Revision of Senegalia in China, and notes on introduced species of Acacia, Acaciella, Senegalia and Vachellia (Leguminosae: Mimosoideae).
The present work represents the first comprehensive taxonomic revision of Acacia sens. lat. (Leguminosae: Mimosoideae) in China, focusing on the indigenous species. Critical reassessments of specimens and re-definition of previously recorded species have resulted in recognising 21 indigenous species under Senegalia, a segregate of the former Acacia sens. lat. Detailed botanical profiles are provided for these species, together with a diagnostic line drawing and distribution map; photographs of living plants are provided for more than half the species. Terser treatments are also provided for the 15 species from four genera that are regarded as major introductions of Acacia sens. lat. to the country: Acacia Mill. (12 spp.), Acaciella Britton & Rose (1 sp.), Senegalia Raf. (1 sp.) and Vachellia Wight & Arn. (1 sp.). An identification key to all Acacia sens. lat. species in China is provided. The indigenous species of Senegalia in China belong to sect. Monacanthea (Vassal) Maslin, comb. nov., and the introduced ones to sect. Senegalia. As a consequence of this study, the number of Senegalia species now recognised for China has almost doubled. Six new species are described: Senegalia clandestina Maslin, B.C.Ho, H. Sun & L. Bai, sp. nov.; Senegalia guangdongensis Maslin, B.C.Ho, H. Sun & L. Bai, sp. nov.; Senegalia obliqua Maslin, B.C.Ho, H. Sun & L. Bai, sp. nov.; Senegalia orientalis Maslin, B.C.Ho, H. Sun & L. Bai, sp. nov.; Senegalia prominens Maslin, B.C.Ho, H. Sun & L. Bai, sp. nov.; Senegalia stipitata Maslin, B.C.Ho, H. Sun & L. Bai, sp. nov. Four new combinations are established: Senegalia garrettii (I.C. Nielsen) Maslin, B.C.Ho, H. Sun & L. Bai, comb. & stat. nov.; Senegalia kerrii (I.C. Nielsen) Maslin, B.C.Ho, H. Sun & L. Bai, comb. & stat. nov.; Senegalia kunmingensis (C. Chen & H. Sun) Maslin, B.C.Ho, H. Sun & L. Bai, comb. & stat. nov.; Senegalia macrocephala (Lace) Maslin, B.C.Ho, H. Sun & L. Bai, comb. nov. Senegalia andamanica (I.C. Nielsen) Maslin, Seigler & Ebinger and S. macrocephala are new records for China. A lectotype is designated for Acacia teniana Harms and 2nd step lectotypifications effected for Acacia delavayi Franch., Acacia insuavis Lace, Acacia pruinescens Kurz and Acacia yunnanensis Franch. Former holotype citations are corrected to lectotype for Acacia hainanensis Hayata, Acacia macrocephala Lace, Acacia oxyphylla Graham ex Benth. and Acacia philippinarum Benth. A neotype is designated for Acacia arrophula D. Don. China is a principal area of species-richness for Senegalia in Asia. Senegalia displays a high degree of endemism within China and almost half the species are endemic or near-endemic, with Yunnan the most species-rich and species-diverse Province.