The researchers also studied the process by which the aggressive species establish new colonies.这句话里的which the aggressive species establish new colonies是个什么从句?by 后面能直接加which吗?

The researchers also studied the process by which the aggressive species establish new colonies.这句话里的which the aggressive species establish new colonies是个什么从句?by 后面能直接加which吗?
The researchers also studied the process by which the aggressive species establish new colonies.
这句话里的which the aggressive species establish new colonies是个什么从句?by 后面能直接加which吗?

The researchers also studied the process by which the aggressive species establish new colonies.这句话里的which the aggressive species establish new colonies是个什么从句?by 后面能直接加which吗?
这里 which 引导的是定语从句 ,which 指代 the process ,which 作介词by 的宾语,在定语从句中,介词后的关系词只能 用 whom / which .\
又如,He bought a telescope through which he could study the sky .