共查询到20条相似文献，搜索用时 15 毫秒
1.
Ken R. Helms 《Evolution; international journal of organic evolution》1999,53(5):1470-1478
Sex-ratio conflict between queens and workers was explored in a study of colony sex ratios, relatedness, and population investment in the ant Pheidole desertorum. Colony reproductive broods consist of only females, only males, or have a sex ratio that is extremely male biased. Colonies producing females (female specialists) and colonies producing males (male specialists) occur at near equal frequency in the population. Most colonies apparently specialize in producing one reproductive sex throughout their life. Allozyme analyses show that relatedness does not differ within male-specialist and female-specialist colonies and they do not appear to differ in available resources. In the population, workers are nearly three times more closely related to females than males; however, the investment sex ratio is near equal (1.01, female/male), which is consistent with queen control. Selection should be strong on workers to increase investment in reproductive females, so why do workers in male-specialist colonies produce only (or nearly only) males? One hypothesis is that queens in male-specialist colonies prevent the occurrence of reproductive females, perhaps by producing worker-biased female eggs. An earlier simulation study of genetic evolution of sex ratios in social Hymenoptera (Pamilo 1982b) predicts that such mechanisms can result in the evolution of bimodal colony sex ratios and queen control. Results on P. desertorum are generally consistent with that study; however, information is not currently available to test some of the model's predictions and assumptions. 相似文献
2.
Eisuke Hasegawa 《Evolution; international journal of organic evolution》1994,48(4):1121-1129
The relative power of queens and workers at controlling sex allocation in the ant Colobopsis nipponicus is investigated in this study. Results show that C. nipponicus completely satisfies Hamilton's assumptions concerning colony social structure: monogyny, monoandry, and no worker reproduction. A genetic survey of the population structure rejects possibilities of local mate competition, local resource enhancement, and local resource competition, which all can bias population-allocation ratios from 0.5. Although these factors are absent, the observed sex-allocation ratio (male investment/total sexual investment; 0.250 ± 0.027) is significantly biased toward females and is not different from the estimated optimal ratio for workers (0.252). Thus, it appears that workers are likely to win in conflicts over sex allocation with queens. 相似文献
3.
Ramiro S. Arrieta;Leonardo Campagna;Bettina Mahler;Irby Lovette;Paulo E. Llambías; 《Journal of avian biology》2022,2022(4):e02887
Demographic factors can affect the frequency of extra-pair paternity (EPP) in birds, as the distribution and availability of potential mates in both space and time influence the rate of encounters between females and males. Over three breeding seasons, we intensively studied the breeding system of a south temperate population of grass wrens Cistothorus platensis by genotyping 73 broods (319 nestlings) and estimating EPP rates for those broods. Using five different radii (80, 160, 240, 320 and 400 m) around each nest with assigned paternity, we examined the effects of local breeding synchrony, male breeding density and adult sex ratio (ASR) on the EPP rate. The majority of extra-pair offspring (~80%) were sired by neighboring males. Neither local breeding synchrony nor ASR consistently explained the EPP rate variation as their effects were only statistically significant within 320 and 400 m. However, the EPP rate increased as the local male breeding density increased within every radius category, strongly suggesting that neighboring male abundance might play an important role in the extra-pair mating behavior in this species. Our study also highlights the relevance of using a local scale approach when studying mating behavior. 相似文献
4.
Helms KR Fournier D Keller L Passera L Aron S 《Evolution; international journal of organic evolution》2004,58(5):1141-1142
A recent study by Fournier et al. (2003) provides important new information on sex allocation in the ant Pheidole pallidula, and proposes a new scenario for sex-ratio evolution in P. pallidula and similar species. However, Helms proposed to the authors that two important conclusions of the study were questionable because of potential problems with the analyses. Here we provide new data and a reanalysis that strengthens the conclusion that colony sex ratio is associated with breeding system (i.e., polygyny or monogyny). However, the proposal that colonies shift from monogyny to polygyny when they become larger and more productive is weakened because there is substantial overlap in productivity between monogynous and polygynous colonies. 相似文献
5.
