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1.
The effect of dominance hierarchy on the use of alternative foraging tactics: a phenotype-limited producing-scrounging game 总被引:2,自引:0,他引:2
Group living is thought to be advantageous for animals, though it also creates opportunities for exploitation. Using food
discovered by others can be described as a producer-scrounger, frequency-dependent game. In the game, scroungers (parasitic
individuals) do better than producers (food finders) when scroungers are rare in the group, but they do worse when scroungers
are common. When the individuals' payoffs do not depend on their phenotype (i.e. a symmetric game), this strong negative frequency
dependence leads to a mixed stable solution where both alternatives obtain equal payoffs. Here, we address the question of
how differences in social status in a dominance hierarchy influence the individuals' decision to play producer or scrounger
in small foraging groups. We model explicitly the food intake rate of each individual in a dominance-structured foraging group,
then calculate the Nash equilibrium for them. Our model predicts that only strong differences in competitive ability will
influence the use of producing or scrounging tactics in small foraging groups; dominants will mainly play scrounger and subordinates
will mostly use producer. Since the differences in competitive ability of different-ranking individuals likely depend on the
economic defendability of food, our model provides a step towards the integration of social foraging and resource defence
theories.
Received: 30 July 1997 / Accepted after revision: 15 November 1997 相似文献
2.
Life history costs of olfactory status signalling in mice 总被引:4,自引:0,他引:4
L. M. Gosling S. C. Roberts E. A. Thornton M. J. Andrew 《Behavioral ecology and sociobiology》2000,48(4):328-332
Large body size confers a competitive advantage in animal contests but does not always determine the outcome. Here we explore
the trade-off between short-term achievement of high social status and longer-term life history costs in animals which vary
in competitive ability. Using laboratory mice, Mus musculus, as a model system, we show that small competitors can initially maintain dominance over larger males by increasing investment
in olfactory status signalling (scent-marking), but only at the cost of reduced growth rate and body size. As a result they
become more vulnerable to dominance reversals later in life. Our results also provide the first empirical information about
life history costs of olfactory status signals.
Received: 15 December 1999 / Revised: 6 June 2000 / Accepted: 24 June 2000 相似文献
3.
The number of males in primate social groups: a comparative test of the socioecological model 总被引:2,自引:2,他引:0
Charles L. Nunn 《Behavioral ecology and sociobiology》1999,46(1):1-13
As applied to polygynous mammals, the socioecological model assumes that environmental risks and resources determine the
spatial and temporal distribution of females, which then sets male strategies for monopolizing fertile matings. The effects
of female spatial distribution (i.e., female number) and temporal overlap (female mating synchrony) have been examined in
comparative studies of primates, but the relative influence of these two factors on male monopolization potential (the number
of males) remains unclear. One particular problem is that female synchrony is more difficult to estimate than female number.
This paper uses multivariate statistical methods and three independent estimates of female synchrony to assess the roles of
spatial and temporal effects in the context of a phylogenetically corrected dataset. These analyses are based on sensitivity
analyses involving a total of four phylogenies, with two sets of branch length estimates for each tree, and one nonphylogenetic
analysis in which species values are used (because male behavior may represent a facultative response to the distribution
of females). The results show: (1) that breeding seasonality predicts male number (statistically significant in six out of
nine sensitivity tests); (2) that expected female overlap, after controlling for female group size using residuals, also accounts
for the number of males in primate groups (significant in eight out of nine tests), and (3) that actual estimates of female
mating synchrony predict male number, again after correcting for female group size (significant in five out of nine tests).
Nonsignificant results are in the predicted direction, and female group size is significant in all statistical tests. These
analyses therefore demonstrate an independent influence of female temporal overlap on male monopolization strategies in mammalian
social systems.
Received: 24 July 1998 / Received in revised form: 5 February 1999 / Accepted: 7 February 1999 相似文献
4.
M. Pyron 《Behavioral ecology and sociobiology》2000,48(2):132-136
Most comparative analyses of relative testes mass find that testes are larger in species in which more sperm competition is
predicted (multiple males mate with individual females). I tested for differences in adjusted testes mass (for body mass)
by spawning mode and by sexual size dimorphism in a comparative analysis of 37 minnow species. No significant differences
were found for testes mass by spawning mode or sexual size dimorphism. These results imply a lack of response to selection
on testes size from sperm competition in minnow species. Possible explanations for the lack of the expected relationship between
testes mass and mating systems in minnows are presented.
