Nuclear and chloroplast DNA phylogeography suggests an Early Miocene southward expansion of Lithocarpus (Fagaceae) on the Asian continent and islands

Bing-Hong Huang,Li-Ping Ju,Yu-Chung Chiang,Pei-Chun Liao,Chih-Kai Yang

doi:10.1186/s40529-018-0244-8

Abstract

BackgroundMost genera of Fagaceae are thought to have originated in the temperate regions except for the genus Lithocarpus, the stone oaks. Lithocarpus is distributed in subtropical and tropical Asia, and its ancestral population is hypothesized to be distributed in tropical regions in Borneo and Indochina. Borneo and the nearby islands (the Greater Sunda Islands) were connected to the Malay Peninsula and Indochina prior to the Pliocene epoch and formed the former Sundaland continent. The Southeast Asian Lithocarpus, is thought to have dispersed between continental Asia and the present Sundaland. The drastic climate changes during the Pliocene and Pleistocene epochs which caused periodic sea-level changes is often used to explain the cause of its diversity. The aim of this study was to establish phylogenetic relationships by analyzing nuclear (nrDNA) and chloroplast (cpDNA) DNA in order to describe and analyze the origin, causes of diversification and historical biogeography of Lithocarpus.ResultsPhylogeny reconstructed through the multiple-species coalescent method with nrDNA and cpDNA revealed that the continental-Asian taxa were clustered at the basal lineages. The derived lineages of tropical Lithocarpus, with the inference of a subtropical ancestral state, imply a southward migration in the Early Miocene period with subsequent in situ diversification in the Greater Sunda Islands. The gradual decrease in temperature since the Middle Miocene period is proposed as a cause of the increase in the net diversification rate.ConclusionsThe historical ancestral origin of Lithocarpus has been suggested to be mainland Asia. Southward migration in the Early Miocene period with subsequent in situ diversification could explain the current diversity of stone oaks in Southeast Asia. This study also considered the multiple origins of stone oaks currently indigenous to the subtropical islands offshore and near mainland China. Our results provide phylogenetic evidence for a subtropical origin of Asian stone oaks and reveal the process of diversification and how it fits into the timeline of major geologic and climatic events rather than local, episodic, rate-shifting events.

Highlights

Most genera of Fagaceae are thought to have originated in the temperate regions except for the genus Lithocarpus, the stone oaks
In Southeast Asia, the emergence of ancient Sundaland, the former continent connecting the Thai-Malay peninsula to Borneo and the Philippine archipelagos, was suggested as a land bridge for species dispersal between Indochina and the Malay Archipelago, but the submergence of the Sunda shelf was the prime barrier for vicariant events between the Malay Archipelago and continental Asia (Lohman et al 2011)
Past climate changes severely affected the biogeographic patterns of Southeast Chinese, Japanese, Korean, and Taiwanese plants such as Cunninghamia konishii (Cupressaceae) (Chung et al 2004), Ainsliaea spp. (Asteraceae) (Mitsui and Setoguchi 2012), Picea jezoensis (Pinaceae) (Aizawa et al 2007), Pinus luchuensis complex (Pinaceae) (Chiang et al 2006), and Ligularia hodgsonii (Asteraceae) (Wang et al 2013)

Summary

Introduction

Most genera of Fagaceae are thought to have originated in the temperate regions except for the genus Lithocarpus, the stone oaks. In Southeast Asia, the emergence of ancient Sundaland, the former continent connecting the Thai-Malay peninsula to Borneo and the Philippine archipelagos, was suggested as a land bridge for species dispersal between Indochina and the Malay Archipelago, but the submergence of the Sunda shelf was the prime barrier for vicariant events between the Malay Archipelago and continental Asia (Lohman et al 2011). (Asteraceae) (Mitsui and Setoguchi 2012), Picea jezoensis (Pinaceae) (Aizawa et al 2007), Pinus luchuensis complex (Pinaceae) (Chiang et al 2006), and Ligularia hodgsonii (Asteraceae) (Wang et al 2013) The distribution of these plants was probably due to dispersal/vicariance events driven by the emergence/submergence of the last glacial East China Sea land bridges (Qiu et al 2011); similar events occurred among fauna (Millien-Parra and Jaeger 1999)

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