Fig. 2

The fate of a transferable gene as a function of \(\beta\) under the stochastic model: The metapopulation of transferable genes will tend to evolve toward a more sessile or itinerate state depending on the level of opportunity (\(\beta\)) to colonize naïve microbial populations by HGT. The two panels show the fate of \(1000\) populations of the transferable gene, each starting with \(\left(y,z\right)=\left(\mathrm{10,10}\right)\), after \({10}^{4}\) ancestor-mappings under the stochastic model. a The transferable gene evolved toward a more sessile state with larger mean indispensability (\(\overline{y }\)) and mean connectivity (\(\overline{z }\)) when \(\beta =0.06\). This was accompanied by a huge reduction in the number of populations, down to only 2 by the end of the simulation. b The transferable gene evolve toward a more itinerant state with smaller mean indispensability (\(\overline{y }\)) and mean connectivity (\(\overline{z }\)) when \(\beta =0.08\). This was accompanied by a more than eight-fold increase in the size of the metapopulation up to 8630 populations of the transferable gene