Ultimate causes and the evolution of altruism

Reconciling the evolution of altruism with Darwinian natural selection is frequently presented as a fundamental problem in biology. In addition to an exponentially increasing literature on specific mechanisms that can permit altruism to evolve, there has been a recent trend to establish general principles to explain altruism in populations undergoing natural selection. This paper reviews and extends one approach to understanding the ultimate causes underlying the evolution of altruism and mechanisms that can realise them, based on the Price equation. From the Price equation, we can see that such ultimate causes equate to the different ways in which the frequency of an altruistic allele in a population can increase. Under this approach, the ultimate causes underlying the evolution of altruism, given some positive fitness costs and benefits, are positive assortment of altruistic alleles with the altruistic behaviour of others, positive deviations from additive fitness effects when multiple altruists interact or bias in the inheritance of altruistic traits. In some cases, one cause can be interpreted in terms of another. The ultimate causes thus identified can be realised by a number of different mechanisms, and to demonstrate its general applicability, I use the Price equation approach to analyse a number of classical mechanisms known to support the evolution of altruism (or cooperation): repeated interaction, ‘greenbeard’ traits, games played on graphs and payoff synergism. I also briefly comment on other important points for the evolution of altruism, such as the ongoing debate over the predominant status of inclusive fitness as the best way to understand its evolution. I conclude by arguing that analysing the evolution of altruism in terms of its ultimate causes is the logical way to approach the problem and that, despite some of its technical limitations, the Price equation approach is a particularly powerful way of doing so.     

Two roads to two sexes: unifying gamete competition and gamete limitation in a single model of anisogamy evolution

Recent studies have revealed the importance of self-consistency in evolutionary models, particularly in the context of male–female interactions. This has been largely ignored in models of the ancestral divergence of the sexes, i.e., the evolution of anisogamy. Here, we model the evolution of anisogamy in a Fisher-consistent context, explicitly taking into account the number of interacting individuals in a typical reproductive group. We reveal an interaction between the number of adult individuals in the local mating group and the selection pressures responsible for the divergence of the sexes. The same underlying model can produce anisogamy in two different ways. Gamete competition can lead to anisogamy when it is relatively easy for gametes to find each other, but when this is more difficult and gamete competition is absent, gamete limitation can provide another route for anisogamy to evolve. In line with earlier models, organismal complexity favors anisogamy. We argue that the early contributions of Kalmus and Scudo, largely dismissed as group selectionist, are valid under certain conditions. Linking their work with the contributions of Parker helps to explain why precisely males keep producing more sperm than can ever lead to offspring: sperm could evolve to provision zygotes but this brings little profit for the effort required, because sperm would have to be equipped with provisioning ability before it is known which sperm will make it to the fertilization stage. This insight creates a logical link between paternal care under uncertain paternity (where again investment is selected against when some investment never brings about genetic benefits) and gamete size evolution.     

Species divergence and seasonal succession in rates of mate desertion in closely related Neotropical cichlid fishes

Across animal taxa, exclusive female offspring care has evolved repeatedly from biparental care, suggesting that the latter becomes evolutionarily unstable under certain conditions. Both the attributes of a species and the environment it experiences can help to predict shifts from one particular care mode to another. Nevertheless, factors inducing differences in care strategies among closely related species, or seasonal variation within species, have been subject to surprisingly little empirical testing. Here, we report the results of a field-based study that examined both among and within species variation in mate desertion in five species of closely related Nicaraguan cichlid fish in the genera Amphilophus and Amatitlania. The results show a link between female body size and male involvement in offspring care. Specifically, the larger the species the less often males were found to provide extended care. Furthermore, we found that solitary females became more common towards the end of the breeding season. We discuss the implications of this finding in the context of previous theoretical and empirical contributions regarding the frequency of offspring desertion by males.     

Survey on the pesticide residues in tea in south India

Tea is considered as a ‘health beverage’ due its antioxidant properties and resultant beneficial effects on human health. Such a beverage should be free from toxic elements such as pesticide residues and heavy metals. A large scale survey of teas produced in the tea factories of south India had been carried out for a period of three years from 2006 to 2008 and 912 tea samples were analysed for the residues of certain pesticides such as dicofol, ethion, quinalphos, hexaconazole, fenpropathrin, fenvalerate and propargite which are used for pest and disease control in tea in this part of the country. The analytical data proved that only less than 0.5 percentage of tea samples had residues of these pesticides. However, residues of pesticides were below their maximum limits in tea, stipulated by the European Union, Codex Alimentarius Commission of FAO/WHO and Prevention of Food Adulteration Act of Govt. of India.     

