An Evolutionary and Applied Perspective of Insect Biotypes

Benjamin Walsh (174) was probably the first to seriously consider the status of insects that morphologically resemble one another so closely that they can only be distinguished on the basis of subtle biological traits such as preference for or the ability to survive on different hosts. Most of Walsh's "phytophagic varieties" now fall under the rubric "biotype," a term employed primarily by applied biologists to distinguish populations of insects and other organisms whose differences are due to a very wide range of underlying causes. The significance of biotypes for both evolutionary and applied fields is not general­ ly appreciated. Our objective is to integrate the current concepts used by evolutionary biologists to describe various patterns and levels of differentiation in insects with the views of the applied biologist. A classification system of insect biotypes, based on the mechanisms underlying their differentiation, is outlined below. We also consider the significance of biotypes in adaptation, speciation, and pest management.