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1.
Comparative analyses have found that relative testis size is a strong predictor of the prevalence of sperm competition for many taxa, including mammals, yet underlying this pattern is the assumption that intraspecific variation in testis size is related to individual fitness. Because intraspecific variation in ejaculate investment underlies interspecific patterns, it is critical to understand the causes and consequences of intraspecific variation in ejaculate investment. We examined relationships between ejaculate investment (testis size and sperm length) and reproductive success, body size and condition in the yellow-pine chipmunk (Tamias amoenus), a small ground squirrel in which sperm competition occurs. We examined genetic estimates of male reproductive success from a wild population of yellow-pine chipmunks and determined that males with large testes had higher annual reproductive success than males with small testes. This result provides empirical support for the numerous comparative studies that indicate testis size is associated with the intensity of sperm competition. In addition, males in good condition had relatively larger testes than males in poor condition, but there was no evidence of sperm length being dependent on condition. Finally, contrary to many predictions, males that invested more in sperm production (relatively heavy testes) produced shorter sperm, not longer sperm, than males that invested less.Communicated by P.M. Kappeler 相似文献
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3.
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
4.
In species where males use alternative reproductive tactics and male phenotypes are confronted with different risks of sperm
competition, theory predicts that between-male-type differences in sperm expenditure may evolve. In the frog Crinia georgiana big males can monopolize females, whereas small males often engage in polyandrous matings. Consequently, big males may experience
a lower risk of sperm competition than do small males. We tested if the predictions from theoretical models can be applied
to the mating system of C. georgiana. Our results showed that small males do not have larger testes relative to their body size compared to their larger counterparts
and that the efficiency with which sperm number, size, motility, and longevity are produced by the testes does not differ
between small and large males in the predicted way. These results are not in alignment with predictions from a loaded raffle
model of sperm competition on sperm expenditure in males with alternative phenotypes. The plasticity in mating tactics used
by C. georgiana males and a high intraseasonal variation in male densities may have prevented the evolution of enhanced sperm performance
in smaller males. A fair raffle in the sperm competition game played by C. georgiana males could also explain the observed patterns in sperm traits. Future investigations determining the parameters responsible
for the deviation from theoretical predictions in this system will test the degree to which current theoretical models can
indeed be applied to species with plastic reproductive tactics. 相似文献
5.
Experience affects mating behavior, but does not impact parental reproductive allocation in a lizard
Daniel A. Warner Clint D. Kelly Matthew B. Lovern 《Behavioral ecology and sociobiology》2013,67(6):973-983
Investment into reproduction is influenced by multiple factors and varies substantially between males and females. Theory predicts that males should adjust their ejaculate size or quality in response to variation in female experience or phenotypic quality. In addition, sperm investment by males may also be influenced by their own status and experience. Although such adjustments of male ejaculate size can impact reproductive success (via fertilization success), fitness returns from male sperm investment may be influenced (either limited or facilitated) by the level of maternal investment. To test this hypothesis, we conducted an experiment that simultaneously evaluated the effect of paternal and maternal experience (which incorporates mating status, age, body size, and other related variables) on paternal sperm investment and maternal reproductive allocation in the lizard Anolis sagrei. During staged mating trials, experienced males were more likely to copulate with females, but these individuals were less likely to transfer sperm during mating than were naïve individuals. Maternal experience had no impact on these mating behaviors. In contrast to expectations, experience and phenotypic quality (of both sexes) had no impact on male ejaculate size or quality (proportion of live sperm) or on maternal reproductive investment (in terms of egg size and yolk steroids). These findings were intriguing given the mating system and past evidence for differential maternal investment in relation to sire quality in A. sagrei. The results found in this study highlight the complexity of reproductive investment patterns, and we urge caution when applying general conclusions across populations or taxa. 相似文献
6.
Testes mass in megachiropteran bats varies in accordance with sperm competition theory 总被引:4,自引:0,他引:4
D. J. Hosken 《Behavioral ecology and sociobiology》1998,44(3):169-177
Sperm competition is a widespread phenomenon influencing a range of characters, including investment in gonadal tissue. Conspecific
proximity is one factor which can influence the risk of sperm competition and hence testicular investment, and decreased confidence
of paternity may be one cost of group living. Aspects of female biology may also influence spermatogenic investment and sperm
morphology. This study examines the associations between relative testes mass and roost-group size across 17 species of Megachiroptera.
