Dealing with time constraints on development: the effect of food availability

Abstract.  1. Life-history theory predicts that organisms should speed up development in response to time constraints. However, acceleration of development carries energetic costs that have to be compensated, e.g. by an increase in foraging rate. For the wing dimorphic water strider Gerris lacustris (L.), the hypothesis was tested that the adjustment of development to time constraints is limited by the availability of food resources.
2. Six cohorts of larvae hatched increasingly late in the season were reared under two feeding regimes. For each cohort and experimental group the physiological time (in degree-days) of larval development was estimated.
3. In both high- and low-food groups there was a significant reduction of physiological time for development towards the end of the season. Furthermore, within cohorts, physiological development time was always lower in the high-food group than in the low-food group. However, there was no significant interaction effect between food treatment and cohort.
4. The results demonstrate that G. lacustris has the flexibility to adjust development to time constraints. In addition, 20% of the 'low-food individuals' developed into the short-winged morph while all of the 'high-food individuals' became long-winged. The limitation of food may thus lead to a reduced allocation of energy into the development of the flight apparatus. This may explain the strong increase in short-wingedness at the end of the season in natural populations, which are highly food limited.