Comparative study of Eastern and Western North American populations of Hippodamia convergens (Coleoptera: Coccinellidae) for endosymbionts

Endosymbionts are maternally inherited bacteria commonly found in the many insects that fill a variety of roles. While some endosymbionts aid in food digestion or protection from parasitoids, others manipulate the host’s reproductive system to promote their own propagation. Some reproductive manipulators create female biased populations by killing male offspring. Among Coccinellids, four endosymbionts are known to act as male-killers: Wolbachia, Spiroplasma, Rickettsia, and Flavobacterium. Several species of Coccinellid have been examined to determine if they share a relationship with any of these four endosymbionts, but the native Coccinellid, Hippodamia convergens, has been overlooked. Hippodamia convergens is found across the United States. Biological control companies in western states collect H. convergens from their aggregation sites in the surrounding Rocky Mountain range and sell them across the country for biological control purposes. This practice of redistributing beetles is allowing populations that may once have been geographically isolated by the mountains to mix and interbreed. To determine if male-killing endosymbionts are present in either region to complicate this process, this study examined four populations of H. convergens from Arizona, California, Illinois, and Kentucky for three of the four known male-killing endosymbionts: Wolbachia, Rickettsia, and Spiroplasma. We determined that none of the endosymbionts tested for were present in the tested individuals. This indicates that H. convergens may not have male-killing endosymbionts present or that they occur at very low levels and were not detected in this study.