Eusociality contradicts a reversed reproduction-longevity trade-off
The evolution theory according to natural selection attempts to explain how organisms maximize their fitness to achieve maximal genetic contribution within the future genetic pool. However, fitness maximization is limited by certain evolutionary constraints such as multiple life-history trade-offs. Based on the competitive allocation of limited resources, trade-offs act as negative correlations between the fitness components when an improvement of one component is associated with a decrement of the other (Fabian and Flatt 2014). One of the major trade-offs is the cost of reproduction, which is the phenomenon where the increased rate of reproduction reduces the longevity of the parent (Reznick 1985; Harshman and Zera 2006). However, the reversed reproduction-longevity trade-off is contradicted by eusocial insects, whose reproductive individuals, which are highly fecund compared to solitary insects, typically exhibit longer lifespans than do non-reproductives within their colonies or solitary insect individuals. Comparative analysis between the lifespan of eusocial reproductives and solitary insects has indicated that the evolution of eusociality is associated with a 100-fold increase in insect longevity (Jemielity et al. 2005). The reproductive individuals of many termite or ant species may live for many decades (Laurent and Genoud 1997; Keller 1998). For example, the mean average lifespans of honeybee queens is 5.6 years, while adults of solitary insect species exhibit lifespans of only 0.1 ± 0.2 years (Keller and Genoud 1997; Keller 1998). The mechanisms underlying the extraordinary lifespan extension of eusocial reproductives are not fully understood.