How should parents adjust the size of their young in response to local environmental cues?

Models of parental investment typically assume that populations are well mixed and homogeneous and have devoted little attention to the impact of spatial variation in the local environment. Here, in a patch‐structured model with limited dispersal, we assess to what extent resource‐rich and resource‐poor mothers should alter the size of their young in response to the local environment in their patch. We show that limited dispersal leads to a correlation between maternal and offspring environments, which favours plastic adjustment of offspring size in response to local survival risk. Strikingly, however, resource‐poor mothers are predicted to respond more strongly to local survival risk, whereas resource‐rich mothers are predicted to respond less strongly. This lack of sensitivity on the part of resource‐rich mothers is favoured because they accrue much of their fitness through dispersing young. By contrast, resource‐poor mothers accrue a larger fraction of their fitness through philopatric young and should therefore respond more strongly to local risk. Mothers with more resources gain a larger share of their fitness through dispersing young partly because their fitness in the local patch is constrained by the limited number of local breeding spots. In addition, when resource variation occurs at the patch level, the philopatric offspring of resource‐rich mothers face stronger competition from the offspring of other local mothers, who also enjoy abundant resources. The effect of limited local breeding opportunities becomes less pronounced as patch size increases, but the impact of patch‐level variation in resources holds up even with many breeders per patch.     

Some highlights in the history of fungi in medicine – A personal journey

The history of the role of fungi in the development of medicine has largely been neglected. Here the early recognition of the germ theory will be discussed in relation to surface infections, the “cholera fungus theory” and recognition of the phenomenon of microbial antagonism. This leads to a short review of the history of those antibiotics produced by fungi, notably penicillin. Finally, the history of the recognition of the potential role fungi play as casual agents of cancer will be discussed; although currently neglected, this work may prove to be of future significance. This history of medical mycology is discussed from the standpoint of my own interest and research into this fascinating, and often overlooked area of medical history.     

Cadmium and health in the 21st Century – historical remarks and trends for the future

The first health effect of cadmium (Cd) was lung damage, reported in workers already in the 1930's, while bone effects and proteinuria were reported in the 1940's. After World War II, a bone disease with fractures and severe pain, the itai-itai disease, a form of Cd-induced renal osteomalacia, was identified in Japan. Subsequently, the toxicokinetics and toxicodynamics of Cd were described including its binding to the protein metallothionein. International warnings of health risks from cadmium pollution were issued in the 1970's. WHO, 1992, identified renal dysfunction as the critical effect and a crude quantitative evaluation was presented. In the 1990's population groups in China exposed to Cd via rice were studied and new information on skeletal, renal and reproductive toxicity of Cd was obtained in the ChinaCad project. There was a decrease in Bone Mineral Density (BMD), an increased prevalence of fractures and an increased urinary content of marker proteins of renal dysfunction among persons with long term exposure to Cd. The development of such biomarkers can be seen as a result of applied 'proteomics' research. Variation in metallothionein gene expression was related to development of renal dysfunction, supporting the usefulness of this 'genomic' approach. The ongoing rapid development of 'genomics' and 'proteomics' technologies will improve possibilities for molecular epidemiology studies in the future, providing an even better basis for preventive action. In many countries, Cd exposures are now under better control than in the past. The target for the 21st century is to achieve a totally acceptable exposure situation without adverse health effects from Cd.     

Effects of insecticides on life history parameters of the aphid parasitoidAphidius rhopalosiphi [Hym.: Aphidiidae]

The effects of four insecticides (two organophosphates, a pyrethroid and a carbamate), applied at different dosages, on different life history parameters of the aphid parasitoidAphidius rhopalosiphi (De Stefani-Perez) were tested. The methods used simulated field conditions in the laboratory. After application on the mummies, only two treatments (parathion and the high dosage of pirimicarb) caused a significant reduction of adult hatching. Fertility and longevity of the wasps were not affected by any of the tested insecticides. Dried residues of parathion, but not of the other insecticides, killed a considerable number ofA. rhopalosiphi females. The searching behaviour of the wasps was affected by demeton-S-methyl and fenvalerate. A direct application of demeton-S-methyl, parathion, and the high dosage of pirimicarb onA. rhopalosiphi females caused high mortality.     

