Diversity and Assemblages of Canopy and Ground Layer Beetles in the Forests of Chitwan National Park, Nepal

Abstract

Beetle assemblages of tropical forest in Nepal are still largely unexplored and the biodiversity they harbor is still poorly known. This study investigated the beetle diversity and its assemblages in canopy and ground layer of Shorea robusta forest and Dalbergia sissoo forest. Thirty trees were selected purposively from four management sectors of Chitwan National park where 4 trees of Shorea robusta and 4 trees of Dalbergia sissoo were selected from each management sector. Canopy and ground layer beetles were sampled by using flight intercept trap and pitfall trap respectively. Thirty two flight intercept traps (16 in Shorea forest and 16 in Dalbergia forest) were hanged in canopy layer and 32 pitfall traps were installed into the ground within 1 m radius of the same tree where the flight intercept traps were hanged in the branches. A total of 25258 beetles belonging to 25 families (142 morphospecies) were recorded from 6 sampling periods between April 5 and July 31, 2016. Species richness was found high in canopy layer compared to ground layer where abundance was high in ground layer in both types of forest. Scarabaeidae was the most prominent family in both ground and canopy layer. Beetle assemblages showed that the herbivore beetles dominated the canopy layer followed by predators in canopy layer in term of both species richness and abundance. However, saprophages were dominant followed by predator in the ground layer. The effects of environmental variables (soil properties, tree properties and climatic factors) had varying effects on the beetle species richness and abundance and their assemblages. Variation of beetles in different types of forest and different layer in different time suggest that the distribution of beetles is structured in time and space.