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1.
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
2.
Parental investment, potential reproductive rates, and mating system in the strawberry dart-poison frog, Dendrobates pumilio 总被引:1,自引:0,他引:1
We studied the effect of relative parental investment on potential reproductive rates (PRRs) to explain sex differences in
selectivity and competition in the dart-poison frog Dendrobates pumilio. We recorded the reproductive behavior of this species in a Costa Rican lowland rainforest for almost 6 months. Females spent
more time on parental care than males, and `time out' estimates suggest that PRRs of males are much higher than than those
of females, rendering females the limiting sex in the mating process. Males defended territories that provide suitable calling
sites, space for courtship and oviposition, and prevent interference by competitors. Male mating success was highly variable,
from 0 to 12 matings, and was significantly correlated with calling activity and average perch height, but was independent
of body size and weight. Estimates of opportunity for sexual selection and variation in male mating success are given. The
mating system is polygamous: males and females mated several times with different mates. Females were more selective than
males and may sample males between matings. The discrepancy in PRRs between the sexes due to differences in parental investment
and the prolonged breeding season is sufficient to explain the observed mating pattern i.e., selective females, high variance
in male mating success, and the considerable opportunity for sexual selection.
Received: 9 June 1998 / Received in revised form: 27 March 1999 / Accepted: 3 April 1999 相似文献
3.
Sex differences in mass loss rate and growth efficiency in Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island 总被引:3,自引:0,他引:3
Christophe Guinet Simon D. Goldsworthy Sue Robinson 《Behavioral ecology and sociobiology》1999,46(3):157-163
We investigated the relationship between the mass gained by a pup during a period of maternal attendance (as an index of
milk intake) and the duration of the preceding foraging trip in relation to the mass-specific rate of mass loss during fasting
periods and the growth rate of Antarctic fur seal (Arctocephalus gazella) pups at Macquarie Island. We found that (1) serially weighed male pups grew significantly faster than females pups and that
(2) fasting female pups lost mass at a significantly higher rate (2.55% day−1) than male pups (2.12% day−1) of the same mass; (3) during periods of maternal attendance, there were no intersexual differences in the amount of mass
gained by pups of the same size, hence (4) female pups required a higher daily mass gain to grow at the same rate as male
pups. Our results show that intersexual differences in growth rate may be accounted for by intersexual differences in mass-specific
rate of mass loss, because females lost 0.42% more of their total mass per day (i.e. 4.2 g kg−1 day−1) compared with male pups of the same body mass. Despite intersexual differences in growth rates, our results indicate equality
of maternal expenditure between the sexes. Intersexual differences in the rate of mass loss may be due to differences in the
metabolic rate, activity level and/or body composition of male and female pups.
Received: 19 August 1998 / Received in revised form: 19 April 1999 / Accepted: 19 April 1999 相似文献
4.
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
5.
Female distribution affects mate searching and sexual selection in male northern water snakes (Nerodia sipedon) 总被引:2,自引:0,他引:2
Mating systems and sexual selection are assumed to be affected by the distribution of critical resources. We use observations
of 312 mating aggregations to compare mate-searching success of male northern water snakes (Nerodia sipedon) in two marshes in which differences in mating substrate availability resulted in more than fourfold differences in female
dispersion. Reproductive males had significantly larger home ranges where females were dispersed than where females were clumped.
The number of females encountered by males increased significantly with male home range size where females were dispersed,
and decreased significantly where females were clumped. Where females were clumped, males were more likely to encounter other
males when they located females. We found no evidence in either population that mate searching was energetically expensive
or that males with relatively more energy had larger home ranges. However, males with greater fat reserves at the start of
the season participated in more mating aggregations when females were dispersed, suggesting that fat reserves could affect
a male’s willingness to attempt mating or to persist in aggregations. When females were dispersed there was weak stabilizing
selection acting to maintain male body size (β=–0.14), but strong directional selection favoring larger (β=0.50) and fatter
(β=0.37) males. Over 7 years, the intensity of selection favoring larger males varied substantially (β=0.14–1.15), but that
variation was not related to variation in the operational sex ratio. We found no evidence of directional selection on either
body size (β=0.05) or fat reserves (β=0.10) of males when females were spatially clumped. Overall, the distribution of females
had a pronounced effect on male behavior, on the factors that affected male success in locating females, and probably on the
extent of sperm competition once females had been located.