Received: 8 November 1999 / Received in revised form: 27 January 2000 / Accepted: 13 February 2000 相似文献
5.
Among primates, group size is highly variable. The standard ecological model assumes that better predation avoidance as group
size increases favours living in larger groups, whereas increased travel costs and reduced net food intake due to within-group
competition for resources set the upper limit. Folivorous primates, however, tend to defy this generalisation in that some
live in small groups despite low costs of feeding competition. To resolve this ’folivore paradox’, it has been suggested that folivore group size is limited by social factors such as male
harassment or infanticide, or that females can disperse more easily and thus maintain group size near optimum levels. In this
paper, we examine the effects of group size on home range size, day-journey length, activity budget and diet in wild Thomas’s
langurs (Presbytis thomasi), which live in one-male multi-female groups with a limited life cycle. We examined only data from the stable middle tenure
phase when factors such as the strength of the breeding male or the way in which groups were formed did not influence ranging
and activities. During this phase, group size affected day-journey length and home range size, and had a minor effect on diet,
but did not influence time spent feeding or resting, allogrooming or birth rates. Hence the upper limit to group size during
the middle tenure phase in Thomas’s langurs is not set by feeding competition. The folivore paradox is not due to frequent
female dispersal in Thomas’s langurs. The timing of female dispersal is not as expected if it serves to keep group sizes near
the ecological optimum, and groups seem to be below this optimum. Instead, female reproductive success is presumably maximised
in small to mid-sized groups because larger groups show a clear trend to experience higher risk of take-over, often accompanied
by infanticide. Because females can redistribute themselves among nearby groups when groups reorganise each time a new male
starts up a new group, females can keep the group small. Thus, a social factor, risk of infanticide, seems to provide the
selective advantage to small group size in Thomas’s langurs.
Received: 29 July 1999 / Revised: 17 November 1999 / Accepted: 15 October 2000 相似文献
6.
Using data from 23 populations of Indian langurs (Presbytis entellus), we show that the proportion of one-male groups is a function of the males’ ability to defend groups of females, as predicted
by the monopolisation model of Emlen and Oring (1977). However, we show that in addition to the number of females in the group
and their reproductive synchrony, home range size is also a factor, probably because it affects a male’s willingness to search
for other groups. These variables in turn are shown to be functions of environmental parameters (rainfall volume and seasonality,
and mean ambient temperature) which probably act via the density of resources and refuges in habitats.
Received: 3 March 1994 / Accepted after revision: 24 June 1996 相似文献
7.
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
8.
T. R. Pope 《Behavioral ecology and sociobiology》2000,48(4):253-267
Evaluation of evolutionary mechanisms proposed to promote cooperative behavior depends on the relative influence of the behavior
on the reproductive success of individuals, the reproductive success of the group in which they interact behaviorally, and
the degree of gene correlation among cooperators. The genetic relationship within cooperative coalitions of female red howler
monkeys was examined for three populations with different densities and growth rates. Patterns of gene correlation change
within coalitions is documented using data from the mitochondrial and nuclear genomes, and long-term census monitoring. Differences
in fecundity and infant survivorship within and between groups of unrelated (rˉ=0) and related (rˉ≥ 0.25) females are compared. Females that emigrate from their natal groups form coalitions with other migrant females. These
coalitions attempt to establish a territory and, once successful in producing offspring, exclude other females from feeding
resources. Females in these coalitions had different mtDNA haplotypes and a genetically estimated mean r of 0, supporting demographic data on emigration patterns indicating that these females rarely have the opportunity to form
coalitions with kin. Patterns of recruitment and rate of matriline development within social groups supported behavioral data
indicating that females actively attempt to promote their own matriline as breeders over that of other females, and that some
matrilines are more successful at this than others. Mean r among females was significantly higher in coalitions established as social groups for several generations (rˉ=0.44). In these groups, females all shared the same mtDNA haplotype, and mtDNA haplotype divergence was significantly higher
between than within groups. Females in coalitions with kin had significantly higher reproductive success than females in unrelated
coalitions in all populations. This difference was not a function of coalition size, number of males, socionomic sex ratio,
or primiparity, although anecdotal evidence suggests that allomothering may compensate for inept new mothers in related coalitions
more often than in unrelated ones. Differences in territory quality could not be ruled out as a potential causal factor in
the saturated populations, but were unlikely in the low-density, growing population. There were substantial differences among
long-established coalitions in overall reproductive output in all three populations, and this was significantly correlated
with the number of breeding females. Increase in coalition size was a function of both group age and the behavioral tolerance
among females. Regardless of the underlying reasons for the patterns observed, reproductive success clearly increases with
degree of gene correlation among females within cooperative coalitions, and coalitions that recruit more daughters produce
more offspring. The nature of the cooperative relationship among group females directly influences both of these outcomes.
