Population genetic variation and historical dynamics of the natural enemy insect Propylea japonica (Coleoptera: Coccinellidae) in China

Propylea japonica (Coleoptera: Coccinellidae) is a natural enemy insect with a wide range of predation in Chinese mainland and is commonly used in pest management. However, its genetic pattern (i.e., genetic variation, genetic structure, and historical population dynamics) is still unclear, impeding the development of biological control of insect pests. Population genetic research has the potential to optimize strategies at different stages of the biological control processes. This study used 23 nuclear microsatellite sites and mitochondrial COI genes to investigate the population genetics of Propylea japonica based on 462 specimens collected from 30 sampling sites in China. The microsatellite dataset showed a moderate level of genetic diversity, but the mitochondrial genes showed a high level of genetic diversity. Populations from the Yellow River basin were more genetically diverse than those in the Yangtze River basin. Propylea japonica has not yet formed a significant genealogical structure in China, but there was a population structure signal to some extent, which may be caused by frequent gene flow between populations. The species has experienced population expansion after a bottleneck, potentially thanks to the tri-trophic plant-insect-natural enemy relationship. Knowledge of population genetics is of importance in using predators to control pests. Our study complements existing knowledge of an important natural predator in agroecosystems through estimating its genetic diversity and population differentiation and speculating about historical dynamics.

Automated summary

This study investigated the population genetics of Propylea japonica in China using nuclear microsatellite sites and mitochondrial COI genes. The results showed moderate genetic diversity in the microsatellite dataset and high genetic diversity in the mitochondrial genes. Populations from the Yellow River basin had higher genetic diversity than those from the Yangtze River basin. While there was no significant genealogical structure, there was some population structure signal, possibly due to gene flow between populations.