Generational coexistence and ancestor's inhibition in bacterial populations.

Generational coexistence in structured environments raises the possibility of a competition between ancestors and descendents. This type of kin competition, and in particular, the possibility that descendents might actively repress the ancestor's dominance, has been rarely considered in microbial evolutionary ecology. The recent discovery of the phenomenon of stationary-phase contact-dependent inhibition of bacterial ancestor cells by late descendents provides a new theoretical perspective to analyze intrapopulational evolutionary changes. The ancestor's inhibition effect might accelerate such changes, particularly when the descendents have acquired small adaptive advantages that are insufficient to rapidly displace the well-settled ancestors in a complex niche. Besides this effect of triggering selection of small genetic differences, the opportunities for intergenerational coexistence in bacteria, where ancestor's inhibition might occur, are reviewed in this work. A theoretical analysis is provided about the explanatory possibilities of the ancestor's inhibition effect in the controversies about intraspecific (in a large sense, including intrapopulational) genetic diversification, and the discontinuities observed in such processes, giving rise to the emergence of individualities and therefore differential units of selection.