Long Term Monitoring in Switzerland Reveals That Strongly Declines in Response to Invasion.

A long-term monitoring was conducted at 40 sites in four different habitats in north-western Switzerland to observe changes in populations of native ladybirds, following the invasion of the Asian harlequin ladybird, . From 2006 to 2017, the same trees and meadows were sampled at least seven times per year using standard protocols. On 15 broadleaved hedges, quickly became the dominant species, representing 60 to 80% of adult ladybirds collected. It was second in abundance at five pine () stands and was a minor component of the ladybird complex at five spruce () stands and in 15 meadows. This survey revealed the severe decline of , which was the most abundant native ladybird on broadleaved trees in 2006-2009 and has almost disappeared since 2010. So far, other native ladybirds do not seem to decline significantly, including species occupying the same ecological niches as . The total number of aphidophagous ladybirds did not decline either, suggesting that the biological control function of ladybirds on aphids living in these habitats has not been affected by the arrival of . Recommendations are given to further assess the impact of on native ladybirds and aphids.