Leptopetalum perpusillum Heenan (Rubiaceae), a New Species From Rarotonga (Cook Islands) and ‘ Eua (Kingdom of Tonga)

A new species of Leptopetalum Hook. & Arn. (Rubiaceae) is segregated from Leptopetalum foetidum (G. Forst.) Neupane & N. Wikstr. Leptopetalum perpusillum Heenan, sp. nov., is distinguished from L. foetidum by its decumbent, low‐growing growth habit, smaller elliptic leaves, short peduncle, compact and few‐flowered inflorescence, and smaller fruit. L. perpusillum has a disjunct distribution, occurring on Rarotonga, Cook Islands, and ‘Eua, Kingdom of Tonga, and in both locations, it occurs on high‐elevation inland bluffs. On ‘Eua, it occurs on cliffs and outcrops of makatea, which are uplifted, inland, and away from the coast, while on Rarotonga, it occurs on volcanic andesite outcrops that protrude above the ridges of the interior tropical forest. L. foetidum is widespread in coastal sites in Melanesia, Micronesia, and Polynesia, including Mangaia and Ngaputoru in the Cook Islands archipelago, and also ‘Eua, where it is sympatric with L. perpusillum . With few populations and limited numbers of plants, the IUCN Red List conservation assessment of L. perpusillum is Vulnerable. Distribution and habitats are noted, and a table compares attributes of L. perpusillum and L. foetidum .