Table 1.

Research questions relating to the evolution of microbial biological markets

Evolution of	Question	Suggested approaches
Variation in partner quality	What is individual variation in market prices?	Descriptive; study microbial individuality
	Is it influenced by level of competition?	Manipulate level of competition; study change in partner quality variation
	Can it be used in an applied way?	Identify best genotypes for systems useful to humans; use experimental evolution to generate variation
Partner discrimination	Can microbes simultaneously evaluate partners and discriminate?	Track nutrients in networks/aggregates of microbes interacting with multiple partners
	For free-living microbes, can (chemotactic) mobility achieve discrimination?	Choice experiments between high- and low-quality partners
	Is discrimination more likely in multicellular than in single-celled microbes?	Descriptive studies; compare occurrence of partner discrimination
	Does spatial structure promote discrimination?	Analyze preference for quality partners in consortia/biofilms vs. in free-living microbes
Markets under volatility	Do trading partners respond to resource volatility according to market hypotheses?	Manipulate resources; track effects on microbial trade
	What (a)biotic factors influence supply/demand of resources and affect trade patterns?	Manipulate conditions to increase/decrease value of a resource; track effects on trade
Hoarding	Do microbes hoard resources?	Track resource storage, particularly in “farmers”
	Do microbes trade hoarded resources at a later stage?	Manipulate market conditions so trade is not beneficial; change supply/demand to see trade increase.