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This is a commentary on three articles on bibliometrics in social work that appear in this issue of the journal. I argue that bibliometrics can make many contributions to the study of the structure and evolution of social work's knowledge base, but it cannot completely remove subjectivity in the evaluation of the scholarship of individual faculty, where legitimate differences of professional opinion will remain.
The bee genus Lasioglossum includes > 1,000 species of bees distributed on all continents except Antarctica. Lasioglossum is a major component of the bee fauna in the Holarctic, Ethiopian, and Asian regions and is an important group for investigating the evolution of social behavior in bees. Given its cosmopolitan distribution, the historical biogeography of the genus is of considerable interest. We reconstructed phylogenetic relationships among the subgenera and species within Lasioglossum s.s., using DNA sequence data from a slowly evolving nuclear gene, elongation factor-1 alpha. The entire data set includes > 1,604 aligned nucleotide sites (including three exons plus two introns) for 89 species (17 outgroups plus 72 ingroups). Parsimony and maximum likelihood analyses provide strong evidence that the primarily Indoaustralian subgenera (Homalictus, Chilalictus, Parasphecodes) form a monophyletic group. Bootstrap support for the Australian clade ranged from 73% to 77%, depending on the method of analysis. Monophyly of the Australian Lasioglossum suggests that a single colonization event (by way of Southeast Asia and New Guinea) gave rise to a lineage of > 350 native Indoaustralian bees. We discuss the implications of Australian monophyly for resolving the "Australian enigma"--the similarity in social behavior among the Australian halictine bees relative to that of Holarctic groups.
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Recognition of relatives is considered a key factor in the evolution of sociality as it ensures that the benefits of altruism flow to those who share the altruist's genes. However, theory predicts that genetically based recognition systems will not persist if the only selection maintaining them derives from the recognition system itself. Kin-recognition systems, therefore, are hypothesized to involve genetic variation maintained by other functions. Polyembryonic wasps are parasites of moth larvae that clonally produce large numbers of offspring and two morphologically distinct castes. Some embryos develop into reproductive larvae that mature into adult wasps, whereas others develop into soldier larvae whose function is defence. Soldiers from Copidosoma floridanum distinguish relatives from non-relatives on the basis of relatedness. Here, we report that the recognition cues used by soldiers derive from the extraembryonic membrane, which also protects these parasites from the host's immune response. This suggests that the kin-recognition system used by C. floridanum may be maintained in part by selection for resistance against the host.
Echolocating bats are auditory specialists, with exquisite hearing that spans several octaves. In the ultrasonic range, bat audiograms typically show highest sensitivity in the spectral region of their species-specific echolocation calls. Well-developed hearing in the audible range has been commonly attributed to a need to detect sounds produced by prey. However, bat pups often emit isolation calls with low-frequency components that facilitate mother-young reunions. In this study, we examine whether low-frequency hearing in bats exhibits correlated evolution with (i) body size; (ii) high-frequency hearing sensitivity or (iii) pup isolation call frequency. Using published audiograms, we found that low-frequency hearing sensitivity is not dependent on body size but is related to high-frequency hearing. After controlling for high-frequency hearing, we found that low-frequency hearing exhibits correlated evolution with isolation call frequency. We infer that detection and discrimination of isolation calls have favoured enhanced low-frequency hearing because accurate parental investment is critical: bats have low reproductive rates, non-volant altricial young and must often identify their pups within large crèches.
It is widely accepted that natal philopatry is a prerequisite for the evolution of sociality. The life-history hypothesis maintains that longevity of adults results in extended territory tenure and thus limits breeding vacancies for offspring, which makes natal philopatry more likely. Here, we tested the importance of longevity for natal philopatry in females of a basal primate, the grey mouse lemur (Microcebus murinus). This species is regarded as being solitary due to its foraging habits but while males disperse, female offspring in this species forgo dispersal and form long-term sleeping groups with their mothers. We tested whether high adult survival could be a cause for natal philopatry of female offspring. In addition, we assessed costs and benefits associated with space sharing between mothers and daughters and whether mothers actively increase survival of daughters by beqeauthal of territories, information transfer about resources or thermoregulation. Contrary to our predictions, adult females had low-survival rates. Space sharing appeared to improve survival of both, mothers and daughters. This could be a result of information transfer about sleeping sites and thermoregulatory benefits. Our results cast doubt on the idea that longevity predisposes species for social traits and provide support for benefits of philopatry.
