Data from: Congruent phylogeographic patterns of eight tree species in Atlantic Central Africa provide insights on the past dynamics of forest cover

Cycles of Quaternary climate change are assumed to be major drivers of African rainforest dynamics and evolution. However, most hypotheses on past vegetation dynamics relied on palaeobotanical records, an approach lacking spatial resolution, and on current patterns of species diversity and endemism, an approach confounding history and environmental determinism. In this context, a comparative phylogeographic study of rainforest species represents a complementary approach because Pleistocene climate fluctuations may have left interpretable signatures in the patterns of genetic diversity within species. Using 1274 plastid DNA sequences from eight tree species (Afrostyrax kamerunensis, A. lepidophyllus, Erythrophleum suaveolens, Greenwayodendron suaveolens, Milicia excelsa, Santiria trimera, Scorodophloeus zenkeri, Symphonia globulifera) sampled in 50 populations of Atlantic Central Africa (ACA), we averaged divergence across species to produce the first map of the region synthesizing genetic distinctiveness and standardized divergence within and among localities. Significant congruence in divergence was detected mostly among five of the eight species and was stronger in the northern ACA. This pattern is compatible with a scenario of past forest fragmentation and recolonization whereby forests from eastern Cameroon and north-eastern Gabon would have been more affected by past climate change than those of western Cameroon (where one or more refugia would have occurred). By contrast, southern ACA (Gabon) displayed low congruence among species that may reflect less drastic past forest fragmentation or a more complex history of vegetation changes. Finally, we also highlight the potential impact of current environmental barriers on spatial genetic structures.

第四纪气候变化旋回被认为是驱动非洲雨林动态与演化的主要因素。然而，过往有关植被动态的多数假说，要么依赖空间分辨率不足的古植物记录，要么基于当前物种多样性与特有性格局——前者空间分辨率有限，后者则混淆了历史进程与环境决定论。在此背景下，针对雨林物种的比较系统地理学（comparative phylogeography）研究可作为有效补充手段：更新世气候波动可能在物种种内的遗传多样性格局中留下可解读的演化信号。

本研究采集了大西洋中部非洲（Atlantic Central Africa, ACA）50个种群的质体DNA序列，共涉及8个树种：Afrostyrax kamerunensis、A. lepidophyllus、Erythrophleum suaveolens、Greenwayodendron suaveolens、Milicia excelsa、Santiria trimera、Scorodophloeus zenkeri、Symphonia globulifera，合计1274条序列。研究通过整合各物种的平均分化数据，绘制了该区域首张综合了种群内与种群间遗传独特性及标准化分化水平的空间地图。

研究检测到显著的物种间分化一致性，该一致性主要集中于8个物种中的5个，且在大西洋中部非洲北部区域表现更为显著。这一格局与过往森林破碎化与再定居的演化情景相符：喀麦隆东部与加蓬东北部的雨林，相较于喀麦隆西部（曾存在一处或多处冰期避难所）的雨林，更易受古气候变化的影响。

与之形成鲜明对比的是，大西洋中部非洲南部（加蓬地区）的物种间分化一致性较低，这一现象或反映出过往森林破碎化程度较轻，抑或该区域的植被变化历史更为复杂。最后，本研究还揭示了当前环境屏障对物种空间遗传结构的潜在影响。