Answer: B.sympatric speciation
Step-by-step explanation:
Sympatric speciation is defined as the development of new species from a living ancestral species as both require to survive in the same geographic area.
Sympatric speciation in a population occurs when the same habitat is shared by a species but they become isolated from each other reproductively. Polyploidy is the common cause of sympatric speciation, where an offspring or group of offspring with twice the usual number of chromosomes will be produced.
Beetles shows Sympatric speciation against the new shrubs and evolved themselves according to the new habitat provided and formed a new species via reproduction.
Hence, the correct option is B.