Variation In Social Organization Research Articles

To b or not to b: A pheromone-binding protein regulates colony social organization in fire ants

A major distinction in the social organization of ant societies is the number of reproductive queens that reside in a single colony. The fire ant Solenopsis invicta exists in two distinct social forms, one with colonies headed by a single reproductive queen and the other containing several to hundreds of egg-laying queens. This variation in social organization has been shown to be associated with genotypes at the gene Gp-9. Specifically, single-queen colonies have only the B allelic variant of this gene, whereas multiple-queen colonies always have the b variant as well. Subsequent studies revealed that Gp-9 shares the highest sequence similarity with genes encoding pheromone-binding proteins (PBPs). In other insects, PBPs serve as central molecular components in the process of chemical recognition of conspecifics. Fire ant workers regulate the number of egg-laying queens in a colony by accepting queens that produce appropriate chemical signals and destroying those that do not. The likely role of GP-9 in chemoreception suggests that the essential distinction in colony queen number between the single and multiple-queen form originates from differences in workers' abilities to recognize queens. Other, closely related fire ant species seem to regulate colony social organization in a similar fashion.

Variability in adult group compositions of a prosimian primate

Many species fall into specific mating-system categories, and that category is usually associated with a suite of behavioral and morphological characteristics. Several lemur species, including Propithecus diadema edwardsi, have been labeled "idiosyncratic" because variation in socionomic sex ratios among groups is consistent with wide variation in social structure. We used several hypotheses founded in behavioral ecology to assess variability in P. d. edwardsi. First we examined 46 group-mating seasons to quantify variability. We then tested predictions that the number of males per group would increase as the number of adult females increased, and the number of males would increase as female mating synchrony increased. Examining variation in offspring survival relative to the number of adult males in a group may tell us which composition is likely to persist into the future, so we also hypothesized that as the number of males in a group increased, fertility and offspring survival would increase. We found an equal distribution of polygynous, polygynandrous, pairs, and polyandrous groups. Furthermore, female distribution and mating synchrony did not predict the number of males, and offspring survival was not correlated with the number of males. Since infants survived equally well in groups of all compositions, sifakas experienced no pressure to maintain a particular number of adult males per adult female. The small number of adults per group (mean=3.2) may result from balancing feeding competition against predator detection. Augmenting the mate pool available from the group with mates from neighboring groups may promote the notable variability seen in the adult group compositions of sifakas.

Role of forage, habitat and predation in the behavioural plasticity of a small African antelope

Summary Ecological influences on social organization can best be measured by comparing populations of a socially variable species living in different environments. We examined causes of variability in social behaviour in a socially plastic small antelope, the oribi, Ourebia ourebi Zimmermann, in Ghana, West Africa. In total, 161 individually identified oribi were observed at five sites along an ecological gradient through dry and rainy seasons. Behavioural observations and ecological data were used to test the relative influence of forage abundance and quality, habitat structure and predation pressure on female dispersion and male social behaviour. Of nine ecological variables that were quantified, forage abundance and quality accounted best for variation in female dispersion among and within study populations. Specifically, female oribi formed larger groups and had smaller ranges where dry season forage was relatively abundant and low in fibre. Male territorial behaviour differed among sites and was related to female home range size. Males were most active in territory maintenance where females had small home ranges, and males defended a female rather than a territory where females ranged widely. These results show that variation in social organization among oribi subpopulations in Ghana reflects female responses to the availability and quality of dry season food resources and male responses to the variable distribution and ranging behaviour of females.

Nesting and life cycle of the Australian green carpenter bees Xylocopa (Lestis) aeratus Smith and Xylocopa (Lestis) bombylans (Fabricius) (Hymenoptera: Apidae: Xylocopinae)

AbstractThis paper expands on previous observations of Australian green carpenter bees by providing information about nesting substrates and the life cycle of Xylocopa (Lestis) aeratus and Xylocopa (Lestis) bombylans from more than 450 colonies from South Australia and New South Wales. Voltinism differs between the two species, but does not appear to vary within species from different locations, such as X. aeratus colonies on Kangaroo Island, South Australia and at Woy Woy, New South Wales. The architecture of nests (unbranched or branched) is related to the substrate diameter and may allow variation in social behaviour because different provisioning strategies can be used in the two nest types. Both species have some multifemale colonies for most of the year and this includes the brood‐rearing period. Differences in voltinism, nest type and the occurrence of multifemale colonies during brood production are likely to lead to variation in social organisation within and between species.

