Collembola (Arthropoda: Hexapoda) Assemblages in the Canopy and Forest Floor along an Elevational Gradient at Mt. Makiling, Philippines

Abstract

Patterns of distribution and diversity of springtails along an elevational gradient in the canopy and forest floor of Mt. Makiling, Philippines were determined, this being the first study conducted on springtail diversity along an elevational gradient and also the first published report of canopy arthropods in the Philippines. Springtails were extracted from soil samples from the floor and those suspended in the canopy of three natural forests at different elevations (tropical lowland evergreen rainforest, lower montane rainforest, and tropical upper montane forest). We predict that elevation and forest strata will have significant effects on the springtail assemblages. A total of 2,287 springtails representing 31 morpho-species and eight families were collected from the study. Across the elevation gradient, mean species richness and mean abundance consistently decrease as elevation increases, but only the mean abundance of the lowland forest is significantly different from that of the lower and upper montane forests. Diversity t-test (p-values less than 0.05) revealed significant differences between different sites and strata. Clustering analysis using the Bray-Curtis similarity index revealed separate groupings of the lowland forests to those of the montane forests. Lastly, the results of PERMANOVA showed that both elevation and strata were found to have significant effects on the overall assemblage of springtails. This study suggests that forest floor species assemblages are closely related to each other unlike those of the canopy, where only the upper montane and lower montane are similar. The results of this study affirm our main hypothesis that springtails (as a group) respond significantly to both elevation and strata in a tropical forest in the Philippines.