Rafflesia harjatiae

Rafflesia harjatiae is a parasitic plant species in the family Rafflesiaceae that is endemic to East Kalimantan, Indonesia. This species was officially described as a new species on January 12, 2026, in the journal Sains Malaysiana through an article titled "Rafflesia harjatiae (Rafflesiaceae) sp. nov., A New Species from East Kalimantan, Indonesia".^[1]

The species was discovered in the lowland forest area of Sepaku, Penajam Paser Utara Regency, and is known to grow as a parasite on vines of the genus Tetrastigma (Vitaceae).^[2]

Rafflesia harjatiae has a flower diameter ranging from 17 to 22 centimeters, classifying it as relatively small within its genus.^[1]

Morphological characteristics described in the scientific publication include:

• Flower diameter of 17–22 cm
• Absence of white blotch patterns ("windows") on the inner part of the diaphragm
• Relatively thick diaphragm with a narrow aperture (opening)
• Presence of a single annulus (distinct from several other species that possess two)
• Number of processi (processes) ranging from 32 to 34 with varying shapes
• Well-developed ramenta, cylindrical to club-shaped (subclavate), with swollen and branched tips
• Number of anthers ranging from 18 to 20
• The inner structure of the disk shows distinct protrusions
• Aperture-to-diaphragm ratio differs from its closest relatives

This combination of characters is not found in any other previously published Rafflesia species.

The specific epithet harjatiae was given in honor of Harjati Hashim Djojohadikusumo for her support of conservation activities and biodiversity research in Indonesia.^[3]

The scientific description was conducted by a research team from the National Research and Innovation Agency (BRIN) and the University of Bengkulu, including Agus Susatya, Ridha Mahyuni, Sudarmono, Dian Latifah, Willie Smits, and Arief Priyadi.^[1]

The existence of this flower has been known since the 1980s within the concession area of PT International Timber Corporation Indonesia Kartika Utama (ITCI-KU), Sepaku. However, for several decades, its taxonomic identity remained uncertain due to its similarity to several other Rafflesia species in Borneo.^[4]

In 2019, Tri Atmoko from the Ministry of Environment and Forestry reported its population, though its species status had not yet been determined. Further research was conducted in 2022 through detailed morphological studies and molecular analysis.

Analysis results showed that this species is morphologically and genetically distinct from all described Rafflesia species in Borneo, including those with morphological similarities such as Rafflesia tengku-adlinii from Sabah, Malaysia, as well as Rafflesia aurantia from the Philippines.^[5]

Its status as a new species is supported by DNA analysis using mitochondrial gene markers such as atp6 and matR.

Phylogenetic analysis results indicate that Rafflesia harjatiae forms a distinct lineage from other Rafflesia species in Borneo. The identified genetic differences reinforce the conclusion that this taxon is a separate biological entity and not a variation of previously known species.^[1]

These findings also provide additional data for phylogenetic studies of Rafflesia in the Borneo region.

To date, Rafflesia harjatiae is only known from a single location in Sepaku, Penajam Paser Utara Regency, East Kalimantan. Based on available data, this species is considered endemic to the region.^[1]

This species grows in lowland dipterocarp forests at an altitude of 325–329 meters above sea level. Its habitat consists of old secondary forests with soil conditions having a pH between 5.4–7 and soil moisture ranging from 73 to 89%.^[1]

As a holoparasitic plant, Rafflesia harjatiae lacks true leaves, stems, or roots, and is entirely dependent on its host from the genus Tetrastigma for nutrients.

Field observations recorded at least six populations with a limited number of flower buds. The flowering period was recorded from November to December.^[1]

Data regarding population size and distribution remain limited. Based on the initial assessment in the scientific publication, the species is categorized as Data Deficient (DD) due to the lack of adequate information concerning its distribution and population trends.^[1]

Although the discovery site is located within a company's conservation area, natural environmental factors such as high rainfall and habitat changes remain potential threats.^[6]