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1.
Summary In a queenright colony of the monogynous slave-making ant Harpagoxenus sublaevis, a subset of workers formed a linear dominance order in which dominance was corrlated with ovarian development, frequency of trophallaxis, length of time spent in the nest, but not body size. Identical dominance orders occurred in queenless colonies. Experiments in which the top-ranking workers were removed from queenless colonies demonstrated that worker dominance behaviour inhibits egg-laying in subordinates. A similar removal experiment showed queens restrict dominance behaviour and egg-laying in workers, probably pheromonally. Observations of slave raids indicated ovary-developed workers spent significantly less time scouting for slaves, and tended to participate less in slave raids, than workers without ovarian development. These findings suggest that potentially fertile H. sublaevis workers aggressively compete for egg-laying rights, consume extra food for egg development, and safeguard their reproductive futures by avoiding risks outside the nest. Hence worker reproduction in this species strongly influences the colony's social structure, nutrient flow, and division of labour, even though all workers in a colony are full sisters. I hypothesize that worker reproduction was formerly even more prevalent in H. sublaevis, with workers following the strategy of raising sisters and producing sons predicted by kinship theory. Its continued existence despite queen opposition conceivably results from selection on orphaned workers to reproduce, and the inability of slave-maker workers to raise female-biased broods. The social organization of H. sublaevis therefore highlights the importance both of worker reproduction and of the concomitant queen-worker conflict over male parentage in Hymenopteran social evolution.  相似文献   

2.
Colonies of the slave-making ant, Harpagoxenus sublaevis, may simultaneously contain workers of several Leptothorax slave species. We observed aggressive interactions among slave-makers, between slavemakers and slaves, and among slaves in 11 mixed colonies. The first two types of aggression appear to be correlated with reproductive competition for the production of males. Aggressive interactions among slaves, however, occurred mainly between slaves belonging to different species. In two colonies, in which one slave species clearly outnumbered the other, the majority attacked and finally expelled all nestmates belonging to the minority species. Our observations thus suggest that in Harpagoxenus colonies a homogeneous colony odor is not always achieved and that heterospecific slaves may occasionally be mistaken for alien ants. Gas chromatographic analyses of ants from mixed colonies similarly show that cuticular hydrocarbon profiles may differ strongly between heterospecific nestmate slaves.  相似文献   

3.
Animal societies, including those of humans, are under constant threat by selfish individuals, who attempt to enforce their own interests at the cost of the group. In the societies of bees, wasps, and ants, such individual selfishness can be prevented by “policing,” whereby workers or queens impede the reproduction of other individuals by aggression, immobilization, or egg eating. In this study, we report on a particular kind of reproduction control in the ant Temnothorax unifasciatus, which can be considered as a selfish act itself. We experimentally induced workers to lay eggs by dividing several colonies into two halves, one with and one without a queen. In queenless colonies, workers established rank orders by aggression and several top-ranking workers started to reproduce. Upon reunification, egg-laying workers mostly stopped behaving aggressively. They were neither attacked by the queen nor by random workers, but instead received infrequent, nondestructive, targeted aggression from a few workers, most of which became fertile when the queen was later removed. The introduction of differentially stained worker-laid and queen-laid eggs in queenright fragments did not lead to a selective removal of worker-laid eggs. Hence, there appears to be no collective worker policing in T. unifasciatus. Instead, reproduction appears to be controlled mostly through a few attacks from high-ranking workers, which, in this way, might attempt to selfishly increase their chances of future reproduction.  相似文献   

4.
Formica subnuda is a facultative slave-making ant, and colonies without slaves are often found. We studied the effect of slave workers on sexual production of F. subnuda by experimentally increasing the proportion of slaves. We added c. 4000 worker pupae of the ant F. podzolica to 15 F. subnuda colonies and kept 15 colonies as controls. The following year we excavated all colonies, counted the proportion of slaves, the total number of workers (colony size) and the number of sexual offspring. The proportion of slaves was significantly higher in the slave-added colonies than in the control colonies. The total production of sexual offspring increased 57% in the treatment colonies in comparison to the controls. When colony size was adjusted to the number of sexual offspring, the treatment colonies produced significantly more sexual offspring than the controls. Slave addition did not alter sex ratios. We suggest that two alternative mechanisms, not mutually exclusive, caused the increase of sexual production in F. subnuda colonies: (1) Most of the added pupae were consumed and stored as fat body in workers at the end of the experimental year; the following spring the excess fat was metabolized and fed to the developing sexual larvae, or (2) a proportion of the added pupae hatched to become slaves; the following spring these slaves foraged actively for protein-rich food for the developing sexual offspring. Received: 27 April 1995/Accepted after revision: 23 October 1995  相似文献   

