Prey species mediated slow and fast development in two aphidophagous ladybird beetles

Extensive research has explored how environmental factors impact the developmental rates of various organisms. However, the phenomenon of developmental rate polymorphism, where individuals within a cohort exhibit either slow or fast developmental rates under fluctuating environmental conditions, remains underexplored. In the current study, we investigated how different prey species (Aphis craccivora Koch, Aphis gossypii Glover, Aphis nerii Boyer de Fonscolombe, Lipaphis erysimi (Kaltenbach) and Rhopalosiphum maidis (Fitch)) affect the slow and fast development rates of two ladybird species, Cheilomenes sexmaculata (Fabricius) and Propylea dissecta (Mulsant), and how these rates influence their reproductive traits. We observed a distinct bimodal distribution pattern for each prey species, with two peaks representing the fast and slow developers. The distribution was skewed depending on the type of prey. Slow developers had a higher proportion of females, lived longer, and had lower body mass. On the other hand, fast-developing females had higher fecundity and egg viability. We observed a higher frequency of slow developers among beetles fed on A. nerii, L. erysimi, and R. maidis and fewer on A. craccivora and A. gossypii. We hypothesised that the observed variation in developmental rates at emergence is due to selective mortality influenced by the prey species, rather than differences in the developmental rates at egg laying. This study lays the groundwork for further research into developmental rate polymorphism, enhancing our understanding of its ecological and evolutionary causes, and aiding in the selection of fast-developing bioagents for biological pest control.