Associations between breeding season duration and investment in spermatogenesis are also examined, as are associations between
female reproductive tract dimensions and testes mass and dimensions of spermatozoa across all bats. Relative testes mass was
significantly positively associated with roost-group size at a species level and after appropriate phylogenetic control (pairwise
comparisons and comparison of independent contrasts). There were no significant relationships between breeding season duration
and relative testes mass. Across all bats, neither testes mass nor sperm length were significantly related to dimensions of
the female tract. The results are discussed in the context of sperm competition.
Received: 7 January 1998 / Accepted after revision: 8 August 1998 相似文献
7.
Norman Owen-Smith 《Behavioral ecology and sociobiology》1993,32(3):177-184
Summary Size dimorphism with males larger than females has been related to the benefits for males of enhanced dominance and hence reproductive success. However, mating gains must outweigh the fitness costs of deferred reproduction and the mortality associated with further growth. The relationships between male age, size and reproduction were assessed for greater kudus (Tragelaphus strepsiceros) in the Kruger National Park in South Africa. Individually identifiable animals were monitored over 10 years, with detailed observations made during six breeding seasons. In the non-breeding season males formed loose all-male groups. Horn grappling and low intensity agonistic interactions fostered dominance rankings. Dominance was age-graded, until males reached full weight at 6 years of age. Males aged 6 and 7 years monopolized courtship and mating, but 5-year-old males secured about 10% of mating opportunities. Few males survived beyond 7 years. Male mortality rate rose steeply with age, so that the functional sex ratio of fertile females per mature male was about 14:1. During the breeding season many female groups remained unattended by a mature male. Reproductive sorting among males occurred largely through variation in survival to full size and maturity. Increased size enhances fighting success and hence dominance. Further growth ceases when the functional sex ratio exceeds the number of mating opportunities that males can effectively achieve during a breeding season. Predation amplifies the mortality cost of continued growth. In the absence of large predators, male-male interactions may be atypically exaggerated. 相似文献
8.
Noboru Okuda Tomohiro Takeyama Yasunobu Yanagisawa 《Behavioral ecology and sociobiology》1997,41(6):363-369
Entire-brood cannibalism by mouthbrooding males of the cardinal fish Apogon doederleini was investigated in temperate waters of southern Japan during two breeding seasons. The rate of cannibalism was 17–18% in
each season and did not differ among age-groups. However, the seasonal pattern of cannibalism differed markedly among age-groups:
young (1- and 2-year-old) males frequently cannibalized early broods, especially the first brood, of the season, whereas cannibalism
by middle-aged (3- and 4-year-old) and old (5- and 6-year-old) males mainly occurred late in the breeding season. We explain
this difference in terms of trade-offs between current and future reproduction. Young males, whose future reproductive success
is enhanced by the growth increment, may allocate more time and energy to growth by cannibalizing early broods. In contrast,
for older males who have had more breeding cycles and grow little, cannibalism could be a way to reverse the deterioration
in their somatic condition that occurs as the breeding season progresses. It is also likely that the current reproductive
loss entailed by the cannibalism is effectively compensated by quick re-mating with another female.
Received: 24 February 1997 / Accepted after revision: 20 July 1997 相似文献
9.
Geir Rudolfsen Rudolf Müller Davnah Urbach Claus Wedekind 《Behavioral ecology and sociobiology》2008,62(4):561-567
The mating behavior and reproductive strategies of Alpine whitefish like Coregonus zugensis (Nüsslin) are poorly understood, probably because they spawn in deep water where direct observations are difficult. In this
study, we interpret life-history and sperm quality traits of fish that we caught from their spawning place. We found that
males invest heavily into gonadal tissue (up to 5.6% of their body weight), which is, in comparison to other fish, consistent
with external fertilization, distinct pairing and moderate to high communal spawning, or no pairing and low to moderate communal
spawning. Sperm competition theory and recent experimental studies on other salmonids predict that males optimize ejaculate
characteristics in relation to the costs of sperm and the level of competition they have to expect: dominant males are predicted
to invest less into ejaculate quality and to have slower spermatozoa than subdominant males. We found that spermatozoa of
older males are slower than those of younger males. Moreover, older males have larger breeding tubercles, a secondary sexual
trait that has, in some previous studies, been found to be linked to good condition and to good genetic quality. Our results
suggest that C. zugensis has age-linked reproductive strategies, that multimale spawning is common, i.e., that sperm competition plays a significant
role, and that older males are on average dominant over younger males at the spawning place. 相似文献
10.