Fournier D Keller L Passera L Aron S 《Evolution; international journal of organic evolution》2003,57(6):1336-1342
Abstract.— We investigated sex allocation in a Mediterranean population of the facultatively polygynous (multiple queen per colony) ant Pheidole pallidula . This species shows a strong split sex ratio, with most colonies producing almost exclusively a single-sex brood. Our genetic (microsatellite) analyses reveal that P. pallidula has an unusual breeding system, with colonies being headed by a single or a few unrelated queens. As expected in such a breeding system, our results show no variation in relatedness asymmetry between monogynous (single queen per colony) and polygynous colonies. Nevertheless, sex allocation was tightly associated with the breeding structure, with monogynous colonies producing a male-biased brood and polygynous colonies almost only females. In addition, sex allocation was closely correlated with colony total sexual productivity. Overall, our data show that when colonies become more productive (and presumably larger) they shift from monogyny to polygyny and from male production to female production, a pattern that has never been reported in social insects. 相似文献
6.
LETICIA AVILÉS 《Biological journal of the Linnean Society. Linnean Society of London》1994,52(2):163-176
Social behaviour involving cooperative prey capture and communal feeding is reported for the first time in the spider family Oxyopidae (lynx spiders), in a web-building species of the genus Tapinillus. This social spider inhabits communal webs that may contain several dozen individuals, including adults of both sexes and juveniles of different cohorts. Its colonies occur in clusters and appear to be long-lived, much like those of non-territorial permanently social species such as Anelosimus eximius (Theridiidae) or Agelena consociata (Agelenidae). However, unlike colonies of these other cooperative spiders, the colonies of the social Tapinillus do not have highly female-biased sex ratios. The possible explanations for this difference are discussed. 相似文献
7.
Although reports on colony demographics for a variety of callitrichid species are available in the literature, to date there has not been a detailed examination of Wied's black tufted-ear marmoset (Callithrix kuhlii). The purpose of this study is to present colony demographics for C. kuhlii from the University of Nebraska at Omaha's Callitrichid Research Center from 1991 to 2002. C. kuhlii are currently held in a number of zoological parks in the United States and abroad; however, the University of Nebraska at Omaha held the only breeding colony in North America. Here we report data on lifespan, sex ratio, litter size, and interbirth interval (IBI) for that captive breeding colony. 相似文献
8.
A. F. G. Bourke 《Journal of evolutionary biology》2015,28(11):2106-2111
Inclusive fitness theory predicts that sex investment ratios in eusocial Hymenoptera are a function of the relatedness asymmetry (relative relatedness to females and males) of the individuals controlling sex allocation. In monogynous ants (with one queen per colony), assuming worker control, the theory therefore predicts female‐biased sex investment ratios, as found in natural populations. Recently, E.O. Wilson and M.A. Nowak criticized this explanation and presented an alternative hypothesis. The Wilson–Nowak sex ratio hypothesis proposes that, in monogynous ants, there is selection for a 1 : 1 numerical sex ratio to avoid males remaining unmated, which, given queens exceed males in size, results in a female‐biased sex investment ratio. The hypothesis also asserts that, contrary to inclusive fitness theory, queens not workers control sex allocation and queen–worker conflict over sex allocation is absent. Here, I argue that the Wilson–Nowak sex ratio hypothesis is flawed because it contradicts Fisher's sex ratio theory, which shows that selection on sex ratio does not maximize the number of mated offspring and that the sex ratio proposed by the hypothesis is not an equilibrium for the queen. In addition, the hypothesis is not supported by empirical evidence, as it fails to explain ‘split’ (bimodal) sex ratios or data showing queen and worker control and ongoing queen–worker conflict. By contrast, these phenomena match predictions of inclusive fitness theory. Hence, the Wilson–Nowak sex ratio hypothesis fails both as an alternative hypothesis for sex investment ratios in eusocial Hymenoptera and as a critique of inclusive fitness theory. 相似文献
9.
