After reaching almost all of the United Kingdom within the past decade, harlequin ladybirds have been given the distinction of being the fastest invading species in the country.
The ladybirds were first discovered to have entered the UK back in 2004. First seen in Essex, they have now managed to spread as far as the Shetland Islands and Cornwall, rightfully earning the title of the fastest alien invading species in the history of the country and overtaking muntjac deer, ring-necked parakeets, American mink and grey squirrels.
Aside from being cannibals, harlequin ladybirds have voracious appetites, preying on native species of ladybirds and consequently endangering at least seven of these species. Included in the species at risk is the popular two-spot, whose population back in 2012 had already dropped to 44 percent. According to experts, the two-spot is showing no signs of recovery.
Although the ladybird is swiftly making its way across the UK, posing a threat to local species in the process, its presence is less costly compared to other kinds of invasive species. For instance, the Japanese knotweed costs the UK about $260 million every year. Overall though, the country spends about $2.7 billion every year to deal with invasive species.
Harlequins may offer some benefit by keeping smaller insects, such as aphids, at bay to protect garden flowers and crops, but it is unclear up to what extent the ladybird contributes to protecting plants. At the same time, there is evidence hinting that native insects have now learned to adapt to the presence of harlequins, preying on the ladybird as well.
The UK Ladybird Survey started in 2005 and has since monitored the activity of harlequin ladybirds. One benefit scientists are deriving now from the survey is that it has helped them get a better grasp at the routes invasive species use to establish their presence. Knowing how invasive species spread will also give scientists clues on how to reduce the ladybird's threat as much as possible.
Many of the non-native species in the UK now have little effect on the environment, although some can be damaging. Scientists are anticipating the arrival of bee-eating Asian hornets, which have already reached France.
Using the lessons they have learned from the harlequin ladybird, scientists are hopeful they may be able to do something to prevent the Asian hornet from establishing a presence in the UK.
"It's about having a plan in place and what to do when it arrives," said Dr. Helen Roy from the Centre for Ecology and Hydrology.
Photo: Denny Chapman | Flickr
