Maintenance of polygenic sex determination in a fluctuating environment: an individual-based model.

R. A. Fisher predicted that individuals should invest equally in offspring of both sexes, and that the proportion of males and females produced (the primary sex ratio) should evolve towards 1:1 when unconstrained. For many species, sex determination is dependent on sex chromosomes, creating a strong tendency for balanced sex ratios, but in other cases, multiple autosomal genes interact to determine sex. In such cases, the maintenance of multiple sex-determining alleles at multiple loci and the consequent among-family variability in sex ratios presents a puzzle, as theory predicts that such systems should be unstable. Theory also predicts that environmental influences on sex can complicate outcomes of genetic sex determination, and that population structure may play a role. Tigriopus californicus, a copepod that lives in splash-pool metapopulations and exhibits polygenic and environment-dependent sex determination, presents a test case for relevant theory. We use this species as a model for parameterizing an individual-based simulation to investigate conditions that could maintain polygenic sex determination. We find that metapopulation structure can delay the degradation of polygenic sex determination and that periods of alternating frequency-dependent selection, imposed by seasonal fluctuations in environmental conditions, can maintain polygenic sex determination indefinitely.

Social structure mediates environmental effects on group size in an obligate cooperative breeder, Suricata suricatta.

Population dynamics in group-living species can be strongly affected both by features of sociality per se and by resultant population structure. To develop a mechanistic understanding of population dynamics in highly social species we need to investigate how processes within groups, processes linking groups, and external drivers act and interact to produce observed patterns. We model social group dynamics in cooperatively breeding meerkats, Suricata suricatta, paying attention to local demographic as well as dispersal processes. We use generalized additive models to describe the influence of group size, population density, and environmental conditions on demographic rates for each sex and stage, and we combine these models into predictive and individual-based simulation models of group dynamics. Short-term predictions of expected group size and simulated group trajectories over the longer term agree well with observations. Group dynamics are characterized by slow increases during the breeding season and relatively sharp declines during the pre-breeding season, particularly after dry years. We examine the demographic mechanisms responsible for environmental dependence. While individuals appear more prone to emigrate after dry years, seasons of low rainfall also cause reductions in reproductive output that produce adult-biased age distributions in the following dispersal season. Adult subordinates are much more likely to disperse or be evicted than immature individuals, and demographic structure thus contributes to crashes in group size. Our results demonstrate the role of social structure in characterizing a population's response to environmental variation. We discuss the implications of our findings for the population dynamics of cooperative breeders and population dynamics generally.

Effectiveness of psychotherapeutic treatment of personality disorder.

BACKGROUND: Psychiatrists have been criticised for failing to develop adequate treatment for personality disorder. Psychotherapeutic treatments are promising, but their effectiveness is uncertain. AIMS: To investigate the evidence for effectiveness of psychotherapeutic treatment for personality disorder. METHOD: Systematic literature review. RESULTS: There is evidence for the effectiveness of psychotherapy for personality disorder. Problems of case identification, comorbidity, randomisation, specificity of treatment and outcome measurement are inadequately addressed. Authors mainly relied on cohort studies. Evidence neither suggests superiority of one type of therapy over another nor indicates which subgroups of patients should be offered psychotherapy as in-patient, day patient, or out-patient. CONCLUSIONS: New research strategies are needed to show that personality change is both measurable and clinically meaningful. Effectiveness studies using randomised controlled designs are required. The literature suggests that effective treatment should be long-term, integrated, theoretically coherent and focused on compliance.

Thick- and thin-skinned organisations and enactment in borderline and narcissistic disorders.

In this paper the author argues that enactment is any mutual action within the patient/analyst relationship that arises in the context of difficulties in countertransference work. Such enactment is common during the treatment of borderline and narcissistic disorders. In order to delineate different forms of enactment, which in his view may be either to the detriment or to the benefit of the analytic process, the author describes a patient who was identified primarily with a sadistic mother and who threatened the analyst with a knife during treatment. Three levels of enactment involving countertransference responses are described of which two, namely a collusive countertransference and a defensive countertransference, were detrimental to the analytic process. The third level of enactment was beneficial but only because the intervention by the analyst was independent of the analytic process and yet in response to it. The author uses Rosenfeld's distinction between thin-skinned and thick-skinned narcissists to illustrate how enactment is most likely when a patient moves between thick-skinned and thin-skinned narcissistic positions. Nevertheless the move between thin and thick-skinned positions presents an opportunity for effective interpretation, allowing progress in treatment.

Borderline personality in Britain: a preliminary study.

Patients admitted to a psychiatric hospital in England were interviewed using both the Present State Examination (PSE) to obtain a standardized diagnosis and the Diagnostic interview for Borderlines (DIB) to measure their borderline status. Comparison of the patients' symptom profiles showed that borderline patients were similar to neurotic patients, but had greater irritability. They were also more likely to receive a clinical diagnosis of hysterical personality disorder with neurotic depression by a British clinician.