Phylogenetic diversity analysis of the community of extremely small populations of Glyptostrobus pensilis

Glyptostrobus pensilis (Staunton ex D. Don) K. Koch, also called the Chinese swamp cypress or water pine, is a well-known relict plant and "living fossil". It is listed as a "Grade Ⅰ" wild plant under the state key protected list, and is only known from extremely small populations in South and South-East China, as well as Vietnam and Laos. It is also categorized as "Critically Endangered" with a decreasing trend according to the IUCN evaluation criteria. We investigated the community vegetation, health status, disturbance factors, and alien invasive plants of 42 wild populations of G. pensilis in China in 2016. Community phylogenetic diversity analysis indicated that the health status of the G. pensilis populations was related to the degree of threat of anthropogenic disturbance. In addition, populations with high phylogenetic diversity values were always in good condition. The presence of alien invasive species in the community will make the phylogenetic structure clustered and result in the decrease of the phylogenetic diversity value. It should be noted, therefore, that the exclusion of anthropogenic activities and elimination of alien invasive plants will improve the health status of populations and individuals, increase the phylogenetic diversity of the community, and enhance the resistance and recoverability of G. pensilis populations.