Cultural transmission in our species works most of the time as a cumulative inheritance system allowing members of a group to incorporate behavioral features not only with a positive biological value but sometimes also with a neutral, or even negative, biological value. Most of models of dual inheritance theory and gene-culture coevolution suggest that an increase, either qualitative or quantitative, in the efficiency of imitation is the key factor to explain the transformation of primate social learning in a cumulative cultural system of inheritance as it happens during hominization. We contend that more efficient imitation is necessary but not enough for this transformation to occur and that the key factor enabling such a transformation is that some hominids developed the capacity to approve or disapprove their offspring's learned behavior. This capacity to approve or disapprove offspring's behavior makes learning both less costly and more accurate, and it transformed the hominid culture into a system of cumulative cultural inheritance similar to that of humans, although the system was still prelinguistic in nature.
Social Hymenoptera show two contrasting strategies of colony reproduction. A reproductive female can raise the first generation of brood alone (independent foundation), or a colony can divide into autonomous parts in which the reproductive female is helped by sterile relatives (fission, budding, swarming). In independent-founding ants, queens can histolize their flight muscles after dispersal; in many species, large flight muscles and metabolic reserves reduce or eliminate the need for risky foraging trips during the vulnerable solitary stage. Colony division is a derived strategy, and we review the selective pressures leading to its occurrence in the different social taxa. In various ants, fission coexists with independent foundation, and alate queens are retained. However, in ants exhibiting obligate fission (e.g. all army ants and many Ponerinae), queens are permanently wingless (ergatoid), or the queen caste is missing altogether. When reproductive females are flightless, dispersal distances and colonization ability are reduced, and there are extensive modifications in mating behavior and resource allocation. We focus on the characteristics of fission in the phylogenetically primitive ants Ponerinae in which both ergatoid queens and gamergates occur. The ground-living habits of ants have permitted extensive changes in the phenotypes of their reproductive females, unlike in wasps and bees.
We examined the distribution and ancestral relationships of genetic caste determination (GCD) in 46 populations of the seed-harvester ants Pogonomyrmex barbatus and P. rugosus across the east-to-west range of their distributions. Using a mtDNA sequence and two nuclear markers diagnostic for GCD, we distinguished three classes of population phenotypes: those with GCD, no evidence of GCD, and mixed (both GCD and non-GCD colonies present). The GCD phenotype was geographically widespread across the range of both morphospecies, occurring in 20 of 46 sampled populations. Molecular data suggest three reproductively isolated and cryptic lineages within each morphospecies, and no present hybridization. Mapping the GCD phenotype onto a mtDNA phylogeny indicates that GCD in P. rugosus was acquired from P. barbatus, suggesting that interspecific hybridization may not be the causal agent of GCD, but may simply provide an avenue for GCD to spread from one species (or subspecies) to another. We hypothesize that the origin of GCD involved a genetic mutation with a major effect on caste determination. This mutation generates genetic conflict and results in the partitioning and maintenance of distinct allele (or gene set) combinations that confer differences in developmental caste fate. The outcome is two dependent lineages within each population; inter-lineage matings produce workers, while intra-lineage matings produce reproductives. Both lineages are needed to produce a caste-functional colony, resulting in two reproductively isolated yet interdependent lineages. Pogonomyrmex populations composed of dependent lineages provide a unique opportunity to investigate genetic variation underlying phenotypic plasticity and its impact on the evolution of social structure.
We develop a two-level selection model in the framework of evolutionary game theory, in which fitness selection at different levels is related to different games. We consider an archipelago of communities, such that selection operates at an individual level inside each community and at a group level whenever evolution of communities is at stake. We apply this model to the evolution of social norms, an open problem of ubiquitous importance in social science. Extensive statistical analysis of our results lead to the emergence of one common social norm, of which the evolutionary outcomes in different communities are simple by-products. This social norm induces reputation-based cooperative behavior, and reflects the evolutionary propensity to promote simple, unambiguous norms, in which forgiveness and repent are welcome, while punishment is implacable.
