Effect of parental age on developmental rate polymorphism of the ladybird beetle, Propylea dissecta

Parental age plays a major role in determining the life history attributes of an organism. Variation in parental age can have a big impact on offspring development, body mass and structure of population. To test the hypothesis that the increase in parental age has negative effects on offspring development of next generation, we observed the effect of parental age on the selected population of developmental variants (slow and fast developers) in a ladybird beetle, Propylea dissecta Mulsant (Coleoptera: Coccinellidae). The newly emerged adults were divided into two lines: Slow and Fast developers on the basis of their total developmental durations. Adult body mass, slow-fast emergence, sex-ratio, percentage of immature survival of newly emerged adults was recorded. Total developmental duration increased with the increase in age across generation and more fast developers were found in the offspring of young age groups; however, only slow developers were produced by old age groups. Offspring of older age showed higher immature mortality which supports slow-growth-higher mortality hypothesis. Thus, it can be concluded that young age beetles show better performance in terms of growth and developmental duration in P. dissecta in comparison to middle age and old age groups.