Speciation is the evolutionary process by which new biological species
arise. The biologist Orator F. Cook seems to have been the first to coin
the term 'speciation' for the splitting of lineages or 'cladogenesis,'
as opposed to 'anagenesis' or 'phyletic evolution' occurring within
lineages.[1][2] Whether genetic drift is a minor or major contributor to
speciation is the subject of much ongoing discussion. There are four
geographic modes of speciation in nature, based on the extent to which
speciating populations are geographically isolated from one another:
allopatric, peripatric, parapatric, and sympatric. Speciation may also
be induced artificially, through animal husbandry or laboratory
experiments. Observed examples of each kind of speciation are provided
throughout.[3]
phyletic
Anagenesis, also known as "phyletic change," is the evolution of species
involving an entire population rather than a branching event, as in
cladogenesis