Formation of new species due to vicariance.
New species are formed from the division of original population into two or more populations (usually of similar size) that have been separated by a geographic barrier, such as volcano, earthquake, etc.
Word origin: From vicariant, from Latin vicārius, vicarious, “substitute, deputy” (adj. and n.), from vicis “turn, change, exchange, substitution.
See also: vicariance, speciation.