Influence of human disturbance on patterns of leaf herbivory at Gazi Bay mangrove forest, Kenya

  • CM Kihia
  • JM Mathooko
  • RK Ruwa
  • WA Shivoga

Abstract

Mangrove herbivores cause leaf serration, perforation and galls prior to leaf abscission. This study compared damage by herbivores on leaves of four  mangrove species at sites under different levels of human physical disturbance, and provides further evidence of the indirect effects of man on these valuable habitats. From 2001 to 2003 leaves collected fortnightly using litter traps were examined for evidence of herbivore damage, e.g. holes, margin damage, and a mix of both holes and margin damage on the leaf, and compared using ANOVA. Of 10 600 leaves examined, 3 604 had evidence of herbivore attack, with margin damage being most prevalent (60%). On Rhizophora mucronata, holes and mixed damage occurred on over 30% of damaged leaves, while margin damage was common to all other species examined. Leaf attack intensity was 14% lower at undisturbed sites, with margin damage being most common. Comparison between corresponding mangrove forest sites in Kenya showed significant increase in margin damage and concurrent decline in holes and mixed damage at disturbed sites. Variation in leaf damage occurrence was attributed to changes in forest structural and biological complexity owing to selective harvesting of flora and fauna that influenced the competitive ability and prevalence of aerial herbivorous guild.

Keywords: attack intensity, boring, leaf serration, selectivity, tree cutting

African Journal of Aquatic Science 2011, 36(3): 235–241

Author Biographies

CM Kihia
Department of Biological Science, Egerton University, PO Box 536, Egerton, Kenya
JM Mathooko
Department of Biological Science, Egerton University, PO Box 536, Egerton, Kenya
RK Ruwa
Kenya Marine and Fisheries Research Institute, PO Box 81651, Mombasa, Kenya
WA Shivoga
Department of Environmental Science, Egerton University, PO Box 536, Egerton, Kenya
Section
Articles

Journal Identifiers


eISSN: 1727-9364
print ISSN: 1608-5914