Passive interplay between resource dynamics and resource consumption may determine the spatio-temporal distribution of a leaf-feeding insect in the canopy of a palm
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Date
2008
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Publisher
Current Science Association
Abstract
In insect–plant systems, it is generally believed that interactions with cause–effect relationships are responsible for spatio-temporal distribution of insects. In contrast, the present study aims at explaining withinplant spatio-temporal patterns in the ‘coconut blackheaded caterpillar–coconut palm’ system through passive resource–consumer interactions (without cause– effect relationship). During outbreaks, populations of the caterpillar have been observed to occur at high densities in the lower canopy of the palm before distributing to the upper canopy. This has led to speculations of ‘preference’ to the lower canopy. The present study indicated that infestation began randomly in a palm, which evidences against the speculations. In spite of an initial random distribution, observations showed that population moved from the lower to the upper canopy at later stages of infestation. Further observations and experiments led to the conclusion that caterpillars move in the canopy in search of uninfested fronds; and moths preferably oviposit among the most recently constructed larval feeding galleries. It means that a frond that was initially infested would be substantially consumed before caterpillars dispersed to fresh fronds. On the basis of these evidences and the dynamics of coconut fronds, we present a logical model, which relies on ‘passive’ resource– consumer interactions, to explain the lower to upper canopy spatio-temporal distribution of infestation in this system.
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Keywords
Canopy dynamics, insect–plant interaction, Opisina arenosella, resource–consumer interaction, within plant distribution
Citation
CURRENT SCIENCE, VOL. 94, NO. 7, 10 APRIL 2008