Nathan Rank

Sonoma State University

Natural enemies and host plant use
Predictions and Study System (Page 3 of 5)

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Predictions of the predation hypothesis for salicylate-using leaf beetles

The chemical ecology of the leaf beetle/willow interaction provides an unusual opportunity to examine how host plant chemistry affects interactions between herbivores and their natural enemies and thereby evolutionarily favors herbivore specialization. The predation hypothesis proposes that beetles specialize on salicylate-rich willows because they are protected from natural enemies on them. From this hypothesis, three predictions may be derived:

  1. Beetles should prefer salicylate-rich willows over salicylate poor ones.
  2. Beetle larvae should survive better on salicylate-rich plants than on salicylate-poor ones.
  3. Natural enemies should be repelled by the beetles' secretion.

I tested these three predictions experimentally for two leaf beetles:

Chrysomela aeneicollis in California

Phratora vitellinae in Finland

Research approach: replication of field experiments on different continents

  • Larvae of both species use host plant salicylates to produce their salicylaldehyde secretion.
  • Both beetles occur in habitats where willow species differ in salicylate content..
  • Working in both systems provides greater insight into general ecological processes.

Chrysomela aeneicollis adult in California

Phratora vitellinae adult in Finland

The field site in Big Pine Creek, with several willow species.

Several willow species also occurred in Finnish field sites

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JJanuary 23, 1999 NER