Behavioral Ecology Vol. 10 No. 1: 105-111
© 1999 International Society for Behavioral Ecology
A trade-off generated by sexual conflict: Mediterranean wrasse males refuse present mates to increase future success
Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 83106, USA
Address correspondence to S. Henson Alonzo, Department of Environmental Studies, University of California, Santa Cruz, CA 95064, USA. E-mail: shalonzo{at}cats.ucsc.edu.
Received 17 April 1998; accepted 18 August 1998.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONDISCUSSIONACKNOWLEDGEMENTSREFERENCES |
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A variety of mechanisms, including intrasexual competition, intersexual conflict, and physiological constraints, can explain patterns of reproduction and the adaptive value of specific behaviors. In a Mediterranean wrasse, Symphodus ocellatus (Labridae), large, nesting males occasionally refuse to spawn with willing females in the presence of small, sneaker males. We explored the possible adaptive significance of this behavior. Nesting males refuse females despite the fact that it reduces their immediate mating success. This nesting-male behavior also decreases female and sneaker mating success and occurs when sneaker males surround the nest. Experiments that decreased the number of sneakers around nests showed that nesting males respond immediately to mating opportunities when fewer sneakers are present, and thus they are not simply constrained by a lack of energy or lack of sperm. Experiments that increased the number of sneakers at the nest caused nesting males initially to refuse spawning opportunities, followed by a subsequent decrease in sneaker presence and an increase in mating rate. We propose that this behavior is the result of a trade-off between immediate mating success and future reproduction created by competition between males and conflict between the sexes. Males reduce their immediate mating success by reducing spawning at the nest; sneaker males subsequently leave, and this decreases mate competition for the nesting male. Unresponsiveness of nesting males also causes sexual conflict between females and nesting males over mating. We argue that this behavior and the existence of a trade-off can only be understood by examining intersexual conflict and intrasexual competition simultaneously.
Key words: mating systems, Mediterranean wrasse, reproductive behavior, reproductive trade-off, sexual conflict, Symphodus ocellatus.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONDISCUSSIONACKNOWLEDGEMENTSREFERENCES |
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The diversity of mating systems and reproductive strategies has long fascinated researchers, and theory has focused on explaining patterns of observed variation and examining the adaptive value of specific behaviors. Many behaviors are believed to be adaptive responses to interactions within or between the sexes (Darwin, 1871
;
Hammerstein and Parker, 1987;
Parker, 1970,
1979,
1983). For example, competition between
males for access to mates or resources can drive the evolution of male
secondary sexual characteristics. Conflict between the sexes is also
recognized as an important factor explaining otherwise counterintuitive
observations such as multiple mating and extrapair copulations in monogamous
birds (Andersson, 1994;
Davies, 1989,
1992;
Hammerstein and Parker, 1987). Although
female mate choice has been well documented, evidence for male choosiness also
exists and is predicted in situations where male fitness is limited by factors
other than access to females (Andersson,
1994; Clutton-Brock and Vincent,
1991; Parker,
1970). Our aim here was to understand the counterintuitive observation that in a Mediterranean wrasse, Symphodus ocellatus, males sometimes refuse to mate with willing females. This behavior could be the result of simple energetic depletion. If males have exhausted their energy or sperm reserves, it may be necessary for them to refuse mates until more energy or more sperm is available. However, they might adopt this behavior as an adaptive strategy to select mates or mating opportunities that increase their overall reproductive success. In S. ocellatus, nesting males do not seem to select mates, but instead go through phases where they simply refuse to mate with visiting females. This extreme form of "choice" does not depend on female identity because females often return and spawn with the same nesting male who refused them earlier (Alonzo and Warner, personal observations). Thus, there are strong indicators that the tactics involved are considerably more complex than simple mate choice.
