Complex effects of fertilization on plant and herbivore performance in the presence of a plant competitor and activated carbon

PLoS One. 2014 Jul 31;9(7):e103731. doi: 10.1371/journal.pone.0103731. eCollection 2014.

Abstract

Plant-herbivore interactions are influenced by host plant quality which in turn is affected by plant growth conditions. Competition is the major biotic and nutrient availability a major abiotic component of a plant's growth environment. Yet, surprisingly few studies have investigated impacts of competition and nutrient availability on herbivore performance and reciprocal herbivore effects on plants. We studied growth of the specialist aphid, Macrosiphoniella tanacetaria, and its host plant tansy, Tanacetum vulgare, under experimental addition of inorganic and organic fertilizer crossed with competition by goldenrod, Solidago canadensis. Because of evidence that competition by goldenrod is mediated by allelopathic compounds, we also added a treatment with activated carbon. Results showed that fertilization increased, and competition with goldenrod decreased, plant biomass, but this was likely mediated by resource competition. There was no evidence from the activated carbon treatment that allelopathy played a role which instead had a fertilizing effect. Aphid performance increased with higher plant biomass and depended on plant growth conditions, with fertilization and AC increasing, and plant competition decreasing aphid numbers. Feedbacks of aphids on plant performance interacted with plant growth conditions in complex ways depending on the relative magnitude of the effects on plant biomass and aphid numbers. In the basic fertilization treatment, tansy plants profited from increased nutrient availability by accumulating more biomass than they lost due to an increased number of aphids under fertilization. When adding additional fertilizer, aphid numbers increased so high that tansy plants suffered and showed reduced biomass compared with controls without aphids. Thus, the ecological cost of an infestation with aphids depends on the balance of effects of growth conditions on plant and herbivore performance. These results emphasize the importance to investigate both perspectives in plant herbivore interactions and characterize the effects of growth conditions on plant and herbivore performance and their respective feedbacks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aphids / growth & development*
  • Charcoal
  • Fertilizers
  • Herbivory*
  • Solidago / growth & development*
  • Tanacetum / growth & development*

Substances

  • Fertilizers
  • Charcoal

Grant support

This study was financially supported by grant WE 3081/15-2 and by a TUM Diversity Scholarship to NMA. Publication of this work was supported by the German Research Foundation (DFG) and the Technische Universität München within the funding program open access publishing. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.