Colour polymorphism in the model aphid pest Myzus persicae as a survival strategy in tritrophic interactions

The peach-potato aphid, Myzus persicae Sulzer, is one of the most destructive agricultural pests worldwide, exhibiting remarkable colour polymorphism, with stable green and red morphs. Previous research has primarily examined isolated traits, leaving a critical gap in understanding how colour variation shapes integrated ecological performance across life history, behaviour, and trophic interactions. Our study addresses this through comprehensive bioassays under controlled conditions, systematically evaluating development, fecundity, population growth, settlement patterns, orientation, mobility, and migration capabilities while assessing predation by Harmonia axyridis Pallas larvae and parasitism by Aphidius gifuensis Ashmead. We demonstrate that green morphs exhibit higher fecundity on mature plants with slower maturation, while red morphs develop faster and perform better on younger plants. Green morphs showed reduced host odour responsiveness, slower movement, with a more limited migration range compared to red morphs. Alate green morphs exhibited significantly higher settlement, and apterous green morphs showed a significantly larger population increase. Crucially, red morphs were significantly more vulnerable to predation, while parasitism showed no morph preference. These integrated findings suggest a trade-off that may reflect a 'fast-slow' life-history continuum within the studied clone, indicating that morph-specific advantages are context-dependent. However, as our study examined a single clone under controlled conditions, further research across multiple clones and field settings is needed to establish the generality of these patterns. Our work provides a novel ecological framework for understanding colour polymorphism maintenance and may inform the development of morph-specific monitoring and biological control for Brassica crops.