GWD-27-Q21":"的用法？

E Q21:“：”的用法？

The coyote is one of several recent ecological success stories:  along with the white-tailed deer, the moose, and other species that are enlarging their natural domains, they have established themselves as supreme adapters in an era when the capability to adjust to the environmental changes wrought by human beings has created a whole new class of dominant large mammals.

1. they have established themselves as supreme adapters in an era when the capability

2. they have established themselves as being supreme adapters in an era when being able

3. it has established itself as a supreme adapter in an era when to be able没主语？

4. it has established itself as being a supreme adapter in an era when its ability

5. it has established itself as a supreme adapter in an era when the ability

 Q1:冒号是不是可以看作逗号？，这样，E的主语就和The coyote一至了？

Q 2:C 是不是因为没主语？

那为何选it,不选they？？

A they have established themselves as supreme adapters in an era when the capability

"they" stands for   "the white-tailed deer, the moose, and other species "???

谢谢！

也就是说冒号前后，两句的主语一般一样。是这样么？