radical separation

radical separation
原文是这样的：
Thousands of years ago a powerful drought dried up Brazil's Madeira River,causing a "radical separation" as dolphin populations were caught on different sides of the newly created rapids,said researcher Manuel Ruiz-Garcia.《New,"Chubbier" River Dolphin Species Found in Bolivia》
似乎是和生物起源有关的一种隔离,但是怎么翻呢……