Integrating tropical ant assembly into biodiversity conservation

Abstract

Tropical ecosystems and their rich biota are increasingly threatened by anthropogenic disturbances. However, limited knowledge on insect taxonomy, distribution, ecology, and lack of political will from governments and conservation agencies prevent the development of effective conservation programmes. Given functional-trait based approach represents a valuable and increasingly-used tool for informing community-wide insect conservation, in this thesis, I first advance its robustness by highlighting potential pitfalls in its measurements induced by the usage of particular sampling method. By comparing pitfall traps and Winkler extractors in shrublands and forests, I found that sampling filters from different methods affected the trait composition and diversity of ant communities asymmetrically. In shrublands and forests, the trait compositions of communities sampled by pitfall traps were dominated by larger sized, slender-shaped and long-legged ants as compared to those sampled by Winklers. The latter method also underestimated the diversity of individual traits related to body size and the size and filling properties of multidimensional trait space. With a better understanding of functional biases of my sampling methods, I re-sampled a baseline ant inventory performed over 20 years ago in Hong Kong and showed the importance of secondary forest succession on recovering microclimatic refuges for species against extreme temperatures. My results show that the comparison of ant assemblages occupying two broad habitat types (non-forested vs. forested) revealed significant community turnover over a 20 years’ period. These compositional turnovers partly arose from non-random replacements of species in terms of their temperature and microhabitat usage preferences, and highlighted the influence of climatic warming and potential buffering effects in the quality and connectivity of microhabitats. Specifically, forests not only provide a canopy buffer moderating understory microclimatic conditions, but also enhance connectivity among refuges for species to persist. In contrast, in non-forested habitats, ant species richness became richer, but homogenization of composition was observed, likely as a result of increased temperatures. Furthermore, I studied the potential of rubber-based agroforest practice for insect conservation and for invasion control in protected areas of Hainan. I found that despite rubber-based agroforest and conventional rubber monoculture presenting similar species richness, the former 1) supports species composition and functional diversity more similar to secondary forests, and 2) reduces tramp ant species occurrence, a novel management incentive. Nonetheless, the results also show that the conservation potential for non-tramp ant species in rubber-based agroforest is not comparable to secondary forest. The study in Hong Kong and Hainan highlight the importance of forest quality and provided potential management directions for bolstering species resilience in an anthropogenic-disturbed world. Next, I expanded the knowledge on ant assembly and their ecology for providing dietary insights of a juvenile of the endangered Chinese pangolin. Finally, to facilitate ant inventory and future ecological work on ants in the Hainan, I present the first checklist of ants specific to Hainan which includes 10 subfamilies, 61 genera, and 194 valid species. Overall, the work presented in this thesis should act as a catalyst to stimulate further studies on insect taxonomy, ecology and conservation in Tropical Asia.