XVI International Botanical Congess

The family Amaranthaceae exhibits several traits of so-called insular speciation in isolated habitats. In the GALÁPAGOS the main diversification and speciation occurs in the subfamily Gomphrenoideae, whereas in Hawaii the subfamily Amaranthoideae exhibits a similar pattern. These differences can largely be explained by the geographical distances to the different source regions. No endemic genus is recognized in Galápogos, whereas Hawaii has one endemic genus and another nearly so. The higher level of endemism in Hawaii is due to the more isolated geographical position and the older geological age of the island chain. In both archipelagos there are several examples of adaptive radiation. Woodiness has evolved in both archipelagos in species with presumed herbaceous ancestors. Endemism in the closely related family Chenopodiaceae is very low, with one single endemic species of Chenopodium in Hawaii. All other members of the family in Hawaii as well as in the Galápogos are naturalized species.