Karen M. Cogliati Bryan D. Neff Sigal Balshine 《Behavioral ecology and sociobiology》2013,67(3):399-408
In many mating systems, males adopt alternative reproductive tactics (ARTs) to maximize reproductive success. In fishes, guarding males often invest more energy into courtship, defense, and paternal care, whereas cuckolding males forego such costs and steal fertilizations by releasing their sperm in the nest of a guarding male. These two tactics have been documented in the plainfin midshipman fish (Porichthys notatus), yet the relative reproductive success of the guarding and cuckolding male tactics remains unknown. In this study, we used microsatellite markers to determine the level of paternity of the guarding type I males. We explored how paternity varied with male phenotype and across the breeding season. Our results revealed the lowest documented levels of paternity in a species with obligate paternal care. Although paternity remained consistently low, it did increase as the breeding season progressed. Male body size did not significantly predict paternity. The low paternity in this species may be explained, in part, by aspects of their reproductive ecology including the duration of parental care period, limited nest availability and competition for nests, as well as the occurrence of nest takeovers. Overall, our findings contribute to the understanding of the ultimate factors underlying ARTs in this species and highlight the importance of investigating reproductive success across the entire breeding season. 相似文献
11.
Sperm allocation in an uncertain world 总被引:3,自引:0,他引:3
Models of optimal sperm allocation are constructed using stochastic dynamic programming techniques, yielding predictions
about sperm allocation when males mate sequentially, breeding time is finite, sperm stores are limited and females vary in
quality. The models suggest that uncertainty of future reproductive opportunities should favour withholding of sperm, so that
males tend to allocate less (for a given level of stored sperm) earlier in the breeding season. This effect is more pronounced
the greater the variance in female quality. We also show that while allocation will be influenced by mate value, it is not
necessarily optimal to allocate preferentially to high-quality females, since the benefits of a higher-quality mate may be
offset by increased risk of rejection of sperm or higher sperm competition. The relationship between mate quality and level
of allocation will depend strongly on the amount of remaining stored sperm, with males whose supplies are depleted being more
likely to favour lower-quality partners.
Received: 12 September 1997 / Accepted after revision: 28 June 1998 相似文献
12.
Filippo Galimberti Simona Sanvito Chiara Braschi Luigi Boitani 《Behavioral ecology and sociobiology》2007,62(2):159-171
Reproductive effort is a key parameter of life history because it measures the resources allocated to reproduction at the
expense of growth and maintenance. Male reproductive effort always had a minor role with respect to female effort both in
the development of theories and in field research. Elephant seals are an ideal subject for reproductive effort studies because
they fast during the breeding season, splitting the phase of energy acquisition from the phase of energy use for breeding.
In this paper, we present results on male reproductive effort (weight loss estimated by photogrammetry) in southern elephant
seals (Mirounga leonina), the most dimorphic and polygynous of all mammal species. We show that total reproductive effort increases with age, with
no sign of late decrease or senescence. Male reproductive effort in this species depends mostly on behavioral factors, i.e.,
the success in competition with other males, and the intensity of interaction with females. A large effort results in large
gains in both mating success and fertilizations. The large reproductive success that a few males are able to achieve come
at a big cost in terms of energy expenditure, but this cost does not seem to affect the likelihood of survival to the following
breeding season. 相似文献
13.
Recent studies have demonstrated that mating with multiple males can be beneficial for females and her offspring even if males contribute nothing but sperm. This was mainly established for species in which sperm from several males mix in the reproductive tract of the female, thus allowing sperm competition and/or female sperm choice. However, in species with last male sperm precedence, female re-mating decides against the previous male by strongly limiting his reproductive success. We tested the effect of female re-mating behaviour using the cellar spider Pholcus phalangioides, which shows strong last males sperm precedence and moderate levels of polyandry under natural situations. We predicted that females prevented from remating even though they are receptive would show reduced reproductive success compared to females that accept two copulations and females that reject a second male, since the latter two treatments were allowed to behave according to their decisions. However, if the number of matings per se had an effect on oviposition or on offspring performance, double-mated females should perform better compared to both treatments of once-mated females. We measured female fecundity and fertility over a period of 140 days, comparable to the species' natural reproductive peak season. Two thousand one hundred and fifty-two offspring from 67 first egg sacs were reared under two feeding levels. We registered development time and survival, and measured offspring adult size and mass. We found a positive effect of double mating, as in this treatment, oviposition probability was higher compared to the other treatments. Interestingly, adult female offspring of the DM treatment that were raised under low food level had a higher condition index compared to those from FS and RM, but development time, size and mass at adulthood were not affected by mating treatment. Female choice only seemed to affect hatching latency of the offspring. Overall, the main predictor of female reproductive output and success was female body size. 相似文献
14.