S. ocellatus is a Mediterranean wrasse found on rocky and eel
grass substrates in shallow coastal waters (<15 m deep)
(Fiedler, 1964;
Voss, 1976). Estimates of adult densities
range from 0.34 to 0.94 individual/m2
(Lejeune, 1985;
Taborsky et al., 1987). There is no
evidence for sex change in this species (Bentivegna
and Benedetto, 1989; Warner and
Lejeune, 1985). The breeding season lasts for approximately 2
months, between May and June (Fiedler,
1964; Lejeune,
1985; Voss, 1976),
during which time the sexes are temporarily dichromatic
(Lejeune, 1985;
Voss 1976). Although the density of nests
varies, mating success does not seem to change during the reproductive season.
Spawning is demersal and occurs daily from sunrise to sunset
(Fiedler, 1964;
Lejeune, 1985). Females spawn every few
days; successful males may spawn multiple times per minute
(Taborsky et al. 1987;
Warner and Lejeune, 1985). Individuals
live up to 2 or 3 years (Lejeune,
1985; Warner and Lejeune,
1985) and reach a maximum of 8.5 cm standard length.
In S. ocellatus, distinct classes of male reproductive behavior
exist (Taborsky et al., 1987). The most
obvious behavior is that of the nesting male. These males build nests out of
algae, court females, and care for the eggs (Gerbe,
1864; Soljan,
1930; Taborsky et al.,
1987). Undefended eggs have no chance of survival
(van den Berghe et al., 1989;
Alonzo and Warner, personal observations), and about one-third of all nests
are deserted by the nesting male before the end of the nest cycle
(Taborsky et al., 1987). The success of
the nest seems to determine the probability of desertion
(Wernerus, 1988;
Wernerus et al., 1989).
Other males in the population perform typical sneaking behavior
(Taborsky, 1994;
Taborsky et al., 1987). These males hover
around actively spawning nests and attempt to join the nesting male's spawns
(Lejeune, 1985;
Taborsky et al., 1987;
Wernerus, 1988). They have mature testes
and are capable of fertilizing eggs (Alonzo and Warner, personal
observations; Warner and Lejeune,
1985). Sneakers move freely between nests, whereas nesting males
tend to remain within a 10-m range the entire season
(Taborsky et al., 1987;
Wernerus et al., 1989). Sneakers are
approximately six times more common than nesting males
(Warner and Lejeune, 1985), and males do
not switch between behavior types during a reproductive season
(Taborsky et al., 1987). Sneakers are
younger than nesting males, which may explain their difference in
frequency; yet sneakers and nesting males appear to be separate life
histories (Alonzo, Taborsky, and Wirtz, in preparation).
Although it is not known if sneaker and nesting male sperm compete, both males produce and release sperm that is capable of fertilizing eggs (Alonzo and Warner, unpublished data). Sneakers produce approximately four times more sperm per spawn than nesting males (Alonzo and Warner, unpublished data). Nesting males thus often find themselves in situations of extreme sperm competition. It is possible that nesting males refuse to spawn with females because of this competition with sneakers. In situations of high sperm competition, nesting males could conceivably gain nothing by spawning. However, nesting males do not consistently refuse to spawn in the presence of sneakers.
Multiple studies on female choice in this species have failed to show any
relationship between male mating success and any intrinsic male or nest
character; nevertheless, nesting-male success varies greatly
(van den Berghe et al., 1989;
Wernerus, 1985,
1988;
Wernerus et al., 1987,
1989). Females visit many nests and will
spawn in only a few of those that they visit
(Taborsky et al., 1987). Females may
visit and spawn in a single nest repeatedly through one day, but they do not
remain loyal to a given male between days or nest cycles
(Taborsky et al., 1987). Females have
been observed traveling up to 100 m between nests
(Taborsky et al., 1987). Females,
however, do seem to spawn with a greater frequency in nests that have had past
mating success (Wernerus, 1988), and they
prefer nests without sneaker males (van den Berghe et
al., 1989). It has been argued that females of this species do not
choose males, but instead choose spawning situations
(Wernerus, 1988;
Wernerus et al., 1989). Because females
return to nests repeatedly, nesting males may be able to delay spawning
without losing females.
