Species complex
![At least six treefrog species make up the Hypsiboas calcaratus–fasciatus species complex.[1]The fly agaric comprises several cryptic species, as shown by genetic data.[2]The African forest elephant (shown) is the bush elephant's sibling species.[3]Mbuna cichlids form a species flock in Lake Malawi.[4]](/uploads/202501/06/Systematics-of-treefrogs-of-the-Hypsiboas-calcaratus-and-Hypsiboas-fasciatus-species-complex-(Anura-ZooKeys-370-001-g0090526.jpg)
In biology, a species complex is a group of closely related species that are very similar in appearance to the point that the boundaries between them are often unclear. Terms sometimes used synonymously but with more precise meanings are: cryptic species for two or more species hidden under one species name, sibling species for two cryptic species that are each other's closest relative, and species flock for a group of closely related species living in the same habitat. As informal taxonomic ranks, species group, species aggregate, and superspecies are also in use.