Social structure of a polygynous tent‐making bat,Cynopterus sphinx(Megachiroptera)

AbstractThe social structure of an Old World tent‐making batCynopterus sphinx(Megachiroptera), was investigated in western India. A combination of census and mark–recapture data over 2 years (1996–98) was used to infer the form of the mating system, compositional stability of social groups and mode of new social group formation. The breeding population ofC. sphinxwas subdivided into diurnal roosting colonies, each of which contained one to five discrete roosting groups and often one or more solitary bats in adjacent roosts. Bats most frequently roosted in stem tents constructed in the flower/fruit clusters of the kitul palmCaryota urens. Temporal variation in social structure was assessed using visual census data for a subset of the study population over 3 years (1995–98) spanning six consecutive reproductive periods. The sex and age composition of diurnal roosting groups indicated a polygynous harem‐forming mode of social organization, as groups invariably contained a single adult male, 1–37 reproductive females and their dependent young (n= 33 harems). Harem size averaged 6.1 adults in the wet season (n= 19,sd= 3.5) and 13.6 adults in the dry season (n= 14,sd= 8.5). The same harem social configuration was maintained year‐round, despite a high degree of synchrony and seasonality in the timing of reproduction. Juveniles of both sexes dispersed after weaning and sexually immature bats were never present in harems at the time of parturition. Adult females often remained associated as roostmates from one parturition period to the next, and group cohesion was unaffected by turnover of harem males. Adult females frequently transferred among roosts within the same colony, and harems underwent periodic fissions and fusions. The founding of new harems most often resulted from the fissioning of previously cohesive harems within the same colony. However, some harems contained disproportionate numbers of yearling females, indicating that new groups are also founded by nulliparous females of the same age cohort. A significant degree of heterogeneity in age composition among harems was revealed in the 1998 dry season, but was unrelated to age‐stratification of tent roosts. Although formation of new harems may be non‐random with respect to age composition of the founders, founding events are not restricted to newly created tents and often involve recolonization of previously occupied roosts.

Social structure and helping behavior in captive elephants

Selective pressures on individual behavior serve to mold social structure and subsequent levels of cooperation in social species, including elephants. Adult Asian (Elephas maximus) and African (Loxodonta africana) elephants have complex social societies that differ markedly between the sexes. Elephant social structure and cooperative behavior may have evolved in part to prepare young elephants to meet the challenges of an expansive environment, predators and parasites. In captivity, such forces are relaxed or eliminated, yet captive elephants display a similar repertoire of behaviors as their wild counterparts. Elephants live in herds of related adult females from several generations. This female social unit is centered on calves and the matriarch. Adult males reside in bachelor herds, singly, or frequent female groups, depending on male age and reproductive condition. In captivity, female elephants are usually housed together, although group size is smaller than in the wild, whereas adult males are generally housed separately from other elephants. Beyond these general similarities between wild and captive settings, captive elephants are housed in a wider range of group sizes, degrees of relatedness, and age structures than would be typical in the wild. This variation in social structure can be used to explore questions about cooperative behavior. Following a comparison of wild and captive social structures for elephants, three such potential avenues for study are discussed. Specifically, research with captive elephants could shed light on the development of social behavior, the functional significance of allomothering, and the ability of elephants to recognize kin or social group members. Beside the potential theoretical implications and insight into wild elephant behavior, the examination of social behavior also has important ramifications for the management of animals in captivity. Zoo Biol 19:447–459, 2000. © 2000 Wiley-Liss, Inc.

