What’s in a Clone: The Rapid Evolution of Aphid Asexual Lineages in Relation to Geography, Host Plant Adaptation and Resistance to Pesticides

Abstract

The term “clone”, coined over a hundred years ago (see Chapter 9), is still in common parlance and widely used throughout the world, but its usage depends on definition, which is still obscure, especially if this involves the concept of genetic fidelity between clone mates rather than just the offspring from an asexual female founder (more correctly, an asexual lineage). To date, there have been no DNA sequencing studies proving such fidelity; on the contrary, the various DNA molecular marker studies performed on aphids display widespread genetic variation within and between different clonal lineages, as expected since mutation is a fundamental property of the DNA and hence the genome itself. In this overview, I use aphids as a model system to show that, rather than being an unchanging evolutionary “dead end”, asexual aphid lineages show rapid and widespread adaptive changes to changing ecological conditions in the field, including in relation to geography, host plant factors, and to insecticide applications. This being so, the so-called clone cannot be a fixed entity in time and space, but like all other living organisms in the real world, is evolving in response to its environment.