Received: 23 November 1998 / Received in revised form: 9 August 1999 / Accepted: 18 August 1999 相似文献
6.
Seasonal variation in the relationship between cellular immune response and badge size in male house sparrows (Passer domesticus) 总被引:7,自引:2,他引:5
Guillermo Gonzalez Gabriele Sorci Florentino de Lope 《Behavioral ecology and sociobiology》1999,46(2):117-122
The immunocompetence handicap hypothesis postulates that secondary sexual traits are honest signals of male quality because
steroid hormones (such as corticosteroids and sex steroids), which are supposed to favor the development of secondary sexual
traits, may also have immunosuppressive effects. Certain secondary sexual traits are not only used as mate choice signals
but also play a role as badges of status. In the house sparrow (Passer domesticus), males have a bib of black feathers which is used both as a signal of social status in male-male interactions and by females
when choosing a mate. We investigated the relationships between bib size and cellular immune response in male house sparrows
during and outside the reproductive season. Males with large badges were found to have lower levels of immunocompetence, as
assessed using a T-cell-mediated immunity assay, during the reproductive season, as predicted by the immunocompetence handicap
hypothesis. Conversely, in November, the correlation between badge size and cellular immune response was positive, possibly
reflecting the better access to trophic resources of large-badged dominant males in winter flocks.
Received: 24 September 1998 / Received in revised form: 2 February 1999 / Accepted: 14 February 1999 相似文献
7.
Exaggerated male eye span influences contest outcome in stalk-eyed flies (Diopsidae) 总被引:3,自引:0,他引:3
Evolution of male weapons or status signals has been hypothesized to precede evolution of female mating preferences for those
traits. We used staged male fights among three species of Malaysian stalk-eyed flies (Diptera: Diopsidae) to determine if
elongated eye span, which is preferred by females in two sexually dimorphic species, influences contest outcome. Extreme sexual
dimorphism, with large males possessing longer eye span than females, is shared by Cyrtodiopsis whitei and C. dalmanni. In contrast, C. quinqueguttata exhibits a more ancestral condition – short, sexually monomorphic eye stalks. Videotape analysis of 20-min paired contests
revealed that males with larger eye span and body size won more fights in the dimorphic, but not monomorphic, species. To
determine if males from the dimorphic species use eye span directly to resolve contests, we competed male C. dalmanni from lines that had undergone artificial selection for 30 generations to increase or decrease eye span. We found that eye
span, independently of body size, determines contest outcome in selected-line males. Furthermore, in both dimorphic species,
the average encounter duration declined as the eye span difference between contestants increased, as expected if males use
eye span to assess opponent size. The number of encounters also increased with age in dimorphic, but not monomorphic, species.
Selected-line males did not differ from outbred males in either fight duration or number of encounters. We conclude that exaggerated
male eye stalks evolved to influence both competitive interactions and female mating preferences in these spectacular flies.
Received: 20 July 1998 / Received in revised form: 2 February 1999 / Accepted: 12 March 1999 相似文献
8.
Changes in male guppy courting distance in response to a fluctuating light environment 总被引:1,自引:0,他引:1
In the guppy (Poecilia reticulata), effective courting by a male requires visual contact with the female. Therefore, environmental light intensity may affect
male display behavior, particularly initial courtship distance. We found that male guppies courted at exact and predictable
distances from the female given a particular light level, both in field and laboratory studies. In lower light levels (<0.1 μmol m−2 s−1), for example at dawn, dusk, or under heavy canopy, males court females at closer and less variable distances (<3 cm). At
higher light levels, which occur during most of the day and with less canopy cover, males often court from twice or three
times further out. Light levels over guppy streams change over relatively short time periods and ranges, correlating with
variation in courtship distances. Laboratory manipulations of irradiance confirmed that courtship distance depends on illumination.