This is associated with substantial genetic differentiation among social groups within populations, creating conditions in
which genetic tendencies towards cooperative behavior can become tightly associated with group reproductive success.
Received: 15 September 1999 / Revised: 27 April 2000 / Accepted: 27 May 2000 相似文献
9.
A. Koenig 《Behavioral ecology and sociobiology》2000,48(2):93-109
Van Schaik’s socioecological model predicts interrelations among food distribution, competitive regimes, and female social
relationships. To test the internal consistency of the model, feeding competition was examined in three differently sized
groups of a forest-dwelling population of Hanuman langurs (Semnopithecus entellus). The nutritional condition of females was used as a direct indicator of feeding competition and related to the seasonal
variation in resource distribution and abundance. Female dominance hierarchies were characterized by displacements. Dominance
hierarchies were significantly linear and relatively stable, but less so with increasing group size. Physical condition correlated
with dominance rank and high-ranking females were in the best condition, indicating within-group contest competition. The
strength of this relationship became less pronounced with increasing group size. The females of the medium-sized group were
in the best physical condition indicating between-group contest plus within-group scramble competition. Closer examination
revealed variable costs and benefits of group foraging with a predominance of within-group scramble competition when food
was more abundant. The results support some basic predictions of the model. Limiting food abundance was bound to ubiquitous
within-group scramble competition. The use of clumped resources translated into differences in net energy gain based on dominance.
In contrast to the predictions, group-size-related costs and benefits were related to food abundance instead of food distribution.
As predicted, within-group contest competition was linked to a linear dominance hierarchy. The absence of nepotism and coalitions
in Hanuman langurs may be attributed to dominance hierarchies that are unstable through time, probably minimizing fitness
gain via kin support.
Received: 25 May 1999 / Received in revised form: 18 February 2000 / Accepted: 25 February 2000 相似文献
10.
Size assessment via a visual signal in snapping shrimp 总被引:2,自引:0,他引:2
Melissa Hughes 《Behavioral ecology and sociobiology》1996,38(1):51-57
Snapping shrimp are highly aggressive decapod crustaceans, with large, asymmetric chelae. Body size determines the outcome
of both inter- and intrasexual interactions. Both the body and chela sizes of mated pairs are correlated, but the body size
correlation is significantly stronger. In competitive interactions between individuals of the same sex, larger individuals
usually win. Because the size of the major chela is a function of body size in both males and females, chela size could be
used to assess body size early in interactions, before engaging in more high risk behaviors. To determine whether the major
chela is used in size assessment, I presented shrimp with isolated chelae. Male snapping shrimp responded aggressively to
isolated chelae when they were fixed open in a display posture, and the degree of aggressive response depended on the relative
size of the chela. These data provide direct experimental evidence for the use of a visual signal in size assessment. Females,
in contrast, responded aggressively to both the open and closed chela, and their responses did not depend on relative size.
This sex difference in response may be due to differences in the value of certain resources, such as shelters, to males and
females: females may be more willing to respond aggressively regardless of the apparent size of their opponent, in order to
acquire more reliable information regarding size, motivation or fighting ability.
Received: 30 December 1994/Accepted after revision: 14 August 1995 相似文献
11.