Contradictory findings in studies of sex ratio variation in roe deer ( Capreolus capreolus )

Patterns of sex ratio variation and maternal investment reported in the literature are often inconsistent. This could be due to intra- and inter-specific variation in social systems, but may also be a result of the a posteriori nature of much of this type of analysis or the testing of models which are inappropriate. Two recent papers reported directly opposed results concerning variation in offspring sex ratios in relation to maternal condition in roe deer, interpreting the results as support for the Trivers and Willard model and for the local resource competition hypothesis, respectively. In this paper, we present data on offspring sex ratios and early juvenile body weight from two long-term studies of this species to test predictions arising from these two models concerning sex biases in litter composition and maternal care. First, we observed no consistent pattern of sex differences in an index of weaning weight or body weight at 1 month old in either population, indicating a lack of sex bias in maternal care. However, in one population, higher maternal body weight was associated with higher juvenile body weight of daughters, but not of sons. Secondly, we found a negative, but not statistically significant, relationship between maternal body weight and litter sex ratio such that heavier females tended to produce more daughters and lighter females to produce more sons. These results indicate that roe females which have additional investment potential available do not invest it in sons, as predicted by the Trivers and Willard model. Our results may provide some support that roe deer are subject to local resource competition acting at the level of the individual mother; however, the fact that particular trends in sex ratio data can be explained in functional terms provides no indication that they are actually adaptive.

How Variations in Social Structure Affect Different Types of Intergroup Bias and Different Dimensions of Social Identity in a Multi-Intergroup Setting

An experimental paradigm was used to examine how manipulations of group status (higher, equal, or lower) and group size (smaller, equal, or larger) affect positive allocation bias, negative allocation bias, and evaluative bias expressed by minority-ingroup members toward majority- and minority-outgroup members. As predicted, in most cases, group status was positively related to bias against a higher status majority outgroup, but negatively related to bias against a lower status minority outgroup. Group size was inversely related to expressions of bias in two of the three studies. Four dimensions of social identity (ingroup attraction, self-ingroup interdependency, intergroup differentiation, and perceptions of the intergroup context) were measured and found to be differentially affected by the manipulations. Status was positively related to most of the dimensions of social identity, but the predicted inverse relationship between group size and social identity received mixed support. Of the four dimensions, self-ingroup interdependency and unfavorable perceptions of the intergroup context were most consistently related to intergroup bias. The implications of these findings for theories of intergroup relations and future research efforts are discussed.

Climate Change and Society

This article traces the long intellectual history that seeks to understand the recursive relationship between variations in the Earth's climate and variations in social structure and cultural practices. Contemporary sociological investigations of this theme have evolved along two paths: the neoidealistic orientation of social constructivism and a neo-realist orientation comprising two complementary approaches. Both orientations are explicated and evaluated, leading to a conclusion that provides programmatic directions.

Feral asses ( Equus africanus): intraspecific variation in social organization in arid and mesic habitats

Feral asses have been studied in the arid habitats of the southwestern United States [Moehlman, P.D., 1974. Behavior and ecology of feral asses ( Equus asinus). PhD dissertation, University of Wisconsin, Madison, 251 pp.; Moehlman, P.D., 1979. Behavior and ecology of feral asses ( Equus asinus). Nat. Geogr. Soc. Res. Reports 1970, 405–411.; Woodward, S.L., 1979. The social system of feral asses ( Equus asinus). Z. Tierpsychol. 49, 304–316] and in the mesic habitat of Ossabaw Island, Georgia [Moehlman, P.D., 1979, ibid; McCort, W.D., 1980. The feral asses ( Equus asinus) of Ossabaw Island, Georgia. PhD dissertation, Pennsylvania State University, University Park, 219 pp]. The feral ass populations in these two locales exhibited intraspecific variation in polygynous mating systems and social organization which were consistent with the ecological classification of mating systems of Emlen and Oring (1977) [Emlen, S.T., Oring, S.W., 1977. Ecology, sexual selection, and the evolution of mating systems. Science 197 (4300), 215–223]. Feral asses in the arid environment have a `resource defense' polygynous mating system, and those in the mesic habitat exhibit `female (harem) defense' polygyny. The intraspecific variation observed in feral asses encompasses the interspecific variation observed in the family Equidae.

