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In biology, a species complex is a group of closely related species very similar in appearance, such that 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. A species complex is in most cases a monophyletic group with a common ancestor, although there are exceptions. It may represent an early stage after speciation, but may also have been separated for a long time period without evolving morphological differences. Hybrid speciation can be a component in the evolution of a species complex. Species complexes exist in all groups of organisms. They are identified by the rigorous study of differences between individual species, making use of minute morphological details, tests of reproductive isolation, or DNA-based methods such as molecular phylogenetics or DNA barcoding. The existence of extremely similar species may cause local and global species diversity to be underestimated. Recognizing similar but distinct species is important for disease and pest control, and in conservation biology. ==Definition== A species complex is typically considered as a group of close, but distinct species.〔 Obviously, the concept is closely tied to the definition of a species. Modern biology understands a species as "separately evolving metapopulation lineage" but acknowledges that the criteria to delimit species may depend on the group studied.〔 Thus, many species defined traditionally, based only on morphological similarity, have been found to comprise several distinct species when other criteria, such as genetic differentiation or reproductive isolation were applied.〔 A more restricted use applies the term to close species between which hybridisation occurred or is occurring, leading to intermediate forms and blurred species boundaries.〔 Some authors apply the term also to a species with intraspecific variability, which might be a sign of ongoing or incipient speciation. Examples are ring species〔〔 or species with subspecies, where it is often unclear if these should be considered separate species.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Species complex」の詳細全文を読む スポンサード リンク
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