The cost of sneaker males to nesting males is not only shared paternity
through sperm competition, but reduced mating success
(van den Berghe et al., 1989). A strong
correlation exists between previous mating success and the number of sneaker
males at a nest (Lejeune, 1985;
Wernerus, 1985,
1988). When sneaker males were
experimentally removed, the mating success of the nest increased threefold
(van den Berghe et al., 1989). Females
obviously prefer nests without sneaker males, as do nesting males. However,
sneaker males prefer nests with high spawning rates, as do other females.
Similarly, the threat of nesting male desertion influences females to choose
nests with high past mating rates. This mating skew correspondingly increases
the skew in sneaker distributions and causes females and sneakers to be in
conflict. Some nests are very successful, but with this success comes many
sneakers. Nesting males that are successful should have behaviors to cope with
the presence of sneakers.
Our previous observations indicated that nesting males sometimes refuse to spawn with willing females. This behavior is only observed, however, in the presence of a large number of sneaker males. In this study, we examined the possible adaptive significance of this behavior as a response to sneaker presence. If this behavior is an adaptive strategy to decrease competition with sneakers, the behavior should respond to changes in sneaker presence at the nest and should increase long-term mating success for nesting males. This behavior could also result simply from complete sperm or energy depletion; the male may be physically unable to court females or to spawn. If this is the case, nesting males should not alter their behavior toward females in response to changes in the number of sneakers at the nest. We first document the circumstances under which mate rejection occurs. We then describe the results of manipulative experiments intended to identify the causes of the behavior.
Research site
Reproductive behavior is easily observed in shallow waters along the coast
of Corsica from May through June (Michel et al.,
1987). All research was conducted under natural conditions near
the University of Liege (Belgium) Marine Laboratory, La Station de Recherches
Sous-Marin et Océanographique (STARESO),
located near Calvi, Corsica, France. A high density of S. ocellatus
individuals is found in Revellata bay near the research station. All
observations were made on the rocky substrate within 200 m of shore above 15 m
depth using scuba equipment. Research was conducted during May and June of
1996 and 1997.
Observations of nesting male unresponsiveness to females
To document the dynamics of the behavior, we first observed nesting males.
We wanted to determine how often and under what circumstances nesting males
become unresponsive to females. Because this behavior had only been seen in
the presence of sneaker males, we focused our observations on nests with many
sneakers present.
Methods
We conducted 30-min observations of nests with a minimum of five sneakers
within 3 m of the nest. Given this basic criterion, nests were chosen at
random. The observer remained between 2 m and 3 m from the nest and as still
as possible throughout the observation. One individual conducted all of the
observations. Every minute, we noted the number of sneakers within 3 m of the
nest. Distances were estimated visually. Females, sneakers, and nesting males
can be differentiated by their behavior and morphology. Nesting males have a
distinct color pattern and are larger than all other individuals in the
population, which easily distinguishes them from sneaker males and from
females. Females can be distinguished from sneaker males by the absence of a
brightly colored spot on their opercules, by the shape of their abdomen and
genital papillae, and by the absence of aggressive behavior from nesting
males. We counted the number of females visiting and spawning in the nest. A
female visiting the nest was defined as any female coming within 10 cm of the
nest. For every female, we noted the nesting male response. Nesting males were
defined as responding to the female if they courted the female ("nest
showing" and "courtship spawning";
Taborsky et al., 1987) and guided the
female into the nest. If nesting males remained away from or tried to block
access to the nest, we considered males unresponsive to females. Females can
ignore a nesting male's unresponsiveness and begin to lay eggs in the nest.
This behavior can induce the nesting male to spawn as well. For each female,
we recorded the nesting male response, the number of times she spawned, and
the number of spawns joined by sneakers. A total of 28 nests were
observed.
