Fig. 1

The fate of a transferable gene as a function of \(\beta\) under the deterministic model: Whether a metapopulation of transferable genes persists or goes extinct depends in part 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 indispensability and connectivity \(\left(y,z\right)=\left(\mathrm{10,10}\right)\), after \({10}^{4}\) ancestor–descendant mappings in the absence of mutations in the indispensability and connectivity of T. In both panels the original \(1000\) populations of T were eliminated after 5100 mappings. The fate of their offspring populations with \(\left(y,z\right)=\left(\mathrm{0,10}\right)\) then depended on \(\beta\). a When \(\beta =0.06\) the offspring populations went extinct after 7120 mappings. b When \(\beta =0.08\) they persisted at an equilibrium of approximately 800 populations. In both cases the environment was predominately selective, the probability of exposure to the neutral state having been set to \(\delta =0.01\) per ancestor–descendant mapping. Extinction would be more rapid for larger values of \(\delta\)