Low phylogeographic diversity in the calcified green macroalga Halimeda macroloba (Bryopsidales) in Southeast Asia

다국어 초록 (Multilingual Abstract)

Southeast Asia is an important marine biodiversity hotspot. Revealing the spatial patterns and environmental driversrelated to population genetic structure in this region is a prerequisite for conservation biogeography and genetics. In thisstudy, we applied two chloroplast markers (tufA and rpl2–rpl16) to evaluate population genetic variation and phylogeographicstructure of the green macroalga Halimeda macroloba (12 populations, 275 individuals) in Southeast Asia. Bothmarkers showed extremely low genetic variation and haplotype diversity in H. macroloba, with no clear phylogeographicseparation between both sides of the Thai-Malay Peninsula (TMP). A postglacial founder effect and predominant asexualreproduction by fragmentation in H. macroloba, together with monsoon-driven ocean currents driving stepping-stonedispersal, may account for the observed remarkable phylogeographic homogeneity around the TMP. However, the tufAand rpl2-rpl16 markers congruently detected a phylogeographic break between the TMP and the eastern South ChinaSea, despite no obvious observable barrier to gene flow. These results raise the importance to take in situ actions to conservethe indicator species Halimeda in an era of ocean acidification and warming.