Steven L. Lima Patrick A. Zollner Peter A. Bednekoff 《Behavioral ecology and sociobiology》1999,46(2):110-116
In socially feeding birds and mammals, as group size increases, individuals devote less time to scanning their environment
and more time to feeding. This vigilance “group size effect” has long been attributed to the anti-predatory benefits of group
living, but many investigators have suggested that this effect may be driven by scramble competition for limited food. We
addressed this issue of causation by focusing on the way in which the scan durations of free-living dark-eyed juncos (Junco hyemalis) decrease with group size. We were particularly interested in vigilance scanning concomitant with the handling of food items,
since a decrease in food handling times (i.e. scan durations) with increasing group size could theoretically be driven by
scramble competition for limited food resources. However, we showed that food-handling scan durations decrease with group
size in an environment with an effectively unlimited food supply. Furthermore, this food-handling effect was qualitatively
similar to that observed in the duration of standard vigilance scans (scanning exclusive of food ingestion), and both responded
to changes in the risk of predation (proximity of a refuge) as one might expect based upon anti-predator considerations. The
group size effects in both food-handling and standard scan durations may reflect a lesser need for personal information about
risk as group size increases. Scramble competition may influence vigilance in some circumstances, but demonstrating an effect
of competition beyond that of predation may prove challenging.
Received: 22 September 1998 / Received in revised form: 1 February 1999 / Accepted: 14 February 1999 相似文献
12.
Male willow warblers have song repertoires which vary in complexity along several dimensions. We examined whether female choice,
as measured by date of pairing, was based on these song characteristics in 4 different years. Pairing date was negatively
correlated with song repertoire size in 1 year, and with song versatility in another year, but there was no consistent effect
of any song characteristic on pairing throughout the years or in the pooled sample. The variable that best explained how soon
a male pairs is male arrival date (only males that had settled territories before the first female arrived were considered
in the analysis). This correlation is consistently significant in all years. This is most parsimoniously interpreted as females
choosing some habitat characteristic in the same way that males do. A small percentage of males (8.3%) attracted and paired
with a second female. The likelihood of becoming polygynous was not explained by any measured song characteristic, but it
was related to arrival date: early males were more likely to pair with two females. Males with large repertoires fledged more
young in their primary nests, and there was a trend for the offspring of these males to have a greater probability of being
recruited into the population. In conclusion, the results show that in most years there is no sexual selection by female preference
on song characteristics, although the data on reproductive success is consistent with the idea of repertoire size being an
indicator of male quality.
Received: 4 June 1999 / Received in revised form: 1 December 1999 / Accepted: 31 December 1999 相似文献
13.
Data on langur (Presbytis entellus) populations were gathered from the literature to test the importance of three selective pressures in determining group size
and composition: predation pressure, intergroup resource defense, and conspecific threat. There were no detectable difference
in the size of groups in populations facing nearly intact predator communities compared to those populations where predators
were severely reduced in number or absent, although there was a trend for the number of adult males per group to increase
in areas with nearly intact predator communities. Using population density as an indirect measure of the frequency of intrusions
into a group’s home range and thereby as an index of the demographic pressure favoring resource defense, we predicted that
higher densities would result in larger defensive coalitions and higher numbers of females per group. This prediction was
not upheld. Our third selective pressure, conspecific threat, encompasses those selective forces resulting from physical attack
on females, infants, and juveniles. Our index of conspecific threat uses the number of non-group males divided by the number
of bisexual groups, because in langurs, the major source of conspecific threat derives from non-group males who, following
group take-over, kill infants, wound females, and expel juveniles from groups. This index of conspecific threat was strongly
related to the mean number of resident females, was weakly related to the mean group size, but was not related to the number
of males in the group. In addition, as predicted, populations with a high index of conspecific threat had higher levels of
juvenile expulsion. These analyses were corroborated by a simulation model which used a computer-generated series of null
populations to calculate expected slopes of immatures regressed on adult females. These randomly generated populations, matched
to means and ranges of real populations, allowed us to determine if deviations of the observed slopes from the expected null
slopes could be explained by variation in predation pressure, population density, or conspecific threat. We found no evidence
that predation pressure was associated with decreases in immature survival in smaller groups, as would be predicted by the
predation-avoidance hypothesis. We found no evidence that immature survival was compromised by small group size in high-density
populations, as would be predicted by the resource-defense hypothesis. However, as the index of conspecific threat increased,
groups with larger numbers of females were more successful than groups with fewer females in reducing mortality or expulsion
of immatures. Overall, conspecific threat received the strongest support as a selective pressure influencing langur group
size and composition, suggesting that this selective pressure should be evaluated more widely as a factor influencing composition
of animal groups.
Received: 23 January 1995/Accepted after revision: 18 February 1996 相似文献
14.
