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1.
Philip L. Munday 《Behavioral ecology and sociobiology》2002,52(3):247-254
Bi-directional sex change in coral-dwelling fishes (genera Gobiodon and Paragobiodon) has been attributed to a growth-rate advantage for females during the non-breeding season. This model predicts that the smallest individual in a newly formed pair should always be female. To determine if a growth-rate advantage exists for female Gobiodon histrio, I monitored the growth of males and females in natural pairs during the breeding and non-breeding season. I then used a manipulative field experiment to test four predictions of the growth-rate advantage model: (1) the larger individual should change sex to male in new pairs containing two females; (2) the smaller individual should change sex to female in new pairs containing two males; (3) neither individual should change sex in heterosexual pairs where the male is larger than the female; and (4) both individuals should change sex in heterosexual pairs where the female is larger than the male. A growth-rate advantage was detected for female G. histrio during the non-breeding season; however, only the first three of the predicted outcomes were observed in the manipulative experiment. Sex change did not occur in heterosexual pairs where the female was larger than the male. Furthermore, growth did not differ between sex-changed and non-sex-changed fish; therefore, the absence of sex change in these pairs is not due to a growth cost to sex change. I propose that the risk of moving among spatially isolated habitat patches and the low probability of finding a mate have been more important than sex-specific differences in growth rates to the evolution of bi-directional sex change in coral-dwelling gobies. 相似文献
2.
To investigate the relative cost of protogynous versus protandrous sex change we induced sex change in each direction in Gobiodon histrio (Gobiidae) and then compared growth, body condition and biochemical condition between sex-changed and non-sex-changed fish in treatment and control groups. Sex change in each direction was induced by establishing pairs of adult males and pairs of adult females on isolated coral colonies. Heterosexual pairs were used as controls. For both males and females, growth and body condition did not vary between fish that changed sex and those that did not. The relatively low cost of sex change, compared to the likely costs of searching for a mate of the correct sex, appears to explain the evolution of bi-directional sex change in coral-dwelling gobies. Lipid concentrations in the liver of males and females that changed sex were reduced by similar amounts (34% and 41%, respectively) compared to male and female controls that did not change sex. Therefore, changes in biochemical condition were approximately equal for fish that sex change in each direction and cannot explain the unequal frequency of sex change in each direction in natural populations of G. histrio. 相似文献
3.
Martine Perret 《Behavioral ecology and sociobiology》1990,27(6):447-454
Summary In order to determine whether social factors influence sex ratio at birth in lesser mouse lemurs, experiments were conducted during 5 successive breeding periods on 51 females. At the beginning of the breeding season, females were either isolated (I) or grouped (G) in heterosexual groups with an increasing number of females (2, 3 or 4). To ensure mating, I females were introduced in a group only during the oestrous period. After mating, both I and G females were isolated during pregnancy and lactation. Reproductive capacities of females in terms of oestrus occurrences (n = 324), impregnations (n–210), pregnancies (n = 136) or abortions (n = 38) or litter sizes (1–3 young) were affected neither by age and parity of females nor by group housing prior to conception. G females produced significantly more sons than daughters (67% males for 189 newborn) while females living alone except during the mating period demonstrated a significant inverse tendency (39.6% males for 96 newborn). Distribution of sexes in litters was statistically different from random and varied according to the shift of sex ratio at birth. In G females, the shift in the sex ratio towards males was consistent across the different groups, independent of the number of females living together, suggesting that the presence of only 1 female is sufficient to induce a bias in the sex ratio. No correlation was found between infant survival at weaning and age, parity or group housing of the mother. The maternal investment allocated to male or female newborn was similar provided the litter contained at least 1 male. In litters without males, growth and survival of female infants were significantly less. These results on sex ratio bias in captive female mouse lemurs agree with directions of bias predicted by the local resource competition model for facultative sex ratio adjustment (Clark 1978). Nevertheless, the pattern observed in mouse lemurs appears to be independent of the nutritional state of the female and of differential maternal investment. 相似文献
4.
