Abundance, distribution and substrate association of Hong Kong stag beetles (Coleoptera: Lucanidae) in secondary forests

Ecological studies conducted on lucanids in Asia are limited, resulting in considerable knowledge gaps in the fundamental ecology of these charismatic species (e.g. larval substrate associations), despite their potential importance in wood decomposition. We conducted 25 transect surveys in secondary forest sites in Hong Kong and sampled wood parameters and site-level wood availability data to test whether these habitat features significantly affected abundance or occurrence of lucanids. Out of 412 wood fragments sampled, we found two species: Prosopocoilus oweni was broadly distributed across sites (but still uncommon at the level of wood fragments occurring in 6.07%) while Nigidius sinicus was comparatively rarer (occurring in 0.73% of examined wood fragments). The dominant species P. oweni was more likely to appear in wood fragments in later decay stages and can be classified as a secondary forest generalist with respect to wood resource utilization. The surveys failed to detect four additional lucanid species known in Hong Kong (Neolucanus sinicus, E. gracilis, P. biplagiatus, and Aegus chelifer) potentially because of their rarity or usage of other habitats or microhabitats. Protection of existing secondary forests in Hong Kong is recommended to secure supply of suitable habitat and resources. Results obtained by standardized surveys can furthermore serve as a baseline for future assessment of lucanid population change. This study provides ecological insights into lucanids within secondary forest ecosystems of subtropical and tropical Asia.