Ecological Entomology (2010) 35, 611-622

Elena L. Zvereva, Oksana Yu. Kruglova and Mikhail V. Kozlov (2010)
Drivers of host plant shifts in the leaf beetle Chrysomela lapponica: natural enemies or competition?
Ecological Entomology 35 (5), 611-622
Abstract: 1. The leaf beetle, Chrysomela lapponica, originally uses the salicyl glucosides (SGs) of its host plants to sequester salicylaldehyde, which serves as a defence against generalist enemies but attracts specialist enemies. However, some populations of C. lapponica have shifted to SG-poor hosts, and their secretions do not contain salicylaldehyde.
2. In was suggested that beetles shift to SG-poor hosts to escape from specialist enemies. To test this hypothesis, we compared field mortality between two populations of C. lapponica that were associated with SG-rich willow, Salix myrsinifolia (Kola Peninsula and Finland) and two populations that fed on SG-poor willows, S. glauca (Ural) and S. caprea (Belarus).
3. Mortality from generalist enemies was significantly higher in Belarus than in three other populations, whereas mortality from specialists did not differ among populations. A specialist predator (syrphid fly larvae, Parasyrphus nigritarsis) and specialist parasitoids (phorid flies, Megaselia spp.) were attracted to the secretions of larvae reared on both SG-rich and SG-poor hosts.
4. Feeding on leaves of S. caprea and S. myrsinifolia both previously damaged by leaf puncturing and by the larvae of potentially competing species Chrysomela vigintipunctata, decreased the weight and prolonged the development of C. lapponica.
5. Thus, populations of C. lapponica that have shifted to SG-poor willow species did not obtain enemy-free space because specialist enemies have developed adaptations to herbivores that switched to a novel host plant. We suggest that in some populations host plant shift was favoured by interspecific competition with the early season SG-using specialist, C. vigintipunctata.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Elena L. Zvereva, Mikhail V. Kozlov

Research topic(s) for pests/diseases/weeds:
environment - cropping system/rotation
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Chrysomela lapponica	Willow (Salix)	Belarus
	Chrysomela lapponica	Willow (Salix)	Finland
	Chrysomela lapponica	Willow (Salix)	Russia (Eur.)
	Chrysomela vigintipunctata	Willow (Salix)
Parasyrphus nigritarsis (predator)	Chrysomela lapponica