For dioecious species, choosing a mate of the same sex can have reproductive costs. For sex-changing animals, however, a lack
of sex recognition may not carry a reproductive cost, as pairs that were initially same-sex can become opposite-sex pairs
as one partner changes sex. The strength of sex discrimination in sex changers, then, should depend on the duration of mating
associations and whether the time of sex change is influenced by social situation (“flexible” sex change). We studied two
species of marine snails that change sex from male to female, one with flexible sex change and long-term or permanent mating
associations (Crepidula fornicata) and one with short-term pairings and relatively fixed time of sex change (Crepidula convexa), to determine whether either species exhibits sex recognition and whether members of C. convexa show stronger sex discrimination. In laboratory experiments, small males, the choosing animals, were placed with either a
male or a female conspecific (no-choice experiments) or given a choice of a male or female (choice experiments). We controlled
for shell length in all experiments, as relative size may influence sex change or choice. Males of both species paired more
often with females than males, but, as predicted, males of C. convexa showed stronger discrimination: When given a choice, no C. convexa male paired with another male. In contrast, some C. fornicata males always chose other males even when given the choice of a female. These results suggest that sex recognition can be
adaptive even for sex changers but demonstrate that the level of sex recognition will depend on other aspects of reproductive
behavior. 相似文献
5.
Varenka Lorenzi Ryan L. Earley Matthew S. Grober 《Behavioral ecology and sociobiology》2006,59(6):715-722
Sex change in marine teleost fishes is commonly regulated by social factors. In species that exhibit protogynous sex change,
such as the bluebanded goby Lythrypnus dalli, the most dominant female typically initiates sex change when a male is removed from the social group. Females can use visual,
chemical or tactile cues to assess the presence or absence of a male. The primary goal of our study was to determine whether
the olfactory and visual presence of a male versus its behavioural interactions with females were important for mediating
sex change. We exposed females to three different treatments: absence of a male, presence of a male that could physically
interact with her and presence of a male behind a barrier that allowed visual and olfactory interactions but prohibited physical
interactions. Sex change occurred in the absence of a male but not in the presence of a male that could physically interact
with the female. The presence of a male behind the barrier did not prevent sex change but affected the timing of sex change.
Season appeared to affect the latency to initiate male typical courtship, with a delay at the end of the reproductive season
only when the male was present behind the barrier. We discuss the seasonal results in terms of L. dalli life history and the potential benefits and costs of changing sex late in the season in the presence or absence of aggressive
reinforcement by the male. Our results identify direct behavioural interactions as an important proximate mechanism in the
social regulation of sex change in L. dalli. 相似文献
6.
Chad C. Smith 《Behavioral ecology and sociobiology》2007,61(9):1349-1358
Operational sex ratio (the ratio of sexually active males to fertilizable females) has a major influence on male competition
for mates and male–female interactions. The contributions of male and female density per se to mating system dynamics, however,
are rarely examined, and the fitness consequences are often inferred rather than quantified. Male mosquitofish (Gambusia affinis) compete aggressively and frequently harass females for copulations, a behavior thought to reduce female fitness. Female
fitness can also be reduced by increases in female density, which may affect food availability, cannibalism rates, and chemical
interactions between females. I manipulated male and female densities of G. affinis to measure their effects on male–male aggression, male harassment toward females, and female fitness. I found that males
chased rivals more often and attempted fewer copulations when female density decreased, but surprisingly male density had
no significant effect on the frequency of these male behaviors. In contrast, males’ agonistic displays toward other males
increased with male density, but display behavior was unaffected by female density. These results suggest that male and female
density do not always contribute equally or at all to the patterns of behavior we observe. Female fitness declined as female
density increased, the opposite pattern expected if male harassment is costly to females. This suggests that a strong, negative
effect of female density overwhelmed any potential costs of male harassment. Sources of female density dependence and the
consequences of changes in male and female density to patterns of male behavior are discussed. 相似文献
7.
The caterpillars of Eucheira socialis westwoodi cooperatively spin and maintain a hollow silken nest and an elaborate network of silken foraging trails on their host plant,
madrone (Arbutus spp.: Ericaceae). Nests typically contain several hundred larvae. Two populations are known to harbor a sex ratio distorter.
The primary sex ratio in these two populations for four generations has been exceedingly male biased (64–79% male). Lepidoptera
larvae are easily sexed using external morphology, allowing us to uniquely mark male and female larvae and to assemble larval
groups of particular sex ratios. We report here the results of experiments on sex-specific larval behavior and physiology
and the effect of colony sex ratio on individual behavior. We found that male larvae spent more time spinning silk on the
nest and less time feeding than female larvae. Males were the first to emerge from the nest and the first to venture out along
trails to feed. Male-biased nests had a significantly greater amount of silk deposited on their surfaces than female-biased
nests. In the field, male-biased nests produced heavier male and female pupae than female-biased nests. Male and female larvae
in 75% male nests became active earlier than males and females in other sex ratio treatments.