Hence, courtship distances may be set by the effect of lighting on signal efficiency, minimization of energy or time expenditures,
or predation risk.
Received: 16 December 1997 / Accepted after revision: 8 August 1998 相似文献
9.
The aim of this study was to investigate reproductive strategies and their consequences in gray mouse lemurs (Microcebus murinus), small solitary nocturnal primates endemic to Madagascar. Previous reports of sexual dimorphism in favor of males and females,
respectively, a high potential for sperm competition and pheromonal suppression of mating activity among captive males, led
us to investigate mechanisms of intrasexual competition in a wild population. Based on 3 years of mark-recapture data, we
demonstrate that sexual dimorphism in this species fluctuated annually as a result of independent changes in male and female
body mass. Male body mass increased significantly prior to the short annual mating season. Because their testes increased
by 100% in the same period and because their canines are not larger than those of females, we suggest that large male size
may be advantageous in searching for estrous females and in enabling them to sustain periods of short-term torpor. In contrast
to reports from captive colonies, we found no evidence for two morphologically distinct classes of males. Finally, we also
show that most adult males are active throughout the cool dry season that precedes the mating season, whereas most adult females
hibernate for several months. This is in contrast to other solitary hibernating mammals, where males typically emerge 1–2
weeks before females. Thus, this first extended field study of M.␣murinus clarified previous conflicting reports on sexual dimorphism and male reproductive strategies in this primitive primate by
showing that their apparent deviation from predictions of sexual selection theory is brought about by specific environmental
conditions which result in sex-specific life history tactics not previously described for mammals. A general conclusion is
that sexual selection can operate more strongly on males without resulting in sexual dimorphism because of independent selection
on the same traits in females.
Received: 6 July 1997 / Accepted after revision: 28 March 1998 相似文献
10.
The genetic mating system of a sex-role-reversed pipefish (Syngnathus typhle): a molecular inquiry 总被引:4,自引:0,他引:4
Adam G. Jones Gunilla Rosenqvist Anders Berglund John C. Avise 《Behavioral ecology and sociobiology》1999,46(5):357-365
In the pipefish Syngnathus typhle as in other species of Syngnathidae, developing embryos are reared on the male's ventral surface. Although much laboratory
research has been directed toward understanding sexual selection in this sex-role-reversed species, few studies have addressed
the mating behavior of S. typhle in the wild, and none has capitalized upon the power of molecular genetic assays. Here we present the first direct assessment
of the genetic mating system of S. typhle in nature. Novel microsatellite loci were cloned and characterized from this species, and employed to assay entire broods
from 30 pregnant, field-captured males. Genetic analysis of 1340 embryos revealed that 1–6 females (mean = 3.1) contributed
to each brooded clutch, the highest rate of multiple maternity yet documented in any pipefish. Evidence of multiple mating
by females was also detected. Thus, this population of S. typhle displays a polygynandrous mating system, a finding consistent with previous field and laboratory observations. Our results,
considered together with similar studies of other syngnathid species, provide preliminary support for the hypothesis that
the genetic mating system is related to the evolution of sexual dimorphism in the fish family Syngnathidae.
Received: 19 January 1999 / Received in revised form: 15 April 1999 / Accepted: 9 May 1999 相似文献
11.