5.
Workers of the Asian hive bee, Apis cerana, are shown to have relatively high rates of worker ovary activation. In colonies with an active queen and brood nest, 1-5% of workers have eggs in their ovarioles. When A. cerana colonies are dequeened, workers rapidly activate their ovaries. After 4 days 15% have activated ovaries and after 6 days, 40%. A cerana police worker-laid eggs in the same way that A. florea and A. mellifera do, but are perhaps slightly more tolerant of worker-laid eggs than the other species. Nevertheless, no worker's sons were detected in a sample of 652 pupal males sampled from 4 queenright colonies. A cerana continue to police worker-laid eggs, even after worker oviposition has commenced in a queenless colony.  相似文献   

6.
Policing behavior that prevents workers from laying male eggs was examined in the monogynous and monandrous ponerine ant Diacamma sp. from Japan, in which a singly mated worker called a “gamergate” reproduces as the functional queen in each colony. Since oviposition by virgin workers is rare in the presence of a gamergate, we separated a portion of workers from the gamergates and induced their oviposition experimentally. When orphaned workers had started to oviposit, they were returned to the original colonies, where they continued to lay eggs for a while. The gamergates and other workers interfered with the laying workers by aggressively taking and finally eating the eggs. In total, 60% and 29% of the worker-derived eggs were eaten by gamergates and non-mother workers, respectively. The observed worker-worker interactions were not driven simply by competition to leave own sons, because non-laying non-orphaned workers interfered with worker reproduction. Furthermore, orphaned workers were usually attacked by non-orphaned workers soon after colony reunification. These results indicate that both queen policing by gamergates and worker policing in this species are mechanisms inhibiting worker oviposition. The gamergate contribution to policing was proportionately larger than that of workers, but among virgin workers, the relationship between dominance rank and contribution to policing was not clear. But about 11% of the eggs were not policed and were added to egg piles, especially in large colonies. Worker policing in a monandrous and monogynous eusocial Hymenoptera contrasts to other recent findings, and possible genetic, social, and ecological factors for its evolution in Diacamma sp. are discussed. Received: 16 November 1998 / Received in revised form: 9 February 1999 / Accepted: 21 February 1999  相似文献   

7.
Summary Colony size and worker polymorphism (headwidth) were determined for fire ant colonies ranging from incipient to 12 years of age. Colonies grew approximately logistically, reaching half size between 21/2 and 31/2 yr and reaching their maximum size of about 220000 workers after 4 to 6 yr. Colony size showed strong seasonal variation. There was some evidence that growth rate may vary with food density. Incipient colonies are monomorphic and consist of small workers only, but as colonies grow, production of larger workers causes the size-frequency distributions to become strongly skewed. These skewed distributions were shown to consist of two slightly overlapping normal distributions, a narrow one defined as the minor workers, and a much broader one defined as the major workers. Major workers differ from minor workers in having been subjected to a discrete, additional stimulation of body growth, resulting in a second normal subpopulation. The category of media is seen to be developmentally undefined. The mean headwidth of the workers in both of these subpopulations increased during the first 6 mo. of colony life, until colonies averaged about 4000 workers. Headwidth of minors declined somewhat in colonies older than about 5 yr, but that of majors remained stable. When the first majors appear, their weight averages about twice that of minors. This increases to about 4 times at 6 mo. and remains stable thereafter. The range of weights of majors is up to 20 times that of minors. Growth of the subpopulation of major workers is also logistic, but more rapid than the colony as a whole, causing the proportion of major workers to increase with colony size. In full sized colonies, about 35% of the workers are majors. Total biomass investment in majors increases as long as colonies grow, beginning at about 10% at 2 months and reaching about 70% in mature colonies. This suggests that major workers play an important role in colony success. The total dry biomass of workers peaked at about 106 g, that of majors at about 72 g. These values then fluctuate seasonally in parallel to number of workers. When colony growth ceases, the proportion of majors remains approximately stable. Colony size explained 98% of the variation in the number of major workers.This is paper No. 18 of the Fire Ant Research Team  相似文献   

