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.

The part of their cladogram that includes genera and sections from Hawaii is shown below, with added shading to show those treated as Hawaiian lobelioids, which do not form a single clade in this study.

Galeatella Trematolobelia Sclerotheca + Apetahia (from other Pacific islands) Some species of Cyanea Clermontia The authors of the 2021 study described the taxonomy of several genera, including Lobelia, as "particularly frustrating" and called for further research.

It was long thought to have been the result of a separate introduction, and its unique combination of characters made it difficult to place.

Rather than drying and splitting apart, the outer (green) wall of the fruit disintegrates, revealing a perforated hard "frame" that allows the tiny wind-dispersed seeds to escape.

The larvae of Drosophilidae flies breed in the rotting bark, leaves, flowers, and fruit of all lobelioids, but primarily Clermontia since it is largest and most common.

Some, such as C. leptostegia of Kauaʻi, can grow to over 9 metres (30 ft) tall - something that is especially notable given the relative thinness of the stem and soft wood.

The purpose of the spines was puzzling, since in most island situations there is a tendency for plants to lose defenses - Hawaiʻi is noted for its nettle-less nettles, mintless mints, and (not quite) thornless raspberries - and no native browsing animals were known.

However, it is now believed that the spines were a defense against the moa-nalo, giant browsing geese and goose-like ducks that formerly inhabited the islands (Givnish et al. 1995).

These include C. arborea, C. comata, and C. pohaku, a cluster of species that formerly inhabited the drier, mesic areas of leeward East Maui where almost no native habitat remains.

Species of Cyanea on each major island tend to differ in flower tube length and mean elevation, apparently reflecting a partitioning of ecological and reproductive resources.

The total number of species of Cyanea can be predicted rather precisely from the height and area of each of the major islands except Hawaiʻi (the Big Island), suggesting that the assembly of Cyanea communities requires more than 0.6 million years (the age of Hawaii) and less than 1.5 million years (the age of Maui) to run to ecological saturation (Givnish et al. 2008).

For example, D. fallax and D. parviflora are both from Hawaiʻi and their flowers are identical; it is possible that they represent different growth forms of the same species (both Delissea and Cyanea are known to undergo changes in vegetative morphology during the lifetime of the plant).