Part 35 Piperaceae - Pittosporaceae
Piperaceae are a family of five or six genera and about 2,750 species with a tropical distribution. The genus Piper consists of over a thousand species with a high representation in the New World tropics. Several of the species would be well known by most readers: P. nigrum is the much used culinary pepper, whether black or white (color is a matter of preparation of the fruit); P. betel is the betel nut used extensively as a masticatory in parts of Asia; and P. methysticum, the source of the kavalactones, active constituents of kava or kava kava. Piper methysticum (see image), known as `awa, pü`awa, or simply as kava, is the only species of Piper that grows in the Hawaiian Islands. It is widely cultivated throughout the Pacific and was brought to the Hawaiian Islands by Polynesian colonists. This plant is easily identified through its prominently swollen joints (see image).
The other representative of the family that occurs in the Hawaiian Islands is Peperomia, which consists worldwide of some 1,650 species (Mabberley, p. 646). The common name for the group in the islands is `ala`ala wai nui. There are 25 species of Peperomia in the Hawaiian Islands, all but two of which are endemics. Most of the endemic species occur in wet forest settings; some are epiphytes. Hawaiian Peperomia species are highly variable leading authorities to suggest that three or four independent migrations may have occurred. Plants of this genus are easily distinguished by their upright spikes of individual flowers. Species identification requires experience but recognizing an `ala`ala wai nui plant should be easy for any visitor not put off by a little warm rainfall. The Pihea Trail on Kaua`i offers excellent opportunity to find many specimens. Peperomia macraeana (see image) is featured here to illustrate the pigmented under-leaf which makes this species one of the easier ones to identify in the field. Other species are illustrated below (with apologies for lack of complete names).
Pittosporaceae are a family of seven genera and 250 species of warm and tropical habitats with a center of diversity in Australia (Mabberley, p. 673). Pittosporum, the genus of interest to us here, consists of about 200 species, many of which are of Southern Hemisphere origin. The Hawaiian Islands are home to 10 endemic and two naturalized species. Visitors to the rainforest of Kaua`i can find P. gayanum (see image), hö`awa or hä`awa, growing along the Pihea Trail (along the boardwalk section). The plants tend to be tall and have their flowers, and eventually, fruits, emerging directly from the stems. The fruits are black and look a bit like wrinkled olives, and are about that size (see image). The young leaves tend to have a tan to light brown wooly surface. Pittosporum kauaiense (see image) can be seen in cultivation in the Limahuli Gardens.
C. E. C. Gemmill, of Waikato University in New Zealand, and colleagues (2002) studied relationships of Pittosporum from Australia, New Zealand, New Caledonia, Fiji, Rarotonga, Tahiti, Tonga, and the Hawaiian Islands using DNA sequence analysis. The Hawaiian natives exhibited 0.0% divergence which indicated a recent colonization, and that the closest related species (technically sister species) occur on Tonga and Fiji. Bird dispersal is the most likely means by which the sticky seeds are transported over long distances.
Gemmill, C. E., G. J. Allan, W. L. Wagner and E. A. Zimmer. 2002. Evolution of insular Pacific Pittosporum (Pittosporaceae): origin of the Hawaiian radiation. Molecular Phylogenetics and Evolution 22: 31-42.
June 21, 2012