YAEL D. LUBIN 《Biological journal of the Linnean Society. Linnean Society of London》1991,43(4):297-311
Colonies of a social spider Achaearanea wau (Theridiidae) from Papua, New Guinea have adult and juvenile sex ratios that are biased towards females, and this probably represents a primary bias at the egg stage. Adult sex ratios are less female-biased than are juvenile sex ratios, and both vary significantly among colonies. Adult sex ratios covary with colony size: small colonies have a larger proportion of males than large ones. The pattern of variation in adult sex ratio may be due to greater mortality of females than of males during maturation. Juvenile sex ratios do not covary with colony size, nor do they differ among populations. Colony size, however, does have a significant effect on survival and dispersal in colonies. I conclude, therefore, that a conditional sex ratio strategy, in which the primary sex ratio of the colony is adjusted to changing demographic patterns, does not occur in A. wau. I suggest that environmental heterogeneity acting on individual reproductive output may be responsible for the observed variation among colonies in juvenile sex ratios. 相似文献
10.
J. J. BOOMSMA† G. C. EICKWORT 《Biological journal of the Linnean Society. Linnean Society of London》1993,48(4):355-377
Population and colony-level sex allocation and nest productivity in the eusocial sweat bee Halictus ligatus Say were studied by excavating nests during one season. The emphasis was on measuring the provision masses, which differ in size and shape depending on the sex of the egg to be laid on them (male-producing provision masses are smaller and more or less round, whereas gyne-producing provision masses are larger and 'loaf-shaped). The primary aim of this study was to test theoretical predictions about female-bias of the sex ratio in the summer brood, both on the population level and on the colony level.
The overall sex ratio of the summer brood was moderately biased towards gynes. A significant positive correlation between the overall size of provision masses (as an estimate for the degree of female bias of the nest sex ratio) and the number of eusocial workers was found. This relationship further improved in partial analyses in which the provision mass weights were adjusted for sampling date, removing the effect of protandry. Foundress size, however, had no effect on the second brood provision masses and neither was there an effect of worker number on the size of gynes and males separately. In the first brood only the size of the foundress had a consistently positive effect on the size of the provision masses and on the size of the emerging daughter workers.
The observed increase of female bias in the nest sex ratio with increasing numbers of eusocial worker bees conforms to optimization predictions following from kin-selection theory. 相似文献
The overall sex ratio of the summer brood was moderately biased towards gynes. A significant positive correlation between the overall size of provision masses (as an estimate for the degree of female bias of the nest sex ratio) and the number of eusocial workers was found. This relationship further improved in partial analyses in which the provision mass weights were adjusted for sampling date, removing the effect of protandry. Foundress size, however, had no effect on the second brood provision masses and neither was there an effect of worker number on the size of gynes and males separately. In the first brood only the size of the foundress had a consistently positive effect on the size of the provision masses and on the size of the emerging daughter workers.
The observed increase of female bias in the nest sex ratio with increasing numbers of eusocial worker bees conforms to optimization predictions following from kin-selection theory. 相似文献
11.
Struhsaker Thomas T. Marshall Andrew R. Detwiler Kate Siex Kirstin Ehardt Carolyn Lisbjerg Ditte Dahl Butynski Thomas M. 《International journal of primatology》2004,25(3):615-658
We evaluated variation in group size and composition of Udzungwa red colobus (Procolobus gordonorum) in relation to gross-habitat and sociological parameters. The endangered species is endemic to the Udzungwa Mountains and nearby forests in the Kilombero Valley of south-central Tanzania. We counted 63 groups in 10 forests, ranging in altitude from 250 to 1,800 m. Group size ranged from 7 to 83 (x = 36.3) individuals and adult sex ratios (females/male) ranged from 1.5 to 7.3 (x = 3.5), excluding solitary individuals. Group size was influenced by several habitat parameters, including tree density, degree of deciduousness, and forest size. Groups were largest in large blocks of mature, moist, mixed evergreen and semideciduous forests, but group size is not correlated with altitude. Groups in a highly degraded forest appeared to have fission-fusion societies. The effect of habitat quality on age-sex composition of groups was most apparent in natality and less so in survivorship of adult females and juveniles. The number of adult males in groups accounted for 50% of the variance in group size and 34–39% of the variance in numbers of adult females in groups. Habitat quality affects natality more than demographic parameters do. Groups with a low proportion of adult females had greater juvenile survivorship, perhaps because of lower food competition between these two classes. We proffer hypotheses based on our study and previous intertaxonal comparisons to explain cause and effect relationships between habitat quality and demography. Finally, our study demonstrates the importance of large blocks of old-growth forest to the conservation of Udzungwa red colobus, and we make recommendations for conservation and research. 相似文献
12.
