Evolutionary Context of Venom in Animals

Abstract

Much of the research on venoms has understandably focused on clinical implications of human envenomation and detailed molecular studies of toxins. However, as with any biological trait, venom exists in an evolutionary context and must be considered as such if we are to gain a full understanding of the biology of animal venoms. Consequently, this chapter aims to provide an overview of the diversity of venom and venomous animals and also a set of evolutionary principles which are particularly applicable here. There has been substantial variation in the definition of “venom” and “venomous” in the literature, so this is discussed first with the aim of giving a definition which encompasses a number of important features of venoms. A survey of the functional diversity of venoms and taxonomic diversity of venomous animals is then provided as an introduction to the evolutionary drivers of venom and how it is distributed across the animal tree of life. The last three sections consider three principles that are important to venom evolution: (1) the composition of venom is variable both between and within species; (2) venom evolves in the context of antagonistic coevolutionary interactions; and (3) venom can have consequences for the ecology and evolution of animals that possess it beyond its direct functions to their behavioral ecology.