Termite collection
Termite samples were collected from Wuhan, Nanjing and Chengdu cities in China. Congeneric R. flaviceps and R. chinensis share common habitat in these regions, which provides ideal conditions for studying the interactions between the two species in hybrid zones. The sampling of R. flaviceps and R. chinensis populations was performed from October 2017 to May 2018 in the three areas indicated above. Alates of the two species were collected during this period, which aided in species identification. In total, we sampled 67 colonies, including 10 R. flaviceps and 15 R. chinensis colonies from Chengdu, 10 R. flaviceps and 15 R. chinensiscolonies from Wuhan, and 10 R. flaviceps and 15 R. chinensis colonies from Nanjing (colonies were assigned to species based on the morphology of alates; see Fig. 1). The distance between the colonies was at least 1000 m to avoid repeated sampling of the same colony. More than 30 individuals (including workers, soldiers and alates) were collected from each colony. All the individuals from the same colony were placed in absolute ethanol and stored at 4°C for genetic analysis.