Studies on Homalomeneae (Araceae) of Borneo XVII: two new species of granite-restricted Homalomena from NW Sarawak

Botanical investigation of the numerous mountain ranges of Sarawak continues to reveal further examples of geologically obligated, geographically isolated novel taxa. Here we describe two new species of Homalomena, Homalomena caput-gorgonis S.Y. Wong and P.C. Boyce and Homalomena succincta S.Y. Wong and P.C. Boyce, belonging respectively to the Selaburensis and Giamensis complexes, from the granites of Gunung Pueh, in northwest Sarawak. The Gunung Pueh-Berumput massif straddles the border between Sarawak’s Kuching Division (Sematan and Lundu districts) and Indonesian Kalimantan Barat (Sambas and Bengkayang regencies). Gunung Pueh-Berumput belongs to the same Upper Cretaceous granites and diorite system as Gunung Gading to the east, and the isolated Gunung Melanau in the far north. Despite repeated searches of the more easily accessible, and much-botanized, Gunung Gading, no other populations of these two novel species have been located. Odoardo Beccari is credited as the first biologist to investigate Gunung Pueh (as “Mt Poe”) during August 1866 (Beccari 1902, p. 161 et seq., & 1904, p. 98 et seq.), and indeed the Type locality “Mt Poe, Sarawak”, is given for several of his Sarawak plants. However, according to Burtt (1964), Beccari’s Gunung Poe is not the same as that named as Gunung Pueh on modern maps, but is actually Gunung Berumput, a more southeasterly peak in the same range.
Geological confirmation for this and all of our field work is much assisted by Hutchison (1989, 2005) and Tate (2001).