Of Terms in Bi­ol­ogy: Sym­pa­try and Al­lopa­try

by Elio

Sym­pa­try means that two species co­ex­ist in the same phys­i­cal area, al­lopa­try that they don't. The et­y­mol­ogy of the suf­fix pa­tris, helps. It comes from the Latin for 'fa­ther­land,' as in 'pa­triot' (or, for those who re­mem­ber the Mar­seil­laise, "Alons en­fants de la Pa­trie").

Fig­ure 1. Sym­pa­try and Al­lopa­try. Source (slide 46). Fron­tispiece: Al­lopatric vs. Sym­patric Spe­ci­a­tion Source (slide 23)

The most com­mon use of these terms is in con­nec­tion with spe­ci­a­tion. Sym­patric spe­ci­a­tion is the evo­lu­tion of a new species from an an­ces­tor with which it shares its habi­tat. Con­trari­wise, in al­lopatric spe­ci­a­tion, ge­o­graph­i­cally sep­a­rated species evolve with­out genes flow­ing be­tween them. Re­lated terms are "para­p­atric" and "peri­patric."

There is con­sid­er­able dis­cus­sion about the ex­tent of these phe­nom­ena in both eu­kary­otes and prokary­otes. Many dis­parate fac­tors seem to be at play, and so are de­f­i­n­i­tions. Ex­am­ples for prokary­otes can be seen in such ar­ti­cles as, among oth­ers (here, here, and here).