Biotone

A biotone is a biogeographical region characterised not by distinctive biota but rather by a distinctive transition from one set of biota to another. They often contain the limits of distribution of the biota of neighbouring regions.

Biotones are especially useful in marine biogeography, where the movement of water may result in substantial overlap in the floral and faunal components of adjacent regions. In such case the regions of overlap is considered a biotone.