Data analysis
First, we calculated and tested for significance the partial correlation
coefficients between the following variables: the number of sneakers at
the nest, the percentage of females to whom nesting males responded, and the
proportion of spawns sneaked. Second, females visiting a nest were divided
into females to whom the nesting male responded and females to whom the
nesting male did not respond. The proportion of females visiting that spawned
and the proportion of spawns sneaked were compared between these two
situations. If possible, we made comparisons using paired t tests. If
the differences deviated significantly from normality according to a
Wilk-Shapiro test (Shapiro and Wilk,
1965; Zar, 1996), we
attempted transformations for normality. If this was unsuccessful, a Wilcoxon
signed-ranks test was used. All tests were two tailed.
Results
All 28 males were both responsive and unresponsive to females during the
30-min observation. Individual nesting-male responsiveness was negatively
correlated with the average number of sneakers present
(Figure 1; r = -.41,
p <.05, n = 28). All other partial correlations were not
significantly different from zero. The proportion of females spawning was
higher when nesting male were responsive to females (mean = 0.44) than when
they were unresponsive (mean = 0.09, t = 7.42, p <.001),
and 50% of spawns were sneaked when nesting males were responsive
compared to 98% when the nesting male was unresponsive (S = 81,
p =.0257).
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Conclusions from observations
Nesting males tend to be more unresponsive when sneakers surround the nest
and are more responsive when the number of sneakers near the nest is low
(Figure 1). There may be a short-term cost
for being unresponsive: the probability a female will spawn is lower and
the probability any spawn that does occur will be joined by a sneaker is
higher when the nesting male is unresponsive to females. Why then would
nesting males actively decrease their mating rate by refusing to spawn with
willing females? At this point, the observational data cannot
distinguish cause from effect. In particular, we do not know whether nesting
male unresponsiveness is causing the change in the number of sneakers present
(e.g., nesting male unresponsiveness attracts sneakers) or simply responding
to it. To examine this behavior in more detail, it was necessary to conduct
experiments.
Experimental manipulations of the number of sneakers at nests
We manipulated the number of sneakers at nests experimentally to examine
the effect of sneakers on nesting-male behavior. If nesting males do not
respond to experimental changes in sneaker number, then we can conclude that
their behavior is not a strategy to decrease competition with sneakers. Males
may simply be energy or sperm limited and, although the behavior decreases
mating success, avoid spawning out of necessity. That is, they may be
unresponsive because they are unable to mate with females regardless of
sneaker number. Nesting males could also refuse to spawn in the presence of
many sneakers simply because their reproductive gain from spawning is
negligible due to sperm competition. Thus, nesting males could be simply
waiting for better spawning opportunities. Nesting male unresponsiveness may
also be a longerterm adaptive strategy in response to sneakers. We know that
past mating success is positively correlated with the number of sneakers at
the nest (Lejeune, 1985;
Wernerus, 1988) and that increased
sneaker presence reduces both the proportion of females spawning in the nest
as well as the mating rate (Alonzo and Warner, in preparation;
van den Berghe et al., 1989). Therefore,
if nesting males can adopt strategies to reduce sneaker presence at the nest,
their individual mating success may be increased in the long term. This could
occur even if the change is only temporary. If males refuse to mate with
females and this leads to lower sneaker presence in the future, male refusal
may represent a trade-off between future and present success. If this is so,
nesting males are predicted to avoid spawning in response to increased sneaker
presence. Subsequently, sneaker presence should decrease and nesting male
success should increase (Figure 2). This
will be adaptive if the time-averaged mating rate of nesting males is higher
than simply spawning in the presence of sneakers continuously.
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This behavior has a dynamic component. If the nesting-male behavior is a strategy in response to conflict with sneakers, then nesting males should respond to manipulated increases in sneaker presence by becoming unresponsive and by increasing responsiveness to females if sneaker number is reduced. In contrast, if the behavior results from energy limitation, males should not respond to experimental manipulation of the number of sneakers present at the nest. If this behavior does result from a trade-off between present and future mating success for the nesting male, then it would follow that the nesting male's success should increase after a period of unresponsiveness, and the number of sneakers at the nest should decrease.
