Reproductive interference and its impact on species interactions in two coexisting ladybird beetles

Interactions between coexisting species can profoundly influence reproductive dynamics, particularly in systems involving heterospecific mating. Previously, we reported that Cheilomenes sexmaculata Fabricius affects the reproductive traits of Propylea dissecta Mulsant. Additionally, a prior study showed that heterospecific males of various ages exhibit varying behavior toward P. dissecta. In continuation of this line of research, we investigated how the mating status of C. sexmaculata males (unmated, once mated, or multiply mated [five times]) affects the reproductive outcomes in P. dissecta, a species commonly used in biological control. Earlier observations of heterospecific mating between C. sexmaculata males and P. dissecta females suggest that such interactions may influence reproductive success in conspecific pairings. Our finding indicate that multiply mated males exhibit increased mating disruption during conspecific interactions but show reduced responsiveness post mating. Conversely, unmated and once mated C. sexmaculata males exert greater reproductive interference, leading to increased heterospecific mating. This interference significantly impacted P. dissecta females, reducing fecundity, and egg viability, likely due to behavioral disruption and the consequences of heterospecific matings. These findings show that such interactions may drive selection for traits that minimize these costs. The interplay between conspecific and heterospecific interactions highlights a complex selective environment shaping reproductive strategies in coexisting species. As both species serve as important biocontrol agents, understanding these interactions is crucial for selecting compatible predator combinations and enhancing the efficiency of integrated pest management programs.