The self-thinning line is a very robust pattern, which can be obtained in modeling studies by a variety of different mechanistic assumptions. Our opinion is that we can only advance in our understanding of mechanisms leading to the self-thinning relationship if we demand that the model also reproduces several other characteristic features (patterns) of the self-thinning process such as the degree of size inequality and the average size. We use a pattern-oriented modeling approach to develop a model of self-thinning under size inequality in overcrowded, even-aged stands, which reproduces these three patterns simultaneously. Our approach is to first develop an initial model based on our current ecological knowledge and then to refine the model by modifying the initial model to derive the model that reproduces all patterns of interest.The initial model is as simple as possible while avoiding incidental, ecologically unjustified, assumptions. It is a further development of zone of influence-simulation models: each plant is described by two circles, one describing a minimum-domain-area and one describing the zone of influence. In the initial model, mortality is “death-by-contact” of minimum-domain-areas and growth is a function of inter-tree competition, i.e. overlapping zones of influence. Model parameterization is based on field data on Acacia reficiens in southern Africa. Simulations follow patches of initially small trees through time for up to 1000 years with five parameters, three describing growth and two describing inter-tree competition. A sensitivity analysis shows that all parameters of the initial model contribute significantly to the number and size of plants through time. The two competition parameters, which describe competitive asymmetry and the size of the zone of influence relative to canopy size, are both important for generating size inequality. Thus, both competitive asymmetry and spatial pattern contribute to size inequality, and their relative importance may vary greatly.The sensitivity analysis suggests that all processes included in the initial model are essential to the evolution of size inequality. However, size inequality under the initial model is below field values, meaning that additional, as yet unconsidered processes, contribute to size inequality. Our best-fit model additionally contains details on growth stochasticity.This study establishes the often-proposed direct link between mortality driven by local competition and self-thinning and highlights the importance of stochasticity in ecological processes. 相似文献
15.
Life history parameters of ”old endemics” and ”new invaders” among the Australian passerines were compared, controlling for
phylogeny by using current, phylogenetic research methods. Old endemics were found to have significantly smaller clutches
and demonstrated significantly more cooperative breeding than the new invaders, whose fledging periods are significantly longer
than those of the old endemics. We argue that breeding under conditions of a small annual food increment during the breeding
season, as is probably the situtation in Australia, is possible only when clutch size is small, or while breeding cooperatively,
or by extending the fledging period. Our data show that the old endemics use the first two options, while the new invaders
employ the third.
Received: 10 February 1999 / Received in revised form: 10 November 1999 / Accepted: 20 November 1999 相似文献
16.
Fluctuating asymmetry (FA) in limb size in female decorated field crickets (Gryllodes sigillatus) was associated with a reduction in the size of the spermatophore and the amount of sperm transferred by males and an increase
in the time taken to transfer a spermatophore following introduction of a female. There was a weaker negative relationship
between limb asymmetry in males and sperm number but no significant relationship between asymmetry in either sex and spermatophylax
size. In line with a previous study, female size did not appear to influence spermatophore production or mating decisions
by males. The results imply that developmental instability affects both gamete production and mating decisions among males,
although the relationships between spermatophore size, sperm number and asymmetry in females are unlikely to be the result
of males perceiving differences in female FA.
Received: 24 July 1999 / Received in revised form: 22 November 1999 / Accepted: 31 December 1999 相似文献
17.
Behavioral and demographic changes following the loss of the breeding female in cooperatively breeding marmosets 总被引:3,自引:0,他引:3
C. Lazaro-Perea C. S. S. Castro R. Harrison A. Araujo M. F. Arruda C. T. Snowdon 《Behavioral ecology and sociobiology》2000,48(2):137-146
Recent models of the evolution and dynamics of family structure in cooperatively breeding vertebrates predict that the opening
of breeding vacancies in cooperatively breeding groups will result in (1) dispersal movements to fill the reproductive position,
and (2) within-group conflict over access to reproduction. We describe the behavioral and demographic changes that followed
the creation of breeding vacancies in three wild groups of cooperatively breeding common marmosets (Callithrix jacchus). Replacement of the breeding female was rapid when no adult females remained in the group, but did not occur for several
months when other adult females were present. Aggression of adult animals towards same-sex potential immigrants was associated
with a period of reduced affiliation, increased intragroup agonism, no intragroup sexual behavior, and frequent extragroup
copulations. This ended with the fissioning of groups along sexual lines. After replacement, multiple males copulated with
multiple females and vice versa, with no increases in sexually related aggression. Female-female conflict was resolved through
infanticide. The lack of direct conflict between males is consistent with cooperative polyandry. After a breeding vacancy
appeared, marmoset groups showed conflict of interests among group members similar to those shown by cooperatively breeding
birds, but they used different behavioral mechanisms to resolve those conflicts. Our data provide important evidence from
a cooperatively breeding mammal to support Emlen’s model for the evolution of vertebrate families, but they suggest that species-specific
inter- and intrasexual competitive strategies should be considered before the model can be applied to other cooperatively
breeding vertebrates.
