What process maintains the persistence of green, red, and yellow pea aphid morphs?
Balancing selection favoring different traits under varying environmental conditions
The continued existence of multiple color morphs—green, red, and yellow—within the same localized aphid population, known as polymorphism, requires specific evolutionary maintenance mechanisms; otherwise, one advantageous color would take over. This maintenance is often attributed to balancing selection. Balancing selection occurs because different traits are selectively advantageous depending on the immediate environmental context. For example, the green morph might offer superior camouflage on young foliage, while the yellow morph might possess better thermal regulation during intense heat, and the red morph might evade a predator active only at specific times. This flux of localized, shifting selective regimes prevents any single genotype from achieving complete dominance.