Methods
Experiments were conducted during May and June of 1997 at the site
described above. During these experiments, each observation lasted 10 min. We
performed two sets of experiments: sneaker decreases and sneaker
increases. For both experiments, we observed 15 different nesting males, and
nests were observed once before and twice after the manipulation. We counted
the number of sneakers present at the nest every minute and averaged this over
the 10-min period. All other variables are totals per 10 min. During each
observation we noted the identity of the males, the number of sneakers
present, the number of females visiting and spawning in the nest, the total
number of spawns, the total number of sneaked spawns, and the number of chases
as described above. Female visits, females spawning, total spawns, and spawns
sneaked were divided into situations in which the nesting male responded or
did not respond to the female when she visited the nest.
For the sneaker decreases experiment, nests with a minimum of five sneakers were selected at random. Each nest was observed for 10 min. Following this observation, we caught sneakers using small, hand-held nets. These males were held nearby in a small, enclosed container. After the number of sneakers present around the nest had been reduced significantly (by a minimum of three), we left the nest undisturbed for 5 min. The nest was then observed a second time as before. Subsequently, the captive males were released away from the nest. Some of these sneaker males rejoined their original nests, while new sneakers appeared as well. After a 30-min period, we observed the nest in the same way a third time. Controls were conducted by following exactly the same protocol, except the sneakers were released immediately after being caught (n = 5).
For the sneaker increases experiment, a nearby nest was covered that had many sneakers present. Most of the sneakers from the covered nest then moved to the focal nest. Therefore, nests were chosen that had sneakers and were in close proximity to another nest (within 5 m) that also had many sneakers present (minimum of five). We observed the focal nest for 10 min. Following this observation, the nearby nest was covered. From pilot observations it was apparent that 20-30 min were necessary for sneakers to leave a nest that had been covered. Therefore, we allowed 30 min to pass after the nest was covered before observing the focal nest again. After a second period of 30 min, the nest was observed for a final 10 min. The nearby nest remained covered for this observation. We conducted controls by following exactly the same protocol, except that we covered an active nest that did not have sneakers present at the nest (n = 5).
Data analysis
For all analyses, we represent female mating success by the proportion of
females spawning. This is an estimate of the probability a given female will
spawn in the nest she is visiting. We use the average number of sneaked spawns
per sneaker to represent the success of sneaker males. This is calculated by
dividing the total number of sneaked spawns per observation by the average
number of sneakers present at the nest. We estimated nesting male success by
the number of pair spawns that were not sneaked per observation. This is a
conservative measure because it assumes the nesting male does not obtain any
fitness from sneaked spawns. Clearly, other possible measures of mating
success exist, but the qualitative results did not differ when variations on
these measures were used.
We conducted analyses separately for sneaker decreases and sneaker
increases. Female, sneaker, and nesting male success were calculated as
described above. If the assumptions of the test were met, comparisons between
the three observations were made using repeated-measures ANOVAs, and
F values are reported. A Friedman's nonparametric, two-way ANOVA was
conducted when variables deviated significantly from normality according to a
Kolmogorov-Smirnov test (Zar, 1996) or
from equal variances according to a Levene-Median test
(Snedecor and Cochran, 1989). In these
cases, we report the chisquare value. Pairwise comparisons were made using the
Student-Newman-Keuls method (Zar, 1996).
The proportion of spawns sneaked could not be compared because in too many
observations the total number of spawns was zero, rendering this measure
undefined.
Results
For the sneaker decreases experiment, the number of sneakers at the nest
differed significantly between observations, indicating that the manipulation
was successful (see Figure 3). Female
visitation rate did not differ significantly between observations, but the
number of females spawning, number of spawns sneaked, and the total number of
spawns were significantly higher in the second (low sneaker number)
observation (Table 1). Chases of sneaker
males by nesting males occurred significantly more often with lower sneaker
numbers (Table 1). Female, sneaker, and
nesting-male success were all significantly higher with lower sneaker numbers
in the second observation (Table 1). The
proportion of females to whom the nesting male responded was significantly
higher in the second observation (Figure
3). Controls indicated that when sneaker number did not increase,
all other variables remained unaffected.
