The Harlequin ladybird has been declared as United Kingdom’s fastest invading species.
The ladybird eats native species and it has reached every corner of the UK.
The harlequin ladybird has now been declared the UK’s fastest invading species. It preys on seven native ladybirds, including the native two-spot, which has slumped 44 per cent.
After first arriving in the UK in Essex in 2004 they are now found from Cornwall to the Shetland Islands.
It is the fastest alien invasion of the UK on record with the rate of advance by grey squirrels, American mink, ring-necked parakeets and muntjac deer far behind them.
Scientists monitoring the spread of the voracious harlequin, which will prey on native ladybirds, said the warnings when it first arrived that it would colonise the country rapidly and was the world’s ‘most invasive ladybird’ have proved correct.
Dr Helen Roy, of the Centre for Ecology and Hydrology, said a decade of sightings recorded by the public as part of the UK Ladybird Survey since 2005 have revealed just how far and fast the harlequin has spread
‘The harlequin is the fastest-spreading alien species on record that I can think of,’ she said, adding that it is now consolidating its presence in the UK.
While sightings of harlequins, Harmonica axyridis, in Scotland are much less common than in England and Wales it has colonised much of the south and has been spotted, though probably hasn’t established over-wintering populations, on the north coast and the Shetland Islands.
The species is believed to be responsible for the decline of at least seven native ladybirds, including the popular two-spot which when last assessed in 2012.
Dr Roy said that there has been no sign of a recovery among two-spots.
The impact of the harlequin has, however, been less costly than other invasive species such as Japanese knotweed which in 2010 was estimated to cost the UK economy £166million annually. Overall, invasive species are estimated to cost £1.7billion each year.
The Harlequins’ backs vary in colour and can be yellow, black or red so they can be difficult to distinguish from native species.
Harlequins might even have some benefits as they prey on a variety of smaller insects, especially aphids which can damage crops and garden flowers, but the extent to which they protect plants is undetermined.
There is also evidence to suggest that native insects may now have adapted to prey on the harlequins, helping to keep numbers in check.
One silver lining to the arrival of the harlequins, said Dr Roy, is that the monitoring scheme has helped scientists better understand the routes, such as being transported by cars, alien species use to invade and how it might be possible to reduce the threat.
Most non-native species have little impact on the environment but a handful are considered to be damaging.
Among those considered unwanted but likely to arrive imminently are the bee-eating Asian hornets – they have already reached France – and the ‘lessons we’ve learnt from the harlequin’ could prove vital to preventing it establishing itself as a ubiquitous species.
The harlequin is the fastest-spreading alien species on record that I can think ofDr Helen Roy, Centre for Ecology and Hydrology
‘It’s about having a plan in place and what to do when it arrives,’ she said.
In a paper published in the journal Ecological Entomology Dr Roy and co-author Peter Brown, of Anglia Ruskin University, said the harlequin ladybird ‘has provided unique and detailed insights into invasion biology’.
They expressed gratitude to the public who have contributed thousands of sightings of ladybirds as part of the monitoring programme: ‘Such surveillance is critical to strategies for early-warning and rapid response.’
The report added: ‘The arrival of [harlequin ladybirds] in Britain was met with trepidation. The dramatic spread of H. axyridis suggests that it is one of the fastest-spreading invaders worldwide.’