Basically, some species have suspicious resemblances to supposedly different species that just happen to live nearby. Often, it would be better design for them to instead resemble some further-away species. And, this is the norm. There are a huge number of good examples. The trees on the remote island of St. Helena are unlike the trees anywhere else on earth.
Sunflowers are the closest relative to the strange gumwood tree and to the various cabbage-trees.
And, the most closely related sunflower is the local sunflower. The scientific explanation is that this volcanic island was originally formed far away from any continent, and therefore started out with no land plants. Eventually, some sunflower seeds managed to get there. Transformed by time and competition and by the demands of their role, they now look like trees. Every other remote island has its own examples.