8.
A quantitative study of worker reproduction in honey bee colonies   总被引:7,自引:0,他引:7  
Summary In 11 Apis mellifera colonies with laying queens, about 0.12% of the males produced derived from eggs laid by workers. This result requires explanation both of why workers produce any males, and, since they do, why they produce so few. Workers may maximize their inclusive fitness by forgoing reproduction, or their sterility may be due to to enforcement of the interests of the queen or those of other workers. The presence of laying workers might then result from developmental noise in the workers, from a failure of communication of the queen's presence, or a failure of enforcement mechanisms. Selection for worker reproduction in colonies following queen loss may also play a role in shaping worker reproduction in colonies with a queen. The hypothesis of worker sterility enforced by other workers seems most likely to be correct, but further studies on these hypotheses are needed.  相似文献   

9.
The fate of queen foundress associations in ants varies across taxa: in some, lethal fighting results in survival of a single queen, while in others, queens coexist long term. One hypothesis for this difference is that selection favors fighting when group sizes are small and tolerance when groups are large. In an experiment with the ant Messor pergandei, we formed small, medium, and large groups with newly mated queens from field populations that have different mean group sizes and differ in whether multiple queens occur in older established colonies. We found that whether queens are eliminated by fighting depends upon region of origin and not group size: regardless of co-foundress number, queens from sites with single-queen adult field colonies displayed agonistic behaviors and their colonies reduced to a single queen, while queens from sites with multiple-queen colonies did not fight and co-foundresses coexisted long term. Worker aggression towards and elimination of queens were also correlated with region of origin. Where fighting occurred, queens were as likely to be killed by workers as by other queens. An aggressive display was the most common form of agonistic interaction among queens, while fighting was relatively rare. We hypothesize that queen displays evolved in response to worker attacks because they increase the probability that workers will eliminate competitor queens. Our results suggest that the evolutionary interests of workers, as well as queens, could be important in determining the evolution and maintenance of queen elimination in foundress associations.  相似文献   

10.
Summary. Proformica longiseta exists as two populations in the Sierra Nevada Mountains in Spain, only one of which is parasitized by the slave-maker ant Rossomyrmex minuchae. To investigate the possible effect of co-evolutionary pressures on cuticular hydrocarbon (CHC) profiles (the presumed nestmate recognition cues), we performed a comparative analysis of the CHC of R. minuchae and P. longiseta colonies from both the allopatric and sympatric populations; the latter includes samples of enslaved as well as free-living workers. Discriminant analyses based on these chemical profiles showed two clear profile groups: the first comprised R. minuchae and both enslaved and free-living P. longiseta from the sympatric population; and the second the allopatric P. longiseta workers. As expected, the profiles of the two sympatric P. longiseta groups (enslaved and free-living) were distinct; but, interestingly, those of the enslaved P. longiseta and its parasite R. minuchae were also distinguishable. This indicates that despite their cohabitation each species maintains its own chemical identity. Profile similarity between the sympatric free-living P. longiseta and its parasite may explain the lower than expected aggression observed during raids. We further speculate that in view of the differences between the sympatric and allopatric population of P. longiseta, co-evolutionary pressures have driven changes in the profile of the former to better match that of its parasite R. minuchae. Such an adjustment may have enabled nests of the sympatric P. longiseta to endure multiple raids by the parasite (due to the reduced aggression) and thus to continue to reproduce despite the damage inflicted by the raids.  相似文献   

11.
We investigated sex allocation in a central European population of the facultatively polygynous ant Leptothorax acervorum. The population-wide sex ratio was found to be quite balanced, with a proportional investment in female sexuals of 0.49. Sex allocation varied considerably between colonies, resulting in split sex ratios. The productivity of colonies was negatively correlated with queen number and positively with colony size. In contrast, the sex ratio (proportional investment in female sexuals) was neither correlated with queen number, colony size, nor total sexual production, but with worker relatedness. The uncoupling of the genetic colony structure and queen number presumably results from frequent queen turnover and colony splitting.  相似文献   

12.
Founding queens of the obligatory social parasite ant Polyergus samurai usurp the host ant Formica japonica colony. The aggressive behaviors of F. japonica workers on the parasite queen disappear after the parasite queen kills the resident queen. To determine whether the parasite queen chemically mimics the host ants, we examined the aggressive behavior of F. japonica workers toward glass dummies applied with various extracts of the parasite queen and host workers. The crude extracts and hydrocarbon fraction reproduced the host workers’ behavior to the live ants. The extracts of the post-adoption parasite queen, as well as the nestmate extracts of F. japonica, did not elicit the aggressive behavior, but the extract of the pre-adoption parasite queen triggered attacks by the host workers. The nestmate recognition of host workers did not change, regardless of contact with the parasite. The gas chromatography and gas chromatography–mass spectrometry analyses indicated that the cuticular hydrocarbon (CHC) profile of the parasite queen drastically changed during the process of usurpation. Discriminant analysis showed the successfully usurped P. samurai queen had colony-specific CHC profiles. CHC profiles of the P. samurai queen who killed the host queen were more similar to those of the host queen than the workers, while the P. samurai queen who usurped the queenless colony had a profile similar to those of host workers. These results suggest that the P. samurai queen usually acquires the CHCs from the host queen during the fight, but from host wokers in queenless host colonies.  相似文献   

