How is the acquisition of a major trait like color via HGT contrasted with host specialization?

HGT is a singular, dramatic event opening a new pathway; specialization is continuous and rapid refinement

The acquisition of a major novel trait, such as the ability to produce yellow pigment through horizontal gene transfer from a fungus, represents a singular, transformative event that fundamentally opens an entirely new evolutionary pathway for the aphid. In contrast, the subsequent fine-tuning of specialization to a specific host plant, achieved through minor genetic adjustments across generations, occurs continuously and rapidly via standard reproductive cycles. This difference highlights two distinct modes of evolution at play: HGT provides a major, rare tool (the machinery), while host race formation represents the constant, rapid optimization of how that tool is utilized within a dynamic environment.