Searching for evidence against the mutualistic nature of hereditary symbioses: A comment on faeth

Abstract

Hereditary symbioses occur when symbionts are transmitted vertically from hosts to their offspring. Given their strong ecological effects and their roles in major evolutionary transitions (Rudgers et al. 2007; Douglas 2008; Haine 2008), understanding their dynamics has attracted substantial interest. Here we critique a recent publication in the American Naturalist (Faeth 2009) that raises general issues in the study of symbiosis. Specifically, we address three questions: (1) What are the appropriate measures of the fitness consequences of symbiosis for the host? (2)How should benefits to hosts be assessed in symbioses that confer protection against natural enemies? (3) What are the appropriate measures of the fitness consequences of symbiosis for the symbiont?