Although the total number of social workers within the academic medical center will probably decrease because of decreasing hospital bed usage, the role for those who remain will be that of a clinical specialist, a sophisticated and adaptable practitioner who can work flexibly under minimal supervision. The valued social work practitioner will be an independent player on the health care team who assumes a significant role which no other member of that team is equipped to take. Advanced training is more important today than ever before in the evolution of social work practice in academic health care. However, this training is not now available within the parameters of the two year master's program.
Schizophrenia is a worldwide, prevalent disorder with a multifactorial but highly genetic aetiology. A constant prevalence rate in the face of reduced fecundity has caused some to argue that an evolutionary advantage exists in unaffected relatives. Here, I critique this adaptationist approach, and review--and find wanting--Crow's "speciation" hypothesis. In keeping with available biological and psychological evidence, I propose an alternative theory of the origins of this disorder. Schizophrenia is a disorder of the social brain, and it exists as a costly trade-off in the evolution of complex social cognition. Paleoanthropological and comparative primate research suggests that hominids evolved complex cortical interconnectivity (in particular, frontotemporal and frontoparietal circuits) to regulate social cognition and the intellectual demands of group living. I suggest that the ontogenetic mechanism underlying this cerebral adaptation was sequential hypermorphosis and that it rendered the hominid brain vulnerable to genetic and environmental insults. I argue that changes in genes regulating the timing of neurodevelopment occurred prior to the migration of Homo sapiens out of Africa 100,000-150,000 years ago, giving rise to the schizotypal spectrum. While some individuals within this spectrum may have exhibited unusual creativity and iconoclasm, this phenotype was not necessarily adaptive in reproductive terms. However, because the disorder shared a common genetic basis with the evolving circuitry of the social brain, it persisted. Thus schizophrenia emerged as a costly trade-off in the evolution of complex social cognition.
Pair formation in social insects mostly happens early in adult life and away from the social colony context, which precludes promiscuity in the usual sense. Termite males have continuous sperm production, but males of social Hymenoptera have fixed complements of sperm, except for a few species that mate before female dispersal and show male-fighting and lifelong sperm production. We develop an evolutionary framework for testing sexual selection and sperm competition theory across the advanced eusocial insects (ants, wasps, bees, termites) and highlight two areas related to premating sexual selection (sexual dimorphism and male mate number) that have remained understudied and in which considerable progress can be achieved with relatively simple approaches. We also infer that mating plugs may be relatively common, and we review further possibilities for postmating sexual selection, which gradually become less likely in termite evolution, but for which eusocial Hymenoptera provide unusual opportunities because they have clonal ejaculates and store viable sperm for up to several decades.
Communication between individuals of a species is likely to increase the capacity to acquire skills useful for survival and propagation and thus may confer important selective advantages. Since interaction occurs between two or more individuals, the selective process is frequency dependent, and the analysis shows that communication cannot initially increase at a reasonable rate when it is limited to random unrelated individuals, so that it is likely to abort for stochastic reasons. However, this bottleneck is removed if the communication process takes place in the nuclear family or among close relatives or if aggregation of communicators occurs because of assortative mating or meeting. Use of the individual conditional fitnesses we have introduced earlier permits an exact analysis. We show that, in general, the initial rate of increase can be geometric if and only if, in the class of selective models considered, the conditional probability of a communicator interacting with another contains a positive constant term. In our discussion of communication, cost factors for the act of communication have been omitted. However, the model has been generalized to include cooperativeness, and also altruism, or competition, by introducing costs. There is a close relationship among these situations, and the same considerations about the initial bottleneck and its resolution also extend to them. The models given here are for haploids but they extend to diploids and the conclusions are similar.