13.
Division of labour is the hallmark of the success of many social animals. It may be especially important with regard to waste management because waste often contains pathogens or hazardous toxins and worker specialisation can reduce the number of group members exposed to it. Here we examine waste management in a fungus-farming, leaf-cutting ant, Acromyrmex echinatior, in which waste management is necessary to protect their vulnerable fungal crop. By marking ants with task-specific paint colours, we found clear division of labour between workers that engage in waste management and those that forage, at least during the fine timescale of the 3-day marking period. This division of labour was influenced by both age and size, with waste management workers tending to be smaller and younger than foragers. The role of preventing contaminated ants from entering the colony was fulfilled mainly by medium-sized workers. When the level of waste was experimentally increased, most of the ants that responded to remove the waste were workers previously engaged in tasks inside the nest rather than external waste workers or foragers. These responding workers tended to be young and medium-sized. Surprisingly, the responding ants were subsequently able to revert back to working within the fungus garden, but the probability of them doing so depended on their age and the length of time they were exposed to waste. The results demonstrate the importance of division of labour with regard to waste management in A. echinatior and show that this is adaptable to changing needs.  相似文献   

14.
Division of labour among workers is central to the organisation and ecological success of insect societies. If there is a genetic component to worker size, morphology or task preference, an increase in colony genetic diversity arising from the presence of multiple breeders per colony might improve division of labour. We studied the genetic basis of worker size and task preference in Formica selysi, an ant species that shows natural variation in the number of mates per queen and the number of queens per colony. Worker size had a heritable component in colonies headed by a doubly mated queen (h 2=0.26) and differed significantly among matrilines in multiple-queen colonies. However, higher levels of genetic diversity did not result in more polymorphic workers across single- or multiple-queen colonies. In addition, workers from multiple-queen colonies were consistently smaller and less polymorphic than workers from single-queen colonies. The relationship between task, body size and genetic lineage appeared to be complex. Foragers were significantly larger than brood-tenders, which may provide energetic or ergonomic advantages to the colony. Task specialisation was also often associated with genetic lineage. However, genetic lineage and body size were often correlated with task independently of each other, suggesting that the allocation of workers to tasks is modulated by multiple factors. Overall, these results indicate that an increase in colony genetic diversity does not increase worker size polymorphism but might improve colony homeostasis.  相似文献   

15.
We analyzed how offspring sex ratio varies with maternal condition in order to obtain evidence on the population structure in two aphid species with different life cycles. When fitness returns per unit investment differ for the production of daughters and sons, selection will favor an increasing investment into the sex with the higher returns. Therefore, the offspring sex ratios of individual mothers should become more biased towards the sex with the higher fitness returns as their condition or fecundity improves. The pattern of sex ratio adjustment we found in Uroleucon cirsii indicates local mate competition among males, while the pattern we found in Rhopalosiphum padi suggests local resource competition among sexual females. This might be the first evidence for local resource competition among females in an invertebrate species. Local mate competition means that fitness returns are limited by the availability of females as mates within local breeding groups, whereas local resource competition means that fitness returns are limited by the availability of resources for females competing within local groups. We discuss how the life cycles of both species fit to these hypotheses.
Joachim L. DaggEmail: Phone: +49-551-393730Fax: +49-551-3912105
  相似文献   

16.
Social Hymenoptera are general models for the study of parent-offspring conflict over sex ratio, because queens and workers frequently have different reproductive optima. The ant Pheidole pallidula shows a split distribution of sex ratios with most of the colonies producing reproductives of a single sex. Sex ratio specialization is tightly associated with the breeding system, with single-queen (monogynous) colonies producing male-biased brood and multiple-queen (polygynous) colonies female-biased brood. Here, we show that this sex specialization is primarily determined by the queens influence over colony sex ratio. Queens from monogynous colonies produce a significantly more male-biased primary sex ratio than queens from polygynous colonies. Moreover, queens from monogynous colonies produce a significantly lower proportion of diploid eggs that develop into queens and this is associated with lower rate of juvenile hormone (JH) production compared to queens from polygynous colonies. These results indicate that queens regulate colony sex ratio in two complementary ways: by determining the proportion of female eggs laid and by hormonally biasing the development of female eggs into either a worker or reproductive form. This is the first time that such a dual system of queen influence over colony sex ratio is identified in an ant.  相似文献   

