Mary Pauline Kriszl E. Gupeteo, Mariedel Louise N. Lanto, Charlene Joyce F. Pon-an (March 2012)
Philippine Science High School Western Visayas Campus – Department of Science and Technology (DOST-PSHS WVC), Brgy. Bito-on, Jaro, Iloilo City 5000, Philippines
ABSTRACT
This study evaluated the insect leaf herbivory and the insect herbivore community on the mangrove species – Avicennia spp., at a site in Brgy. Balabago, Jaro, Iloilo City. Despite its widely recognized essence in other forested ecosystems or the so called ‘mangals’ is often unexplored and downplayed. It is believed that mangrove leaves are less palatable and nutritious than the leaves of other tree species and that herbivory levels are less than found in other ecosystems. Nearly all mangrove herbivory studies have measured damage on discrete leaf samples collected in one point in time. this approach fails to detect entirely consumed leaves, or partly damaged leaves that have been abscised. These leaves can be accounted for by an alternative method that makes repeated herbivory estimates on tagged leaves. Application of photogravimetric method in this study reveals that the overall estimated herbivory in Avicennia spp. leaves is 11.80%. This species had average loss of 11.15% leaf area in upper canopy, and an average of 12.45% leaf area loss in lower canopy. it was found out that there is average insect leaf herbivory on Avicennia spp. (Api-Api) in Brgy. Balabago, Jaro, Iloilo City. Nine hundred leaves of Avicennia spp. were sampled and were found out that a greater proportion of the leaves were affected by herbivory in varying degrees of consumption by insects and mostly less than 25% of the leaf area was consumed. A vertical zonation of herbivory was observed with an increasing trend from upper to lower canopy.The overall estimate of herbivory in mangroves revealed that insects consumed as much as 78% of the foliage of the leaf, and a leaf loss of 4% is common among the leaves. The prominent damage inflicted on the leaves is incursion along the margin, caused by chewing, non-skeletonizing, or mining beetles. Galls, leaf mines and leaf gazes were observed. This study demonstrates that: mangroves support a diverse and distinctive insect herbivore community and; leaf herbivory is much higher than previously reported. These results indicate that the role of herbivorous insects in mangal ecosystem is more significant than previously thought and that its evaluation needs to go well beyond simple static measures of leaf area missing and leaf damage area from the mangrove leaves.