive effect of age on extra-pair success and attracting a second female, polygynous
males were no more likely to sire extra-pair fledglings. Overall, polygynous males fledged more genetic offspring than monogamous
males, but first-year polygynous males lost a greater share of within-pair paternity. A literature review suggests that this
adverse effect of polygyny on within-pair paternity is frequent among birds, inconsistent with the prediction that females
engage in extra-pair copulation with successful males to obtain good genes. Furthermore, a male's share of paternity was repeatable
between years, and among females of polygynous males within years, such that a compatibility function of extra-pair copulations
was likewise unsupported. Instead, we suggest that the observed patterns are most consistent with a fertility insurance role
for extra-pair copulations, which does not exclude the greater opportunity for sexual selection through differential ability
of males to gain paternity. 相似文献
15.
Emily R. A. Cramer Terje Laskemoen Oddmund Kleven Katie LaBarbera Irby J. Lovette Jan T. Lifjeld 《Behavioral ecology and sociobiology》2013,67(11):1845-1853
Postcopulatory sexual selection (PCSS) in internally fertilizing vertebrates is a topic of great interest, yet relatively little is known about the characteristics of sperm and ejaculates that confer an advantage in PCSS. In this study, we investigated several measures of sperm morphology that potentially contribute to fertilization success under PCSS. We tested whether sperm morphology related to success in PCSS (via extra-pair paternity) in house wrens (Troglodytes aedon). We found no evidence that sperm morphology differed between extra-pair sires and the within-pair males they cuckolded, nor that sperm morphology correlated with the proportion of within-pair offspring sired, the number of extra-pair offspring sired, or the total annual reproductive success. Male behavioral strategies may affect the probability that their sperm compete with other males’ sperm and that their sperm succeed under competition. Effects of these behavioral strategies, as well as differences between males in sperm number, could mask the effects of sperm morphology on the outcome of PCSS. Despite moderate levels of extra-pair paternity, selection on sperm may be relatively weak in house wrens. Further work is needed to understand general patterns in how sperm morphology relates to fertilization success within species. 相似文献
16.
The Shiner Perch (Cymatogaster aggregata Gibbons) exhibits a viviparous reproductive mode and long-term female sperm storage, two biological features that may predispose
this fish species for both intense sperm competition and frequent multiple paternity within broods. To test these hypotheses,
we used polymorphic microsatellite markers to identify sires and quantify paternal contributions to the progeny arrays of
27 pregnant females from a natural population of C. aggregata. The number of sires per brood ranged from one to eight (mean 4.6), typically with skewed distributions of fertilization
success by the fathers but no correlation between sire number and brood size. The extraordinarily high incidences of multiple
paternity in this species probably are due in part to high rates of mate encounter, but selection pressures related to the
avoidance of maternal–fetal incompatibility may further have promoted the evolution of polyandrous mating behaviors in this
female-pregnant species. Our genetic data are consistent with the hypothesis that viviparity, long-term sperm storage, and
extreme polyandry are interrelated reproductive phenomena that should promote the evolution of post-copulatory sperm competition
and/or cryptic female choice in these fishes. 相似文献
17.
Sperm competition or sperm selection: no evidence for female influence over paternity in yellow dung flies Scatophaga stercoraria 总被引:2,自引:0,他引:2
L. W. Simmons P. Stockley R. L. Jackson G. A. Parker 《Behavioral ecology and sociobiology》1996,38(3):199-206
Recent studies of non-random paternity have suggested that sperm selection by females may influence male fertilization success.
Here we argue that the problems originally encountered in partitioning variation in non-random mating between male competition
and female choice are even more pertinent to interpreting patterns of non-random paternity because of intense sperm competition
between males. We describe an experiment with the yellow dung fly, Scatophaga stercoraria, designed to partition variance in the proportion of offspring sired by the second male, P
2, between males and females, and to control for sperm competition. Large males were shown to have a higher P
2 than small males but P
2 was independent of the size of the female’s first mate. This result might suggest an absolute female preference for large
males via sperm selection. However, large males have a higher constant rate of sperm transfer and displacement. After controlling
for this effect of sperm competition, large males did not achieve higher paternity than small males. We argue that a knowledge
of the mechanism of sperm competition is essential so that male effects can be controlled before conclusions are made regarding
the influence of sperm selection by females in generating non-random paternity.
