Distribution Dynamics of Diplopanax stachyanthus Hand.-Mazz. (Mastixiaceae) and Its Implications in Relict Mastixioid Flora Conservation

Abstract

Climate is a key driver shaping the distribution pattern of organisms. Cenozoic climate change has led to extensive biota turnover. Untangling the distribution dynamics of a representative lineage of flora can provide deep insights into biodiversity conservation. Diplopanax is a notable relict lineage of the Tertiary mastixioid flora with abundant fossils in the Northern Hemisphere. Diplopanax stachyanthus Hand.-Mazz. is a representative relic lineage of the mastixioid flora, which was once widespread in the Northern Hemisphere of the early Tertiary period, but with only endemic distribution in the (sub)tropical humid forests of East Asia. It offers a unique chance to understand how climatic drivers shape the Boreotropical flora. In this research, we investigated the distribution dynamics of D. stachyanthus at the last glacial maximum (LGM), mid-Holocene (MH), current, and three periods of the future (2041–2060, 2061–2080, and 2081–2100) at four shared socio-economic emissions scenarios pathways. Our results indicated that the Precipitation of the Wettest Quarter (32.6%), the Precipitation of the Driest Quarter (21.2%), and the Precipitation of the Coldest Quarter (17.3%) are the key factors affecting its distribution. The current high suitable distribution areas are primarily in southern China and northern Indo-China. The enforced winter monsoon seasons in East Asia since the late Pliocene period are the key climatic drivers reducing its once widespread distribution in the Northern Hemisphere. Under future scenarios, centroid transfer analysis suggests that its distribution center will shift southwestward, but the potentially suitable habitats in the coastal regions of southern China and northern Indo-China will be lost. These coastal populations should be prioritized for ex situ conservation. Expanding the nature reserve within its long-term stable distribution range in southwest China is an effective strategy for the in situ conservation of the ancient mastixioid flora.