Definitions

Hawaiian_lobelioids

Hawaiian lobelioids

This is the largest plant radiation in the Hawaiian Islands, and indeed the largest on any island archipelago, with 116 species. The six genera can be broadly separated based on growth habit: Clermontia are typically branched shrubs or small trees, up to 7 m tall; Cyanea and Delissea are typically unbranched or branching only at the base, with a cluster of relatively broad leaves at the apex and the fruit a berry; Lobelia and Trematolobelia have long thin leaves down a single, non-woody stem and capsular fruit; and the peculiar Brighamia have a short, thick stem with a dense cluster of broad leaves and elongate white flowers.

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 more recent DNA sequence evidence (Givnish et al., 1996) it now believed that all are derived from a single introduction. This was likely a Lobelia-like species that arrived about 15 million years ago, when French Frigate Shoals was a high island and long before the current main islands existed.

Many species have beautiful and spectacular flowers, especially the Lobelia and Trematolobelia. Unfortunately, they are also highly vulnerable to feeding by feral ungulates such as pigs; the stems are only partly woody, and contain few defenses against herbivory. The bark contains a milky (but apparently non-poisonous) latex, and is often chewed by rats and pigs. Seedlings are also vulnerable to disturbance by pig digging, and in areas with high densities of pigs it is not uncommon to find the only lobelioids being epiphytic on larger trees or on fallen logs.

Brighamia

Brighamia is quite unlike the other genera, with a succulent stem and long, thin, tubular flowers. It was long thought to have been the result of a separate introduction, and its unique combination of characters made it difficult to place. These characters are the result of adaptation to growing on cliffs and pollination by the endemic Hawaiian hawkmoth, Manduca blackburni. This moth is now itself listed as endangered, surviving mainly on the southern slopes of Maui, well away from where Brighamia live. Some pollination may be done by closely-related alien hawkmoths such as the tomato hornworm and sweet potato hornworm. Despite their inaccessible habitat on cliffs, Brighamia are sometimes hand-pollinated by botanists to ensure seed set. Both species are now extremely rare. The genus is named in honour of the first director of the Bernice P. Bishop Museum, William Tufts Brigham.

Brighamia species

† species believed to be extinct
* species is listed Endangered

Lobelia

Lobelia is a cosmopolitan genus of over 350 species, including common ornamentals. However, many lobelioid genera are derived from it and it is highly paraphyletic. Eventually the 13 endemic Hawaiian species will probably be recognized as a separate genus. They are divided into two sections based on flower color and other characters. Like Brighamia and Trematolobelia, the fruit is a dry capsule. These species are probably the closest in appearance to the original Hawaiian colonist.

Lobelia species

section Galeatella (flowers red or yellow to white)

  • Lobelia gaudichaudii* A. DC – Oahu
  • Lobelia gloria-montis Rock – Maui, Molokai?
  • Lobelia kauaensis (A. Gray) A. Heller – Kauai
  • Lobelia villosa (Rock) St. John & Hosaka – Kauai

section Revolutella (flowers blue or magenta)

  • Lobelia dunbarii Rock – Molokai
  • Lobelia grayana F. Wimmer – Maui
  • Lobelia hillebrandii Rock – Maui
  • Lobelia hypoleuca Hillebr. – Kauai, Oahu, Molokai, Lanai, Maui, Hawaii
  • Lobelia monostachya* (Rock) Lammers – Oahu†
  • Lobelia niihauensis* St. John – Niihau†, Kauai, Oahu
  • Lobelia oahuensis* Rock – Oahu
  • Lobelia remyi Rock – Oahu†
  • Lobelia yuccoides Hillebr. – Kauai, Oahu

† species believed to be extinct
* species is listed Endangered

Trematolobelia

Trematolobelia is distinguished from Lobelia by its unique dispersal method. 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. They can be quite spectacular when in flower, with multiple flower branches and hundreds of flowers. Individual plants live for 5-10 years before flowering and dying.

Trematobelia species

  • Trematolobelia grandifolia (Rock) – Hawaii
  • Trematolobelia kauaiensis (Rock) – Kauai
  • Trematolobelia macrostachys (Hook & Arnott) A. Zahlbr. – Oahu, Molokai†, Lanai†, Maui, Hawaii†
  • Trematolobelia singularis* St. John – Oahu

† species believed to be extinct
* species is listed Endangered

Clermontia

Clermontia, with 22 species, are the most common of Hawaiian lobelioids. Unlike Cyanea, which are typically found in dense forest, Clermontia are frequently found in more open areas and edges, and therefore persist better when forests become fragmented. Nevertheless, there are still many endangered species. The flowers are often large and spectacular; in section Clermontia, the calyx lobes are similar in color and size to the corolla, giving the appearance of a flower with twice the normal number of petals.

Clermontia is a very important host for many species of Hawaiian Drosophilidae. The larvae of these flies breed in the rotting bark, leaves, flowers, and fruit of all lobelioids, but primarily Clermontia since it is largest and most common.