Karen J. Nutt 《Behavioral ecology and sociobiology》2007,61(11):1651-1663
Current mating system theory predicts that the number of females breeding in a group will depend on the number of females
in the group and the accessibility of unrelated males, whereas the number of males breeding in a group will depend on the
ability of males to control access to reproductive females. By combining information on group composition with genetic data,
I determined whether breeding patterns in a rock-dwelling rodent, Ctenodactylus gundi, were concordant with these expectations. C. gundi breeding patterns varied from facultative monogamy to uni-male polygyny to multi-male polygyny. The number of reproductive
individuals of each sex in a group increased with group size. Whereas communal breeding among related females tended to increase
female reproductive success, males breeding in the same group were unrelated to other group members and seemed to compete
over access to matings. While some males were assigned offspring from neighboring social groups, most group-living males successfully
monopolized the reproduction of females within their group. There was no evidence that females had multiply sired litters,
although some bred with alternative males in separate breeding attempts. Although numerous individuals were not assigned as
parents or offspring, genetic information enabled me to determine that most unassigned individuals were philopatric group
members, whereas only a few were unrelated immigrants into their current social group. Together, these results provide evidence
that C. gundi social groups represent fairly distinct reproductive units whose breeding patterns are dependent on group size and composition
in accordance with theoretical predictions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
15.
Male pine engravers, Ips pini (Coleoptera: Scolytidae), assist their mates during reproduction by removing the debris that accumulates while females excavate
oviposition tunnels in the phloem tissue of host tree bark. Although duration of paternal care and male reproductive success
are positively correlated, large males leave their mates and brood sooner than small males. We address two hypotheses to
explain the earlier departure of larger males from their breeding galleries: (1) females oviposit most rapidly when paired
with large males, thereby reducing the length of time that paternal care increases male reproductive success, (2) larger males
have better prospects for future reproduction, and thus leave their galleries in search of new breeding opportunities sooner
than smaller males. Contrary to the first hypothesis, when females were paired either with large or small males, there was
no effect of male size on their rate of oviposition. Consistent with the second hypothesis, males that initiated breeding
galleries were larger than males from the general population. In addition, large males flew farther and faster on flight mills
than small males, which may indicate that large males have an advantage in locating suitable breeding sites. Thus, we suggest
that large male pine engravers leave their galleries earlier than small males because large individuals have better prospects
for future reproduction.
Received: 30 November 1997 / Accepted after revision: 23 May 1998 相似文献
16.
Summary Male passerine birds store sperm in a cloacal protuberance during the breeding season. We consider three hypotheses to explain interspecific variation in relative cloacal protuberance size. The copulation efficiency hypothesis states that a relatively large cloacal protuberance facilitates sperm transfer and predicts more rapid copulation in species with larger protuberances. There is insufficient data to test this idea rigorously, but we found no evidence for such an effect. The spermatozoa size hypothesis is a non-functional hypothesis which states that cloacal protuberance size is merely a consequence of sperm size, and predicts that species with larger spermatozoa have relatively larger cloacal protuberances. Sperm length was positively correlated with protuberance size, providing support for this hypothesis, although it seems unlikely that variation in sperm size alone is sufficient to account for variation in protuberance size because the numbers of sperm stored in the cloacal protuberance were also positively correlated with its size. The sperm competition hypothesis states that the cloacal protuberance is a sperm store and predicts that when sperm competition is intense, as measured by male copulation frequency and or mating system, males will have relatively large protuberances and testes mass. The sperm competition hypothesis was supported: in a comparative study in which we controlled for phylogenetic effects, relative cloacal protuberance size was significantly and positively correlated with copulation frequency. Across all mating systems protuberance size was also positively correlated with the mass of seminal glomera tissue, the number of sperm stored in the seminal glomera, and with relative testes size. These results suggest that where sperm competition is intense, a large cloacal protuberance is required to maintain a large sperm reserve for a high copulation rate.Correspondence to: T.R. Birkhead 相似文献
17.