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For the sneaker increases experiment, the number of sneakers at the nest was significantly higher in the second observation (Figure 4). Female visitation rate was higher in the second (high sneaker number) observation than both the third and first (Table 2). Number of females spawning and total number of spawns were greatest in the first observation (Table 2). The number of spawns sneaked did not differ between observations (Table 2). The number of chases by nesting males was highest in the first observation and lowest in the second observation (Table 2). Nesting males responded to proportionally fewer females in the high sneaker number observation (Figure 4). Female, sneaker, and nesting male success were all higher in the first and final observation period than in the second (Figure 4, Table 2). Controls indicated that when sneaker number did not increase, all other variables remained unaffected.
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Conclusions from experiments
Males responded to experimental changes in sneaker presence. When sneaker
number was decreased, nesting males became more responsive to females
immediately, and those same males became unresponsive again when the number of
sneakers at the nest increased. This argues against energy or sperm depletion
in the sense that males were capable of courtship and spawning as soon as the
number of sneakers decreased. Similarly, when sneaker number was increased,
males went from being responsive to being unresponsive. Nesting males may
simply avoid high-competition spawning situations. However, a period of
unresponsiveness was also followed by decreased sneaker number and increased
mating success in later spawning periods. Note that this occurred despite the
fact that nothing was done experimentally to decrease sneaker number in the
final observation.
Comparing the results of the two experiments, one can see that the mating
success of nesting males is not only determined by the number of sneakers at
the nest (Tables 1 and
2). Nesting males with experimentally
reduced sneaker numbers have much higher mating success than nesting males
with the same number of sneakers present naturally. This difference in mating
success can be explained by the history of these nests. Past mating success at
the nest is positively correlated with sneaker presence
(Lejeune, 1985), so nests with many
sneakers have had a higher past success than nests with fewer sneakers.
Females prefer nests with a high past history of success but avoid spawning
with sneakers (van den Berghe et al., 1987). Therefore nests with
experimentally reduced sneaker numbers are preferred by females.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONDISCUSSIONACKNOWLEDGEMENTSREFERENCES |
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Nesting males reduce their own spawning rate in response to the presence of sneakers despite the fact that this reduces their immediate success. This reduction in mating ultimately leads to decreased sneaker presence and increased mating success. The fact that nesting males switch back and forth between responsiveness and unresponsiveness indicates these males are not simply inactive. In fact, males begin spawning immediately when the sneaker number at the nest is reduced, indicating no lack of ability to spawn. In unmanipulated nests, males also cycle naturally between periods of responsiveness and unresponsiveness. Given that males are able to spawn, it appears that males are actually altering their behavior in response to the spawning situation. Nesting males seem to choose the conditions under which to mate. Even if nesting male unresponsiveness is influenced by energy or sperm allocation, it still occurs in response to sneaker presence. This is distinct from energy or sperm depletion, where male spawning would be driven by internal, not external, conditions. Furthermore, nesting males may not only be avoiding high-competition spawning situations by reducing their immediate mating success, but they also experience increased future mating success. These observations and experiments support the idea of a trade-off occurring between present and future mating success. Although life-history trade-offs are well documented, this is the first demonstrated trade-off between present and future mating success that is generated by sexual conflict.
To demonstrate that this is an adaptive strategy, it should be shown that a
nesting male using this strategy of unresponsiveness has greater overall
mating success than a male that simply remains responsive to all females.
