Taxonomy groups plants in part by the kind of fruit. Phylogenetics groups plants by their lineage and then ask where in history, and when, specific kinds of fruits evolved in particular lineages. Both approaches recognize that convergent evolution of kinds of fruits has occured many times, but phylogenetics identifies when and where they occured. By the biological definition, a species is a population of individuals that can breed and exchange genes with themselves but not with other individuals. Can't really test all possibilities.
Speciation results in two species derived from a single progenitor species.
The two new species no longer exchange genes for a variety of reasons below. No intent, no intelligence Plants do NOT adapt in order to better reproduce Mutation, selective pressure, drift, etc may change allele frequencies of many genes. These may change a character that affects reproductive success. Sequence and timing of major changes in Life. Role of reducing atmosphere, oxygen, oxygen atmosphere, ozone.