We studied sexual selection in the red bishop, Euplectes orix, a colonial, polygynous weaverbird widely distributed over sub-Saharan Africa. Male reproductive success measured in terms
of the number of nests accepted by females and the number of eggs and nestlings in all the nests on a male's territory varied
considerably. The standardized variance (variance/mean2) in male reproductive success ranged from 0.505 to 1.737 in different years, indicating a high potential for sexual selection
in this species. An analysis of genetic parentage for 432 nestlings by non-radioactive, multilocus DNA fingerprinting confirmed
that male reproductive success (number of young sired on the territory) in this species can be reliably estimated by the measures
introduced above. In all 4 study years there was a strong positive correlation between male mating success and the total number
of nests that males built in their territories. The number of nests built can be partitioned into the number of weeks a male
held a territory and his nest-building performance. Both factors exert a significant positive effect on male mating success
and in combination explained between 53.3 and 86.3% of the variation in male reproductive success. Male morphological characters
were found to be of no importance. Males that established a territory in the following season built more nests and held their
territories for longer than males that did not establish a territory in the following season, suggesting that these measures
might be indicators of male condition and quality. Male nest-building performance (number of nests built per week) seems to
be unrelated to male condition or quality.
Received: 8 January 1999 / Received in revised form: 7 June 1999 / Accepted: 13 June 1999 相似文献
12.
Carola Borries Kristin Launhardt Cornelia Epplen Jörg T. Epplen Paul Winkler 《Behavioral ecology and sociobiology》1999,46(5):350-356
Hypotheses about the evolution of gregariousness and social organisation in primates are based on ecological explanations
as well as on social factors such as conspecific threat (especially infanticide by males). The social explanation fits well
with the conditions found in strepsirrhine primates and furthermore explains why infanticide in anthropoid primates living
in one-male groups mainly occurs when the resident male (protector) is replaced. However, whether it likewise fits to the
conditions in multimale groups will depend on the role of resident males as infant protectors, which has rarely been examined.
We investigated long-term data of wild Hanuman langurs (Presbytis entellus) inhabiting a forest near the village of Ramnagar (southern Nepal). Twenty-two eye-witnessed attacks on infants by males
were analysed in connection with male residency, paternity (DNA analyses) and sexual behaviour. Adult males played a major
role in infant defence (65%). Only the genetic father or males who had been residents when the infant was conceived were observed
to protect infants. Males who immigrated after a female had conceived may later attack her infant and were never observed
to defend it. lt seems that the males took only copulations with potentially fertile females but not with pregnant females
as clues for paternity. In the light of these results it seems likely that the risk of infanticide is an important determinant
in female-male associations even in anthropoid primate multimale groups.
Received: 22 December 1998 / Received in revised form: 30 April 1999 / Accepted: 1 May 1999 相似文献
13.
Male dung beetles, Onthophagus taurus, are dimorphic for a secondary sexual trait, head horns. Horned males participate in the production of brood masses while
hornless male do not. Here we examine the reproductive performance of females mated with males exhibiting alternative horn
morphologies. We found that exposure to males may be costly for females in that it reduced the total number of brood masses
produced. However, females paired with horned males produced significantly larger brood masses than females paired with hornless
males or females producing broods alone. We discuss the possible selection pressures that may underly horn evolution in this
genus.
Received: 22 August 1997 / Accepted after revision: 19 January 1998 相似文献
14.
David J. Able 《Behavioral ecology and sociobiology》1999,46(6):423-428
Darwin predicted that scramble competition for access to reproductive females would result in sexual dimorphism of locomotory
structures, but direct evidence for this is extremely rare. I examined the relationship between variation in tailfin size
and mating success in a field and laboratory study of red-spotted newts, Notophthalmus viridescens. Over three breeding seasons, male tailfin size was positively correlated with variation in male amplexus frequency, and
indirectly correlated with male insemination frequency. In a laboratory study, I confirmed that males' ability to capture
females is affected by variation in tailfin size. This is the first study to show that naturally occurring variation in male
locomotory structures affects male mating success. It corroborates the prediction that scramble competition leads to sexual
selection on locomotory structures and, potentially, to dimorphism in these structures.
