Genetic diversity and biogeography of the Hawaiian cordage plant, olonā ( Toucharida latifolia; Urticaceae), based on RAPD markers

Touchardia latifolia (Urticaceae) is an endemic species to the Hawaiian Islands. Although widespread and extensively cultivated by early Hawaiians for cordage, populations are now greatly diminished and increasingly rare. Reproductively dioecious, T. latifolia is expected to have high genetic diversity. However, it is thought that diversity may be reduced because of the reduction in the number of populations and their size. Examination of random amplified polymorphic DNA (RAPD) markers from seven populations indicates that genetic diversity (based on individual similarities) is in fact low relative to other dioecious and outcrossing Hawaiian species. Patterns within islands are not correlated with geographic distance; therefore, loss of diversity is likely associated with genetic drift. In contrast, variation among islands is associated with island biogeography and therefore colonization from one island to another was probably progressive down the island chain.