Lysimachia robusta Handel-Mazzetti, a perennial herb species of the family Primulaceae, is endemic to the southern Hengduan Mountains in south-west China. Previously it had only been collected three times, in 1911, 1912 and 1913, by George Forrest and Edward Butts Howell, and was described in 1928 (H. Handel-Mazzetti, 1928, Notes from the Royal Botanic Garden, Edinburgh, 16, 116). According to the three type collections (George Forrest 9286, 11997; Edward Butts Howell 49) at the herbaria of the Royal Botanic Garden Edinburgh and the Institute of Botany, Chinese Academy of Sciences, this species is only known from Tengyüeh (now Tengchong) and the Shweli-Salween divide, in the southern Hengduan Mountains, an area of c. 400,000 ha in western Yunnan. Surveys (Qinghai-Tibet Plateau Expedition in 1982 and Gaoligongshan Biodiversity Survey in 1998–2007) close to the type locations and adjacent areas were not able to locate the species.
With the joint support of the National Natural Science Foundation of China (Grant No. 31570212, 31770228), the National Key Program of the Ministry of Science and Technology (Grant No. 2017FY100100) and the Talent Project of Yunnan (Grant No. 2015HB092), the Kunming Institute of Botany surveyed for any remnant L. robusta in the southern Hengduan Mountain range during June–August in 2018. Approximately 1,100 individuals in flower were discovered in three separate sites in grassy wetlands at an altitude of 1,730 m. The total area of occupancy of the species is c. 800 m2. This suggests that it should be categorized as Critically Endangered on the IUCN Red List on the basis of criterion B2ab (i,ii,iii,v). Also, because of its restricted distribution, small population size, and habitat degradation, it should be included in the list of Plant Species with Extremely Small Populations in China (Ma et al., 2013, Biodiversity and Conservation, 22, 803–809). My survey and interviews with local people indicated that the main threats to this species are its small population size, the development of its wetland habitat for tourism in the last 15 years—leading to an increasing number of people picking the flowers for their ornamental value—and habitat loss because of road construction. Urgent and effective measures need to be taken to protect this species.
The Kunming Institute of Botany is now carrying out studies on the population genetics of L. robusta and its genetic relationships to other Lysimachia species of the southern Hengduan Mountains, to obtain a better understanding of the microevolution of this species. In collaboration with staff of nature reserves, I am planning to collect seeds of L. robusta for propagation and for potential restoration of the species in the wild. The southern Hengduan Mountains are currently managed as a nature reserve by the local government. However, more attention should be paid to wetlands in this region, because this is the only known natural habitat for the remnant L. robusta.