Received: 16 April 1999 / Received in revised form: 16 May 1999 / Accepted: 12 June 1999 相似文献
15.
Juan Moreno Santiago Merino Jaime Potti Ana de León Rosa Rodríguez 《Behavioral ecology and sociobiology》1999,46(4):244-251
We manipulated parental work load without changing brood size in a population of pied flycatchers Ficedula hypoleuca by removing two primaries (7 and 9) from each wing of females, thus reducing wing area and increasing flight costs. At other
nests, we offered supplementary food in the form of live mealworms (10–20 g daily from hatching) to reduce brood demand and
thus parental foraging costs. Other nests were left as controls. The daily energy expenditure of females feeding 12-day-old
nestlings was measured with doubly labelled water D2
18O. Females in both treatments expended the same amount of energy, fed at the same rate and had similar body masses to birds
in the control group. No effect of treatment on male mass and feeding effort was detected. More nestlings, however, died in
nests of handicapped females. Nestlings of handicapped females had significantly lower body mass and haematocrit values than
nestlings in food-supplemented nests, with nestlings in control nests occupying an intermediate position. The effects of both
treatments on nestling mass, haematocrit values and mortality rates were only noticeable in nests infested with mites. Maternal
energy expenditure is apparently constrained and offspring pay the costs imposed by reduced provisioning rate or increased
demand caused by ectoparasites, while receiving benefits when food supply improves. The presumption that avian reproductive
costs derive from changes in a flexible energy output may not be met in many cases.
Received: 24 October 1998 / Received in revised form: 15 March 1999 / Accepted: 26 April 1999 相似文献
16.
In many salmonid species, males exhibit morphological dimorphism associated with alternative mating behaviors. ”Precocious
males” have a small body size with little or no development of sexual characters and adopt sneaking to gain access to females,
while ”migratory males” of large body size and well-developed secondary sexual characters fight. We quantified selection on
precocious male parr of masu salmon (Oncorhynchus masou) under simulated natural conditions to examine the contribution of morphology to sneaking success. In contrast to the prediction
that sneaking behavior favors small body size, we detected selection favoring relatively large body size for sneaking success.
This selection pressure was caused by the dominance hierarchy within parr and may have been facilitated by indifference of
dominant migratory males to parr. Unlike the secondary sexual characters exhibited by migratory male salmon, such as the hooked
snout and humped back, no morphological characters other than body size contributed to the reproductive success of masu salmon
parr. This non-contribution may have been responsible for the lack of development of sexual characters in precocious males.
Received: 15 November 1999 / Accepted: 20 May 2000 相似文献
17.
Akiko Matsumoto-Oda 《Behavioral ecology and sociobiology》1999,46(4):258-266
For female chimpanzees (Pan troglodytes schweinfurthii) in the Mahale Mountains National Park, Tanzania, the most common mating pattern is opportunistic. In such opportunistic
matings, females copulated promiscuously but not randomly. This study describes female mate choice during 1-year observation
of six females who exhibited regular genital-swelling cycles. During the study period, 169 opportunistic matings and four
restrictive matings were recorded over the course of 51 days. As female estrus progressed, mating frequency and the number
of adult male mating partners increased, although the number of potential mating partners did not change. Criteria of female
choice examined were the direction and consent/rejection of courtship, proximity maintenance, and female grooming. Adult-male
courtships were successful more often than those of adolescent males. During the earlier phase of estrus, females copulated
rather promiscuously with many males. But during the later phase of estrus when the likelihood of conception is expected to
be highest, they copulated repeatedly with high-ranking adult males. There was a positive correlation between female grooming
frequency and mating frequency when the likelihood of conception was greatest. Female chimpanzees are thought to choose high-ranking
males as fathers of their offspring. Moreover, female chimpanzees may adopt one or both of two mating strategies, i.e., a
many-male strategy and a best-male strategy.
Received: 23 November 1998 / Received in revised form: 12 April 1999 / Accepted: 26 April 1999 相似文献
18.
