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- Title
WHY DOES THE LEAF BEETLE GALERUCELLA LINEOLA F. ATTACK WETLAND WILLOWS?
- Authors
Sipura, Mika; Ikonen, Arsi; Tahvanainen, Jorma; Roininen, Heikki
- Abstract
The willow-feeding leaf beetle (Galerucella lineola F.) attacks its host plant, tea-leafed willow (Salix phylicifolia L.), heavily in damp habitats, but less so in welldrained soils. To confirm this general observation and to explore the factors affecting habitat and host-plant use by this beetle, we collected data from 12 study sites in Finland during two consecutive years. All sites included three habitats: (1) water, where the willows were growing in permanently waterlogged soils, (2) flood zone, where the willows underwent periods of flooding, and (3) dry zone, where the willows grew in well-drained soils. G. lineola was, on average, 16 times more abundant on willows growing directly from water as compared to willows in well-drained soils nearby. To explain this, we proposed three general hypotheses. (1) The food-quality hypothesis states that the apparently stressed willows growing in waterlogged soils provide superior food for the beetles. (2) The predation hypothesis states that open water surface around the willows in wetlands impedes dispersal of predators providing enemy-free space for the beetles. (3) The climate hypothesis states that wetlands provide better abiotic conditions for the adults, eggs, or larvae of this leaf beetle. These hypotheses were tested by using observational data and by performing both laboratory and field experiments. Contrary to the food-quality hypothesis, adult beetles preferred S. phylicifolia grown in dry habitats both for food and oviposition medium in the laboratory, and produced fewer eggs when fed on willow leaves from wetlands. Consistently, larvae performed poorly on leaves from wetland willows in the laboratory, most probably due to low water content of the leaves, also rich in phenolic secondary compounds and poor in nitrogen. The densities of crawling predators did not differ between the habitats, and the predation experiments revealed no difference in predation pressure between the habitats. However, during a...
- Subjects
GALERUCELLA; WILLOWS; INSECT-plant relationships
- Publication
Ecology, 2002, Vol 83, Issue 12, p3393
- ISSN
0012-9658
- Publication type
Article
- DOI
10.1890/0012-9658(2002)083[3393:WDTLBG]2.0.CO;2