Assessing potential habitat suitability of parasitic plant: A case study of Rafflesia arnoldii and its host plants

Abstract

Rafflesia are obligate endo-holoparasitic plants with the genus Tetrastigma playing an important role as their host plants. Rafflesia arnoldii is one of Indonesian endemic plants that grows in Sumatra island. This island is also known to have eleven species of Tetrastigma . Three of them are known as host plants of R. arnoldii , namely Tetrastigma curtisii, T. pedunculare and T. leucostaphylum . Unfortunately, it is not possible to survey the entire native distribution range of R. arnoldii and its host plants due to practical constraints. Species Distribution Modeling using Maximum Entropy (MaxEnt) is considered to be an alternative way to understand the potential regions that are suitable for a species. Predicting habitat suitability of a parasitic plant through predicting its host plant distribution may be a useful approach. The model prediction from MaxEnt for all host species has an AUC value more than 0.70, indicating the model adequately classified the occurrence records of R. arnoldii and its host plants. Suitable habitats for R. arnoldii were predicted to occur along the Bukit Barisan Mountain range from Lampung to Aceh, mostly in Lampung, Bengkulu, West Sumatra and Aceh. However, the suitable habitats of R. arnoldii estimated from host plants were predicted to occur predominately in Lampung, Bengkulu, West Sumatra, North Sumatra and Aceh. The important environmental variables affecting the occurrence of R. arnoldii and its host plants are mean temperature, slope, elevation, soil organic carbon and soil type. Rafflesia species can be found in various soil types, but mostly in Humic Andosols, Humic Acrisols, Orthic Acrosols, Dystric Fluvisols, Dystric Cambisols and Eutric Fluvisols based on the actual data points and predicted habitats. The suitable habitats of R. arnoldii based on its host plants were predicted to be mostly outside conservation areas, but suitable habitats were predicted inside approximately 46 conservation areas. The findings of this study may be used by the Government of Republic Indonesia, c.q. Ministry of Environment and Foresty for establishing protected areas and conservation-based management improvement and could also help inform the R. arnoldii listing status in IUCN red list category in the future.