请教gwd1 里一句话的结构

chenping0123

就是讲三文鱼的文章

Low levels of straying are crucial, since the process provides a source of novel genes and a mechanism by which a location can be repopulated should the fish there disappear。

should在这里面是什么个用法，想不通

月桂女神B

by which by是介词提前 所以should在fish前也是提前了 所以是因为介词的缘故倒装 我觉得是。。。您可以再想想