Changes in taxonomic and functional diversity of dung beetles along a forest disturbance gradient in tropical karst ecosystems on islands of Vietnam

Tropical karst ecosystems are an exceptionally unique and important landscape element of South East (SE) Asia. Unfortunately, these ecosystems have been increasingly disturbed due to forest conversions to anthropogenic land uses, illegal logging, and limestone quarrying. Karst regions have a high degree of endemic species, so their loss is likely to have negative consequences for species conservation as well as ecological processes. We investigated dungbeetle communities from primary forests (PF), old secondary forests (>15 years since abandonment, OSF), young secondary forests (<10 years since abandonment, YSF), and Acacia plantations (<10 years old, AP) of karst ecosystems on Cat Ba Island (northern Vietnam). Our main aim was to provide a thorough and quantitative assessment of the taxonomic and functional diversity of dung beetles in the examined forests, and subsequently to determine the value of specific types of disturbed forests for biodiversity conservation. In total, 1458 dung beetles of 34 taxa were recorded. Community composition varied significantly among the forest types and was broadly separated into two groups: old-growth forests (i.e., PF and OSF) and young-growth forests (i.e., YSF and AP). While YSF and AP hosted severely impoverished dung-beetle communities, OSF with a high forest canopy cover and high ground vegetation cover harbored species-rich dung-beetle communities similar to those found in PF. However, functional diversity significantly differed between PF and OSF. The data also revealed that community responses were due to changing patterns of trait compositions rather than species richness.