To evaluate the role of individual recognition in the evolution of cooperation, we formulated and analyzed genetic algorithm model (EvCo) for playing the Iterated Prisoner's Dilemma (IPD) game. Strategies compete against each other during each generation, and successful strategies contribute more of their attributes to the next generation. Each strategy is encoded on a 'chromosome' that plays the IPD, responding to the sequences of most recent responses by the interacting individuals (chromosomes). The analysis reported in this paper considered different memory capabilities (one to five previous interactions), pairing continuities (pairs of individuals remain together for about one, two, five, or 1000 consecutive interactions), and types of individual recognition (recognition capability was maximal, nil, or allowed to evolve between these limits). Analysis of the results focused on the frequency of mutual cooperation in pairwise interactions (a good indicator of overall success in the IPD) and on the extent to which previous responses by the focal individual and its partner were associated with the partner's identity (individual recognition). Results indicated that a fixed, substantial amount of individual recognition could maintain high levels of mutual cooperation even at low pairing continuities, and a significant but limited capability for individual recognition evolved under selection. Recognition generally increased mutual cooperation more when the recent responses of individuals other than the current partner were ignored. Titrating recognition memory under selection using a fitness cost suggested that memory of the partner's previous responses was more valuable than memory of the focal's previous responses. The dynamics produced to date by EvCo are a step toward understanding the evolution of social networks, for which additional benefits associated with group interactions must be incorporated.
Heterozygosity at loci affecting resistance against parasites can benefit host fitness. We predict that, in haplodiploid species, haploid males will suffer decreased parasite resistance relative to diploid females. We suggest that elevated susceptibility in haploid males has shaped the evolution of social behaviour in haplodiploid species. Male susceptibility will select for behavioural adaptations that limit males' exposure to pathogens and that limit male transmission of pathogens within and between colonies. The relatedness-asymmetry hypothesis that has been advanced to explain female-only workers does not make these predictions. We review the relevant evidence for genetic effects on parasite resistance in insects and summarize empirical evidence that relates to the haploid-susceptibility hypothesis.
This paper reviews recent advances in field endocrinology, a focus as well as a method in primatology and behavioral ecology that permits the examination of social behavior and life history through hormonal investigations in natural settings. Endocrine data complements the traditional behavioral data collected by field scientists by providing quantitative measures for the examination of adaptive tradeoffs, costs of social strategies, and reproductive and social significance of mating events. Further, investigations of the physiological mechanisms of reproductive constraint provide tests of the adaptive significance of reproductive skew in cooperative and competitive breeders. Hormone data also can provide insights into the costs of competition and aggression and the role of temperament in individual reproductive success and the evolution of social systems. New, noninvasive methods for the collection of this information have augmented and expanded field endocrinology through the use of techniques that do not require potentially confounding physical or physiological manipulations. Specifically, urine and fecal samples can be collected from free-ranging animals and contain gonadal and adrenal hormones that parallel profiles of serum hormones. Sampling, preservation, extraction, and assay methods for the analysis of excreted steroids are reviewed along with the species and questions to which these methods have been applied.
Hamilton's rule provides the foundation for understanding the genetic evolution of social behavior, showing that altruism is favored by increased relatedness and increased productivity of altruists. But how likely is it that a new altruistic mutation will satisfy Hamilton's rule by increasing the reproductive efficiency of the group? Altruism per se does not improve efficiency, and hence we would not expect a typical altruistic mutation to increase the mean productivity of the population. We examined the conditions under which a mutation causing reproductive altruism can spread when it does not increase productivity. We considered a population divided into temporary groups of genetically similar individuals (typically family groups). We show that the spread of altruism requires a pleiotropic link between altruism and enhanced productivity in diploid organisms, but not in haplodiploid organisms such as Hymenoptera. This result provides a novel biological understanding of the barrier to the spread of reproductive altruism in diploids. In haplodiploid organisms, altruism within families that lowers productivity may spread, provided daughters sacrifice their own reproduction to raise full-sisters. We verified our results using three single-locus genetic models that explore a range of the possible reproductive costs of helping. The advantage of female-to-female altruism in haplodiploids is a well-known prediction of Hamilton's rule, but its importance in relaxing the linkage between altruism and efficiency has not been explored. We discuss the possible role of such unproductive altruism in the origins of sociality. We also note that each model predicts a large region of parameter space were polymorphism between altruism and selfishness is maintained, a pattern independent of dominance.