Avian growth and development rates and age-specific mortality: the roles of nest predation and adult mortality

Previous studies have shown that avian growth and development covary with juvenile mortality. Juveniles of birds under strong nest predation pressure grow rapidly, have short incubation and nestling periods, and leave the nest at low body mass. Life-history theory predicts that parental investment increases with adult mortality rate. Thus, developmental traits that depend on the parental effort exerted (pre- and postnatal growth rate) should scale positively with adult mortality, in contrast to those that do not have a direct relationship with parental investment (timing of developmental events, e.g. nest leaving). I tested this prediction on a sample of 84 North American songbirds. Nestling growth rate scaled positively and incubation period duration negatively with annual adult mortality rates even when controlled for nest predation and other covariates, including phylogeny. On the contrary, neither the duration of the nestling period nor body mass at fledging showed any relationship. Proximate mechanisms generating the relationship of pre- and postnatal growth rates to adult mortality may include increased feeding, nest attentiveness during incubation and/or allocation of hormones, and deserve further attention.     

Atlantic salmon growth in strongly food-limited environments: Effects of egg size and paternal phenotype?

I manipulated egg size and followed individual mass trajectories from the egg stage in Atlantic salmon to test for effects of size, and for interactions between size and paternal body mass, on offspring performance in strongly food-limited environments. Egg size had a strong effect on body mass at yolk absorption, causing juveniles originating from large eggs to outgrow their siblings from small eggs. This corroborates previous findings of egg size effects under more benign environments, and demonstrates that positive effects of egg size on offspring success are manifested even under strong food-limitation. Previously reported negative effects of being large during the critical period for survival in dense populations are thus likely related to social interactions, rather than to effects of density on total food abundance in the environment. The effect of egg size on offspring performance, and hence the optimal egg size, was independent of paternal body mass.     

Panbiogeography: Its origin,metamorphosis and decline

From the viewpoint of 2007, one can trace the history of an interesting and contentious trend in biogeography and evolution that began with Croizat’s concept of panbiogeography in 1958. After a quiescent period of about 16 years, some young biologists in New York and in New Zealand read Croizat’s books and became enthusiastic supporters of his ideas. In New York, in the early 1970s, panbiogeography was combined with a part of Hennig’s phylogenetic method to create vicariance biogeography. In 1986, the name of the latter was changed to cladistic biogeography. In the meantime, Croizat’s followers in New Zealand sought to maintain panbiogeography in its original form without reference to phylogeny. This idea reached its peak of popularity in 1989–1990 and then began to fade. In comparison, cladistic biogeography became much more widespread, especially when its followers began publishing laudatory books and papers. Its decline became noticeable after the turn of the century as the dispersal counterrevolution began to have its effect. It served a useful purpose by engaging the interest of young biologists who otherwise may not have become aware of biogeography.     

Stochastic payoff evaluation increases the temperature of selection

We study stochastic evolutionary game dynamics in populations of finite size. Moreover, each individual has a randomly distributed number of interactions with other individuals. Therefore, the payoff of two individuals using the same strategy can be different. The resulting "payoff stochasticity" reduces the intensity of selection and therefore increases the temperature of selection. A simple mean-field approximation is derived that captures the average effect of the payoff stochasticity. Correction terms to the mean-field theory are computed and discussed.     

The nature and dynamics of world religions: a life-history approach

In contrast with tribal and archaic religions, world religions are characterized by a unique emphasis on extended prosociality, restricted sociosexuality, delayed gratification and the belief that these specific behaviours are sanctioned by some kind of supernatural justice. Here, we draw on recent advances in life history theory to explain this pattern of seemingly unrelated features. Life history theory examines how organisms adaptively allocate resources in the face of trade-offs between different life-goals (e.g. growth versus reproduction, exploitation versus exploration). In particular, recent studies have shown that individuals, including humans, adjust their life strategy to the environment through phenotypic plasticity: in a harsh environment, organisms tend to adopt a ‘fast'' strategy, pursuing smaller but more certain benefits, while in more affluent environments, organisms tend to develop a ‘slow'' strategy, aiming for larger but less certain benefits. Reviewing a range of recent research, we show that world religions are associated with a form of ‘slow'' strategy. This framework explains both the promotion of ‘slow'' behaviours such as altruism, self-regulation and monogamy in modern world religions, and the condemnation of ‘fast'' behaviours such as selfishness, conspicuous sexuality and materialism. This ecological approach also explains the diffusion pattern of world religions: why they emerged late in human history (500–300 BCE), why they are currently in decline in the most affluent societies and why they persist in some places despite this overall decline.     