Received: 11 September 1998 / Received in revised form: 24 February 1999 / Accepted: 27 March 1999 相似文献
8.
Gobiid fishes of the genus Gobiodon live in strong association with certain reef-building corals that vary considerably in size and architecture. These fishes hence are excellent model systems for studying evolutionary adaption to specific microhabitats. Using a sample of Gobiodon histrio and G. rivulatus and their most important host corals (Acropora digitifera and A. gemmifera) from the northern Red Sea, we assess (1) how corals that are occupied by gobies differ in their architecture from colonies that are not occupied and (2) how fish body shape is associated with the architecture of their host coral. Fish body shape was assessed by geometric morphometric techniques. Coral measurements included colony size, branch length (BL), and interbranch as well as branch tip distance of adjacent branches, for which we applied a new and non-destructive measurement technique based on casts of two-component epoxy resin. The most important factor influencing the occupation of corals was a BL of more than 5 cm. The distance between coral branches was clearly related to the width of the fishes and hence constrained overall fish size. G. histrio and G. rivulatus differ in adult body shape as well in their allometric development of lateral body compression, resulting in different maximum body sizes attainable in the restricted interbranch space of corals. The strong dependence of coral-associated fishes on large coral colonies with specific architectures increases the extinction risk of fishes within deteriorating coral reefs. 相似文献
9.
An evaluation of the social organization and sexual system of eusocial species of Synalpheus has been hindered because it has not been possible to determine the sexual composition of colony helpers (workers). The external
sexual characters typically used to sex caridean shrimps are lacking in Synalpheus. We used SEM sexing technique to determine the sexual composition of helpers in colonies of Synalpheus regalis, S. rathbunae, S. chacei, S. rathbunae A (see Morrison et al. Mol Phylogen Evol 30:563–568, 2004), and S. filidigitus. Colonies consisted of both sexes and sex ratios of helpers generally conformed to 50:50 female to male. Females were characterized
by gonopores with U-shaped slits on the coxae of the third pereopods (first walking legs) while males had oval gonopore openings
on the coxae of the fifth pereopods (third or last walking legs). In S. chacei, S. filidigitus, and S. rathbunae A, a few helpers were found that had both male and female gonopores (intersexes). All three reproductive females (queens) of
S. filidigitus examined were intersexes. Sexing of helpers allowed us to test some hypotheses about sexual differences in helper morphology
that might indicate task specialization (division of labor). Male helpers were not different from female ones in body size
(except in S. regalis: males somewhat larger) and in fighting chela size. The lack of sexual dimorphism in these characters suggests no male–female
specialization in colony tasks such as defense. The presence of male and female helpers similar in size suggests that the
sexual system of these eusocial species is gonochoristic, although protandry of some sort in S. filidigitus can not be ruled out. The intersexuality observed in a few individuals may be due to developmental anomalies, protandry,
or even simultaneous hermaphroditism. Finally, the sexing technique allowed us to establish that new colonizers of unoccupied
sponges in S. rathbunae are a single male and female of helper size. 相似文献
10.
The mating system of Abdopus aculeatus incorporates sneaker matings, mate guarding, sex-specific body patterns, frequent copulations, and male–male competition
for mates, making it more similar to that of aggregating decapod cephalopods than any previously known octopus social system.
Large male–female A. aculeatus occupy ‘Adjacent’ (GA) dens and copulate frequently in mate-guarding situations over successive days. Nearby individuals copulate in ‘Temporary
guarding’ (GT) and ‘Transient’ (T; non-guarding) situations, the latter of which can involve ‘Sneaker’ (S) mating. In a focal animal study
of these octopuses in the wild (Sulawesi, Indonesia) we addressed the hypotheses that they demonstrate: (1) precopulatory
mate choice, (2) differential copulation rates by individuals employing different mating tactics, and (3) distant sex identification.
We quantified daily copulation rates of A. aculeatus of reproductive size as well as aspects of copulation duration, display, mate-competition, and mate rejection. Mating tactic
correlated with daily copulation rates. ♂GA spent significantly more time copulating than did ♂T, while ♀GA spent more than twice as much time per day in copula than did other females. Sneaker copulations lasted longer than those by males adopting other tactics. Mate-guarding was an
effective and important tactic used by males to temporarily monopolize mating with apparently non-selective females. Males
demonstrated clear pre-copulatory mate choice by guarding and mating repeatedly with large females (typically ♀GA). While foraging alone away from the den, ♂G procured ‘Transient’ copulations with unguarded females. However, mate-guarding
reduced the amount of time ♂G were alone and may impede their ability to seek out new mates. Low-copulation rates by ♀T, the
smallest female tactic on average, may reflect this trade-off between mate preference and mate-searching by males, or non-receptivity
of some females. A male-typical body pattern (black and white stripes) appeared to facilitate distant sex identification.
