You’re right, it’s wrong, but not that wrong. Several sources indicate the majority of Ilex species occur in South America and Asia, so that was probably what they meant to say. Ilex paraguariensis is limited to Brazil, Paraguay, Uruguay and Argentina, and are clearly the “Ilex trees” referred to in the second sentence quoted. So, yeah, it’s imprecise and syntactically sloppy but not that far out, and not the main point of the paper, but as Jack Reacher says, “details matter”.