Newly discovered Hawaiian flower endangered

This video is called Colors of Hawaii – The Flowers of Hawaii.

New to Nature No 116: Cyanea kauaulaensis

This Hawaiian bellflower has only just been described – but is already on the danger list

Quentin Wheeler

Sunday 5 January 2014

There are no clearer bellwethers of the widening biodiversity crisis than newly named species that are already critically endangered when christened. A recent example is the bellflower Cyanea kauaulaensis described from Maui by Dr Hank Oppenheimer of the University of Hawaii and Dr David H Lorence of the National Tropical Botanical Garden in Kalaheo. Sadly, this new plant joins nearly 200 native species in Hawaii that have fewer than 50 known individuals in the wild and that are the focus of Hawaii’s Plant Extinction Prevention Program. This lovely plant belongs to the lobelioid bellflowers, all of which are endemic to this island chain. With 125 species, the lobelioids constitute the greatest plant species radiation not only of Hawaii, but of any archipelago on Earth.

Lobelioids belong to the family Campanulaceae that has about 2,000 species around the world with notable diversity in areas of the northern hemisphere. The bellflower family often have milky sap and they vary in habit from short herbaceous forms to shrubs and small trees. Cyanea is the largest of the lobelioid genera with 78 known species that are typically un-branching or branching near their base, bearing a cluster of leaves at the their top and fleshy fruits in season.

While the new species has been observed to grow to two to four metres, some members of the genus attain more than nine metres. Their spindly appearance may relate, in part, to their growing in dense forests where light is limited and where shelter from strong winds permits the survival of such wispy forms.

DNA studies have confirmed that lobelioids are monophyletic, that is, they have all descended from a single common ancestral species that found its way to Hawaii 8-10m years ago. In spite of their evolutionary success measured in numbers of species, lobelioids are ecologically vulnerable. They do not tolerate disturbances of their surrounding forest well and their populations have been diminished by grazing feral pigs, among other stresses. A number of species have not been seen in the wild for years and are most likely already extinct.

Variation in the length of their tubular flowers and elevations where different species are found imply partitioning among species by both environmental factors and a diversity of pollinators. Spines and thorns on the leaves and stems of many Cyanea seemed curious at first to botanists as there were no native animal grazers in Hawaii and in their absence on islands plants tend to loose such defenses. As it turns out, there used to be large geese and ducks on the islands before they were hunted to extinction long before the arrival of European explorers.

Cyanea kauaulaensis is endemic to a couple of leeward valleys on the western end of the island of Maui. Its many-branched habit combined with undivided glabrous and unarmed leaves, small and narrow corollas, and bright orange nearly round to oval fruits distinguish it from all other members of the genus. A dozen or so specimens were collected in 1989 during a botanical survey of land owned by Pioneer Mill, but they were misidentified as C. glabra, a species previously known from windward eastern Maui and thought possibly extinct. C. kauaulaensis, however, is restricted to riparian sites growing on talus or basalt boulder-strewn slopes along both sides of perennial streams. Kaua’ula valley has a large, amphitheatre-shaped head and is bordered by impressive canyon walls reaching 700m that limit direct sunlight to mid-day. Annual rainfall is high, averaging about 3,000mm.

The plants were found growing in clumps. Bent branches were seen to take root and form runners producing erect stems or growing vine-like. Up to six metres in length, these vegetative expansions were frequently leaning on or tangled with nearby plants. The new species flowers from late summer through January and produces mature fruits in March and April. Because of its small numbers and limited geographic range, it is considered critically endangered. It may have lost its avian pollinators and dispersers of its seeds and may be vulnerable to floods, landslides, slugs, rats and competing non-native plant species among other threats.