Random sperm use and genetic effects on worker caste fate in Atta colombica leaf-cutting ants

Sperm competition can produce fascinating adaptations with far-reaching evolutionary consequences. Social taxa make particularly interesting models, because the outcome of sexual selection determines the genetic composition of groups, with attendant sociobiological consequences. Here, we use molecular tools to uncover some of the mechanisms and consequences of sperm competition in the leaf-cutting ant Atta colombica, a species with extreme worker size polymorphism. Competitive PCR allowed quantification of the relative numbers of sperm stored by queens from different males, and offspring genotyping revealed how sperm number translated into paternity of eggs and adult workers. We demonstrate that fertilization success is directly related to sperm numbers, that stored sperm are well-mixed and that egg paternity is constant over time. Moreover, worker size was found to have a considerable genetic component, despite expectations that genetic effects on caste fate should be minor in species with a low degree of polyandry. Our data suggest that sexual conflict over paternity is largely resolved by the lifetime commitment between mates generated by long-term sperm storage, and show that genetic variation for caste can persist in societies with comparatively high relatedness

Years of potential life lost and life expectancy in schizophrenia: a systematic review and meta-analysis

Background Several studies and meta-analyses have shown that mortality in people with schizophrenia is higher than that in the general population but have used relative measures, such as standardised mortality ratios. We did a systematic review and meta-analysis to estimate years of potential life lost and life expectancy in schizophrenia, which are more direct, absolute measures of increased mortality. Methods We searched MEDLINE, PsycINFO, Embase, Cinahl, and Web of Science for published studies on years of potential life lost and life expectancy in schizophrenia. Data from individual studies were combined in meta-analyses as weighted averages. We did subgroup analyses for sex, geographical region, timing of publication, and risk of bias (estimated with the Newcastle-Ottawa Scale). Findings We identified 11 studies in 13 publications covering all inhabited continents except South America (Africa n=1, Asia n=1, Australia n=1, Europe n=7, and North America n=3) that involved up to 247 603 patients. Schizophrenia was associated with a weighted average of 14·5 years of potential life lost (95% CI 11·2–17·8), and was higher for men than women (15·9, 13·8–18·0 vs 13·6, 11·4–15·8). Loss was least in the Asian study and greatest in Africa. The overall weighted average life expectancy was 64·7 years (95% CI 61·1–71·3), and was lower for men than women (59·9 years, 95% CI 55·5–64·3 vs 67·6 years, 63·1–72·1). Life expectancy was lowest in Asia and Africa. Timing of publication and risk of bias had little effect on results. Interpretation The effects of schizophrenia on years potential life lost and life expectancy seem to be substantial and not to have lessened over time. Development and implementation of interventions and initiatives to reduce this mortality gap are urgently needed. Funding None