The subject of the first clause is The coyote, which is singular.eitijan wrote:Why 'they' is wrong in original sentence?
The other species listed at the beginning of the second clause are part of a modifier, and so rather than referring to the listed animals or to species, they is meant to refer to The coyote. So they, which is plural, is incorrect, and the correct pronoun to use is the singular it.
This sentence version contains a typical GMAT trick of a type that you need to look out for. Verbiage is inserted between two related words, such as a subject and verb or a pronoun and its antecedent, and that verbiage obscures the relationship between the two words and often somehow makes the wrong choice seem right, as is the case in this question.
Often, you can make which choice is correct more clear by considering how the sentence would look without the inserted verbiage. In this case you would have the following.
The coyote is one of several recent ecological success stories; it has established itself ...
