14 research outputs found
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
Fecundity and fertility of ladybird beetle Harmonia axyridis after prolonged cold storage
Substrate Marking by an Invasive Ladybeetle: Seasonal Changes in Hydrocarbon Composition and Behavioral Responses
The multicolored Asian ladybeetle, Harmonia axyridis (Pallas), aggregates inside dwellings during the winter to survive the
cold. Recent published reports have highlighted that overwintering individuals use hydrocarbon markings deposited on
surfaces by conspecifics to orient toward aggregation sites. In the current study, monthly GC-MS analyses revealed seasonal
modifications in the chemical profile of substrate markings deposited by moving individuals. The markings of overwintering
ladybeetles contained larger proportions of heptacosadiene, nonacosadiene, hentriacontadienes, and methyl-nonacosanes,
along with a lower proportion of heptacosene and nonacosene. This finding suggests the importance of the unsaturated
and/or branched hydrocarbons in the H. axyridis aggregation process. Subsequently, we conducted behavioral assays to test
whether (1) there is seasonal variation in the behavioral response of H. axyridis individuals toward substrate markings
deposited by conspecifics in the same physiological state and (2) the observed behavioral modification is due to a change in
ladybeetle sensitivity and/or a change in the chemical composition of the substrate marking. The results indicate that
overwintering individuals exhibit a stronger ‘‘following’’ response toward conspecific substrate markings. This behavior is
linked to both the physiological state of ladybeetles and the specific chemical profile of the marking biomolecules
deposited under overwintering conditions