Received: 4 April 1995 / Accepted after revision: 17 October 1995 相似文献
18.
Ben C. Sheldon Pete Davidson Gabriella Lindgren 《Behavioral ecology and sociobiology》1999,46(3):141-148
There is increasing evidence that sexual selection may be intense even in socially monogamous birds, resulting from both
mate choice and sperm competition. We studied these two modes of sexual selection experimentally by removing paired male collared
flycatchers, Ficedula albicollis, from their mates for 2 days and investigating the factors that influenced the likelihood of a replacement male appearing
and how the removals influenced paternity. Replacement males (usually neighbouring males) appeared at 81% (n = 37) of nests where males were removed. The likelihood of this appearance was unaffected by the probable reproductive value
of the female's clutch to the replacing male. A replacement was, however, less likely when the original male had a large forehead
patch, a trait previously shown to be subject to sexual selection in this population. Experimental removal of males increased
the level of sperm competition: 74% of experimental broods were multiply sired, compared to 29% of unmanipulated broods in
a previous study. Only two factors predicted how paternity was shared between males: removed males fathered more young if
removed closer to laying, and if they had larger forehead patches. The former result is consistent with last-male sperm precedence
determining paternity, whereas the latter adds to other evidence that forehead patch size is the target of female preference
in this species. Our results suggest that females exert some control over male replacement, and also that they may influence
the fertilisation success of males by behavioural means.
Received: 15 July 1998 / Received in revised form: 16 March 1999 / Accepted: 28 March 1999 相似文献
19.
The theory of life history evolution assumes trade-offs between competing fitness traits such as reproduction, somatic growth,
and maintenance. One prediction of this theory is that if large individuals have a higher reproductive success, small/young
individuals should invest less in reproduction and allocate more resources in growth than large/old individuals. We tested
this prediction using the common toad (Bufo bufo), a species where mating success of males is positively related to their body size. We measured testes mass, soma mass, and
sperm stock size in males of varying sizes that were either (1) re-hibernated at the start of the breeding season, (2) kept
without females throughout the breeding season, or (3) repeatedly provided with gravid females. In the latter group, we also
estimated fertilization success and readiness to re-mate. Contrary to our predictions, the relationship between testes mass
and soma mass was isometric, sperm stock size relative to testes mass was unrelated to male size, fertilization success was
not higher in matings with larger males, and smaller males were not less likely to engage in repeated matings than larger
males. These results consistently suggest that smaller males did not invest less in reproduction to be able to allocate more
in growth than larger males. Causes for this unexpected result may include relatively low year-to-year survival, unpredictable
between-year variation in the strength of sexual selection and low return rates of lowered reproductive investment. 相似文献
20.
The operational sex ratio (OSR) may influence the intensity of competition for mates and mate choice and is therefore thought
to be a major factor predicting the intensity and direction of sexual selection. We studied the opportunity for sexual selection,
i.e., the variance in male reproductive success and the direction and intensity of sexual selection on male body mass in bank
vole (Clethrionomys glareolus) enclosure populations with experimentally manipulated sex ratios. The opportunity for sexual selection was high among male-biased
OSRs and decreased towards female-biased OSRs. Paradoxically, selection for large male body mass was strongest in female-biased
OSRs and also considerable at intermediate OSRs, whereas at male-biased OSRs, only a weak relationship between male size and
reproductive success was found. Litters in male-biased OSRs were more likely to be sired by multiple males than litters in
female-biased OSRs. Our results suggest that the intensity and direction of sexual selection in males differs among different
OSRs. Although the direction of sexual selection on male body mass was opposite than predicted, large body mass can be favored
by sexual selection. Naturally varying OSRs may therefore contribute to maintain variation in male sexually selected traits. 相似文献