Eco-evolutionary"fitness"in 3 dimensions: absolute growth, absolute efficiency, and relative competitiveness

Competitions can occur on an absolute scale, to be faster or more efficient, or they can occur on a relative scale, to “beat” one’s competitor in a zero-sum game. Ecological models have focused on absolute competitions, in which optima exist. Classic evolutionary models such as the Wright-Fisher model, as well as more recent models of travelling waves, have focused on purely relative competitions, in which fitness continues to increase indefinitely, without actually progressing anywhere. This manuscript proposes a new way to describe both at the same time. It begins with a revised version of r/K-selection theory. r continues to describe maximum reproductive speed, but the new version of K, with a different subscript, now describes parsimoniousness in territory use, a group-selected, anti-tragedy-of-the-commons trait. A third dimension c of fitness is then added to this novel system, one which is unitless and normalized, and hence capable of capturing the population genetics concept w of a strictly relative, genetically-limited competitive race. MacArthur’s original version of r/K-selection theory is shown to confound parsimoniousness K with competitive ability c, despite the fact that available data suggests a negative correlation between the two; here they are disentangled. A rotation of the resulting three-dimensional system provides a population genetic underpinning for Grime’s universal adaptive strategy theory of ruderals (selected for high r), stress tolerators (selected for a combination of high r and high K), and competitors (selected for a combination of high r and high c).