17.
In sexually promiscuous mammals, female reproductive effort is mainly expressed through gestation, lactation, and maternal care, whereas male reproductive effort is mainly manifested as mating effort. In this study, we investigated whether reproduction has significant survival costs for a seasonally breeding, sexually promiscuous species, the rhesus macaque, and whether these costs occur at different times of the year for females and males, namely in the birth and the mating season, respectively. The study was conducted with the rhesus macaque population on Cayo Santiago, Puerto Rico. Data on 7,402 births and 922 deaths over a 45-year period were analyzed. Births were concentrated between November and April, while conceptions occurred between May and October. As predicted, female mortality probability peaked in the birth season whereas male mortality probability peaked in the mating season. Furthermore, as the onset of the birth season gradually shifted over the years in relation to climatic changes, there was a concomitant shift in the seasonal peaks of male and female mortality. Taken together, our findings provide the first evidence of sex differences in the survival costs of reproduction in nonhuman primates and suggest that reproduction has significant fitness costs even in environments with abundant food and absence of predation.  相似文献   

18.
J. J. Gonor 《Marine Biology》1973,19(4):278-280
Examination of large numbers of the echinoid Strongylocentrotus purpuratus (Stimpson) in the years 1969, 1970 and 1971 indicated that the sex ratio at Yaquina Head, Oregon (USA) was significantly different from 1:1, with males predominating. During 1968, 1970 and 1971 at Boiler Bay and Whale Cove, Oregon, the sex ratio did not differ significantly from 1:1 but, in 1969 at Boiler Bay, the proportion of males was 0.61. Two functionally hermaphroditic individuals were found among the 1,354 Yaquina Head echinoids examined, but none were found at Boiler Bay in an equal number of individuals. The hypothesis is proposed that S. purpuratus is a labile gonochorist, with a multiple, autosomal, sex-determining mechanism whose expression may be influenced by the environment.  相似文献   

19.
Summary Colonies of the ponerine Ophthalmopone berthoudi were collected throughout the year. The queen caste is absent. Dissection of large numbers of workers revealed that many of them (up to 100 in one nest) are inseminated and produce eggs. The ovaries are small and contain very few mature oocytes, indicating that there is a slow rate of egg-laying. Workers are produced throughout the year, and all are capable of becoming functional reproductives. However, only those that are sexually-attractive during the limited period of male activity become mated. Thus the percentages of mated laying workers (=gamergates) fluctuate seasonally (Fig. 2). Successive generations of gamergates do not overlap. Observation of nests in the field and in the laboratory indicated that gamergates were never active above ground. There is no aggression between them, and their numbers are not socially regulated. There are few interactions between gamergates and non-reproductive workers, and the former do not acquire more food during termite meals. The notion of parental oppression is undermined by the complete loss of the meen caste, while the nature of the breeding system of this ant leads to the prediction of low relatedness between nestmates.  相似文献   

20.
The pay-off of deserting and leaving a mate to care for the offspring alone is generally assumed to depend mainly on the availability of alternative mating partners and on the potential spawning rate of males and females. Eretmodus cyanostictus is a monogamous mouthbrooding cichlid in which the clutch is successively incubated first by the female and then by the male. It has been suggested that parents are constrained to monogamy due to low remating probabilities for both sexes. We tested this hypothesis by varying the sex ratio experimentally. Mate desertion by either sex was not significantly higher when additional potential mates were present (males: 8.3%, females: 0%) than when there were no other same-sex conspecifics present (males: 0%, females: 0%). Males lost their mate to a male intruder during their incubation in 26.7% of cases. Pair members were more active and showed more aggression when same-sex conspecifics were present. Behavioural differences between treatments were strongest during the incubation period of a given sex. If no desertion takes place, sexual conflict may be expressed also on a second level, the amount of parental care each parent provides. Indeed, males took the offspring later when additional females were present, although male incubation time did not differ between treatments. A hitherto undescribed display behaviour of females was clear evidence of a conflict about the timing of shift of young. In conclusion, offering alternative mating opportunities did not strongly favour mate desertion in E. cyanostictus. It rather revealed a conflict between mates about when to shift the young.Communicated by M. Abrahams  相似文献   

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