The Hologenome Concept: Helpful or Hollow?

Area of Science:

• Evolutionary Biology
• Microbial Ecology
• Symbiosis Research

Background:

• Growing recognition of microbial symbionts' impact on host development and fitness.
• Emergence of the hologenome concept (host + microbiome genomes) for evolutionary interpretation.
• Prevalence of misconceptions regarding symbiont evolution in host-associated communities.

Purpose of the Study:

• To clarify misconceptions about symbiont evolution and natural selection.
• To critically evaluate the hologenome theory in the context of host-symbiont associations.
• To distinguish between association and coevolutionary benefit for hosts.

Main Methods:

• Conceptual analysis of evolutionary processes in host-microbe systems.
• Examination of evidence for natural selection acting on symbionts.
• Critique of interpretations based on host specificity and microbiome similarity.

Main Results:

• Symbionts can maintain intimate associations without evolving to benefit hosts.
• Host-specific microbial communities or similarity among related hosts do not prove coevolution or host benefit.
• Hologenome-level selection is not a universal explanation for host-symbiont dynamics.

Conclusions:

• Symbiont evolution does not automatically equate to host benefit.
• Careful evaluation is needed to infer coevolution and selective advantage in host-associated microbes.
• The hologenome concept requires nuanced application, avoiding assumptions of universal selection for host benefit.