ON THE LIFE-HISTORY AND SYSTEMATIC POSITION OF THE ORGANISMS CAUSING DRY TOP ROT OF SUGAR CANE

Resumen en inglé

Disentangling pre- and postnatal maternal age effects on offspring performance in an insect with elaborate maternal care

Maternal effect senescence has attracted much recent scientific interest. However, the age-related effects of pre- and postnatal maternal age are often conflated, as these naturally originate from the same individual. Additionally, many maternal effect senescence studies fail to account for potential biases associated with selective disappearance. Here we use a cross-fostered laboratory population of a burying beetle, Nicrophorus vespilloides, to examine both the effects of female pre- and postnatal maternal age on offspring life-history traits and the postcare outcomes of mothers while accounting for selective disappearance of postnatal caregivers. Neither pre- nor postnatal maternal age affected offspring longevity or larval weight at hatching, and postnatal age had no effect on postcare maternal outcomes except to confirm the presence of actuarial senescence. There was weak evidence for concave relationships between two larval traits (dispersal weight and survival) and the age of egg producers. Selective disappearance of caregivers had no clear effect on any of the measured offspring traits. Contrary to predictions from evolutionary theory, maternal effect senescence and reproductive effort increases do not always manifest, and current theory may be insufficient to account for the true diversity of aging patterns relating to maternal care

Triparental ageing in a laboratory population of an insect with maternal care

Parental age at reproduction influences offspring size and survival by affecting prenatal and postnatal conditions in a wide variety of species, including humans. However, most investigations into this manifestation of ageing focus upon maternal age effects; the effects of paternal age and interactions between maternal and paternal age are often neglected. Furthermore, even when maternal age effects are studied, pre- and post-natal effects are often confounded. Using a cross-fostered experimental design, we investigated the joint effects of pre-natal paternal and maternal and post-natal maternal ages on five traits related to offspring outcomes in a laboratory population of a species of burying beetle, Nicrophorus vespilloides. We found a significant positive effect of the age of the egg producer on larval survival to dispersal. We found more statistical evidence for interaction effects, which acted on larval survival and egg length. Both interaction effects were negative and involved the age of the egg-producer, indicating that age-related pre-natal maternal improvements were mitigated by increasing age in fathers and foster mothers. These results agree with an early study that found little evidence for maternal senescence, but it emphasizes that parental age interactions may be an important contributor to ageing patterns. We discuss how the peculiar life history of this species may promote selection to resist the evolution of parental age effects, and how this might have influenced our ability to detect senescence

Experimental and comparative analyses of maternal age and senescence

Senescence is often described as an age-related physiological deterioration accompanied with declining fertility and increasing mortality, and it is believed to be the result of declining forces of natural selection. A manifestation of senescence that has attracted much recent interest is the detrimental effect of increasing maternal age acting on offspring traits. However, uncertainty arises when attempting to describe the prevalence and ubiquity of this third form of ageing and the evolutionary causes for diversity in ageing trajectories. Here I address the following questions: (1) How are maternal age effects distributed across taxa? And (2) Can an evolutionary perspective help us to understand the observed diversity in maternal age effects and demographic senescence? I addressed these through (i) a cross-fostering ageing experiment using a laboratory population of burying beetle, Nicrophorus vespilloides to decouple the separate effects of increasing pre- and postnatal maternal age, whilst accounting for the potential bias of selective disappearance. I found no evidence for maternal age effects or effects deriving from selective disappearance. These results suggest that current theory may be insufficient to account for the true diversity in ageing patterns. (ii) A meta-analytical review of maternal effect senescence to investigate the prevalence and diversity of maternal effect ageing patterns and the performance of an evolutionary model to predict observed patterns. We found taxa-wide evidence for maternal age effects on offspring survival. However the direction of these effects was based on phylogenetic constraints with laboratory and natural-mammal species showing a decline, but natural-bird species showing an ambiguous effect of maternal age. The evolutionary model was shown to improve in performance compared to evolution-agnostic demographic models when describing maternal effect ageing in natural populations. This result suggests an evolutionary cause to maternal effect senescence. (iii) Lastly, I performed a comparative analysis of vital rate selection across the tree of life. Using extensive existing databases of life history data coupled with predictions from two evolutionary theories, I derived correlations between predicted and observed vital rates across multiple animal species. I found that whilst natural selection had weak predictive power when describing patterns of mortality, age-specific fertility patterns showed extensive departures from evolutionary predictions. Additionally, I found that several biological processes were readily contributing to non-conformance of Hamilton-like ageing. Taken together, we provide convincing evidence to suggest that both natural selection and biological processes have helped shape the vast diversity of observed ageing rates that exist across the tree of life