Modelling the long-term morphological evolution of the Clyde Estuary,Scotland, UK

The long-term morphodynamic response of the Clyde Estuary to any possible change in environmental forcing associated with global climate change and human interference is examined here using a model based on a systems approach. The model, which uses Boolean Algebra as its formal mathematical language, provides a qualitative insight into the long term morphodynamic behaviour of the estuarine system, at this level without the need for detailed and quantitative hydrodynamic and morphodynamic process knowledge or extensive data resources. The model predictions suggest that the long-term morphological changes in the Clyde Estuary largely depend on the fluvial flow of the River Clyde. Salt marshes in the upper reaches of the estuary were found to be the most vulnerable morphological feature of the estuary. In the event of increased river flow in the future, a likely situation according to climate change scenarios, saltmarshes will deplete or disappear altogether, irrespective of the sediment influx into the estuary. Changes to waves and tides will also contribute to the evolution by taking the estuary through significantly different intermediate morphological states whilst evolving towards a stable end state.     

Near-critical free-surface flows: real fluid flow analysis

An open channel flow with a flow depth close to the critical depth is characterised by a curvilinear streamline flow field that results in steady free surface undulations. Near critical flows of practical relevance encompass the undular hydraulic jump when the flow changes from supercritical (F > 1) to subcritical (F < 1), and the undular weir flow over broad-crested weirs where the flow changes from subcritical (F < 1) to supercritical (F > 1). So far these flows were mainly studied based on ideal fluid flow computations, for which the flow is assumed irrotational and, thus, shear forces are absent. While the approach is accurate for critical flow conditions (F = 1) in weir and flumes, near-critical flows involve long distances reaches, and the effect of friction on the flow properties cannot be neglected. In the present study the characteristics of near-critical free-surface flows are reanalysed based on a model accounting for both the streamline curvature and friction effects. Based on the improved model, some better agreement with experimental results is found, thereby highlighting the main frictional features of the flow profiles.     

Predator–prey models: an application for the plankton dynamics of lake Geneva

In this paper we present a hierarchical Bayesian analysis for a predator–prey model applied to ecology considering the use of Markov Chain Monte Carlo methods. We consider the introduction of a random effect in the model and the presence of a covariate vector. An application to ecology is considered using a data set related to the plankton dynamics of lake Geneva for the year 1990. We also discuss some aspects of discrimination of the proposed models.     

Confronting Management Challenges in Highly Uncertain Natural Resource Systems: a Robustness–Vulnerability Trade-off Approach

This paper presents a framework for the study of policy implementation in highly uncertain natural resource systems in which uncertainty cannot be characterized by probability distributions. We apply the framework to parametric uncertainty in the traditional Gordon–Schaefer model of a fishery to illustrate how performance can be sacrificed (traded-off) for reduced sensitivity and hence increased robustness, with respect to model parameter uncertainty. With sufficient data, our robustness–vulnerability analysis provides tools to discuss policy options. When less data are available, it can be used to inform the early stages of a learning process. Several key insights emerge from this analysis: (1) the classic optimal control policy can be very sensitive to parametric uncertainty, (2) even mild robustness properties are difficult to achieve for the simple Gordon–Schaefer model, and (3) achieving increased robustness with respect to some parameters (e.g., biological parameters) necessarily results in increased sensitivity (decreased robustness) with respect to other parameters (e.g., economic parameters). We thus illustrate fundamental robustness–vulnerability trade-offs and the limits to robust natural resource management. Finally, we use the framework to explore the effects of infrequent sampling and delays on policy performance.     

A Method for Ensemble Wildland Fire Simulation

An ensemble simulation system that accounts for uncertainty in long-range weather conditions and two-dimensional wildland fire spread is described. Fuel moisture is expressed based on the energy release component, a US fire danger rating index, and its variation throughout the fire season is modeled using time series analysis of historical weather data. This analysis is used to characterize the seasonal trend in ERC, autocorrelation of residuals, and daily standard deviation and stochastically generate artificial time series of afternoon fuel moisture. Daily wind speed and direction are sampled stochastically from joint probabilities of historical wind speed and direction for the date range of the fire simulation period. Hundreds or thousands of fire growth simulations are then performed using the synthetic fire weather sequences. The performance of these methods is evaluated in terms of the number of ensemble member simulations, one- versus two-dimensional fire spread simulations, and comparison with results from 91 fires occurring from 2007 to 2009. Simulations were found to be in consistent agreement with observations, but trends indicate that the ensemble average of simulated fire sizes were consistently larger than actual fires whereas the farthest extent burned by fires was underestimated.