Environ Exp Biol (2019) 17: 137–149

Arthropod functional feeding groups as indicators of small-scale disturbance: a first approach in Mt. Manunggal, Cebu Island, Philippines

Abstract

The growing pressure placed by human disturbances on natural resources creates a need for quick and precise answers about the state of conservation of different ecosystems worldwide. Hence, identifying and making use of ecological indicators becomes an essential task in the conservation of tropical ecosystems. This study assessed the effects of small-scale disturbances on terrestrial arthropods and select functional feeding groups (FFGs) that could be used as ecological indicators in one of the protected areas of Central Cebu Protected Landscape. Arthropods were sampled within Mt. Manunggal, Cebu Island, Philippines, both in highly-disturbed (S1) and less-disturbed sites (S2) of CCPL from October 2017 to March 2018. Arthropods were collected using a combined transect-quadrat method, where 24 quadrats were established within six transects (20 × 20 m) in S1 and S2. All data were analyzed using Odum and Barrett’s formulae for abundance and richness, Shannon Wiener index for diversity and Pielou’s index for evenness. A total of 12 403 arthropods under ten distinct FFGs were recorded, whose abundance contrasted across S1 and S2, with scavenger feeders showing the highest abundance (S1: n = 2363; 19.05%) while seed feeders with the lowest abundance (S1: n = 9; 0.13%; S2: n = 38; 0.67%). In S1, there were n = 6759 under 48 arthropod families while n = 5644 under 45 arthropod families were recorded in S2. The diversity index of arthropod assemblages in both sites (S1: H’ = 1.94; S2: H’ = 1.93) was classified in the medium category, indicated by H’ > 3.87. The evenness value in range 0.40 < e < 0.60 also indicated a medium number of arthropods in both sites. The abundance of arthropods was higher in the highly-disturbed site, and this pattern seems to be an adequate indicator of anthropogenic disturbance. This novel approach in categorizing arthropods based on FFGs provides an important complement to link contrasting patterns of composition to differences in forest functioning and habitat disturbances across geographical and environmental gradients. This study underlines that habitat disturbances are the main driver of the variation in arthropod diversity. Potential applications for FFGs as indicators include the choice and evaluation of sites for the establishment of protected areas, elaboration of management plans, and the assessment of ecological impacts due to human disturbances, either for the purpose of licensing or legal compensation.