What is a fish species ?

摘要

The formal processes of alpha-taxonomy ensure that species have uniquenames and can be identified. No similar process is mandatory forinfraspecific variation, so the species is a uniquely important practicalterm. At present, there is little agreement of the definition of aspecies. In the last 30 years, numerous concepts have been proposed. Thenature of fish species is reviewed. Clonal inheritance of nuclear genesoccurs in several lineages. Hybridization is frequent, often leading tointrogression, which may lead to extinction of species. Species may havehybrid origins. There is good evidence for parallel speciation in similarhabitats. There are clearly exceptions to the cladistic assumption ofdichotomous branching during speciation. Sibling species may exist with nodiscernible niche differentiation.