Vegetation dynamics and the evolution of Metrosideros polymorpha in Hawaii
The most prevalent endemic Hawaiian rainforest tree, Metrosideros polymorpha, demonstrates ecological release by its wide ecological amplitude, which is reflected in a similarly wide genetic variation among its populations. While the species has occupied an unusually broad spectrum of soil substrates in the Hawaiian rainforest biome, its perpetuation is not equally successful, even in the absence of competition. Recurring population crashes have occurred on all soil substrates but spatially larger and more severe diebacks recorded on poorly drained soil substrates seem to indicate incomplete adaptation over broad habitat segments. It is suggested that adaptive radiation in this species involves ecological release with subsequent setbacks through stand-level or mass dieback, often associated with recolonization and regrowth, a process whereby better adapted successional races tend to evolve.