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.