Feral asses ( Equus africanus) of Volcano Alcédo, Galapagos: behavioral ecology, spatial distribution, and social organization

Feral asses were studied on Volcano Alcédo, Galapagos Islands, Ecuador, during the wet season of 1980. On the volcano rim during March/April, two stable groups were observed to have a `female (harem) defense' polygynous mating system [Emlen, S.T., Oring, S.W., 1977. Ecology, sexual selection, and the evolution of mating systems. Science 197 (4300), pp. 215–223] and social behavior patterns and feeding ecology similar to feral asses living in a habitat where forage and climate are similar, e.g., Ossabaw Island, Georgia [Moehlman, P.D., 1979. Behavior and ecology of feral asses ( Equus asinus). Nat. Geogr. Soc. Res. Rep., 1970, pp. 405–411; Moehlman, P.D., 1997. Feral asses ( Equus africanus): intraspecific variation in social organization in arid and mesic habitats. J. Appl. Anim. Behav. Sci., this issue; McCort, W.D., 1980. The feral asses ( Equus asinus) of Ossabaw Island, Georgia., PhD Dissertation, Pennsylvania State University, University Park, 219 pp.].

Evolution of sociality in the allodapine bees: a review of sex allocation, ecology and evolution

Comparative studies provide one of the most powerful means of assessing the relative roles of selective agents underlying social evolution in insects. Because of the wide variation in social organisation, sex allocation and ecological traits within and between species of allodapine bees, this group provides a wealth of material for such comparative work. Recent studies on Australian allodapine bees are reviewed here and their consequences for understanding social evolution are discussed. Studies to date suggest the following trends: (i) benefits of group living appear to be linked to preventing brood failure rather than to increased brood rearing efficiency; (ii) female-biased sex allocation, when it occurs, is linked to benefits of group living and kinship among nestmates, and is probably mediated via local fitness enhancement; (iii) female-biased sex allocation patterns do not usually coincide with opportunities for sib-rearing and are therefore unlikely to facilitate eusociality; (iv) relatedness within colonies is usually high, but in some species females will nest with unrelated females if kin are not available; and (v) phylogenetic studies suggest that opportunities for sib-rearing, arising from brood development patterns and colony phenology, are plesiomorphic for the exoneurine group, but in at least one phylogenetically distal clade, Exoneura sensu stricto, the evolution of large group size and social complexity coincides with the loss or reduction of opportunities for sib-rearing. Assured fitness return models may be applicable to weakly social allodapine species, but do not predict patterns of eusociality. Instead, Australian studies suggest that the evolution of large group size and marked reproductive skew is linked with the need to defend against enemies at the nest, rather than high levels of relatedness, female biased sex allocation or opportunities to rear siblings.

Queen lifespan and colony characteristics in ants and termites

Comparative studies are increasingly used to identify factors responsible for the evolution of plant and animal phenotypes and social insects provide ideal systems for such studies as a result of their modular growth and their bewildering diversity in social organization. Here I review data on the lifespan of queens in ants and termites because such data are highly relevant for comparative analyses on life-history. Lifespan has been reported in 53 ant and 10 termite species. Information on the mode of colony founding and number of queens per colony is also provided for the 53 ant species. Finally, I suggest that students of social insects would greatly benefit if information on colony characteristics, individual phenotypes and behaviour would become available for a larger number of species, perhaps on a database that would be accessible on the web.

On Emergency Decisions, Egalitarianism, and Group Selection

Previous articleNext article No AccessDiscussion and CriticismOn Emergency Decisions, Egalitarianism, and Group SelectionPolly WilessnerPolly WilessnerBox 9448, Eros, Windhoek, Namibia ([email protected]). 6 XII 97 Search for more articles by this author Box 9448, Eros, Windhoek, Namibia ([email protected]). 6 XII 97PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Current Anthropology Volume 39, Number 3June 1998 Sponsored by the Wenner-Gren Foundation for Anthropological Research Article DOIhttps://doi.org/10.1086/204744 Views: 17Total views on this site Citations: 1Citations are reported from Crossref © 1998 by The Wenner‐Gren Foundation for Anthropological Research. All rights reservedPDF download Crossref reports the following articles citing this article:Rebecca H. Schwendler Diversity in social organization across Magdalenian Western Europe ca. 17–12,000 BP, Quaternary International 272-273 (Sep 2012): 333–353.https://doi.org/10.1016/j.quaint.2012.03.054