Although mating and aggression were often initiated before contact between individuals, same-sex copulations and intense male–female
aggression were rare. By contrast frequent male–female copulations and intense male–male aggression were consistent behavioral
components of mating in A. aculeatus at these sites. Because the behavioral and ecological characters conducive to this complex system are not exclusive to A. aculeatus, it is possible that other octopuses exhibit some or all of these behaviors.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
11.
Jaimie T. A. Dick Robert W. Elwood W. Ian Montgomery 《Behavioral ecology and sociobiology》1995,37(6):393-398
Previous studies have shown that differential predation by males on moulted female congenerics may be largely responsible for the elimination and replacement of the native Irish freshwater amphipod Gammarus duebeni celticus by the introduced G. pulex. Predation of moulted females occurs both shortly after their release from precopulatory mate-guarding and whilst they are being guarded by their mates. In the present study, two hypotheses concerning the underlying cause(s) of the differential predation pattern are tested. Firstly, female G. d. celticus may be more vulnerable to predation than female G. pulex due to the former being released from precopula guarding with the new exoskeleton in a less hardened state. Secondly, G. pulex may be an inherently more aggressive species than G. d. celticus during predatory interactions over guarded females. The first experiment indicated that differential predation was not mediated by species differences in the state of the female exoskeleton at the time of release from precopula by guarding males. The second experiment, however, showed that male G. pulex were significantly more aggressive than male G. d. celticus in attacking both guarding male congenerics and guarded moulted female congenerics. In addition, in defence against predatory attacks, paired male and female G. pulex were significantly more aggressive than paired male and female G. d. celticus. These differences in aggressive behaviour led to a significantly higher frequency of predation on G. d. celticus females than on G. pulex females, and also explains this finding in previous studies. It is concluded that differential predation due to differences in aggressive behaviour may explain the pattern of replacement between these species. 相似文献
12.
Surveys of the coral-inhabiting snailCoralliophila violacea (Lamarck) (=C. neritoidea Kiener) were made on shallow fringing reefs (<8 m deep) around Hsiao-Liuchiu, Taiwan, between July and October 1990. The snails were aggregated into patches on the surface of massive poritid coral colonies. Coral colonies >40 cm in diameter were more likely to bear patches of snails than smaller colonies, and also to have more snails. The coralliophilids ranged from 5 to 30 mm in aperture length. The sex ratio of the population was biased toward males (539:279), with only a few small individuals of indistinguishable sex. Snails between 6 and 10 mm were all males, while most snails with aperture lengths 20 mm were females. Judging from the distinct size ranges of males and females within patches and from the observed degeneration of the penis, the snails may have changed sex from male to female with increasing size. Sex-change may occur across a wide size range (10 to 20 mm). The correlation of smallest female size and largest male size among patches indicates that snail size at sex-change is peculiar to each individual patch. Those females in patches with a single female (but many males) were significantly smaller than females in multiple-female patches. It is likely that in the absence of females males change sex at a smaller size, whereas in the presence of large females males delay sexchange until they have reached a larger size. The plasticity of size at sex-change may be adaptive and a result of natural selection at the individual level. 相似文献
13.
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
14.
Condition-dependent control of paternity by female purple martins: implications for coloniality 总被引:9,自引:0,他引:9
Proposed causal links between extra-pair copulation (EPC) and colony formation in socially monogamous birds hinge on the
question of which sex controls fertilizations. We examined in colonial purple martins Progne subis (1) whether EPCs were forced or accepted by females, and (2) the degree to which apparently receptive females were able to
obtain EPCs against their mates’ paternity defenses. Paternity analyses of multilocus DNA fingerprinting confirmed previous
findings of a marked relationship between age class and extra-pair fertilizations (EPFs), with young males losing paternity
of 43% (n = 53) of their putative offspring compared to 4% (n = 85) by old males. All assignable extra-pair offspring were sired by old males, with one male obtaining most EPFs each year.
