Aggregate species consist of a a group of taxa, usually lower taxa such as subspecies and varieties.
All three are displayed on the genus Phyllanthus page. The aggregate species is indicated by the blue Agg. code
The reason for introducing the concept is that many records, by us and others, are to species level only. In these cases, we don't know to which variety the record belongs. However, we can still use them at the aggregate species level. Each of the varieties also has its own page with information and records.