Examining growth rate and starvation endurance in pit-building antlions from Mediterranean and desert regions

Stressful or stochastic environments may have significant selective effects, leading to increased plasticity or stress resistance. Starvation is a type of stress commonly encountered among organisms inhabiting stochastic environments. Indeed, starvation endurance is an important trait, especially in sit-and-wait predators, which experience frequent fluctuations in prey arrivals because of their limited mobility. Differences in starvation endurance between antlions originating from Mediterranean (benign and predictable) and desert (harsher and stochastic) regions were investigated by exposing them to starvation in a fully factorial experiment using climate chambers simulating Mediterranean or desert climatic conditions. A trade-off between growth rate and starvation endurance was also investigated by feeding the antlions at two different frequencies pre-starvation. Additionally, the existence of growth compensation was tested for by measuring relative growth rate when feeding was resumed post-starvation. Population of origin did not significantly affect rates of body mass loss during starvation or relative growth rates when feeding was resumed. Antlions that were fed less frequently during the feeding phase lost mass faster during the starvation phase, but grew faster during the compensation phase. This study emphasises the importance of testing responses to stress when investigating life-history trade-offs. Some phenotypic differences between populations might be apparent only when exposing the experimental organisms to external stress. Conversely, phenotypic differences apparent under stress-free conditions might be masked by the effects of the stress factor. Adopting such an integrative approach allows elucidation of the level of plasticity in response to stress in different populations.