Recentcompetitiontheory

Fortunately, research on competition theory has revived, and has increased great­ly over the past two decades. For example, Peter Chesson’s (2000a) Annual Reviews article on competition has been cited at an accelerating rate over the years, and now has several thousand citations.

In spite of this sizeable number of publications and citations, the theory seems to have lost direction. While a resource-based approach has continued to be used by some quantitative ecologists, particularly in systems involving planktonic algae (e.g., Huisman and Weissing 2001; Litchman and Klausmeier 2001), its use by ecologists as a whole has diminished (as noted by McPeek 2019a). Many recent papers on com­petition theory have concentrated on models that lack resources (Levine et al. 2017; Saavedra et al. 2017; Hart et al. 2018). Even when a resource-based approach has been used, the component functions have, in the vast majority of studies, been drawn from early literature, and have failed to reflect the range of possibilities that are likely to occur among consumer species exhibiting adaptive behaviour in a food web context. One consequence of this is that we still know very little about how somewhat more realistic models differ in their dynamic behaviour from the ‘first generation' models. A further consequence of the concentration on historical functional forms is that little effort has been devoted to determining functional forms that actually exist in natural systems.

This historical inertia of the theoretical work means that there is still little ability to predict how measurable changes in the environment will alter population sizes in groups of competing species, and competition between species is still mostly absent from analyses of applied problems such as harvesting and conservation. Although interspecific competition in natural communities is unlikely to involve only isolat­ed pairs of species, a large fraction of recent analyses are restricted to two-species competition, often with only two resources, and usually without any other foodweb context.

Evidence for the uncertain standing of competition theory is not simply the opin­ion of a few specialists. Reiners et al. (2017) analysed a survey of over 1300 members of the Ecological Society of America, to determine which concepts practising ecolo­gists found most useful. ‘Lotka-Volterra Models' was the lowest ranked concept on their list, even though ‘competition' was ranked in the top ten. In a separate anal­ysis of the influence of a long list of ecological concepts using figures on citation frequency (McCallen et al. 2019), the top ranked concept was ‘models’. It could be that these opinions reflect the viewpoint of this introductory chapter. However, the models employed in much of the recent literature share many of the same limitations as the LV model, and the LV itself continues to be the primary or exclusive model in many high-profile theoretical works. The problem seems to be twofold: (1) that most field workers only regard theory as useful if it is something that can be ‘tested' in relatively short-duration experiments; and (2) the majority of theoreticians have not been interested in a systematic exploration of how the most likely modifications of the simplest models alter their dynamics and outcomes.

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