Parapatric speciation

Parapatric speciation is a form of speciation that occurs due to variations in mating frequency of a population within a continuous geographical area. In this model, the parent species lives in a continuous habitat, in contrast with allopatric speciation where subpopulations become geographically isolated. Niches in this habitat can differ along a environmental gradient, hampering gene flow, and thus creating a cline.

An example [ [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16639420 "Evolution in closely adjacent plant populations X: long-term persistence of pre-reproductive isolation at a mine boundary."] Heredity. 2006 Jul;97(1):33-7. Epub 2006 Apr 26. Abstract.] of this is the grass "Anthoxanthum", which has been known to undergo parapatric speciation in such cases as mine contamination of an area. This creates a selection pressure for tolerance to those metals. Flowering time generally changes (in an attempt at character displacement—strong selection against interbreeding—as the hybrids are generally ill-suited to the environment) and often plants will become self-pollinating.

Another example is ring species.

ee also

*Adaptive radiation
*Cladistics
*Evolutionary radiation
*Phylogenetics
*Taxonomy

References

[http://evolution.berkeley.edu/evolibrary/article/_0_0/speciationmodes_04 "Parapatric speciation."] in "Understanding Evolution" at evolution.berkeley.edu