Biodiversity Assessment of Syrphid Flies (Diptera: Syrphidae) Within China

Syrphid flies (Syrphidae) are among the most significant groups of insect pollinators with approximately 6300 described species worldwide. Within China, more than 15% species have been reported but their diversity and distribution pattern are not well understood. Based on recent collections and published literature records, this study aimed to assess the species diversity, richness, evenness, and distribution pattern of Syrphidae in China. Biodiversity was measured using various indices such as Simpson’s diversity index, the Shannon–Wiener diversity index, Simpson’s reciprocal index, the Shannon equitability index, and the Margalef index. The results indicated that most of the indices showed highest values within Sichuan, Shaanxi, Yunnan, Taiwan, Tibet, and Gansu provinces. However, the lowest values of most of these indices were seen in Tianjin, Chongqing, and Hongkong. The ranges of these values were 0.69–5.55, 0.67–1.00, and 1.44–46.26 for the Shannon–Wiener index, Simpson’s index, and the Margalef index, respectively. Based on UMAP (Uniform Manifold Approximation and Projection) clustering approaches, all provinces of China were divided into two groups where group 1 showed 16 provinces having similar values to each other in a UMAP1 and UMAP2 plot, whereas 17 provinces were categorized into group 2. This clustering was further refined by a hierarchical clustering dendrogram where group 2 was further refined into two subgroups, where three provinces were separated into one small group including Hongkong, Chongqing, and Tianjin because of the lowest values of most of the indices. These results provide significant insights into the species richness and distribution of syrphid flies and inform strategies to help maintain these pollinators to support sustainable agriculture.