Leaf Herbivore Preference in a Tropical Mangrove Forest Impacted by Human Physical Disturbance

Abstract

The consumption of mangrove leaves prior to litterfall has received scant attention by most researchers in the Western Indian Ocean region. The impact of human disturbance on herbivory is also poorly understood. This study compared rates of leaf attack among mangrove species at four sites with differing levels of human disturbance. Leaf specimens used for determination of herbivory were obtained from littertraps at the sites. The number of leaves with evidence of herbivore attack and area of leaf consumed were determined and compared. Disturbed sites had greater evidence of human activity such as tree cutting, roads and collection of bait. 34% of leaves examined were attacked by herbivores, with Rhizophora mucronata being most attacked (38%). However, Avicennia marina leaves which had lower attack, lost most leaf area to herbivores (12% of leaf area). Disturbed sites had lower rates of leaf attack but higher leaf area losses, especially at the disturbed sites. Rhizophora mucronata attack intensity decreased by over 50% at disturbed sites. Human physical disturbance is selective for mangrove flora and fauna and may change predominance of host tree preferred by the herbivores leading to lower rates of herbivory.