Adaptiveradiations in natural populations of prokaryotes: innovation is key

Abstract

Pr okar yote di v ersity makes up most of the tr ee of life and is crucial to the functioning of the biospher e and human health. Howev er, the patterns and mechanisms of pr okar yote di v ersification hav e r ecei v ed r elati v el y little attention compar ed to animals and plants. Adapti v e radiation, the rapid di v ersification of an ancestor species into multiple ecologically divergent species, is a fundamental process by which macrobiological diversity is gener ated. Here , w e discuss whether ecological opportunity could lead to similar bursts of di v ersification in bacteria. We explore how adapti v e radiations in pr okar y otes can be kic kstarted by horizontally acquired key inno vations allo wing linea ges to inv ade new niche space that subsequentl y is partitioned among di v ersifying specialist descendants. We discuss how nov el adapti v e zones are colonized and exploited after the evolution of a key innovation and whether certain types of ar e mor e pr one to adapti v e r adiation. Radiation into nic he specialists does not necessarily lead to speciation in bacteria when barriers to recombination are absent. We propose that in this scenario, niche-specific genes could accumulate within a single lineage, leading to the evolution of an open pangenome.