Philippine Rafflesia: Emerging patterns in floral morphology and distribution

Abstract

The Philippines is one of the centers of diversity of the genus Rafflesia (Rafflesiaceae). At present, 13 Rafflesia species have been recorded in the country. Prior to 2013, only 10 species of Rafflesia were found in the Philippines. Afterwards, two species have been described while one species has been resurrected. Morphological characteristics of the 13 species of Rafflesia in the Philippines were synthesized, from which an updated identification key is provided. Based on an analysis of the emerging patterns in morphology and distribution of Philippine Rafflesia, floral diameter remained a key differentiating trait in Rafflesia taxonomy. There is a significant inverse relationship between floral diameter and latitudinal distribution. The distribution map of all Philippine Rafflesia species, with their floral diameters drawn to scale, is presented wherein all species, except R. speciosa, occurred in only one island. Of the more than 7100 islands that make up the Philippine Archipelago, Rafflesia had been found in only five islands, which corresponded to three Pleistocene islands: the Greater Luzon, Greater Mindanao and the Greater Negros Panay.