Southeast Asia includes four overlapping biodiversity hotspots: Indo-Burma, Philippines, Sundaland and Wallacea (Myers et al. 2000; Sodihi et al. 2004). Southeast Asia covers about 4.5 million km2, which is approximately 3 % of earth’s total land area. There is, however, approximately 20 to 25 % of Earth’s higher plant species in this area (Myers et al. 2000). It is crucial to understand the biodiversity for conservation and sustainable development in the shadow of climate change and growth of economics and population. Biological surveys and scientific research of biodiversity have a long history in Southeast Asia and several hypotheses for biogeography have been proposed (e.g. Che et al. 2010; Hou and Li 2017). However, the species richness of biodiversity is far underestimated. Taxonomy, including discoveries of new taxa, taxonomic revision and inventory, is the precondition of our conservation and sustainable development. Although frontiers of taxonomy and systematics biology, integrated taxonomy and genomics are main trends, the taxonomic work of checklist, flora and description of new taxa are far from sufficient in Southeast Asia. Many species will become extinct before we know that they even exist in Southeast Asia. Although it is a daunting task, it is extremely urgent to investigate, understand and conserve our biota.