Are exotic lady beetles eating our native lady beetles into decline?

Species loss is occurring globally at a rapid pace almost on par with a mass extinction. Maintaining biodiversity is important in order to support diverse ecosystem functions. Consequently it is imperative we address this high rate of species loss. In order to do so it is necessary to understand the mechanisms behind species decline. It is known that exotic invaders are the second leading threat to biodiversity. In the case of native lady beetle (Coccinellidae) decline, exotic lady beetles are often cited as the culprit.

Native lady beetle species across the US have been in decline for several decades, which coincided with the establishment of a series of exotic lady beetle species. One theory is that direct competition through predation by exotics is the primary cause of native lady beetle decline.

This study examined the contribution of direct competition by exotics on populations of four native species. Collections from alfalfa fields were made in 13 Midwestern states. A total of 2,500 beetles were collected. A minimum of 30 individuals per species were needed before that sample was included for statistical analyses. Species specific primers were designed and PCR was preformed to examine gut contents of exotic lady beetles. Results that were unclear from the PCR were further examined by sequencing. Results of this study will clarify the rates of intraguild predation that occur among lady beetles.