Perception of dead conspecifics increases reproductive investment in fruit flies

Adaptive plasticity in life-history traits is often critical to maximize fitness in the face of environmental heterogeneity. For example, many organisms respond to a threat to their survival (and hence residual reproductive value) by adaptively increasing their investment into current reproduction (i.e. “terminal investment”). 
A key to successful terminal investment is the use of adequate environmental cues to extrinsic mortality sources. In species that live at high population densities, the presence of dead conspecifics could potentially act as a reliable cue to extrinsic mortality sources (e.g. via pathogens).
We experimentally tested this idea using the model organism Drosophila melanogaster, a pest species that experiences marked demographic shifts. We monitored the reproductive output of young mated females during repeated bouts of egg-laying in the presence (i.e. dead-exposed) or absence (i.e. controls) of dead conspecifics, interspersed by mating periods where dead conspecifics...