Vanessa L. Bonanno Albrecht I. Schulte-Hostedde 《Behavioral ecology and sociobiology》2009,63(6):835-846
Sperm competition is widespread in mammals and occurs when ejaculates from two or more males compete within the female’s reproductive
tract to fertilize the ova. Enlarged testes are associated with sperm competition because they produce sperm, but the accessory
glands produce fluids and proteins that are also important for fertilization success. Sperm morphology can also have consequences
for fertilization success because of its influence on sperm motility. Red squirrels engage in multiple mating, and thus sperm
competition is likely. Here, we assess levels of multiple paternity in a natural population of red squirrels, test the prediction
that testis size is correlated with size of the accessory glands and sperm morphometry, and test the prediction that ejaculate
investment is condition-dependent. Five of six litters (83%) showed evidence of multiple paternity, indicating that sperm
competition is likely to have occurred. Testis size was correlated with the size of all three accessory glands (prostate,
seminal vesicle, epididymides), and there was a generally positive relationship between the size of the accessory glands and
sperm length. Sperm morphology showed significant variation in size and shape among individual male squirrels. There was no
evidence of condition dependence of testis size or the size of the accessory glands, but sperm midpiece length was negatively
related to body condition. Further work should include determining the fitness consequence of variation in sperm morphometry,
testis size, and accessory gland size, and determining the effects of variation in ejaculate investment on sperm motility. 相似文献
18.
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
19.
Merja Otronen 《Behavioral ecology and sociobiology》1994,35(1):33-38
Male fertilisation success in relation to male size and the mating situation (ordinary pair formation with a single, nonvirgin female vs. take overs) was examined in the fly Dryomyza anilis. In ordinary matings, large males achieved higher fertilisation success than small ones when they were the second to mate with the female. Take overs differ from ordinary pair formation in that the second male experiences intensified sperm competition. This is because in take overs the female is not able to discharge any of the sperm inseminated by the first male as she usually does before a new mating. Compared with ordinary matings, take overs reduced the fertilisation success of the second male by 8–10%, whereas that of the first male was 7–14% higher in take overs. Even though the intruder was always larger than the paired male his superior fertilisation success did not compensate for the effect of the sperm already present in the female. In D. anilis, males can increase their fertilisation success by tapping the female's external genitalia with their claspers or having several copulation bouts per mating. Thus, in a take over, the intruder could respond to the intensified sperm competition by performing more tapping sequences per copulation bout or more copulation bouts per mating. In matings observed in the wild, males performed more tapping sequences after a take over than after pair formation with a single female, although the difference was not significant. The results show that there are differences in fertilisation success between males of different size. In addition, different mating situations can result in considerable variation in the fertilisation success of an individual male. Higher fertilisation success for the first male after a take over may be significant, in particular, for the reproductive success of small males, which frequently lose their females to large males. 相似文献
20.
Variation in reproductive potential usually occurs among individuals of both sexes; for example, some individuals may carry
more gametes or be able to continue to generate more gametes in their reproductive life than others. Therefore, to maximize
their reproductive success, both sexes are expected to show adaptations for mate choice. However, most authors concentrated
on how females choose their mates with the belief that females invest more in reproduction than males, and males are generally
eager to pair with any female. In this paper, we report our work on a polygamous moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), with special emphasis on male pre- and in-copulation mate choice in relation to the reproductive
quality and re-copulation potential of females. We show that in E. kuehniella, younger and heavier females have significantly higher reproductive value than older and lighter ones, and male sperm supply
significantly decreases over successive copulations. Males exercise pre-copulation mate choice by selecting females with higher
reproductive potential for copulation and in-copulation mate choice by allocating more sperm to females with higher reproductive
potential. However, high-quality females are more likely to re-copulate than low-quality ones, and allocation of more sperm
to females by males does not increase female reproductive outputs. It is suggested that the allocation of more sperm to high-quality
females functions to increase sperm competitiveness against rivals. 相似文献