13.
William J. Hamilton 《International journal of primatology》1985,6(5):451-462
The age-sex composition of a chacma baboon (Papio ursinus)population changed following a 5-month interval of extreme food and water shortages. Mortality was significantly greater among
adult females, juveniles, and infants than among adult males. The probable basis of 19 of 22 deaths during the interval of
food and water shortage was starvation caused by drought conditions which localized water sources, reducing access to food
resources. This resulted in a long-term (> 6-year) shift in adult sex ratios within this three-troop population, from 1.04
to 1.42-1.58 adult and subadult males per adult female. Patterns of intertroop interaction were also influenced by food scarcity,
which determined which troop was most seriously affected. 相似文献
14.
Intragenomic conflict has the potential to cause widespread changes in patterns of genetic diversity and genome evolution. In this study, we investigate the consequences of sex‐ratio (SR) drive on the population genetic patterns of the X‐chromosome in Drosophila neotestacea. An SR X‐chromosome prevents the maturation of Y‐bearing sperm during male spermatogenesis and thus is transmitted to ~100% of the offspring, nearly all of which are daughters. Selection on the rest of the genome to suppress SR can be strong, and the resulting conflict over the offspring sex ratio can result in the accumulation of multiple loci on the X‐chromosome that are necessary for the expression of drive. We surveyed variation at 12 random X‐linked microsatellites across 16 populations of D. neotestacea that range in SR frequency from 0% to 30%. First, every locus was differentiated between SR and wild‐type chromosomes, and this drives genetic structure at the X‐chromosome. Once the association with SR is accounted for, the patterns of differentiation among populations are similar to the autosomes. Second, within wild‐type chromosomes, the relative heterozygosity is reduced in populations with an increased prevalence of drive, and the heterozygosity of SR chromosomes is higher than expected based on its prevalence. The combination of the relatively high prevalence of SR drive and the structuring of polymorphism between the SR and wild‐type chromosomes suggests that genetic conflict because of SR drive has had significant consequences on the patterns of X‐linked polymorphism and thus also probably affects the tempo of X‐chromosome evolution in D. neotestacea. 相似文献
15.
16.
We examined the relationship between colony performance and the distribution of worker sizes within colonies in the ant species, Formica obscuripes. We manipulated the distribution of worker sizes within colonies and found that experimental colonies whose distributions mimicked the natural distributions retained a larger percentage of colony biomass over three weeks when fed on honeydew, relative to colonies composed of only large or only small workers. In natural colonies most of the variation in worker sizes was found within, as opposed, to between colonies, suggesting that homeostatic mechanisms within colonies regulated the distribution of worker sizes. While there were no disjunctions in the distribution of worker sizes within colonies, the distribution tended to be bimodal. This study demonstrates that the distribution of worker sizes within colonies is important even for ant species that lack discrete worker castes. Received 31 October 2006; revised 26 December 2006; accepted 4 January 2007. 相似文献
17.
