Structure, Diversity and Adaptive Traits of Seasonal Cycles and Strategies in Ants

This chapter is a review of data on structure, diversity and adaptive properties of sea- sonal cycles in ants. Most tropical ants demonstrate homodynamic development. They do not show any developmental delays and all-year round the ontogenetic stages from egg to pupa exist in their nests. Some of the quasi-heterodynamic species have permeated into the regions with warm temperate climate but a true diapause did not evolve. Most temperate and all boreal climate ants are true heterodynamic. They manifest a real winter diapause (prospective dormancy) in their annual cycle. Thus, a variety of forms of dormancy, which were found in ants, extend from elementary quiescence to deep diapause. Heterodynamic ants use two main seasonal strategies with respect to brood rearing: strategy of concentrated brood rearing ( Formica type) and strategy of prolonged brood rearing ( Aphaenogaster type, Myrmica type). The larval stages at which diapause can occur are extremely variable among ants. The evolution of seasonal life cycles and possible ways of origin of diapause in ants are discussed. The subtropical (quasi-heterodynamic) and tropical (preadaptational) evolutionary paths to true hetero- dynamic development are considered. It is concluded that similar seasonal adaptations could arise in the evolution of ants independently many times and usually are not tightly bound to the taxonomic position of species.