The ecological significance of alternative life-history styles

Abstract

A brief review is provided of the concept of alternative life-history styles and its relevance to ecology and natural resource management. Recent findings that organisms are more flexible than was previously thought are emphasized. It has long been recognised that animals (and plants) may follow different trajectories in their development in preparation for the nature of the co-evolving environment. Several names have been given to the phenotype pairs which arise from these dichotomies (such as r- and K-strategists, generalists/specialists, maintenance and dispersal phenotypes, etc.), but there has been little attention to the mechanism behind the dichotomies since the pioneering work of Waddington and others. Recent investigations on epigenesis in a variety of animal groups have revealed that the saltatory mode of development (combined with paedomorphosis) provides the mechanism for the choice of alternative life-history styles (ALHS). The significance of ALHS in ecology is examined with particular reference to the niche, P/B ratios, diversity and ecological successions. The relationship between ALHS and environmental predictability is then investigated and discussed in the context of ideas on chaos and co-evolution. Knowledge of ALHS has direct relevance to nature conservation, the management of invasive organisms, fisheries and aquaculture. An attempt is made to amalgamate the various ideas on ALHS into a single hypothesis which expresses the universality of dichotomies in nature.