Most of the world's largest flowers (genus Rafflesia) are now on the brink of extinction

Abstract

Societal Impact StatementRafflesia is the genus that contains the world's largest flowers. Despite their global appeal, most of the 42 known species are now at risk of extinction. Urgent action is needed to protect these remarkable flowers. A combined approach to conservation is recommended, including a greater level of habitat protection and support for local community action groups. Rafflesia is a suitable new icon for conservation in the Asian tropics.SummaryThe genus Rafflesia, which includes the world's largest flowers, has aroused curiosity among scientists for centuries and features prominently in local culture across Southeast Asia. The plant has long been used in ethnobotanical medicine and, more recently, as a source of revenue from ecotourism. But despite its acclaim, Rafflesia remains poorly understood in many respects. Taxonomy is disputed, new species are described each year, and the plant has proven recalcitrant to cultivation. This has hindered conservation, and most of the 42 known species are now severely threatened, yet only one is listed by the International Union for Conservation of Nature (IUCN). We estimate that 60% of Rafflesia species face a severe risk of extinction (equivalent to Critically Endangered [CR]). Moreover, we predict that at least 67% of known habitats fall outside protected areas, exacerbating their vulnerability. Alarmingly, recent observations suggest taxa are still being eradicated before they are even known to science. We present recent scientific discoveries and probable extinctions and highlight case studies of conservation success, with a focus on the role of local people. We propose a multi‐pronged conservation approach combining strengthened taxonomy, ex situ propagation, ecotourism, and an extension of protected areas. We suggest action devolved to local communities and awareness campaigns linked to social media networks will be crucial outside of protected jurisdictions. Finally, we propose to establish Rafflesia as a new icon for plant conservation in the Asian tropics. A combined approach might just save some of the world's most remarkable flowers, most of which are now on the brink of being lost.

What explains the high island endemicity of Philippine Rafflesia? A species distribution modeling analysis of three threatened parasitic plant species and their hosts

“…Rafflesia populations at lower elevations are also likely to be the most prone to habitat destruction as land is converted for residential and agricultural use because they are typically close to places where people live and work (Hughes, 2017). Other Rafflesia species, in the Philippines as in other countries, face similar challenges (e.g., Kusuma et al, 2022;Renjana et al, 2022;Malabrigo et al, 2023).…”

“…Rafflesia species have been referred to as the giant pandas of the plant world, given their rarity, bizarre endoholoparasitic lifestyle, their large and foul-smelling flowers (Josephson, 2000), and their importance as icons of plant conservation. The Philippine archipelago is home to at least 14 of the 32 to 42 currently recognized Rafflesia species (Nickrent, 1997;Pelser et al, 2011Pelser et al, onwards, 2019Galindon et al, 2016;Siti-Munirah et al, 2021;Malabrigo et al, 2023). All are of conservation concern based on IUCN criteria (IUCN Standards and Petitions Committee, 2019) or those used by the Philippine Department of Environment and Natural Resources (Pelser et al, 2011 onwards;Galindon et al, 2016;DENR, 2017;Malabrigo et al, 2023): four species are considered Critically Endangered, nine Endangered, and one Vulnerable.…”

“…The Philippine archipelago is home to at least 14 of the 32 to 42 currently recognized Rafflesia species (Nickrent, 1997;Pelser et al, 2011Pelser et al, onwards, 2019Galindon et al, 2016;Siti-Munirah et al, 2021;Malabrigo et al, 2023). All are of conservation concern based on IUCN criteria (IUCN Standards and Petitions Committee, 2019) or those used by the Philippine Department of Environment and Natural Resources (Pelser et al, 2011 onwards;Galindon et al, 2016;DENR, 2017;Malabrigo et al, 2023): four species are considered Critically Endangered, nine Endangered, and one Vulnerable. Thirteen of these are each only found on one island.…”

“…We tested this hypothesis for three species of Rafflesia (R. lagascae Blanco [1845], R. lobata Galang and Madulid [2006], R. speciosa; Figure 2) and their Tetrastigma hosts using a species distribution modeling approach. Rafflesia speciosa and R. lobata are currently classified as Endangered and R. lagascae is considered Vulnerable (Pelser et al, 2011 onwards;Malabrigo et al, 2023). A better understanding of differences between the observed and potential distributional patterns of Rafflesia species can inform their conservation management by identifying areas that have environmental conditions suitable for both parasite and host.…”

Rafflesia balatociana (Rafflesiaceae), a new species from the Cordillera Central, Luzon, the Philippines

“…ex (Thomson 1820) is a genus of parasitic plants that famously includes the world's largest flowers (Nais 2001). There are 42 accepted species of Rafflesia in the Malesian Floristic Region (Adam et al 2022;POWO 2023), and in the last two decades, the Philippines has been established to be a center of diversity for the genus (Barcelona et al 2009;Pelser et al 2019;Malabrigo et al 2023). Rafflesia occurs on five major islands of the Philippines: Luzon, Mindanao, Samar, Negros, and Panay.…”