Reciprocal effects between host phenotype and pathogens: new insights from an old problem.

Area of Science:

• Ecology
• Evolutionary Biology
• Pathogen Dynamics

Background:

• Host phenotype and pathogen infection relationships are often viewed as unidirectional (cause or consequence).
• Reciprocal effects, where host traits influence infection and infection impacts traits, are common but underappreciated.
• Trophically transmitted pathogens exemplify this, where host growth traits increase infection risk and pathogens reduce growth.

Purpose of the Study:

• To review empirical evidence for reciprocal effects in host-pathogen interactions.
• To present a conceptual model predicting how reciprocal effects bias interpretations of host-phenotype/pathogen-infection relationships.
• To propose future research directions and discuss implications.

Main Methods:

• Literature review of empirical studies on host-pathogen reciprocal effects.
• Development of a qualitative model to illustrate bias in observed relationships.
• Discussion of analytical and theoretical approaches.

Main Results:

• Empirical evidence supports widespread reciprocal effects in host-pathogen systems.
• Reciprocal effects can create spurious correlations or mask true relationships.
• Existing analytical frameworks may misinterpret host-pathogen dynamics without accounting for feedback loops.

Conclusions:

• Reciprocal effects are a fundamental aspect of host-pathogen interactions.
• Future research must incorporate these bidirectional influences for accurate understanding.
• Accounting for reciprocal effects has significant implications for disease ecology, evolution, and management.