What term describes aphid groups specializing on specific host plants in decades?

Host races

Aphid specialization often begins with the formation of host races. These races represent distinct groups of aphids that have evolved to specialize on particular host plants. This specialization can occur with remarkable rapidity, sometimes establishing distinct preferences or adaptations within just a few decades. The pea aphid complex serves as a prime illustration, featuring lineages that, despite morphological similarity, exhibit reproductive isolation based on their preferred hosts, such as alfalfa versus clover. This rapid divergence into specialized races is a key driver of diversification, often initiated when an aphid lineage successfully adapts to overcome the unique chemical defenses or resistance mechanisms of a new host plant, acting as a powerful selective filter.