Reluctance and loss of progeny fitness when relatives mated: A case study in a predatory ladybird, Propylea dissecta

Abstract

Abstract We investigated mating reluctance with relatives and its influence on the quantitative progeny and its fitness using a predatory ladybird, Propylea dissecta. For this purpose, we compared mating behaviour, mating duration and post-mating response in the form of fecundity, egg-viability, progeny-development, weight and fitness when mating occurred between relatives (father-daughter, mother-son, and siblings) with unrelated ladybird couples. Females of P. dissecta, particularly those belonging to earlier (mother) or later generation (daughter) exhibited strong mating reluctance than those of same generation (sibling) relatives. This reluctance was lacking in unrelated female ladybirds. A similar pattern was reflected in the mating duration and post-mating responses, as unrelated females mated for the longest duration with high fecundity, oviposition period and percentage of egg viability. Furthermore, the first progeny suffered the implication of mating with relatives in the form of delayed development, lighter developmental stages and reduced fitness with those experiencing maximum whose parents were not of the same generation. These parameters were optimal in the progeny of unrelated parents. These results alarm the process of mass-rearing, where the ladybirds are augmented giving no consideration to the parental line and allowing mating between relatives, which may result in inbreeding depression, thereby deteriorating the quality of progeny and impeding the biocontrol programmes.