ALT The cover of the American Journal of Botany special issue on polyploidy.

ALT Conceptual diagram of historical biogeographic patterns expected to be observed under the ‘centers of arrival’ hypothesis (on the left) and the ‘centers of polyploidization’ hypothesis (on the right). Under the ‘centers of arrival’ scenario, polyploidization occurs across the globe but is followed by higher rates of antiequatorial movement relative to diploids. Under the ‘centers of polyploidization’ scenario, we expect to see higher rates of polyploidization in poleward environments.