Impact of Life History Theory on Host Competence through the Selection of Divergent Immunological Strategies: Understanding Why Resilient Species Might Also Be Poor Disease Dilution Agents

Disease dilution, the reduction in infection risk with increased host diversity, has recently attracted attention as one of the many indispensable services provided by rich ecological communities. Immunological variation seems to play an important role in many dilution mechanisms, with non-competent hosts acting as dead ends for various generalist pathogens. Interestingly, life pace in host species has been previously correlated in literature with two distinct immunological strategies that might directly influence host dilution potential. Evidence that fast-paced organisms evolutionarily approach infection differently than slow-paced ones supports the idea that reproductively prolific species might also be more competent hosts, favoring the persistence and spread of infectious diseases through investing more in tolerance mechanisms. Less ecologically resilient hosts, in this case, would assume the role of less competent hosts that buffer disease transmission, since their evolved immunological strategy is more efficient when dealing with repeated pathogen encounters. Competence to generalist pathogens, therefore, should be maximized in fast paced species and minimized in slow paced species when dictated by either resistance based or tolerance based immunological profiles. Life history variation gradients might help reprioritize conservation efforts and control the spread of emergent infectious diseases by revealing common traits in optimal dilution agents.