A selective trade-off for territoriality and non-territoriality in the polymorphic damselfly Mnais costalis

Males of the damselfly Mnais costalis occur as territorial orange-winged 'f ighter' males or non-territorial clear-winged 'sneaker' males. Their morph life histories differ considerably but the estimated lifetime reproductive success is the same for the two morphs. In this study we compared the devel opmental and reproductive costs associated with the two morphs. Orange-wing ed male and female reproductive costs resulted in a decline in adult fat re serves with increasing age. In contrast, the fat reserves of clear-winged m ales remained constant with adult age. Body size was positively correlated with mating success in orange-winged males, but had no influence on the mat ing success of clear-winged males. The orange-winged male flight muscle rat ios (FMRs) were significantly higher than the clear-winged male and Female FMRs. However, there was no difference in the size-corrected fat reserves o f the two morphs; both had higher fat reserves than females. The gain in ma ss between eclosion and reproduction in orange-winged males and females was almost double the mass gained by clear-winged males, suggesting that clear -winged male development is less costly An experiment in which pre-reproduc tive levels of nutrition were manipulated confirmed this.