Ancient Geographical Barriers Drive Differentiation amongSonneratia caseolarisPopulations and Recent Divergence fromS. lanceolata.
Glacial vicariance is thought to influence population dynamics and speciation of many marine organisms. Mangroves, a plant group inhabiting intertidal zones, were also profoundly influenced by Pleistocene glaciations. In this study, we investigated phylogeographic patterns of a widespread mangrove speciesSonneratia caseolarisand a narrowly distributed, closely related speciesS. lanceolatato infer their divergence histories and related it to historical geological events. We sequenced two chloroplast fragments and five nuclear genes for one population ofS. lanceolataand 12 populations ofS. caseolarisacross the Indo-West Pacific (IWP) region to evaluate genetic differentiation and divergence time among them. Phylogenetic analysis based on sequences of nuclear ribosomal internal transcribed spacer and a nuclear generpl9for allSonneratiaspecies indicate thatS. lanceolataindividuals are nested withinS. caseolaris. We found strong genetic structure among geographic regions (South China Sea, the Indian Ocean, and eastern Australia) inhabited byS. caseolaris. We estimated that divergence between the Indo-Malesia and Australasia populations occurred 4.035 million years ago (MYA), prior to the onset of Pleistocene. BARRIERS analysis suggested that complex geographic features in the IWP region had largely shaped the phylogeographic patterns ofS. caseolaris. Furthermore, haplotype analyses provided convincing evidence for secondary contact of the South China Sea and the Indian Ocean lineages at the Indo-Pacific boundary. Demographic history inference under isolation and migration (IM) model detected substantial gene flow from the Sri Lanka populations to the populations in the Java Island. Moreover, multi-locus sequence analysis indicated thatS. lanceolatawas most closely related to the Indian Ocean populations ofS. caseolarisand the divergence time between them was 2.057 MYA, coinciding with the onset of the Pleistocene glaciation. Our results suggest that geographic isolation driven by the Pleistocene ice age resulted in the recent origin ofS. lanceolata.
State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, Sun Yat-Sen University Guangzhou, China.
Yuchen
Y
Yang
Trop WATER, James Cook University, Townsville QLD, Australia.
Norman C
NC
Duke
State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, Sun Yat-Sen University Guangzhou, China.
Fangfang
F
Peng
State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, Sun Yat-Sen University Guangzhou, China.
Jianfang
J
Li
State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, Sun Yat-Sen University Guangzhou, China.
Shuhuan
S
Yang
Hainan Dongzhai Harbor National Nature Reserve Haikou, China.
Cairong
C
Zhong
State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, Sun Yat-Sen University Guangzhou, China.
Renchao
R
Zhou
State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, Sun Yat-Sen University Guangzhou, China.
Suhua
S
Shi
Pleistocene glaciations; Sonneratia; genetic differentiation; mangroves; secondary contact