Equivalence relations on ecosystems

TL;DR

This paper proposes a framework for comparing ecosystems based on the proportional population growth rates of species, emphasizing organism-centric equivalence over superficial property differences, and discusses implications for ecosystem dynamics and natural selection.

Contribution

It introduces an equivalence relation on ecosystems based on species growth rates, shifting focus from external properties to organism-centric comparisons.

Findings

Ecosystem equivalence is defined via species growth rates.

Organism-centric comparison can inform dissimilarity measures.

Ecosystem dynamics differ on equivalence classes from external observations.

Abstract

In abstract terms, ecosystem ecology is about determining when two ecosystems, superficially different, are alike in some deeper way. An external observer can choose any ecosystem property as being important. In contrast, two ecosystems are equivalent from the point of view of the organisms they contain if and only if for each species, the proportional population growth rate does not differ between the ecosystems. Comparative studies of ecosystems should therefore focus on patterns in proportional population growth rates, rather than patterns in other properties such as relative abundances. Popular activities such as measuring dissimilarity, and representing dissimilarity via ordination, can then be done from the point of view of the organisms in ecosystems. Summarizing the state of an ecosystem under this approach remains challenging. In general, the dynamics on equivalence classes of ecosystems defined in this way are structurally different from the dynamics of ecosystems as seen by an external observer. This may limit the extent to which natural selection can act on ecosystem structure.