Despeciation

Despeciation is the loss of a unique species of animal due to its combining with another previously distinct species.^[1] It is the opposite of Speciation and is much more rare. It is similar to extinction in that there is a loss of a unique species but without the associated loss of a biological lineage.

Example of three-spined sticklebacks

The three-spined stickleback (Gasterosteus aculeatus)

For example, Taylor et al.'s genetic analysis of three-spined sticklebacks across six lakes in southwestern British Columbia found two distinct species in 1977 and 1988 but only one combined species in data from 1997, 2000, and 2002.^[2] They concluded that external factors had imperiled the living conditions of the two species, thus eliminating the evolutionary specializations that had kept them unique.

References

1. "Despeciation". Stedman's Medical Dictionary. Retrieved 28 December 2012.
2. Taylor EB, Boughman JW, Groenenboom M, Sniatynski M, Schluter D, Gow JL (February 2006). "Speciation in reverse: morphological and genetic evidence of the collapse of a three-spined stickleback (Gasterosteus aculeatus) species pair.". Mol Ecol.