Clermontia species

section Clermontia (calyx lobes similar to petals)

  • Clermontia calophylla F. Wimmer – Hawaii (Kohala)
  • Clermontia drepanomorpha* Rock - Hawaii (Kohala)
  • Clermontia grandiflora Gaud. - Molokai, Lanai, Maui
  • Clermontia hawaiiensis (Hillebr.) Rock - Hawaii (Puna, Kau)
  • Clermontia kakeana Meyen - Oahu, Molokai, Maui
  • Clermontia kohalae Rock - Hawaii (Kohala, Hamakua)
  • Clermontia lindseyana* Rock - Hawaii, Maui (east)
  • Clermontia micrantha (Hillebr.) Rock - Lanai, Maui (west)
  • Clermontia montis-loa Rock - Hawaii (Hilo, Puna, Kau)
  • Clermontia multiflora Hillebr. - Oahu†, Maui (west)†
  • Clermontia oblongifolia* Gaud. - Oahu, Molokai, Lanai, Maui
  • Clermontia pallida Hillebr. - Molokai
  • Clermontia parviflora Gaud. ex A. Gray - Hawaii (windward)
  • Clermontia persicifolia Gaud. - Oahu
  • Clermontia samuelii* C. Forbes - Maui (east)

section Clermontioideae (calyx lobes short, green)

  • Clermontia arborescens (H. Mann) Hillebr. – Molokai, Lanai, Maui
  • Clermontia clermontioides (Gaud.) A. Heller – Hawaii (Kau, Kona)
  • Clermontia fauriei H. Lév – Kauai, Oahu
  • Clermontia peleana* Rock – Hawaii, Maui?
  • Clermontia pyrularia*
  • Clermontia tuberculata
  • Clermontia waimeae

† species believed to be extinct
* species is listed Endangered

Cyanea

This is the largest and most morphologically diverse group of Hawaiian lobelioids, with 66 species (give or take, depending on whether some populations are considered subspecies or species). Most grow as a single stem or as a cluster branching near the ground, but a few (such as C. stichtophylla) grow as multi-branched shrubs. Some, such as C. leptostegia of Kauai, can grow to over 9 m tall - something that is especially notable given the relative thinness of the stem and soft wood.

Part of the reason Cyanea are able to grow tall stalks is that they tend to grow in deep forest, often in narrow gulches on the older islands, where there is little wind. This characteristic of growing under dense cover also makes them more sensitive to disturbance of the forest.

An interesting character of many Cyanea is their tendency to grow spines or thorns on the stem and leaves (see the photo of Cyanea platyphylla). This is most pronounced in younger plants, and some species undergo a kind of metamorphosis as they mature, to the extent that different growth stages were described as separate species, due in part to the presence or absence of spines. The purpose of the spines was puzzling, since in most island situations there is a tendency for plants to lose defenses - Hawaii 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 ducks and geese that formerly inhabited the islands. These birds were apparently driven extinct by the Hawaiians before Europeans reached the islands, but their evolutionary effects live on.

Many species are now extinct or have not been seen in decades. 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. Because they are particularly sensitive to disturbance by pigs, Cyanea are often the first plants to disappear, even when the forest as a whole appears relatively healthy.

