有关onwhich的深度解析Fewerotterswouldhaveallowedseaurchinpopulationsonwhichtheotterspreyedtoexpandandtheurchins'grazingpressureonkelpforeststoincrease.这句话,求大神深度解析其中onwhich用法,不要单翻译

Question

有关on which的深度解析
Fewer otters would have allowed sea urchin populations on which the otters preyed to expand and the urchins' grazing pressure on kelp forests to increase.
这句话,求大神深度解析其中on which用法,不要单翻译,意思我懂,要有深度的
不要把语法扔上去，最好来点通俗易懂的

Answer 1

分析如下：
1.这句话的虚拟谓语would have allowed后面跟了两个并列的“宾语+宾补”的结构,即allow ...to expand and .to increase.这也是整个句子的框架.
2.allow的第一个宾语sea urchi populations后面带了个由“介词on +关系代词which"引导的定语从句.之所以选择介词on,是因为定语从句中的谓语动词prey（不及物动词）搭配的需要,prey+on构成词组,表达“捕食”的意思.
3.另外,句中and这个并列连词后省略了与第一分句完全相同的结构“Fewer otters would have allowed"
若有不明白,欢迎继续提出来探讨.