British ladybird species struggling to compete with alien invaders

Fifth of native ladybird species in decline across the British Isles, first comprehensive census shows •  In pictures: The great harlequin ladybird invasion More than one-fifth of native ladybird species are in decline across the British Isles as environmental changes and competition from voracious alien invaders take their toll on the insects’ numbers. The grim outlook for 10 of the 47 ladybird species found in the UK and Ireland is revealed in the first comprehensive census compiled with help from tens of thousands of volunteer spotters. Distribution maps drawn up from sightings over the last 20 years show worrying declines in the common 10- and 14-spot ladybirds, and numbers of rarer species, including the unusual water and hieroglyphic ladybirds, have also suffered substantial falls. The environmental factors behind the declines are not affecting all species equally, however. The survey shows substantial increases in the populations of five ladybird species, including the 24-spot and pine varieties. Some native ladybirds are struggling to survive alongside species that have recently become established in Britain. A decline in the two-spot ladybird has been blamed on the arrival and spectacular rise of the Asian harlequin ladybird, which was introduced into Europe to control pests. The harlequin arrived from the continent in 2003. It is larger, breeds faster, competes with others for food and even preys on the larvae of smaller insects, such as the two-spot ladybird. The species is now common in England and Wales and has recently been sighted in Scotland. Helen Roy, of the Centre for Ecology and Hydrology (CEH) in Oxfordshire, and one of the authors of the Ladybird Atlas of Britain and Ireland, said: “What’s quite striking is that in the same way as butterflies and moths have seen very common species going into decline, we’re seeing the same happen with ladybirds. “What is particularly worrying about the declines is that many of these are common species, the ones people will be most familiar with in their gardens. We have not unravelled all the causes behind the declines, but a warming climate and changes in land use are expected to have an impact. “They are telling us there are changes going up through the food chain. Ladybirds can be used as indicators of wider changes in our environment,” Roy said. Contrary to popular perception, ladybirds are top predators in their ecological niches. Their voracious appetites for plant-destroying aphids and small, parasitic-scale insects have made them a favourite among gardeners. They thrive in warmer conditions and are most diverse in southern England, but many species are now extending their ranges in Scotland as temperatures become more inviting. The kidney spot ladybird, which resembles a miniature bowler hat daubed with two red spots, has been recorded in Scotland for the first time in recent years, “almost certainly as a consequence of climate change”, Roy said. An explosion in orange ladybirds, which feed on mildew, is thought to be linked to warmer, damper conditions in parts of Britain in the past two decades. One of the greatest surprises recorded by the survey is the recolonisation of Britain by the 13-spot ladybird, which was once considered extinct here. Sightings of the ladybird in Cornwall, Devon and the New Forest suggest the insects are becoming re-established after arriving from the Channel islands or France. Ladybirds can be carried on cars and ferries, but have also been known to travel long distances over water on air currents. Further analysis of the survey data will give researchers unique insights into the ecological roles of different species of ladybird and how they respond to changes in their habitat and the environment. A project was begun in the 1960s to compile records of ladybird sightings across the British Isles. Originally filled with sightings from experts, it has since been opened up to include amateur enthusiasts. Sightings are usually backed up with specimens or photographic evidence before a record is made official. The earliest record included in the publication is that of a rare 13-spot ladybird seen near Oxford in 1819. The most commonly recorded species, with 27,000 records, is the seven-spot ladybird, closely followed by the harlequin, with over 25,000 records. The atlas is a collaborative project between researchers at the CEH, Anglia Ruskin University, Clifton College and the wildlife enthusiast Robert Frost. Peter Brown, at Anglia Ruskin, said the response from volunteer ladybird spotters was “staggering”, and crucial to assess changes in the insects’ distributions over time. The survey is an ongoing project that will continue to monitor ladybird populations in the years ahead. Insects Wildlife Biodiversity Ian Sample guardian.co.uk

Posted by on June 15, 2011. Filed under News, Politics, World News. You can follow any responses to this entry through the RSS 2.0. You can skip to the end and leave a response. Pinging is currently not allowed.