The comparison of five Diellia taxa in the Hawaiian Islands demonstrated the different stage structures of their populations. Diellia erecta occurred on four islands, and the overall status of the species may be classified as normal. When the stage structure of each particular local population of D. erecta was investigated, it became evident that populations on different islands were in completely different conditions. The population on Oahu was clearly dynamic in character. It represents a recently colonized patch in the historical distribution area, situated on a lava cliff and thus protected from disturbance. The population on Hawaii was in a normal condition. It grows in the historical distribution area, known since 1927 (G.W. Russ 36, 37, Herbarium Pacificum Bishop Museum (BISH)), but is experiencing frequent long droughts resulting in fluctuations in spore production and new establishments. The population on Molokai was classified as regressive. Historically it was one of the largest populations (Wagner 1951). Because of trampling and browsing by feral goats, the size of the population has been remarkably reduced, and suitable habitat may be found only in small patches of native forest on steep slopes in the upper part of gulches. Occasional occurrence of new colonizations (Aguraiuja and Perlman 2002; R. Aguraiuja and J. Lau, 2003 personal communication) show that there may still be potential for the establishment of new dynamic local populations. The population on Maui was in the worst condition, since it consisted of only a few mature individuals. One may hypothesize that local populations, ranked as Oahu–Hawaii– Molokai–Maui, represent a sequence of dynamic colonization events, following by a shift in colonization and (or) extinction balance, leading gradually to the development of a regressive population, and finally to extinction.