Complex sentence: In the South-West of Western Australia, "Z. aethiopica" was introduced for horticulture, but has become a widespread and conspicuous weed of watercourses, heath, and wetter pastures.
Split into simpler sentences: In the South-West of Western Australia, "Z. aethiopica" was introduced for horticulture. It has become a widespread and conspicuous weed of watercourses, heath, and wetter pastures.