Contrary to the hypothesis that EPCs are forced, EPF frequency within age class did not increase with seasonal increases in
the number of males per fertile female. Whereas the male control hypothesis predicted that the male age class that mate-guarded
more would be cuckolded less, the reverse was true: young males guarded significantly more intensely. The male age class difference
in cuckoldry could not be explained by the possibility that young and inexperienced females (which are usually paired to young
males) were more vulnerable to forced copulation because EPFs were unrelated to female age. These findings suggest that females
(1) pair with old males and avoid EPCs, or (2) pursue a mixed mating strategy of pairing with young males and accepting EPCs
from old males. The receptivity to EPCs by females paired to young males put them in conflict with their mates. Two factors
determined the paternity achieved by young males: (1) the relative size of the male to the female, with young males achieving
much higher paternity when they were larger than their mates, and (2) the intensity of mate-guarding. Both variables together
explained 77% of the variance in paternity and are each aspects of male-female conflict. Given female receptivity to EPCs,
mate-guarding can be viewed as male interference with female mating strategies. We conclude that EPCs are rarely or never
forced, but the opportunity for females paired to young males to obtain EPCs is relative to the ability of their mates to
prevent them from encountering other males. Evidence of mixed mating strategies by females, combined with other features of
the martin mating system, is consistent with the female-driven “hidden lek hypothesis” of colony formation which predicts
that males are drawn to colonies when females seek extra-pair copulations.
Received: 23 March 1995/Accepted after revision: 14 January 1996 相似文献
15.
Individuals of species that change sex from male to female may gain a “size advantage” from that sex change; that is, as males
become larger, they become female, thus increasing their fecundity with their size. However, males could also gain an early
and different reproductive size advantage by choosing large females as mates. While male preference for large females has
been observed in many dioecious species, we know little about male size preference in sex-changing species. In choice experiments,
we examined whether males of two congeneric species of marine sex-changing snails, Crepidula fornicata and C. convexa, chose large females over small ones as partners. We also used choice tests to see whether males of C. fornicata, a species whose members form long-term, multi-animal stacks, would choose two females in a stack over a single female. Surprisingly,
males of neither species showed a preference for large females, in spite of the documented fecundity advantage associated
with large female-size. Males of C. fornicata chose slightly, but not significantly, more single females than stacks, suggesting that neither number nor size drives mate
choice in these animals. Key factors that may influence this lack of size preference include long association time, the likelihood
of sperm competition, and the cost of extended mate search; it may also be that sex-change itself, the very factor that creates
female-biased sexual size dimorphism in these species, prevents size preference, as males may gain sufficient reproductive
advantage from eventually becoming large females themselves to offset any benefit of choosing large females. 相似文献
16.
K. E. Ruckstuhl A. Manica A. D. C. MacColl J. G. Pilkington T. H. Clutton-Brock 《Behavioral ecology and sociobiology》2006,59(5):694-703
We analysed 16 years of census data gathered on the island of Hirta (archipelago of St. Kilda) to investigate the effects
of castration, population density, sex ratio, season and group type on habitat use and social segregation of Soay sheep. From
1978 to 1980, 72 male lambs were castrated. We used this experiment to study how a change in reproductive status could affect
sociality and habitat choice of these males. Males, females and castrates were all segregated outside the rutting season in
autumn. Castrates were the least segregated from females in spring and summer but were most segregated from them during the
pre-rut. The more equal the sex ratios, the higher was the degree of social segregation. The three sex classes used similar
habitat types, namely, Holcus agrostis, Agrostis festuca and Calluna habitats. Holcus agrostis and Agrostis festuca were top- and second-ranked in female and castrate habitat use, while Holcus agrostis and Calluna were the two top habitat types used by rams. It is unclear why males included Calluna heath habitats, but it cannot be excluded that they might have shifted their use depending on forage availability. A lack
in differences in habitat use between castrates and females suggests that body size differences alone cannot be the driving
factor for habitat segregation in male and female Soay sheep and that there are reasons other than body size that could motivate
reproductive males to use additional habitat types, such as Calluna heath. Although habitat use shifted from one habitat type to the next between low- and high-population-density years and
between seasons, there was no clear link between population density and how different groups (male, female or castrate) used
these areas. We discuss effects of reproductive status, population density and sex ratio on social segregation and habitat
use and suggest that these factors need to be taken into account when investigating causes of sexual segregation in ungulates. 相似文献
17.
