Document: ROB-3-23-5

Host plant heterogeneity, habitat persistence, and the evolution of phytophagous insect life-histories.

DENNO, R.F.*

University of Maryland, College Park, MD 20742 USA ¹

Abstract:
An inherent difference in stoichiometry between phytophagous insects (10% nitrogen content on average) and their host plants (2% nitrogen content) suggests that nitrogen is generally limiting for these consumers and places fundamental constraints on their growth. Moreover, when high-nitrogen opportunities are provided by host plants, they are frequently scattered among a mosaic of less nutritious alternatives and are ephemeral in nature. The life history strategies that allow phytophagous insects to cope with spatial and temporal changes in plant quality are diverse, but tend to fall into one of two major categories, namely dispersal or feeding compensation. Using salt marsh-inhabiting planthoppers (Hemiptera: Delphacidae) as a model system, evidence is provided: (1) for an antagonistic trade-off between dispersal ability (flight muscle development) and compensatory feeding (development of cibarial musculature), (2) that competitive ability is positively associated with compensatory feeding because feeding-induced reductions in plant nitrogen are better tolerated, and (3) that compensatory feeding is associated with reduced flight capability in persistent habitats. Thus, habitat persistence not only underlies the dispersal strategies of planthoppers, but it also appears to dictate their options for meeting nitrogen demands and to influence their competitive ability with other species of phytophagous insects. This may explain why mobile species selectively colonize nitrogen-rich host plants, are generally poor competitors, and are preadapted for becoming agricultural pests in nitrogen-rich, ephemeral habitats.

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This abstract is being presented at: 2:40 PM in session:
Symposium # 23: Why Variation is Not Just Noise: The Influence of Variability on Plant-Herbivore and Plant-Pathogen Interactions.