No time to die: evolution of a post-reproductive life stage

In some species, permanent curtailment of reproduction part-way through the lifespan of adult females is a feature of their evolved life history. The existence of such a post-reproductive life stage is apparently rare; reasonably robust evidence for this is confined to only six species (humans, Asian elephants and four whales). That it occurs at all appears to contradict our view of natural selection operating to maximize fitness and special circumstances must exist to explain its occurrence. We evaluate the main hypotheses posited to explain the evolution of this life stage, why it occurs in a restricted group of animals, and why only in females. We bring together literature from multiple biological disciplines and levels of enquiry, ranging through evolutionary ecology, developmental biology, physiology, neuroscience, molecular biology, and human medicine. We conclude that while time-limited fertility is not in itself adaptive, the duration of subsequent survival is likely to be linked to inclusive fitness benefits. We present a new hypothesis which posits that the duration of female fertility in certain long-lived, highly encephalised species, with no post-natal oogenesis, is limited by the need for intense screening of oocyte mitochondria. This is required to support endothermy coupled with the very high energy requirement for the development and maintenance of the exceptionally large brain size required for complex social living. This limits the number and shelf-life of oocytes, creating an antagonistically pleotropic effect that is beneficial to the production of high performing offspring but carries the later life cost of time-limited female fertility. But the end of the fertile period is no time to die. Inclusive fitness benefits arising from protracted parental care of offspring, overlapping generations, and kin group structures means that continued survival of post-reproductive females is favoured by selection. We suggest further lines of research to test these ideas

Technology-enhanced simulation for healthcare professionals: A meta-analysis

AimThere have been substantial changes in the simulation technology landscape, in particular virtual reality (VR), during the past decade, which have resulted in increased abundance and decreased cost. We therefore updated a previous meta-analysis conducted in 2011, aiming to quantify the impact of digital technology-enhanced simulation (T-ES) compared with traditional teaching in physicians, physicians-in-training, nurses, and nursing students.DesignWe conducted a meta-analysis consisting of randomized controlled trials published in English between January 2011 and December 2021 in peer-reviewed journals indexed in seven databases. Moderators for study duration, instruction, type of healthcare worker, type of simulation, outcome measure, and study quality rated by Medical Education Research Study Quality Instrument (MERSQI) score were included in our model and used to calculate estimated marginal means (EMMs).ResultsThe overall effect of T-ES was positive across the 59 studies included in the analysis compared with traditional teaching [overall effect size 0.80 (95% CI 0.60, 1.00)]. This indicates that T-ES is effective in improving outcomes across a wide variety of settings and participants. The impact of T-ES was found to be greatest for expert-rated product metrics such as procedural success, and process metrics such as efficiency, compared with knowledge and procedure time metrics.ConclusionsThe impacts of T-ES training on the outcome measures included in our study were greatest in nurses, nursing students and resident physicians. T-ES was strongest in studies featuring physical high-fidelity mannequins or centers, compared with VR sensory environment T-ES, though there was considerable uncertainty in all statistical analyses. Further high-quality studies are required to assess direct effects of simulation training on patient and public health outcomes

The distribution of the Lansing Effect across animal species

Maternal senescence is the reduction in individual performance associated with increased maternal age at conception. When manifested on adult lifespan, this phenomenon is known as the “Lansing Effect.” Single-species studies report both maternal age-related increases and decreases in adult lifespan, but no comprehensive review of the literature has yet been undertaken to determine if the Lansing Effect is a widespread phenomenon. To address this knowledge gap, we performed a meta-analysis of maternal aging rates taken from all available published studies. We recovered 78 estimates from 22 studies representing 15 species. All studies taken together suggest a propensity for a Lansing Effect, with an estimated average effect of maternal age on offspring’s adult lifespan of between -17% and -22%, depending upon our specific choice of model. We failed to find a significant effect of animal class or insect order but given the oversampling of insect species in the published literature and the paucity of vertebrate studies, we infer that only rotifers and insects yet demonstrate a tendency toward expressing the phenomenon

Editorial: Ecological and evolutionary relevance of phenotypic plasticity in a changing world

No abstract available

Fitness benefits of dietary restriction

Dietary restriction (DR) improves survival across a wide range of taxa yet remains poorly understood. The key unresolved question is whether this evolutionarily conserved response to temporary lack of food is adaptive. Recent work suggests that early-life DR reduces survival and reproduction when nutrients subsequently become plentiful, thereby challenging adaptive explanations. A new hypothesis maintains that increased survival under DR results from reduced costs of overfeeding. We tested the adaptive value of DR response in an outbred population of Drosophila melanogaster fruit flies. We found that DR females did not suffer from reduced survival upon subsequent re-feeding and had increased reproduction and mating success compared to their continuously fully fed (FF) counterparts. The increase in post-DR reproductive performance was of sufficient magnitude that females experiencing early-life DR had the same total fecundity as continuously FF individuals. Our results suggest that the DR response is adaptive and increases fitness when temporary food shortages cease