M. S. Mooring A. A. McKenzie Benjamin L. Hart 《Behavioral ecology and sociobiology》1996,38(4):259-266
The lesser mouse lemur (Microcebus murinus) is a prosimian primate which presents evidence of sex ratio bias of offspring that agrees with the direction of bias predicted
by the local resource competition model for facultative sex ratio adjustment. That is, females overproduced sons when grouped
prior to mating, whereas isolated females exhibited the opposite tendency. In this solitary species, social communication
relies heavily on urinary chemical signals. To test the hypothesis that sex biases induced by social factors may be linked
to urinary cues, isolated females were exposed (n = 76) or not (control group, n = 16) to urinary cues from other reproductively active females from the beginning of the breeding season (induced by long
photoperiod) until oestrus. During that period, females were either continuously (n = 17) or partially (n = 59) exposed to chemosignal stimulation. Females in oestrus were placed in contact with a breeding male and subsequently
isolated until they gave birth. All females entered oestrus but the timing of oestrus was significantly delayed by 1 week
in urine-exposed females. A general depressive effect of long-term urine exposure on fecundity was demonstrated, involving
fewer impregnations, higher abortion frequency and smaller litter sizes. Among females giving birth (n = 55) to a total of 129 young, a significant positive correlation was found between sex ratio bias towards males and the
duration of urine exposure. However, the shift in sex ratio at birth depended on the duration of urine stimulation during
a sensitive period extending from the beginning of the long photoperiod until the beginning of the follicular phase. In the
absence of urinary cues during the sensitive period, females significantly overproduced daughters (32% males of 53 newborn).
As urine exposure increased during the sensitive phase, the proportion of males in litters increased from 54% males (n = 50) in partially urine-exposed females to a significant bias towards males (69.2% of 26 newborn) in totally exposed females.
The biased sex ratio in response to chemical cues did not show consistent relationships with maternal body weight, parity
or litter size. Although the intrinsic mechanisms involved in sex-biased conceptions are not known, chemical cues could interact
with the photoperiodic control of gonadotropin secretions.
Received: 14 January 1995/Accepted after revision: 26 November 1995 相似文献
18.
19.
Martin Plath Katja Kromuszczynski Ralph Tiedemann 《Behavioral ecology and sociobiology》2009,63(3):381-390
Males often face strong mating competition by neighboring males in their social environment. A recent study by Plath et al.
(Anim Behav 75:21–29, 2008a) has demonstrated that the visual presence of a male competitor (i.e., an audience male) affects
the expression of male mating preferences in a poeciliid fish (Poecilia mexicana) with a weaker expression of mating preferences when an audience male observed the focal male. This may be a tactic to reduce
sperm competition, since surrounding males likely share intrinsic preferences for female traits or copy mate choice decisions.
Here, we examined the hypothesis that a same-sex audience would affect female mate preferences less than male mating preferences. Our hypothesis was based on the assumptions that (1) competition for
mates in a fashion that would be comparable in strength to sperm competition or overt male–male aggression is absent among
Poecilia females, and (2) P. mexicana females typically form female-biased shoals, such that almost any female mate choice in nature occurs in front of a female
audience. Poecilia females (P. mexicana, surface and cave form, and the closely related gynogenetic Poecilia formosa) were given a choice between a large and a small male, and the tests were repeated while a conspecific, a heterospecific,
or no audience female (control) was presented. Females spent more time in the neutral zone and, thus, less time near the males
during the second part of a trial when an audience was presented, but—consistent with predictions—females showed only slightly
weaker expression of mate preferences during the second part of the tests. This decline was not specific to the treatment
involving an audience and was significantly weaker than the effect seen in the male sex. 相似文献
20.
Julie E. Elie Nicolas Mathevon Clémentine Vignal 《Behavioral ecology and sociobiology》2011,65(12):2197-2208
Same-sex sexual behaviors are well documented in both captive and wild animals. In monogamous species, these behaviors are
often exclusive, each individual having only one same-sex partner. A bias in sex ratio has been proposed as a social context
yielding same-sex pair-bonding, but this hypothesis has rarely been tested. Focusing on a life-long pair-bonding songbird,
the zebra finch Taeniopygia guttata, we tested whether same-sex pairing results from a shortage of individuals of the opposite sex. By experimentally skewing
the sex ratio towards members of one sex, we observed a greater proportion of same-sex pair-bonds of that sex. Moreover, we
assessed whether the quality and stability of social interactions were equivalent in same-sex and male–female pairs. Male–male
and female–female same-sex bonds display the same behavioral characteristics as male–female ones: they are intense, highly
selective, and stable affinitive relationships involving the same behavioral displays already described in wild birds. Moreover,
same-sex male bonds were sufficiently strong not to split up when individuals were given the opportunity to reproduce with
females. Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival
(e.g., resources defense, fighting against predators, etc.), we propose that same-sex pairing in the zebra finch may result
from the pressure to find a social partner. 相似文献