Received: 23 November 1999 / Received in revised form: 28 March 2000 / Accepted: 1 April 2000 相似文献
18.
The effects of testosterone on antibody production and plumage coloration in male house sparrows (Passer domesticus) 总被引:9,自引:3,他引:6
Many bird species have patches of colour in their plumage, contrasting with their basic coloration, which are used to display
and signal status to conspecifics. These are called ’badges of status’, because they are believed to be low-cost signals of
social status. For a signalling system to be evolutionarily stable, cheating must be controlled. The conventional view is
that there is frequent testing, which uncovers cheats. Recently, the immunocompetence handicap hypothesis (ICHH) suggested
that signals may be dependent on testosterone for their development, with a cost being imposed through immune suppression.
We report experiments on house sparrows (Passer domesticus) which show that testosterone significantly influences the size of the bib (a ’badge of status’). The ultimate effect of
the testosterone manipulation was to impair antibody production, as predicted by the ICHH. However, testosterone manipulations
also changed the levels of the ’stress hormone’ corticosterone. The level of corticosterone was also related to the degree
of immunosuppression. After controlling for the effect of corticosterone, testosterone enhanced the birds’ ability to produce
antibodies, counter to the ICHH. The hypothesis therefore must be modified. We suggest that testosterone has a dual effect:
it leads to immunosuppression through a mechanism involving corticosterone but, conversely, leads to increased immunocompetence
probably via dominance influencing access to resources.
Received: 5 March 1999 / Received in revised form: 1 October 1999 / Accepted: 16 October 1999 相似文献
19.
L. Hughes B. Siew-Woon Chang D. Wagner N. E. Pierce 《Behavioral ecology and sociobiology》2000,47(3):119-128
The mating system of the Australian lycaenid butterfly, Jalmenus evagoras, is highly unusual compared to most other Lepidoptera. Characteristics of this system, which has been termed an ’explosive
mating strategy,’ include the formation of an intensely competitive mating aggregation of males, a highly male biased operational
sex ratio, a lack of discrimination and mate choice by both sexes, a high variance in male mating success, and female monogamy.
In this study, we tested the hypothesis that multiple mating by males imposes physiological costs resulting in smaller spermatophores,
and that this results in a fitness cost to females. We found that male J. evagoras transferred only 2.2% of their eclosion weight during their first mating, consistent with the hypothesis that males of monandrous
species produce a relatively small investment. The wet weight of the ejaculate declined by an average of 27% at the second
mating and the dry weight by 29%, and an intermating interval of 5–9 days was needed for the ejaculate to return to the size
at the first mating, regardless of male size or age. Wet ejaculate mass increased proportionally with male size, though dry
mass was proportionally larger in smaller males. Ejaculate mass tended to increase with male age at both first and second
matings. Female characteristics, in general, did not affect ejaculate mass, although the wet weight of the ejaculate was positively
associated with female weight at the second mating. Copulation duration increased from 2.4 h to approximately 3 h at the second
mating, and to over 4 h at the third and fourth matings. Fecundity was positively correlated with female size but not with
mating history, copulation duration, or any other characteristics measured for either males or females. Female longevity declined
significantly as the number of times the male partner had previously mated increased. We conclude that despite the small male
investment in ejaculate, the costs of multiple mating may nonetheless be significant, as indicated by the reduction in ejaculate
mass, an increase in copulation duration, and reduction in female lifespan with increasing mating number.
Received: 22 January 1999 / Received in revised form: 28 July 1999 / Accepted: 18 September 1999 相似文献
20.
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