For intersexual selection to occur, it is necessary that females choose between males. It is now well appreciated that constraints
exist, which preclude females sampling all the available males in a population. These constraints are likely to have caused
the evolution of sampling rules (such as the “best-of-n” rule) by which females sample males. Here we investigate the impact of female subsampling of the male population, not on
the evolution of sampling behaviour, but on the population-level correlation between a male trait and currencies such as reproductive
success. This study is important as it illustrates when population-level correlations can be safely used to infer the presence
and strength of sexual selection in the field. We find that the correlation between a male trait and a mate choice variable
rises steeply as the number of males sampled by each female increases, flattening above seven to ten males sampled. This shape
is found to be remarkably robust, and little affected by, for example, the mate choice variable used, by noise in assessment,
by sampling behaviour depending on female quality, or by population size. The only variable found to have a large impact is
male clumping according to their “quality”. If females are sampling about four males, the maximum correlation that can be
found at the population level is in the range 0.4–0.6, perhaps as little as 0.1 if males are strongly clumped. A recent review
of the literature suggests that four is the average number of males that females sample. Thus, the absence of a strong correlation
cannot by itself be used to infer that sexual selection is weak, as it may be due to females sampling few males.
Received: 18 May 1998 / Accepted after revision: 18 July 1998 相似文献
19.
A multi-factorial experiment on heart rate variations in the intertidal crab Pachygrapsus marmoratus
A multi-factorial experiment was designed to investigate the effect of the following factors on the cardiac activity of the
intertidal crab Pachygrapsus marmoratus: respiratory medium (air, water), temperature (four levels, 10, 17.5, 25, 32.5 °C), season (winter, summer) and body size
(two levels, carapace ≤21 mm and carapace >21 mm). The results showed that the heart rate of P. marmoratus increased linearly with temperature and decreased when the specimens were exposed to air rather than water. Moreover, the
heart rate values in summer were lower than those in winter at the corresponding temperature and body size. The summer heart
rate–temperature regression line was laterally (to the right) shifted with respect to the winter line, suggesting a seasonal
acclimation. Body size affected heart rate only at the acclimation temperature (17.5 °C), while no significant effect was
detected at lower or higher temperatures. During the reproductive season a separate experiment was carried out to assess the
effect of sex and reproductive status on heart rate. No significant difference was found among mean values of males, berried
females and females without eggs. The results of the present study confirm the high physiological plasticity of this species,
suggesting that P. marmoratus is a truly amphibious crab, able to deal with both water- and air-breathing during its activity.
Received: 5 January 1999 / Accepted: 7 July 1999 相似文献
20.
By scoring the chromosome number of developing embryos, we show that the sex ratio bias of the African social spider Stegodyphus dumicola Pocock is the result of an overproduction of female embryos. Only 17% of 585 embryos sexed from 14 egg sacs were male, a
significant departure from a 1:1 sex ratio. We also explored the possibility of direct control of the sex of individual offspring
in this species by examining the variance in the number of males per sac and the spatial distribution of male and female embryos
within the sacs. We postulated that a variance in the number of males per sac lower than binomial (i.e., underdispersed or
precise sex ratios) or a non-random distribution of male embryos within the sacs would suggest direct control of the sex of
individual offspring. We found that the variance in the number of males per sac was indistinguishable from binomial and significantly
larger than expected under exact ratios. Likewise, the spatial distribution of male embryos within three sacs examined was
no more clustered than expected by chance. The sex ratio biasing mechanism in this species, therefore, apparently only allows
control of the mean sex ratio but not of its variance. We present randomization and Monte Carlo methods that can be applied
to test for departures from a random spatial arrangement of male and female embryos in an egg mass and for departures from
binomial or exact ratios when not all members of a clutch have been sexed.
Received: 21 October 1998 / Received in revised form: 23 March 1999 / Accepted: 26 April 1999 相似文献