Highlighting the plight of threatened lianas: Distribution, dynamics, and potential habitat areas of a critically endangered species

Lianas are a major component of tropical rainforests, contribute to its biodiversity and are beneficial for wildlife and ecosystems functioning. Some tropical lianas are known to be invasive and could slow down tree growth. As a consequence, lianas are often disregarded in conservation programs. Eleutharrhena macrocarpa (Menispermaceae) is a critically endangered liana primarily restricted to the primary rainforests of southern Yunnan. It is used to showcase the status of threatened lianas and highlight their conservation status by providing the number of individuals, distribution, current age structure and future dynamics, and potential habitat areas. From 2019 to 2021, we conducted the first field survey for this species along its distribution range. We drew the current age structure by using base diameter and predicted age structure dynamics by using the static life table. We predicted potential habitat areas under different climate scenarios by using Maxent modeling. We found 105 individuals, distributed in 26 different populations, and most individuals belonged to the I to III age classes. The static life table predicted that most individuals will die after age class III. This may be the result from the reduction of canopy gaps or a natural selection process. 42.3% of populations only had a single individual, and those populations may disappear without conservation efforts. Potential habitat areas are declining under all 3 future climate scenarios and parts of Xishuangbanna prefecture in Yunnan, northwestern Myanmar and northern Laos are relatively stable under those climate scenarios. Hence, we suggest Xishuang-banna national nature reserves as a priority conservation area. This study reflects the imperiled status of E. macrocarpa and shows how field survey, age structure, the static life table, morphological comparisons and Maxent could provide conservation ideas for the estimated 1700 threatened tropical lianas in the world.