European ladybirds under threat from alien predator

Published: 6 February 2012 at 12:07

Anglia Ruskin scientist researches the effects of the invasive harlequin ladybird

A new study, co-authored by Dr Peter Brown of Anglia Ruskin University, provides compelling evidence that the arrival of the invasive non-native harlequin ladybird to Europe has led to a rapid decline in historically-widespread species of ladybirds in Britain, Belgium and Switzerland.

The report, published today in the scientific journal Diversity and Distributions, shows that harlequin ladybirds are displacing some native ladybirds, most probably through predation and competition.  The harlequin was first found in Belgium in 2001 and in Britain and Switzerland in 2004.  Previously its arrival had been predicted to threaten native biodiversity but, until now, the effect on native species had not been quantified.

By examining thousands of ladybird distribution records collected through public participatory surveys, the research team was able to show that in Britain seven out of the eight species studied declined substantially since the arrival of the harlequin. 

A particularly dramatic decline in the 2-spot ladybird was noted, showing a decline by 44% in Britain and 30% in Belgium over the five years following the arrival of the harlequin.  Similar patterns of decline were found in ladybird abundance data (number of individuals) collated from systematic surveys of deciduous trees in Belgium, Britain and Switzerland.

Distribution data was collated largely through public participatory surveys.  In Britain, a Coccinellidae Recording Scheme has been run by the Centre for Ecology & Hydrology since 1971, and the database contains over 100,000 observations.

The ladybird abundance data for Britain was derived from surveys at sites across Cambridgeshire – in St Ives, Huntingdon and Fordham – which consisted primarily of deciduous trees.

Anglia Ruskin’s Dr Peter Brown said:

“Long-term datasets such as those used in this work, and our recent atlas of ladybirds of Britain and Ireland, are invaluable. We are extremely grateful to the thousands of volunteer recorders who have contributed their ladybird findings to the surveys. Results from our local field surveys show the same trends as those from the national public recording.”

Tim Adriaens from the Research Institute for Nature and Forest (INBO) in Belgium said:

“Within the insect world ladybirds are as iconic as panda bears and they provide an incredibly useful ecological function by keeping aphids in check.  At the continental scale the arrival of the harlequin could impact on the resilience of ecosystems and severely diminish the vital services that ladybirds deliver.”
Dr Helen Roy of the UK’s Centre for Ecology & Hydrology, who is the lead author on the report, said: “This study provides strong evidence of a link between the arrival of the harlequin ladybird and declines in other species of ladybird, a result that would not have been possible without the participation of so many members of the public gathering ladybird records across Britain, Belgium and Switzerland.”