The group contains morphologically divergent species, and was long thought to have derived from at least three introductions: one for "Lobelia" and "Trematolobelia", one for "Brighamia", and one for "Clermontia", "Cyanea", and "Delissea". Based on recent DNA sequence evidence (Givnish et al., 1996, 2008) it now believed that all are derived from a single introduction. This was likely a "Lobelia"-like species that arrived about 13 million years ago, when Gardner Pinnacles and French Frigate Shoals were high islands and long before the current main islands existed.