Family strategies, inheritance systems and the care of the elderly in historical perspective : eastern and western Finland

When structuring the famous North West European household system, Hajnal excluded Finland on the assumption that the household system in Finland in the 18th and 19th centuries varied radically from the Northwest European pattern and more closesly resembled the one described as Eastern European (Hajnal 1965, 1983). Studies on local and regional level have revealed different family patterns not only in urban and rural environments but also in the countryside in the east and the west. In western Finland stem-families were common while in eastern Finland multiple family households with horizontal extension are frequently found. The origin of these differences can be traced to diverging systems within the framework of pre-industrial rural primary production. The economy created a favourable ground for specific arrangements of landownership and inheritance. Landless households in the east and the west were less complex in structure, and overall figures are largely affected by variation in social structure. The capacity of coping with old age changed over time. In the 18th century a large proportion of the elderly could be cared for within the stem or multiple family systems. However, the increasing social stratification in the 19th century placed many elderly people in a difficult position. The more that is known about how families functioned in the past, the clearer it becomes, that for different types of societies and at different times families have developed strategies to cope with restraints put upon them, and have * Address all communications to Beatrice Moring, Cambridge Group for the History of Population and Social Structure 27, Prumpington Street, Cambridge CB2 1QA, England.

Israeli women entrepreneurs: An examination of factors affecting performance

Israeli women entrepreneurs: An examination of factors affecting performance

DETERMINANTS OF PRIMATE SOCIAL ORGANIZATION: COMPARATIVE EVIDENCE AND NEW INSIGHTS FROM MALAGASY LEMURS

ABSTRACTThe aim of this review is to summarize newly available information on lemur social systems, to contrast it with the social organization of other primates and to relate it to existing models of primate social evolution. Because of their evolutionary history, the primates of Madagascar constitute a natural experiment in social evolution. During millions of years of isolation, they converged with other primates only in the most fundamental way in the evolution of solitary, pair‐living and group‐living species, but deviate in several respects within these basic categories of social organization. Solitary lemurs remain poorly studied, but their social organization appears to be broadly similar to that of other solitary primates, even though the unexpected lack of sexual dimorphism may indicate that similar types of social organization can give rise to different mating systems. The determinants of a solitary lifestyle remain elusive. Pair‐living lemurs show striking convergences with other monogamous primates in several behavioural traits, but also deviate in that the majority of species are at least partly nocturnal and do not exhibit direct paternal care of dependent young. Group‐living lemurs have not evolved single‐male groups, male‐bonded and multi‐level societies, and polyandrous groups may also be lacking. Female philopatry is common, but female bonds are generally weakly developed and eviction of females from natal groups is not unusual. Group‐living lemurs also differ from anthropoids in that their groups have even adult sex ratios, smaller average size and may split up on a seasonal basis. Feeding competition, predation risk and reproductive competition can not fully explain these unusual aspects of lemur social organization. It has therefore been suggested that the social consequences of the risk of infanticide and of recent changes in activity may be ultimately responsible for these idiosyncracies of group‐living lemurs, an explanation largely supported by the available evidence. Thus, social factors and fundamental life‐history traits, in addition to ecological factors, contribute importantly to variation in social systems among lemurs, and possibly other primates. However, neither the diversity of lemur social systems, nor the evolutionary forces and mechanisms operating in these and other primates are yet fully understood.

