The agency problem on microbial markets

Version 1.2 (3 APR 24)

Agents, traders, and levels of adaptation

It can be problematic to identify the entities that act as agents on biological markets, especially in the case of microbes. The same applies to eusocial insects, clones of plants, symbiotic organisms such as lichens, to name a few examples.

The market paradigm implies that one can distinguish ‘traders’ that choose among trading partners and can outbid competing traders in order to be preferred by partners. Traders are the entities that implement heritable trading strategies that are shaped by natural selection. In that sense the ‘agency problem’ runs parallel to the ‘levels of selection’ question (or better the ‘levels of adaptation’ question according to Gardner & Grafen (2009) J.Evol.Biol. 22 p659), but the relevant time scales are different. Traders implement trading strategies in real time that evolve over evolutionary time.

By the way, I have the impression that some biologists have to take the ‘levels of adaptation’ issue more seriously. One still encounters reasoning seemingly based on the assumption that natural selection acts at the level of species by people that are obviously not familiar with the ‘group selection’ debate that raged through behavioural/evolutionary ecology in the 1960ies.

Partner choice

Invoking the market paradigm makes little sense if one cannot establish the occurrence of partner choice, best by the mechanisms by which that choice is implemented. Showing the existence of partner choice by testing the difference in preference between partners belonging to two (or more) different species will probably work best in experiments with microbes. This should, however, not be confused with the way partner choice drives the evolution of trading strategies, which is by causing fitness differences between members of the same species.

Partner choice elicits outbidding competition, which in turn causes changes in supply-demand ratios to cause changes in exchange rates of commodities, e.g. between goods such as metabolites and services such as the production of defensive toxins. The next hurdle to take is identifying the choosing agents and their targets. The latter do not necessarily have to be the same type of entities as the former.

Firms

A biological entity that is composed of multiple individuals, such as a colony of eusocial insects, a lichen, or a biofilm, but acts as a single trader on a biological market, can be likened to what is called a ‘firm’ in the jargon of economics. In human societies firms, which can be formed by large numbers of individuals that execute a number of different tasks in different roles, can implement trading strategies, choose their partners, and outbid other firms and/or individuals. A firm can be compared to a boat carrying many people that all float or sink together. The criterion for comparing a group of organisms to a firm, and consider that group as a single trader or agent on a biological market, is their interdependency when it comes to survival and reproduction. That reminds again of units of selection: natural selection acts at the level of individuals, for a large part at least, because individuals can be likened to packages of genes: all manage to send copies into the next generation or none do. Meiosis and recombination will cause copies of genes from each package to part ways, sooner or later depending on their relative position in the genome, and form newly combined packages in the form of new individuals. The entities subject to market dynamics are individuals, however, and not independent genes.

 last update of this page:  25 SEP 24