For wild primates, demography studies are increasingly recognized as necessary for assessing the viability of vulnerable populations experiencing rapid environmental change. In particular, anthropogenic changes such as habitat loss and fragmentation can cause ecological and behavioral changes in small, isolated populations, which may, over time, alter population density and demographic structure (age/sex classes and group composition) in fragment populations relative to continuous forest populations. We compared our study population of Endangered black howler monkeys (Alouatta pigra) in 34 forest fragments around Palenque National Park (PNP), Mexico (62 groups, 407 individuals), to the adjacent population in PNP, protected primary forest (21 groups, 134 individuals), and to previous research on black howlers in fragments in our study area (18 groups, 115 individuals). We used χ2 and Mann–Whitney U tests to address the questions: (a) what is the current black howler demographic population structure in unprotected forest fragments around PNP? (b) How does it compare to PNP's stable, continuous population? (c) How has it changed over time? Compared to the PNP population, the fragment populations showed higher density, a significantly lower proportion of multimale groups, and significantly fewer adult males per group. The population's age/sex structure in the fragmented landscape has been stable over the last 17 years, but differed in a higher proportion of multifemale groups, higher density, and higher patch occupancy in the present. In the context of conservation, some of our results may be positive as they indicate possible population growth over time. However, long-term scarcity of adult males in fragments and associated effects on population demographic structure might be cause for concern, in that it may affect gene flow and genetic diversity. The scarcity of adult males might stem from males experiencing increased mortality while dispersing in the fragmented landscape, whereas females might be becoming more philopatric in fragments. 相似文献
18.
Wiernasz DC Sater AK Abell AJ Cole BJ 《Evolution; international journal of organic evolution》2001,55(2):324-329
Mating success in the western harvester ant, Pogonomyrmex occidentalis, increases with male size. We tested the hypothesis that increased mating success increases male fitness and the fitness of colonies that make large males by comparing the sperm content of males prior to and at the conclusion of the mating swarm. The number of sperm a male initially possesses is a function of male size, and large males transfer a greater proportion of their sperm than do small males. For colonies, the payoff per unit of investment is an increasing function of male size, and investment in large males is not equivalent to investing in a larger number of small males. Allocation ratios in species that show size variation in reproductives may need to be modified by the individual fitness functions. 相似文献
19.
1. Here we examine how sex ratio variation in house sparrow broods interacts with other demographic traits and parental characteristics to improve the understanding of adaptive significance and demographic effects on variation in sex ratio. 2. The sex ratio in complete broods did not deviate significantly from parity (54.9% males). 3. There was sex-specific seasonal variation in the probability of recruitment. Male nestlings that hatched late in the breeding season had larger probability of surviving than early hatched males. 4. An adaptive adjustment of sex ratio should favour production of an excess of males late in the breeding season. Accordingly, the proportion of male offspring increased throughout the breeding season. 5. A significant nonlinear relationship was present between sex ratio and age of the female. However, there was no relationship between parental phenotype and standardized hatch day that could explain the observed seasonal change in sex ratio. 6. The sex-specific number of offspring recruited by a pair to subsequent generations was closely related to the brood sex ratio. 7. These results indicate an adaptive adjustment of sex ratio to seasonal variation in environmental conditions that affects the offspring fitness of the two sexes differently. Our results also suggest that such a sex ratio variation can strongly influence the demography and structural composition of small passerine populations. 相似文献
20.
PAUL F. DONALD 《Ibis》2007,149(4):671-692
Offspring sex ratios in wild bird populations, and the extent to which they vary from the equality expected by random genotypic sex determination, have received much recent attention. Adult sex ratios (ASRs) in wild birds, on the other hand, remain very poorly described, and many of the questions about them posed by Ernst Mayr in 1939 remain unanswered. This review assesses population-level sex ratio patterns in wild bird populations, with an emphasis on the ASR. A quantitative assessment of over 200 published estimates of ASR, covering species from a wide range of taxa, regions and habitats, supported Mayr's assertion that skewed ASRs are common in wild bird populations. On average, males outnumbered females by around 33%, and 65% of published estimates differed significantly from equality. In contrast, population-level estimates of offspring sex ratio in birds did not generally differ from equality, and mean ASR across a range of wild mammal species was strongly female-skewed. ASR distortion in birds was significantly more severe in populations of globally threatened species than in non-threatened species, a previously undescribed pattern that has profound implications for their monitoring and conservation. Higher female mortality, rather than skewed offspring sex ratio, is the main driver of male-skewed ASRs in birds, and the causes and implications of this are reviewed. While estimates of ASR in wild bird populations may be subject to a number of biases, which are discussed, there is currently no quantitative evidence that an ASR of one male to one female represents the norm in birds. A better understanding and reporting of ASRs in wild bird populations could contribute greatly to our understanding of population processes and could contribute much to theoretical and applied research and conservation. 相似文献