Assessing the ecological risk posed by a recently established invasive alien predator: Harmonia axyridis as a case study

Invasive alien predators are a serious threat to biodiversity worldwide. However, there is no generic method for assessing which local species are most at risk following the invasion of a new predator. The harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), is an alien in Europe and many other parts of the world where it affects other species of ladybirds through competition for food and intra-guild predation (IGP). Here, we describe a method developed to assess which European ladybird species are most at risk following the invasion of H. axyridis. The three components of the risk assessment are: the likelihood that the assessed native species encounters H. axyridis in the field, the hazard of competition for food, and the IGP hazard. Thirty native European ladybird species were assessed through data obtained from field observations, laboratory experiments and literature reviews. The species that are considered most at risk are found on deciduous trees, have immature stages which are highly vulnerable to IGP by H. axyridis, and are primarily aphidophagous. These species should be the focus of specific studies and possibly conservation actions. The risk assessment method proposed here could be applied to other alien predators which are considered a threat to native species through competition and predation

Current and potential management strategies against Harmonia axyridis

This paper reviews the current and potential methods to control the harlequin ladybird, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an Asian predatory beetle invasive in Europe and the Americas where it has become a human nuisance, a grape and wine pest and a threat to native biodiversity. Current methods to manage this invasive species include: techniques to mechanically prevent adult beetles from entering buildings in autumn or to remove aggregates of beetles inside buildings, e.g. using various trapping methods; the use of insecticides on buildings or in vineyards to prevent aggregation in houses or on grapes; cultivation practices in vineyards to lower the impact of the ladybird on grape production and wine quality; remedial treatments for wine tainted by the ladybird. Other methods are presently being developed or considered. Semiochemicals could be used as deterrents or as attractants to develop more efficient trapping systems in buildings and open fields. Natural enemies include pathogens, parasitoids, predators and a parasitic mite but few of them show potential as biological control agents. While management methods presently used or under development may eventually solve the problems caused by beetles aggregating in buildings or vineyards, the issue of H. axyridis populations outcompeting native species is much more challenging. Only the sudden adaptation of a native natural enemy or the importation of a natural enemy from the area of origin of the ladybird may ultimately lower population densities. The problems linked to the importation of an Asian natural enemy of H. axyridis are discussed

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Predation of native coccinellids by the invasive alien Harmonia axyridis (Coleoptera: Coccinellidae): detection in Britain by PCR-based gut analysis

1. The harlequin ladybird, Harmonia axyridis, is an invasive alien species that arrived in Britain in 2003 and has spread across most of the country. 2. This spread has been accompanied by a decline in some native coccinellid species, in particular, the two spot ladybird Adalia bipunctata and the ten spot ladybird Adalia decempunctata. One reason for this decline could be intraguild predation (IGP) of the Adalia species by H. axyridis. 3. A DNA-based approach was used to look for evidence of coccinellid IGP in the wild. Adalia bipunctata- and A. decempunctata-specific Polymerase chain reaction primers were developed to analyse the gut contents of field collected H. axyridis larvae for the presence of Adalia DNA. Harmonia axyridis larvae (156) were collected from lime trees at four sites in eastern England over 3 years. 4. Adalia bipunctata DNA was detected in 7.7% and A. decempunctata DNA in 4.5% of H. axyridis larvae. DNA from both Adalia species was detected in two larvae. 5. This is the first demonstration of specific IGP interactions between H. axyridis and other coccinellid species in wild populations in Britain

Harmonia axyridis implicated in native European ladybird declines

Rates of global extinction are orders of magnitude higher than historical estimates and show no sign of slowing. The Convention on Biological Diversity and the 10th Conference of the Parties (Nagoya in 2010), identified invasive alien species (IAS) as one of five major pressures driving biodiversity loss, and ultimately extinction of species. However, there are few examples of causal relationships between IAS and species declines. IAS afford a unique opportunity to accurately assess threats to biodiversity because the time at which an IAS arrives within an ecosystem is often known, unlike other drivers of change. We examined trends in distribution of native ladybirds from large-scale and long-term annual citizen-science surveys before and after the arrival of the predatory harlequin (or Asian) ladybird Harmonia axyridis, an IAS that is rapidly expanding across North America and Europe. We report rapid, dramatic and ongoing declines in the distribution of formerly common and widespread native ladybirds in direct response to the arrival of H. axyridis in Belgium and Britain. The dramatic decline of A. bipunctata over the five years following the arrival of H. axyridis is of particular note. Trends in ladybird abundance revealed similar patterns of declines in ladybirds across Belgium, Britain and Switzerland. Together, these parallel analyses show H. axyridis to be displacing native ladybirds with a high niche overlap, probably through predation and competition. Such rapid biotic homogenisation at the continental scale could impact on the resilience of ecosystems and severely diminish the services they deliver