However, all of the nesting males in this study cycled between responsiveness
and unresponsiveness, and thus we have no direct measure of the mating success
of the alternative. We do know that nesting male mating success is lower in
the presence of sneakers (van den Berghe et al.,
1989) and that past mating success at the nest is positively
correlated with sneaker presence (Lejeune,
1985; Wernerus, 1985,
1988). Therefore, continuous
responsiveness is expected to attract more sneakers, reducing nesting male
mating success through increased sperm competition and decreased
attractiveness to females. In contrast, unresponsiveness decreases sneaker
number, and previous studies have shown that experimental reductions of
sneakers can increase mating rates threefold at the nest
(van den Berghe et al., 1989). Thus, the
decreased mating success caused by unresponsiveness may be compensated for by
increased mating success as sneaker numbers decrease. In fact, it is possible
that nesting males simply delay spawning and do not actually experience a
decrease in total mating. As continued responsiveness would actually increase
competition at the nest, it appears that this nesting male strategy, although
decreasing short-term mating success, could actually have greater overall
success than simply remaining responsive to females.
Although this behavior occurs in response to conflict between sneakers and nesting males, it causes conflict between the sexes. Nesting males, by becoming unresponsive, decrease female mating success. Therefore, intrasexual conflict creates conflict between the sexes. Females prefer nests with a high history of success, presumably to avoid nesting-male desertion, which causes the mating success to be extremely skewed among nests. Because few successful nests exist in the first place because of female choice patterns, female behavior actually generates the conflict between males. Female behavior, in turn, is driven by nesting-male desertion. Thus, conflict between the sexes over desertion creates conflict between males over sneaking; the resulting nesting-male behavior in turn causes conflict between females and nesting males. One of the major lessons from this study is that the reproductive behavior of this species can only be understood by simultaneous consideration of interactions between males and between the sexes.
Although the importance of intersexual conflict and intrasexual competition in determining mating systems is widely recognized, these processes are usually treated independently. In reality, the fitness of reproductive strategies will depend on the outcome of both within- and between-sex conflicts. Recent models examining multiple-linked dynamic programming games have indicated that conflict within and between the sexes can generate trade-offs between present and future fitness (Alonzo and Warner, in preparation). We have found evidence for a trade-off between present and future mating success in this species that is generated by conflict both within and between the sexes. These trade-offs, though similar to life-history trade-offs, are created by sexual conflict and reproductive behavior of other individuals in the population. We expect these types of trade-offs to be as common as sexual conflict and competition within a sex, and we suggest that by considering trade-offs we will obtain a clearer understanding of reproductive behavior and mating systems in general.
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ACKNOWLEDGEMENTS |
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TOPABSTRACTINTRODUCTIONDISCUSSIONACKNOWLEDGEMENTSREFERENCES |
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We thank Jennifer Caselle, Michael Sheehy, Steve Swearer, and Lisa Wooninck for many helpful discussions during this study. We are grateful to Marc Mangel and two anonymous reviewers, whose comments greatly improved this manuscript. We also thank all of the staff of La Station de Recherches Sous-Marin et Océanographique for their endless help in making this research possible and enjoyable. This research was supported by a National Science Foundation (NSF) predoctoral fellowship to S.H.A., NSF grant IBN-87-00948 to S.H.A. and R.R.W., NSF grants INT-932278 and IBN9507178 to R.R.W., a Sigma Xi Grant-in-Aid-of-Research to S.H.A., an Animal Behavior Society Research Grant to S.H.A., and an American Association of University Women American Dissertation Fellowship to S.H.A.
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REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONDISCUSSIONACKNOWLEDGEMENTSREFERENCES |
|---|
Andersson MB, 1994. Sexual selection. Princeton, New Jersey: Princeton University Press.
Bentivegna F, Benedetto F, 1989. Gonochorism and seasonal variation in the gonads of the labrid Symphodus ocellatus.J Fish Biol 34:343-348.
Clutton-Brock TH, Vincent PH, 1991. Sexual selection and the potential reproductive rates of males and females.Nature 351:58-60.[Medline]
Darwin C, 1871. The descent of man and selection in relation to sex. London: Murray.
Davies NB, 1989. Sexual conflict and the polygamy threshold. Anim Behav 38:226-234.
