Science Facing Aliens - Invasive Alien Species in Belgium - Belgian ...

Measuring the impact of Harmonia axyridis intraguild predation
on native coccinellids in the field
Louis HAUTIER 1 , Jean-Claude GRÉGOIRE², Pierre CALLIER³, Gilles SAN MARTIN 3,4
Jean-Pierre JANSEN 1 & Jean-Christophe DE BISEAU 3
1
Département Lutte biologique et Ressources phytogénétiques, Centre wallon de Recherches
agronomiques, Rue de Liroux, 2, B-5030 Gembloux, Belgium
2
Lutte biologique et Ecologie spatiale, Université Libre de Bruxelles, CP 160/12, Av. F.D.
Roosevelt 50 – 1050, Brussels, Belgium
3
Eco-Ethologie évolutive, Université Libre de Bruxelles, CP 160/12, Av. F.D. Roosevelt 50 -
1050 Brussels, Belgium
4
Present address: Écologie comportementale et conservation de la biodiversité , BDIV ,
Université catholique de Louvain, Croix du Sud 4 B-1348 Louvain-la-Neuve, Belgium
Introduction
The Multicoloured Asian Ladybird, Harmonia axyridis Pallas, was introduced in 1997 in
Belgium for aphid biological control (Adriaens et al. 2003). In less than five years, this
ladybird has invaded the whole of Belgium in urban, agricultural and semi-natural habitats
and has an overlapping niche with that of several native species (Adriaens et al. 2008). In
parallel, a decline of native ladybird species such as Adalia bipunctata (L.) and Adalia
decempunctata (L.), was observed in tree habitats in Brussels (San Martin et al. in prep). The
causes of this decline are not clearly identified and could be due to competition with or to
intraguild predation by, H. axyridis. Intraguild predation (IGP) is defined as “killing and
eating of species that use similar resources” (Polis et al. 1989); this interaction is very
frequent in aphidophagous guilds because aphids are limited resources (Lucas 2005). Several
laboratory studies have reported that H. axyridis acts as an intraguild predator of
Cecidomyiidae, Coccinellidae and Chrysopidae (Koch 2003, Pell et al. 2008, Ware &
Majerus 2008), except for interactions with the ladybird Anatis ocelata (L.) (Ware & Majerus
2008). However, laboratory conditions are extreme circumstances for interactions and are
considered a worst case. Under field conditions, IGP can be influenced by many factors such
as extraguild prey (e.g; aphids), possibility of intraguild prey escape, and importance of niche
overlap.
To follow IGP by H. axyridis on native coccinellids in field conditions, a new method
for detecting IGP was developed based on the detection of exogenous alkaloids from native
ladybirds in H. axyridis larvae, using gas chromatography - mass spectrometry (Hautier et al.,
2008). With this detection method, IGP by H. axyridis in lime trees (Tilia spp.) was studied in
twenty sites in Brussels between June and July 2008. 40 to 110 branchs of lime tree,
depending on site size, were beaten with a stick above a sweep net (65 cm in diameter and
130 cm in depth). H. axyridis larvae were isolated in microtubes and were kept in a freezer at
-20°C until alkaloid analysis.
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