House Rule XVI.5.a reads:

"Divisibility
5. (a) Except as provided in paragraph (b), a question shall be divided on the demand of a Member, Delegate, or Resident Commissioner before the question is put if it includes propositions so distinct in substance that, one being taken away, a substantive proposition remains."

I originally thought this could be applied to the text of a bill that would become part of the law code, but since Sen. Sanders didn't mention it, I think it must only pertain to the action being taken in the legislature. But it does require only one member to effect the separation.

Just because horses originated in North America doesn't mean they're not invasive now. By that argument, lions are invasive in Africa, because they originated in Europe. (They did.) Horses weren't in North America for so long that they weren't part of the ecosystem--that makes them invasive by definition (becoming part of the ecosystem by relocation rather than evolution).

However, that implies nothing about whether they are helpful or harmful to the current ecosystem, and the caller would be well advised to learn that you shouldn't say one thing when you mean another. "Invasive" is an emotionally charged term, but the solution to people's misinterpretation of a term is not to abandon it to their misinterpretation and start using another term, which they may just as easily misinterpret, but to teach people the exact meaning of the term that is being applied correctly.