Davies NB, 1992. Dunnock behaviour and social evolution. Oxford: Oxford University Press.
Fiedler VK, 1964. Verhaltensstudien an Lippfischen der Gattung Crenilabrus (Labridae, Perciformes). Z Tierpsychol 21:521-591.
Gerbe Z, 1864. Observations sur la nidification des Crenilabres. Rev Mag Zool Ser 2 16:255-258.
Hammerstein P, Parker GA, 1987. Sexual selection: games between the sexes. In: Sexual selection: testing the alternatives (Bradbury JW, Andersson MB, eds). Chichester: Wiley; 119-142.
Lejeune P, 1985. Etude écoéthologique des comportements reproducteur et sociaux des Labridae méditerranéens des genres Symphodus (Rafinesque 1810) et Coris (Lacepede 1802). Cah Ethol Appl 5:1-208.
Michel CH, Lejeune P, Voss J, 1987. Biologie et comportement des Labridés europeens.Rev Fr Aquarial Herpetol 14:1-80.
Parker GA, 1970. Sperm competition and its evolutionary consequences in the insects. Biol Rev 45:525-567.
Parker GA, 1979. Sexual selection and sexual conflict. In: Sexual selection and reproductive competition in insects (Blum MS, Blum NA, eds). New York: Academic Press;123 -166.
Parker GA, 1983. Mate quality and mating decision. In: Mate choice (Bateson P, ed). Cambridge: Cambridge University Press; 141-166.
Shapiro SS, Wilk MB, 1965. An analysis of variance
test for normality (complete samples). Biometrika
52:591-611.
Snedecor GW, Cochran WG, 1989. Statistical methods. Ames: University of Iowa Press.
Soljan T, 1930. Nestbau eines adriatischen Lippfisches. Z Morphol Okol Tiere 17:145-153.
Taborsky M, 1994. Sneakers satellites and helpers: parasitic and co-operative behavior in fish reproduction.Adv Study Behav 21:1-100.
Taborsky M, Hudde B, Wirtz P, 1987. Reproductive behaviour and ecology of Symphodus Crenilabrus ocellatus a European wrasse with four types of male behaviour. Behaviour 102:82-118.
van den Berghe E, Wernerus F, Warner RR, 1989. Female choice and the mating cost of peripheral males. Anim Behav 38:875-884.
Voss J, 1976. A propos de quelques poissons de la
Méditerranée:
le genre Symphodus Rafinesque, 1810: Symphodus
(Crenilabrus) melops L., Symphodus ocellatus
Forsk
l, 1775. Rev Fr Aquariol
3:93-98.
Warner RR, Lejeune P, 1985. Sex change limited by parental care: a test using four Mediterranean labrid fishes genus Symphodus. Mar Biol 87:89-99
Wernerus FM, 1985. Etude des parametres orientant le choix du partenaire au cours de la reproduction chez Symphodus melanocercus (Risso 1981) et Symphodus ocellatus (Forskal 1775), Labrides mediterraneens. Liege, Belgium: Memoire de Licence, Universite de Liege.
Wernerus FM, 1988. Etude des mécanismes sous-tendent les sytèmes d'appariement de quatre espèces de poissons labridés méditerranéens des genres Symphodus Rafinesque, 1810 et Thalassoma Linne, 1758. Cah Ethol Appl 9:117-320.
Wernerus FM, Lejeune P, van den Berghe EP, 1989. Transmission of mating success among neighboring males in the Mediterranean labrid fish, Symphodus ocellatus. Biol Behav 14:195-206.
Wernerus FM, Michel Ch, Voss J, 1987. Introduction a l'etude de la selection sexuelle chez Symphodus ocellatus (Forskal 1775) et S. melanocercus (Risso 1810) poissons Labrides mediterraneens. Cah Ethol Appl 7:19-38.
Zar JH, 1996. Biostatistical analysis. Englewood Cliffs, New Jersey: Prentice Hall.
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