Alternative phenotypes within mating systems

Phenotypic plasticity is widespread in insect development, life history, physiology, and behaviour. Plastic responses to environmental and social conditions are central to the remarkable adaptability of insects and their evolutionary histories. This chapter explores the intrasexual variation in behaviours and morphologies found in insect mating systems, specifically the evolution of alternative means by which individuals obtain fertilizations, generally referred to as ‘alternative mating tactics’, or ‘alternative mating phenotypes’ (AMPs). Two systems are discussed: gryllid field crickets and onthophagine dung beetles, chosen because their reproductive biology is well known, and because their contrasting degrees of behavioural plasticity and morphological specialization between alternative phenotypes illustrate the diversity of AMPs that has evolved in insects. The genetic models proposed for the evolution and maintenance of such dimorphisms are discussed, and the occurrence of AMPs in insects more generally reviewed. Finally, the limited evidence for AMPs in female insects is discussed.