From Wikipedia https://en.wikipedia.org/wiki/Species https://en.wikipedia.org/wiki/Species >While the definitions given above may seem adequate at first glance

From Wikipedia https://en.wikipedia.org/wiki/Species https://en.wikipedia.org/wiki/Species >While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. [...] If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that a lineage should be divided into multiple chronospecies, or when populations have diverged to have enough distinct character states to be described as cladistic species.