Hawaiian Lobelioids

The Hawaiian Islands comprise a diverse range of plant species, many of which are unique to the globe. One group, in particular, stands out because it represents the most prominent plant radiation on an archipelago, not only in Hawaii. 

The Hawaiian Lobelioids (Campanulaceae) are members of the Lobelia genus, which includes the gorgeous cardinal flower (Lobelia cardinalis) and the big blue Lobelia (Lobelia siphilitica). However, the six genera that comprise the Hawaiian Lobelioids radiation are considerably distinct.

Hawaiian Lobelioids

Hawaiian Lobelioids are a genus of flowering plants in the Campanulaceae family entirely native to the Hawaiian Islands. With approximately 125 species, this is the most diverse plant radiation in the Hawaiian Islands, if not the world. 

The six genera are classified into categories based on their developmental habits: Cyanea and Delissea are normally unbranched or only branch at the base, with a cluster of moderately broad leaves and meaty fruits at the apex; Clermontia are often branched shrubs.

Hawaiian Lobeliads are the most extensive plant family, the bellflower or lobelia family, in the flora of the world’s largest mountainous islands (from the seafloor to the peak). They represent adaptive radiation in plants (Campanulaceae). Endemic Hawaiian Campanulaceae species, arising from a single migratory event 13 million years ago, are found on seven of the eight inhabited Hawaiian Islands. The islands vary in height from less than 100 metres to over 4000 metres above sea level and exhibit extraordinary habitats.

Hawaiian Lobelioids Types

Long assumed to be the result of Lobelia, Brighamia, Clermontia, Cyanea, and Delissea; the group encompasses morphologically different species. It is currently thought that all descend from a single introduction based on new DNA sequence data.

Brighamia

With a succulent stem and tall, slender, tubular blooms, Brighamia stands out from the other genera. It was long assumed to be the outcome of a different introduction, and its unusual shape made it impossible to locate. These characteristics are because of the indigenous Hawaiian hawkmoth, Manduca blackburni, pollinating the plants on cliffs.

Lobelia

It is a large genus with over 350 species, many of which are common ornamentals. Nevertheless, it is the source of many lobelioid taxa and is very paraphyletic. Hawaiian plants are split into two groups based on flower colour and other characteristics. Depending on the blossom’s colour and other characteristics, lobelia’s fruit is a dry capsule like those of Brighamia and Trematolobelia. Being one of the common Hawaiian Lobelioids types, these species are the most similar to the original Hawaiian colonists in appearance.

Trematolobelia

It is one of the Hawaiian Lobelioids types that differs from lobelia in that it has a different mechanism of dissemination. The fruit’s exterior (green) wall disintegrates instead of drying and splitting apart. Showing a perforated hard frame through which the tiny wind-dispersed seeds can escape. They are a stunning sight with many flower stems and hundreds of blooms. Before blooming and dying, individual plants can live for 5–10 years.

Clermontia

This type may be found in more open places and on wood fringes. Thus they have a higher chance of surviving when the forest fragments. Despite this, there are still a large number of endangered species. The flowers are generally enormous and showy. In Clermontia, the calyx lobes are identical in colour and size to the corolla, giving the impression of a flower having twice as many petals.

Cyanea

With over 70 species, Cyanea is the most morphologically and wide-ranging diversified group of Hawaiian Lobelioids. Most have a single stem or a cluster of stems branching near the ground, while a few, like C. stictophylla, have multi-branched shrubs. Cyanea may develop long stalks partly because they grow profusely in dense forests, particularly in small clusters on ancient islands.

Delissea

Delissea is akin to Cyanea in many aspects, but the bloom and fruit are the main differences. It is significant partly because it has been through so much: just three of the nine species remain, and one (D. undulata) is extinct in the wild. Specimens obtained in the late 1800s are known for several species. Further, the species have relatively little information about them, and their classification as species is debatable.

Flowers in many species, particularly in Lobelia and Trematolobelia, are gorgeous and striking. As the stems are only partially woody and have minimal herbivory protections, they are particularly vulnerable to eating by antelopes and feral pigs.

Conclusion

Hawaiian Lobelioids are a genus of flowering plants in the Campanulaceae family, entirely native to the Hawaiian Islands. With over 125 species, this is the most significant plant radiation in the Hawaiian Islands and maybe the largest on any archipelago. As native only to Hawaii, management of conservation of Hawaiian Lobeliads is under exploration and discussion.