Historical and environmental influences on hedgerow snail faunas

In three areas of the English Midlands, composition and diversity of hedgerow snail faunas are influenced both by historical and environmental differences between hedges. Soil aciditv and climate are the most important environmental factors. Hedges originating in or near woodland have richer faunas than those planted in open fields, and some snail species are indicators of woodland origin. Snail diversity also increases with the age of the hedge, but this effect is slight in hedges over 100 years old. It is suggested that these differences are primarily due to the poor dispersal of snails rather than to existing environmental differences between hedges of differing age and origins, and the results are compared with the very similar ones obtained for plants. Historical influences on the distribution ol slow-dispersing organisms may be of very general importance, even in comparisons of adjacent habitats with considerable temporal stability.     

The influence of maternal age and mating frequency on egg size and offspring performance in Callosobruchus maculatus (Coleoptera: Bruchidae)

Maternal age influences offspring quality of many species of insects. This observed maternal age influence on offspring performance may be mediated through maternal age effects on egg size, which in turn may be directly influenced by the female's nutritional state. Thus, behaviors that influence a female's nutritional status will indirectly influence egg size, and possibly offspring life histories. Because males provide nutrients to females in their ejaculate, female mating frequency is one behavior which may influence her nutritional status, and thus the size of her eggs and the performance of her offspring. In this paper, I first quantify the influences of maternal age on egg size and offspring performance of the bruchid beetle, Callosobruchus maculatus. I then examine whether nutrients transferred during copulation reduce the magnitude of maternal age effects on egg size and larval performance when mothers are nutrient-stressed. Egg size and egg hatchability decreased, and development time increased, with increasing maternal age. Multiple mating and adult feeding by females both resulted in increased egg size. This increase in egg size of females mated multiply did not translate into reduced development time or increased body size and egg hatchability, but did correlate with improved survivorship of offspring produced by old mothers. Thus, it appears that because the influence of mating frequency on egg size is small relative to the influence of maternal age, the influence of nutrients derived from multiple mating on offspring life history is almost undetectable (detected only as a small influence on survivorship). For C. maculatus, female multiple mating has been demonstrated to increase adult female survivorship (Fox 1993a), egg production (Credland and Wright 1989; Fox 1993a), egg size, and larval survivorship, but, contrary to the suggestion of Wasserman and Asami (1985), multiple mating had no detectable influence on offspring development time or body size.     

Herbivore-constructed leaf shelters on Salix eriocarpa shoots affect arthropod communities

We observed the abundance of leaf shelters, aphids, other herbivores, and predators on willow trees, Salix eriocarpa, from May to October 2003. There was a positive correlation between the growth rate of aphids and the number of ants per shoot, suggesting ant attendance to aphids. Although the mean abundance of leaf shelters per shoot was rather low (1.7–2.2) throughout the observation period, aphids preferred to use shoots with leaf shelters compared with those without leaf shelters. The abundance of ants was positively influenced by the presence of leaf shelters and aphids from May to August. The abundance of other herbivores was positively influenced by leaf shelters, but negatively influenced by aphid presence from May to August. Furthermore, leaf shelters had a positive effect on the abundance of predators from July to October. These data suggest that a relatively low abundance of naturally occurring leaf shelters per shoot influenced the arthropod communities on S. eriocarpa, and the effect of those leaf shelters on each type of arthropod varied according to the season.     

Successful theory development in biology: A consideration of the theories of oxidative phosphorylation proposed by Davies and Krebs,Williams and Mitchell

The chemiosmotic theory is normally attributed to Peter Mitchell's formulation published in Nature in 1961. However, the essential elements of the theory were published 9 years earlier by Davies and Krebs. Why, then, was this earlier formulation overlooked? The success of Mitchell's theory is examined in comparison with those of Davies and Krebs and of Williams.