DataSheet1_Impact of persistent barrier to gene flow and catastrophic events on red algae evolutionary history along the Chilean coast.docx

Historical vicariance events, linked to the existence of stable physical barriers to gene flow, generate concordant genetic breaks in co-distributed species while stochastic processes (e.g., costal uplift) could cause species-specific genetic breaks as a result of local strong demographic bottlenecks or extinction. In Chile, previous studies show that the area of the 30°S-33°S could correspond to a stable barrier to gene flow that have affected the genetic structure of various algae and marine invertebrates. Here we sequenced two organellar genes (COI and rbcL) in four taxonomically accepted co-distributed red seaweeds species characterized by a low dispersal potential: Mazzaella laminarioides, M. membranacea, Asterfilopsis disciplinalis, and Ahnfeltiopsis vermicularis. Our results revealed the existence of ten strongly differentiated linages in the taxa studied. Strong genetic breaks, concordant in both space and time (divergence estimated to have occurred some 2.9–12.4 million years ago), were observed between taxa distributed across the 33°S. Conversely, in the Central/South part of the Chilean coast, the localization of the genetic breaks/sub-structure observed varied widely (36°S, 38°S, 39°S, and 40°S). These results suggest that a major historical vicariance event has modeled the genetic structure of several Chilean marine organisms in the north of the Chilean coast during the mid-Miocene, while more recent stochastic events and genetic drift could be the driving forces of genetic divergence/structuration in the central-southern part of the coast.与阻碍基因交流（gene flow）的稳定物理屏障相关的历史隔离事件（vicariance events），可在同分布类群中形成一致的遗传断裂（genetic breaks）；而随机过程（如海岸抬升）则可因局部强烈的种群瓶颈（demographic bottlenecks）或灭绝事件，引发物种特异性的遗传断裂。在智利，既往研究表明，30°S至33°S海域可作为阻碍基因交流的稳定屏障，影响了多种藻类与海洋无脊椎动物的遗传结构。本研究对4个经分类学确认、具备低扩散潜力的同分布红藻物种的两个细胞器基因（organellar genes，COI与rbcL）进行了测序，所涉物种分别为：Mazzaella laminarioides、M. membranacea、Asterfilopsis disciplinalis及Ahnfeltiopsis vermicularis。研究结果显示，所研究的类群中共存在10个高度分化的支系（lineages）。在33°S沿线分布的类群之间，观测到了空间与时间维度均一致的强烈遗传断裂：经估算，其分化时间约为290万至1240万年前。与之相反，在智利海岸中南部区域，观测到的遗传断裂/亚结构位置差异显著，分别位于36°S、38°S、39°S与40°S。上述结果表明，中新世中期智利北部海域曾发生过一次重大历史隔离事件，塑造了多种智利海洋生物的遗传结构；而海岸中南部区域的遗传分化与结构形成，则可能由近期的随机事件与遗传漂变（genetic drift）驱动。