Local variability in population structure and density of the protogynous reef herbivoreSparisoma viride

We compare the (relative) abundance of life phases [juveniles (JU), initial phase (IP) and terminal phase (TP) fish], social categories (territorial and group adults), and fish following alternative mating styles, in three local populations of the protogynous reef herbivore,Sparisoma viride, on the fringing reef of Bonaire (Netherlands Antilles). In order to determine the adaptive significance of variations in social organization, they are related to the density of conspecifics and other herbivores and to the availability of food, shelter and mating sites. The most striking difference is the high abundance of JU and group fish at one location (Playa Frans) and the total absence of group fish at another (Red Slave). These differences are coherent with a gradient in population density, total herbivore density, scarid grazing pressure, and reproductive output, all of which are highest at Playa Frans and lowest at Red Slave. Exposure to waves and currents shows an inverse trend. The differences in the relative abundance of territorial fish can be explained by the concept of economic defendability, which is reduced at higher population density. In a life history context, small TP group males represent ‘bachelors’ that sacrifice current reproduction for better future prospects. As predicted by life history theory, early sex change is promoted at sites where the future rewards are higher (higher spawning rates of large TP males) and where the costs incurred during the bachelor phase are reduced (more spawning opportunities for group TP males). At Red Slave an alternative male mating style (‘streaking’) appears to be promoted by the lack of a refuge for group TP males and by a dense gorgonian canopy, allowing IP males to reside inside territories. We conclude that most observed differences in population structure can be considered adaptive in an ecological and in a life history context. Population density is a major factor in both contexts. Analysis of the variability in adult density in relation to JU density and the availability of food and shelter indicates that theS. viride populations at Bonaire are not totally controlled by stochastic processes. Considering the small spatial scale and the high dispersal of the planktonic embryos and larvae, the observed variability in behavioural and life history traits ofS. viride points to a high degree of phenotypic plasticity.

Reproductive conflicts in cooperative associations of fire ant queens (Solenopsis invicta)

In ants, unrelated queens frequently associate to initiate a colony cooperatively. The joint reproductive effort of the cofoundresses increases growth and survival of the incipient colony. However, such associations are unstable. Soon after emergence of the first workers, queen-queen and queen-worker fights lead to the death or expulsion of all but one cofoundress. Because no sexual offspring are produced in incipient colonies the surviving queen monopolizes the entire future reproductive success of the colony. Two factors, the queens9 relative fighting ability and their relative contribution to worker production (assuming that workers can recognize and selectively favour their mother) have been proposed to influence the survival prospects of individual queens within associations. The effect of these two factors was tested in the fire ant Solenopsis invicta. Initial size differences, a potential measure of the queens9 fighting ability, affected the outcome of the conflicts, so that the initially heavier queen was more likely to survive. Differential loss of mass by initially equal nestmates also affected survival, with the queen losing more body mass being more likely to die. The manipulation of the queens9 relative contribution to the worker brood did not significantly affect the queens9 survival probability, suggesting that workers are unable to favour their mother.

Size, Life-History Traits, and Social Organization in the Canidae: A Reevaluation

Any selective advantages of large body size may be counteracted by an increase in energetic costs associated with reproduction. In canids, larger female body size has been sug- gested to be associated with increasingly altricial young, larger litter sizes, and an increase in female pre- and postpartum energetic investment in offspring. It is hypothesized that the chang- ing costs of reproduction with increasing body size result in a size-related diversity of canid reproductive life histories and social organization. Smaller canid species require less postpartum investment and thus tend toward polygyny and have a skewed dispersal ratio toward males. Larger species, with greater prepartum investment, require greater male investment in the rear- ing of offspring and thus tend to be group living. Using data on canid life histories, a phylogeny of the Canidae based on 383 base pairs of mitochondrial DNA, and an autoregressive compara- tive method, we found this hypothesis was not supported. Strong isometric relationships be- tween neonate weight and female weight indicate that neonate size is constrained by female size directly or by parameters co-varying with female body size. Female weight accounted for only 26% of the variance in litter size, and no correlation was found between litter size and neonate weight. This result implies that female prenatal investment can be adjusted only by litter size (and not by neonate or litter weight), which in turn may be adjusted according to resource availability, an explanation supported by field and laboratory studies. In general, we hypothesize that much of canid interspecific and intraspecific variation in social structure may be explained by focusing on proximate enivironmental mechanisms, specifically resource avail- ability.