The scientific output of W. D. Hamilton can be broadly split into two parts; the first dealing with inclusive fitness and the evolution of social behaviour while the second part focused on the role of parasites in the evolution of sex. This change in research interest was marked by a classic paper published in this journal in 1980, ‘Sex versus non-sex versus parasite’. To mark Hamilton's death I consider the historical background and influence of this paper.
[Show abstract][Hide abstract] ABSTRACT: Recently W.D. Hamilton and colleagues proposed a provocative new theory to explain the adaptive significance of autumnal leaf colours. They suggested that these colours were signals produced by the trees to warn potential insect herbivores of their defensive ability and tested this theory by an analysis of data on aphid species richness on different tree species. Here we argue that the principal assumptions of their theory do not match current knowledge of plant pigment biochemistry and aphid ecology. We therefore present further adaptive explanations for autumn leaf colours and suggest alternative reasons for the reported relationship between tree leaf colour and aphid species richness.
[Show abstract][Hide abstract] ABSTRACT: Ecological science is often organised as a hierarchical series of entities: genes, individuals, populations, species, communities, ecosystems and biosphere. Here, I consider an alternative process-based approach to ecology, and analyse the nature of the fundamental processes in ecology. These fundamental processes are discussed in the context of the following question: 'for any planet with carbon-based life, which persists over geological time scales, what are the minimum set of ecological processes that must be present?' I suggest that the following processes would be present on any such planet: energy flow, multiple guilds, ecological trade-offs leading to within-guild biodiversity, ecological hypercycles, merging of organismal and ecological physiology, carbon sequestration and possibly photosynthesis. Nutrient cycling is described as an emergent property of these fundamental processes. I discuss reasons why a biosphere based on a single species with no nutrient cycling is very unlikely to exist. I also describe the concept of 'Gaian effect'. This suggests that some processes will always tend to extend the lifespan of a biosphere in which they develop (positive Gaian effect) while others could either increase or decrease (negative Gaian effect) such a lifespan. These ideas are discussed in the context of astrobiology, ecosystem services, conservation biology and Gaia theory.
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