Trematolobelia Zahlbr. ex Rock

In 1891, Viennese botanist Alexander Zahlbruckner segregated the species then named Lobelia macrostachys into a new genus based on its unique form of dehiscence. In this species, dehiscence was via irregular pores on the capsule walls and not via loculicidal valves. He named the new genus Trematocarpus, but this name had already been used for a genus of red algae (Kützing, 1843). Rock, in 1913, at Zahlbruckner's suggestion renamed the genus Trematolobelia. (Lammers, 2009; Rock, 1919). trema- (τρημα) is Greek for hole - referring to the holes on the capsule used in the unique form of dehiscence.

The species was first described by Hooker and Arnott (1832) based on a specimen of Trematolobelia macrostachys collected by George Tradescant Lay who stayed on the islands for nine months while the Beechey expedition (1825-1828) headed north to the Bering Strait. Lammers (2009) says that during that time, Lay collected this specimen of T. macrostachys from the Ko'olau range above Honolulu.

Three of the species have a one-to-one correspondence with a volcano. All T. kauaiensis are found on Kaua'i and all Trematolobelia found on Kaua'i are T. kauaiensis. Similarly, T. kaalae belongs to the Wai'anae range and T. auriculata belongs to Lana'i. There are two Trematolobelia on Hawai'i, the big island: T. grandifolia is restricted to Kohala and T. wimmeri overlaps in Kohala, but also occurs all along the windward side of the island down to Kīlauea. These two can be told apart by the pubescence of the raceme, the color of the corolla and the length/width ratio of the leaf. In the Ko'olau range, both T. macrostachys and T. singularis occur. T. singularis occurs only near the summit of Kōnāhuanui and is a quite unique species with only a single terminal raceme and very different flowers from the other Trematolobelia. On Moloka'i can be found T. macrostachys, plus Rock collected a single specimen of the summer flowering T. rockii. Finally, on Maui, only T. macrostachys is known.

species	island
Trematolobelia kauaiensis	Kaua'i
Trematolobelia singularis	Ko'olau range
Trematolobelia kaalae	Wai'anae range
Trematolobelia macrostachys	Ko'olau, M, Mo
Trematolobelia auriculata	Lāna'i
Trematolobelia rockii	Moloka'i
Trematolobelia grandifolia	Kohala
Trematolobelia wimmeri	Windward Hawai'i

Sources:

• Descriptions of Trematolobelia prior to the Zahlbruckner naming the new genus
  • Hooker & Arnott, 1832 (as Lobelia macrostachys);
  • G. Don, 1834 (as Lobelia macrostachys);
  • Presl, 1836 (as Delissea macrostachys);
  • De Candolle, 1838 (as Lobelia macrostachys);
  • Gaudichaud, 1842 (as Lobelia macrostachys);
  • Gray, 1861 (as Lobelia macrostachys);
  • Mann, 1868 (as Lobelia macrostachys);
  • Wawra, 1873 (as Lobelia macrostachya);
  • Hillebrand, 1888 (as Lobelia macrostachys);
• Zahlbruckner, 1891 (as Trematocarpus);
• Rock, 1913;
• Rock, 1919;
• Degener, 1934;
• Wimmer, 1953;
• Wagner et al., 1990.