Fig. 6. A hypothetical scenario for sap-feeding insect gut-associated bacteria acquisition during switching from a suitable (blue encircled leaf) to a less-suitable (red encircled leaf) host plant.

Each generation (bottom circles), the insect (upper yellow halve) acquires new bacteria (colored bacilli) from the host plant (bottom green halve) or by indirect parent-to-offspring transmission mechanisms (represented by the same bacilli over generations), which modify its gut microbiota community. This process can last until a community providing a local optimal performance is assembled. Smileys represent insects’ performance on the host plant, ranging from low (red) to high (blue) performance. The dynamics of both plant and insect microbiomes is represented by gain/loss of bacilli at each generation.