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Biomedical subjects

William J Sutherland

Publications and source records attributed to William J Sutherland.

10 recordsLinked to original sources
PubMed2006

Selection for protection in an ant-plant mutualism: host sanctions, host modularity, and the principal-agent game.

Retaliation against cheaters can prevent the breakdown of cooperation. Here we ask whether the ant-plant Cordia nodosa is able to apply retaliatory sanctions against its ant symbiont Allomerus octoarticulatus, which patrols new shoots to prevent herbivory. We test the hypothesis that the modular design of C. nodosa physiologically ties the growth of housing (stem swellings known as domatia) to the successful development of the attached leaves. We experimentally simulated herbivory by cutting leaves from patrolled shoots and found that the domatia on such 'cheated' shoots suffered higher mortality and lower growth than did controls, evidence for a host sanction. On the other hand, patrolling is costly to the ant, and experiment shows that non-patrollers run a low risk of being sanctioned because most leaves (and the attached domatia) escape heavy herbivory even when patrollers are absent. This suggests that cheaters might enjoy a higher fitness than do mutualists, despite sanctions, but we find that patrolling provides a net fecundity benefit when the colony and plant exceed a minimum size, which requires sustained ant investment in patrolling. These results map directly onto the principal-agent (P-A) game from economics, which we suggest can be used as a framework for studying stability in mutualisms, where high sampling costs and cheating do not allow market effects to select for mutual benefits.

Animals↗
PubMed2005

Seasonal matching of habitat quality and fitness in a migratory bird.

When species occupy habitats that vary in quality, choice of habitat can be critical in determining individual fitness. In most migratory species, juveniles migrate independently of their parents and must therefore choose both breeding and winter habitats. Using a unique dataset of marked black-tailed godwits (Limosa limosa islandica) tracked throughout their migratory range, combined with analyses of stable carbon isotope ratios, we show that those individuals that occupy higher quality breeding sites also use higher quality winter sites. This seasonal matching can severely inflate inequalities in individual fitness. This population has expanded over the last century into poorer quality breeding and winter habitats and, across the whole population; individual birds tend to occupy either novel or traditional sites in both seasons. Winter and breeding season habitat selection are thus strongly linked throughout this population; these links have profound implications for a wide range of population and evolutionary processes. As adult godwits are highly philopatric, the initial choice of winter habitat by juveniles will be critical in determining future survival, timing of migration and breeding success.

Animal Migration↗
PubMed2005

The best solution.

Explore the source record for details and available documents.

Adaptation, Physiological↗
PubMed2004

The need for evidence-based conservation.

Much of current conservation practice is based upon anecdote and myth rather than upon the systematic appraisal of the evidence, including experience of others who have tackled the same problem. We suggest that this is a major problem for conservationists and requires a rethinking of the manner in which conservation operates. There is an urgent need for mechanisms that review available information and make recommendations to practitioners. We suggest a format for web-based databases that could provide the required information in accessible form.

Journal Article↗
PubMed2003

Parallel extinction risk and global distribution of languages and species.

There are global threats to biodiversity with current extinction rates well above background levels. Although less well publicized, numerous human languages have also become extinct, and others are threatened with extinction. However, estimates of the number of threatened languages vary considerably owing to the wide range of criteria used. For example, languages have been classified as threatened if the number of speakers is less than 100, 500, 1,000, 10,000, 20,000 or 100,000 (ref. 3). Here I show, by applying internationally agreed criteria for classifying species extinction risk, that languages are more threatened than birds or mammals. Rare languages are more likely to show evidence of decline than commoner ones. Areas with high language diversity also have high bird and mammal diversity and all three show similar relationships to area, latitude, area of forest and, for languages and birds, maximum altitude. The time of human settlement has little effect on current language diversity. Although similar factors explain the diversity of languages and biodiversity, the factors explaining extinction risk for birds and mammals (high altitude, high human densities and insularity) do not explain the numbers of endangered languages.

Altitude↗
PubMed2002

Behavioural models of population growth rates: implications for conservation and prediction.

Conservation biologists often wish to predict how vertebrate populations will respond to local or global changes in conditions such as those resulting from sea-level rise, deforestation, exploitation, genetically modified crops, global warming, human disturbance or from conservation activities. Predicting the consequences of such changes almost always requires understanding the population growth rate and the density dependence. Traditional means of directly measuring density dependence are often extremely difficult and have the problem that if the environment changes then it is necessary to remeasure the density dependence. We describe an alternative approach that does not require such long datasets and can be used to predict the density dependence under novel conditions. Game theory can be used to describe behavioural decisions that individuals make in response to interference, prey depletion, territorial behaviour or social dominance, and the resultant fitness consequences. It is then possible to predict how survival or reproductive output changes with population size. From this we can then make predictions about the responses of populations to environmental changes. We will illustrate how this can be applied to a range of species and a range of applied problems.

Animals↗
PubMed1999

Measures of Inequality Are Not Equal.

Inequalities in reproductive success or resource acquisition are fundamental to evolution and population ecology. There is, however, no unique way to measure inequality. We review 21 measures used to quantify it and clarify the conceptual difference between inequality and skewness. In two very different families of distributions, all indices except three give higher values for more unequal distributions of resources, although some of them are poor at distinguishing between similar inequality values. When applied correctly by testing against a null hypothesis of no inequality among individuals, most indices can therefore be used to detect deviations from randomness, but with varying ease as most lack statistical tables and rely on resampling techniques instead. As an example to test the performance of the 21 indices, we used each index to analyze 71 data sets of unequal mating success in leks. In pairwise comparisons, 24% of the indices fail to show a positive intercorrelation. This reflects differences in how indices incorporate variation in the number of competitors and mean acquisition of the resource. All indices are sensitive to these aspects if inequality is measured in data arising from different distributions. These results illustrate the general conclusion that a unique "best" solution is not available; each measure presents its own definition of inequality. The choice of an inequality index requires specifying the null expectations and interpreting deviating values in relation to the biological question being addressed. This means, for example, considering individual male mating success in the context of lekking or relating the mass distribution of individual plants to alternative hypotheses about competition in plant population ecology. When sample sizes vary, testing robustness by using several measures is advisable.

leks↗