Fitness

The fitness concept of evolutionary ecology differs from that of population genetics. The former is geared towards dealing with long term evolution through the repeated invasion of mutants for potentially complicated ecological scenarios, the latter with short term changes in relative frequencies of types for heavily simplified ecological scenarios. After a discussion of the conditions allowing for the definition of a general invasion fitness concept, among which that reproduction should be clonal, a framework is built within which the definition can be formalized. Recipes are given for calculating (proxies for) fitness in a large variety of instances. The main use of invasion fitness is in ESS calculations. Only under ecologically very special conditions ESSes can be calculated from optimization principles. These conditions are detailed, as well as the, even more special, conditions under which evolution maximizes r or Ro. The invasion fitness concept extends to any aggregates treatable as meta-individuals. Individual- and meta-individual-level invasion fitness coincide when the latter is larger than per capita within aggregate growth. Calculating invasion fitness through a meta-individual route often works beyond calculations based on inclusive fitness arguments, but provides less insight. Mendelian diploids are aggregates of clonally reproducing genes. Conditions are given for when predictions for virtual cloning diploids coincide with those from gene-based calculations