Data from: Population genetics of Manihot esculenta ssp. flabellifolia gives insight into past distribution of xeric vegetation in a postulated forest refugium area in northern Amazonia

The Guianas have often been proposed as a forest refugium; however, this view has received little testing. Studies of population genetics of forest taxa suggest that the central part of French Guiana remained forested, while the southern part (currently forested) may have harboured more open vegetation. Insights into the population structure of species restricted to non-forested habitats can help test this hypothesis. Using six microsatellite loci, we investigated the population genetics of French Guianan accessions of Manihot esculenta ssp. flabellifolia, a taxon restricted to coastal savannas and to rocky outcrops in the densely forested inland. Coastal populations were highly differentiated from one another, and our data suggest a recent colonization of these savannas by M. esculenta ssp. flabellifolia in a west-to-east process. Coastal populations were strongly differentiated from inselberg populations, consistent with an ancient separation of these two groups, with no or low subsequent gene flow. This supports the hypothesis that the central part of the region may have remained forested since the last glacial maximum, impeding the establishment of Manihot. Contrary to coastal populations, inselberg Manihot populations were strikingly homogeneous, at a broad spatial scale. This suggests they were connected until recently, either by a large continuous savanna area, or by smaller, temporary disturbed areas shifting in space.

圭亚那地区常被视为森林避难所（forest refugium），但该观点尚未得到充分验证。针对森林类群的群体遗传学研究显示，法属圭亚那中部始终保持森林覆盖，而当前仍为森林的南部区域可能曾发育更为开阔的植被。对局限于非森林生境物种的群体结构进行解析，有助于验证该假说。
我们利用6个微卫星位点（microsatellite loci），对法属圭亚那的扇叶木薯（*Manihot esculenta* ssp. *flabellifolia*）种质资源开展了群体遗传学分析——该类群仅分布于沿海稀树草原以及密林内陆的岩石露头生境。研究发现沿海种群之间存在高度遗传分化，数据显示扇叶木薯近期以自西向东的路径拓殖了这些稀树草原生境。
沿海种群与岛山（inselberg）种群之间存在显著遗传分化，这与两个类群早期分化后几乎无或仅有极低水平后续基因交流的情况相符。该结果支持“自末次冰盛期以来该区域中部始终保持森林覆盖，从而阻碍了扇叶木薯的定植”这一假说。与沿海种群不同，岛山种群在较大空间尺度上表现出显著的遗传均质性，这表明二者直至近期仍存在基因交流，这种联系可能依托于大片连续的稀树草原区域，或是随空间动态变化的小型临时扰动生境。