Superspecies is a term used to describe a group of closely related organisms that are different enough from other species to be considered an entity. These organisms have usually diverged from each other in isolation, remaining largely or entirely geographically separated. Taxonomists group them as superspecies because they have evolved to the species level and exhibit distinct characteristics and genetic variations.
The concept of superspecies was introduced by E. Mayr and B. Rensch and has proven to be useful in studying evolution and zoogeography. However, the absence of a formalized notation for superspecies in Linnaean nomenclature has somewhat hindered its use. It is proposed that brackets (= square parentheses) should enclose the first named species of a superspecies, for example, superspecies Bubo [bubo], or Bubo [bubo] virginianus to indicate that virginianus is a member of the superspecies Bubo [bubo]. The term “allospecies” is suggested for the species comprising a superspecies.
Superspecies can be further classified into “semi-species,” which are forms believed to be subspecies but approaching or possibly of species status. These semi-species are indicated by parentheses, for example, Accipiter (gentilis) atricapillus. The use of parentheses should be restricted to indicating semi-species, while brackets are used for superspecies.
Superspecies can also be seen within a species complex, which is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in a species complex may be able to hybridize with each other, further blurring any distinctions. Other terms used synonymously but with more precise meanings include cryptic species, sibling species, species flock, species group, species aggregate, and macrospecies.
These complex rankings and the existence of extremely similar species can sometimes make it challenging to draw dividing lines between species. However, the rigorous study of morphological details, tests of reproductive isolation, and DNA-based methods like molecular phylogenetics and DNA barcoding can help identify and differentiate species within a complex.
The understanding and recognition of superspecies and species complexes are important for various fields such as disease and pest control, conservation biology, and understanding biodiversity. By accurately identifying and classifying these groups, scientists can better understand their evolutionary relationships, study their adaptations, and develop effective conservation and management strategies.