Distribution modeling of Tetrastigma species (Vitaceae) in the Philippines

Abstract

Tetrastigma Planch. is a genus of woody climbers from the grape family (Vitaceae) with at least 24 known species in the Philippines. It is the exclusive host of the endangered parasitic Rafflesia R.Br. As far as we know, studies on the species distribution of Philippine Tetrastigma species to determine their suitable habitats is wanting. Although Philippine Tetrastigma species are not endangered, information on the suitable habitats of these species can provide preliminary information on the habitat suitability of the endangered Rafflesia species. In this study, we utilized Maximum Entropy (Maxent) to predict potential suitable areas of three Tetrastigma species – Tetrastigma loheri, Tetrastigma cf. magnum and Tetrastigma sp. A – under present climate and soil conditions in the Philippines. Our models showed that suitable areas for Tetrastigma species are found in the eastern and western side of the Philippines and are not usually found further inland in large islands such as Luzon and Mindanao. The top environmental predictors of habitat suitability are mean annual temperature, temperature seasonality, clay content, and precipitation of the coldest quarter. The common suitable habitats of all three Tetrastigma species were found on the western portion of the Philippines that include mountainous regions that have relatively cool temperature and low clay content. Because Tetrastigma is the only host of Rafflesia, our findings suggest that the suitable habitats of Rafflesia are likely to follow the same geographic distribution and preferred environmental conditions. Until species distribution studies on Rafflesia is available, this preliminary information from this study can help in formulating conservation management plans for the endangered parasitic Rafflesia.