This study investigated the relationship between the presence of harlequin ladybird (Harmonia axyridis) in the UK in 2004-05 and atmospheric events in the same period. Verified H. axyridis records were modelled against atmospheric events, combining chemical transport models (CTM) and numeric weather prediction (NWP) models, where ladybirds were treated as coarse particles.
Data were sorted into two temporal groups, 1st June – 1st October 2004, and 1st April – 1st October 2005. When modelled using a Generalised Linear Model (GLM), there was a positive association between all variables (uplift, transport, turbulent mixing, wet deposition, and dry deposition) and H. axyridis records at distances less than 200km from the European continental coast. At distances greater than 200km from the European continental coast with the same values, there was no association.
While indirect introductions may account for the presence of H. axyridis further north in the UK, the model showed that air currents are likely to be the primary method for this species’ dispersal and arrival.
Siljamo, P., Ashbrook, K., Comont, R.F. and Skjøth, C.A. (2020). Do atmospheric events explain the arrival of an invasive ladybird (Harmonia axyridis) in the UK? PLoS ONE 15 (1): e0219335.