Cyanea species

  • Cyanea aculeatiflora Rock - Maui (east)
  • Cyanea acuminata* (Gaud.) Hillebr. - Oahu
  • Cyanea angustifolia* (Cham.) Hillebr. - Oahu, Molokai, Lanai, Maui
  • Cyanea arborea Hillebr. - Maui (east)†
  • Cyanea asarifolia St. John - Kauai
  • Cyanea asplenifolia (H. Mann) Hillebr. - Maui
  • Cyanea calycina Lammers - Oahu
  • Cyanea comata Hillebr. - Maui (east)†
  • Cyanea copelandii* Rock - Maui (east), Hawaii
  • Cyanea coriacea (A. Gray) Hillebr. - Kauai
  • Cyanea crispa* Gaud. - Oahu
  • Cyanea degeneriana F. Wimmer - Hawaii
  • Cyanea dolichopoda Lammers & Lorence - Kauai†
  • Cyanea dunbarii* Rock - Molokai†
  • Cyanea eleeleensis (St. John) Lammers - Kauai
  • Cyanea elliptica (Rock) Lammers - Lanai, Maui
  • Cyanea fauriei H. Lév - Kauai
  • Cyanea fissa (H. Mann) Hillebr. - Kauai
  • Cyanea giffardii Rock - Hawaii†
  • Cyanea glabra* (F. Wimmer) St. John - Maui (east)†
  • Cyanea grimesiana* Gaud. - Oahu, Molokai, Lanai, Maui, Hawaii†
  • Cyanea habenata (St. John) Lammers - Kauai
  • Cyanea hamatiflora* Rock - Maui (east), Hawaii
  • Cyanea hardyi Rock - Kauai
  • Cyanea hirtella (H. Mann) Hillebr. - Kauai
  • Cyanea horrida (Rock) Degener & Hosaka - Maui (east)
  • Cyanea humboldtiana* Gaud. - Oahu
  • Cyanea kahiliensis (St. John) Lammers - Kauai
  • Cyanea kolekoleensis (St. John) Lammers - Kauai
  • Cyanea koolauensis* Lammers Givnish & Sytsma (new name for Rollandia angustifolia) - Oahu
  • Cyanea kunthiana Hillebr. - Maui
  • Cyanea lanceolata Gaud. - Oahu
  • Cyanea leptostegia A. Gray - Kauai
  • Cyanea linearifolia Rock - Kauai†
  • Cyanea lobata* H. Mann - Lanai, Maui (west)
  • Cyanea longissima (Rock) St. John - Maui (east)†
  • Cyanea longiflora* Wawra - Oahu
  • Cyanea macrostegia* Hillebr. - Lanai, Maui
  • Cyanea mannii* (Brigham) Hillebr. - Molokai
  • Cyanea marksii Rock - Hawaii (Kona)
  • Cyanea mceldowneyi* Rock - Maui (east)
  • Cyanea membranacea Rock - Oahu
  • Cyanea obtusa (A. Gray) Hillebr. - Maui†
  • Cyanea parvifolia C. Forbes - Kauai
  • Cyanea pilosa A. Gray - Hawaii
  • Cyanea pinnatifida* (Cham.) F. Wimmer - Oahu
  • Cyanea platyphylla* (A. Gray) Hillebr. - Hawaii
  • Cyanea pohaku Lammers - Maui (east)†
  • Cyanea procera* Hillebr. - Molokai†
  • Cyanea profuga C. Forbes - Molokai†
  • Cyanea purpurellifolia Rock - Oahu
  • Cyanea pycnocarpa (Hillebr.) F. Wimmer - Hawaii†
  • Cyanea quercifolia (Hillebr.) F. Wimmer - Maui (east)†
  • Cyanea recta* (Wawra) Hillebr. - Kauai†
  • Cyanea scabra Hillebr. - Maui (west)
  • Cyanea shipmanii* Rock - Hawaii
  • Cyanea solenacea Hillebr. - Molokai
  • Cyanea solenocalyx Hillebr. - Molokai
  • Cyanea spathulata (Hillebr.) A. Heller - Kauai
  • Cyanea st.-johnii* Hosaka - Oahu
  • Cyanea stictophylla* Rock - Hawaii (Kona, Kau)
  • Cyanea superba* (Cham.) A. Gray - Oahu
  • Cyanea sylvestris A. Heller - Kauai
  • Cyanea tritomantha A. Gray - Hawaii
  • Cyanea truncata* (Rock) Rock - Oahu
  • Cyanea undulata* C. Forbes - Kauai†

† species believed to be extinct
* species is listed Endangered

Delissea

Delissea is similar to Cyanea in many ways, differing primarily in the flower (with a small knob on the dorsal side) and fruit (dark purple; most Cyanea fruit are orange, though some are also purple or blue). It is notable in part because it has suffered so much: only three of the nine species known to science are still extant, and one of these (D. undulata) is extinct in the wild. Several species are known only from type specimens collected in the late 1800s. Several species are very poorly known, and their status as species is questionable. For example, D. fallax and D. parviflora are both from Hawaii 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). Delissea lauliiana was known only from the type, which was destroyed in Berlin during World War II. All three of these are believed to be extinct, and unless new specimens turn up there is no way to resolve questions about them.

Delissea species

section Delissea (nearly straight flowers 14-26 mm long)

  • Delissea fallax Hillebr. - Hawaii†
  • Delissea lauliiana Lammers - Oahu†
  • Delissea parviflora Hillebr. - Hawaii†
  • Delissea rhytidosperma* H. Mann - Kauai
  • Delissea undulata* Gaud. - Niihau†, Kauai†, Maui†, Hawaii

section Macranthae (curved flowers 37-60 mm long)

  • Delissea laciniata Hillebr - Oahu†
  • Delissea rivularis* (Rock) F. Wimmer - Kauai†
  • Delissea sinuata Hillebr. - Oahu†, Lanai†
  • Delissea subcordata* Gaud. - Oahu

† species believed to be extinct
* species is listed Endangered

References

  • Wagner, W. L., D. R. Herbst, and S. H. Sohmer. 1990. Manual of the Flowering Plants of Hawaii. University of Hawaii Press, Honolulu

The standard reference for Hawaiian plant taxonomy.

  • Givnish, T. J., E. Knox, T. B. Patterson, J. R. Hapeman, J. D. Palmer, and K. J. Sytsma. 1996. The Hawaiian lobelioids are monophyletic and underwent a rapid initial radiation roughly 15 million years ago. Annual Meeting of the Botanical Society of America. American Journal of Botany 83 (6 suppl.):159.

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