Parasitoid speciation and diversification
Peter A. Hambäck, Niklas Janz, Mariana P. Braga
Abstract
Parasitoid wasps may well be the most species rich animal group on Earth, and host-parasitoid interactions may thereby be one of the most common types of species interactions. Understanding the major mechanisms underlying diversification in parasitoids should be a high priority, not the least in order to predict consequences from high extinction rates currently observed. The two major hypothesis explaining host-associated diversification are the escape-and-radiate hypothesis and the oscillation hypothesis, where the former assumes that key innovations are major drivers of radiation bursts whereas the latter rather assumes that diversification depends on processes acting on the standing genetic variation that influence host use. This paper reviews the recent literature on parasitoid speciation in light of these major hypotheses to identify potential key innovations and host use variability underlying diversification. The paper also calls upon recent theoretical advances from a similar system, plant-butterfly interactions, to provide short-cuts in the development of theories explaining the high diversity of parasitoid wasps. • Host race formation is common in hymenopteran parasitoids. • Key innovations have not yet been connected to radiation events in hymenopteran parasitoids. • Dynamic host use through evolutionary time could be a major factor underlying diversification.