Population structure of the German cockroach, Blattella germanica, shows two expansions across China

© 2016, Springer International Publishing Switzerland.The German cockroach is one of the world’s most widespread invasive species. From uncertain origins, it appears in historical records in Europe over 300 years ago, with the first records in China date from 100 years ago. Since the 1990s, the German cockroach has dominated indoor environments across China. A genetic analysis of 599 individuals from nine cities across China found two genetic clusters; one dominant in the North and the other dominant the in South of the country. Weak but significantly positive isolation by distance was observed for the entire country; however, when broken into different geographical scales, the significantly positive correlation can be only observed in between cities or city to suburb range (10–221 km). Two factors may have contributed to the spread of the German cockroach in China, which correspond to these two clusters: central heating systems in the north built during the 1960s, and air-conditioning systems in the south built during in the 1990s. The spread of modern, long distance transport systems, such as railways, may have contributed to the lack of geographic patterns, yet it is likely that other factors have been important in determining patterns.