Renate Zindel

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

Abstract.  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.

Detecting arthropod intraguild predation in the field

The process of biological control carries a distinct risk that an alien biological control agent (BCA) will become established as an invasive alien species with an associated threat to the local ecosystem biodiversity. It is imperative that a wide-ranging environmental risk assessment (ERA) is performed before the release of any BCA. This should include considering various potential but difficult to observe ecological interactions between the BCA and members of the native community, including disruption of intraguild relationships. Detection of intraguild predation (IGP) events involving predatory arthropods in the field can be done by analyzing their gut contents. Polymerase chain reaction (PCR) is a sensitive and specific tool to identify target prey DNA within a predator’s gut. This paper reviews the efficiency of a DNA based approach for detecting IGP in the field, compared with detection by the use of monoclonal antibodies or gas chromatography. Prey specificity, detection times after prey consumption, capacity for quantification, multiple prey targeting and the time and costs involved in developing and using the different methods are considered.

The role of the bacterial community in the nutritional ecology of the bulb mite Rhizoglyphus robini (Acari: Astigmata: Acaridae)

The biology of many arthropods can only be understood when their associated microbiome is considered. The nutritional requirements of the bulb mite Rhizoglyphus robini Claparede (Acari: Astigmata: Acaridae) in the laboratory have been shown to be very easily satisfied, and in the field the mites prefer fungus‐infected over uninfected plants. To test whether symbiotic bacteria facilitate the survival of R. robini on a temporarily nutritionally unbalanced diet, we investigated the composition of its microbiome. Using 454 pyrosequencing of 16S rRNA gene fragments, 3 genera were found to dominate the bacterial community: Myroides (41.4%), Serratia (11.4%), and Alcaligenes (4.5%); the latter 2 are known to include chitinase‐producing species. Laboratory experiments demonstrated that mite fecundity is significantly higher (2 times) on fungus than on controls (sterilized potato dextrose agar and filter paper). Also, when mite homogenate was applied to a chitin layer, the halo produced through degradation was clearly visible, while the saline control did not produce a halo. We thus concluded that R. robini utilizes fungal chitin, at least to a certain extent, as a food source with the help of its associated bacteria. This information supports the general concept of multigenome organisms and the involvement of bacteria in the mites nutritional ecology.—Zindel, R., Ofek, M., Minz, D., Palevsky, E., Zchori‐Fein, E., Aebi, A. The role of the bacterial community in the nutritional ecology of the bulb mite Rhizoglyphus robini (Acari: Astigmata: Acaridae). FASEB J. 27, 1488–1497 (2013). www.fasebj.org

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.

Isolation of Serratia marcescens involved in chitin degradation in the bulb mite Rhizoglyphus robini

There is an increasing awareness of the importance of the microbiome of arthropods to understand their host’s biology. In the bulb mite, Rhizoglyphus robini, associated bacteria have been found to be involved in its chitinolytic abilities. The bulb mite, a plant pest feeding on below-ground parts of mostly Liliaceae crops, prefers fungus-infested plants. Moreover its fitness is higher when feeding on a fungal food source than when feeding on non-infected plants. In this study we isolated a chitinolytic bacterium from mite homogenate and identified it molecularly as Serratia marcescens (Bizio 1823), which is a model organism for chitin degradation. Precise identification of the bacterium can be important for the development of biological control programs of the mite as well as for further studies investigating Serratia marcescens and its chitinolytic machinery.