TheRafflesiaceae are a family of rareparasiticplants comprising 36 species in 3 genera found in thetropical forests of east and southeast Asia, includingRafflesia arnoldii, which has the largest flowers of all plants. The plants areendoparasites of vines in the genusTetrastigma (Vitaceae) and lack stems, leaves, roots, and any photosynthetic tissue. They rely entirely on their host plants for both water and nutrients, and only then emerge as flowers from the roots or lower stems of the host plants.

Rafflesiaceae
Rafflesia keithii flower
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Malpighiales
Family:	Rafflesiaceae Dumort.
Genera[1]
Rafflesia R.Br. ex Gray Rhizanthes Dumort. Sapria Griff.

Rafflesiaceae flowers mimic rotting carcasses in scent, color, and texture to attract their pollinators, carrion flies. For this reason, some flowers of the familyRafflesia are nicknamed "corpse flowers". Most members of Rafflesiaceae possess a large, bowl-shaped floral chamber formed by aperianth tube and a diaphragm. This diaphragm is the opening for carrion fly pollinators and is surrounded by attractive sterile organs. Flowers are generallyunisexual, and can range from tens of cm to over a meter large.^[2][3]

Past taxonomic works have varied as to the classification of Rafflesiaceae. The classification of Rafflesiaceae has been somewhat problematic due to their highly reduced vegetative parts, modified reproductive structures, and anomalousmolecular evolution (Davis 2008). Rafflesiaceae lacksrbcL and otherplastid genes commonly used forphylogenetic inference in green plants. In fact, Molina et al. (2014) found that a genus ofRafflesia is the first parasitic plant studied containing no recognizable remnants of thechloroplast genome.

Most traditional classifications that were based entirely on morphological features considered Rafflesiaceaesensu lato (in the broad sense) to include nine genera, but the heterogeneity among these genera caused early workers, such as Harms (1935), to recognize four distinct groups that were then classified as tribes (still within Rafflesiaceae). This tribal system was followed by Takhtajan et al. (1985).

The first molecular phylogenetic study (using DNA sequences) that showed two of these tribes were not related was by Barkman et al. (2004). This study showed three genera (corresponding to tribe Rafflesieae, that is,Rafflesia,Rhizanthes, andSapria) were components of the eudicot order Malpighiales. The genusMitrastemon (tribe Mitrastemoneae) was shown to be unrelated and a member of the order Ericales. Later that year, Nickrent et al. (2004), using additional molecular data, confirmed the placements by Barkman et al. (2004) and also examined the positions of the two other tribes, Cytineae (Bdallophyton andCytinus) and Apodantheae (Apodanthes,Berlinianche, andPilostyles). Nickrent et al. (2004) showed Cytineae was related to Malvales and Apodantheae to either Malvales or Cucurbitales. Apodantheae has since been confirmed to be in the Cucurbitales (Filipowicz and Renner 2010).

Thus, the group traditionally classified as a single family, Rafflesiaceae, was actually composed of at least four distinct and very distantly related clades, with their similarities due toconvergent evolution under their common parasitic lifestyle. A goal of taxonomy is to classify together only plants that all share a common ancestor, i.e., are monophyletic. Thus, the original Rafflesiaceaesensu lato is currently split into four families:^[4]

• Rafflesiaceae (sensu stricto):Rafflesia,Rhizanthes,Sapria — order Malpighiales
• Mitrastemonaceae:Mitrastemon — order Ericales
• Cytinaceae:Bdallophyton,Cytinus — order Malvales
• Apodanthaceae:Apodanthes,Berlinianche,Pilostyles — order Cucurbitales

These four families can be easily distinguished by floral and inflorescence features:

• Rafflesiaceae: inferior ovary, large flowers occurring singly
• Mitrastemonaceae: superior ovary, flowers occurring singly
• Cytinaceae: inferior ovary, flowers in inflorescences
• Apodanthaceae: inferior ovary, small flowers occurring singly (but arising in clusters from host bark)

Early work on higher-level relationships was able to place Rafflesiaceae (in the strict sense) within the orderMalpighiales, but was not able to resolve the closest ancestor within the order.^[5] A 2007 phylogenetic analysis found strong support for Rafflesiaceae being derived from withinEuphorbiaceae as traditionallycircumscribed, which was surprising as members of that family typically have very small flowers. According to this analysis, the rate of flower size evolution was more or less constant throughout the family, except at the origin of Rafflesiaceae – a period of about 46 million years between when the group split from the Euphorbiaceaesensu stricto, and when the existing Rafflesiaceae split from each other – where the flowers rapidly evolved to become much larger before reverting to the slower rate of change.^[6]

To maintainmonophyletic families, in 2016 theAPG IV system separated the familyPeraceae from the Euphorbiaceae.^[7] A summary cladogram is shown below,^[6] with family placements in theAPG IV system.^[7]

A more recent study has been provided by Liming Caiet al. (2021)^[8]

A number ofmitochondrial genes in the Rafflesiaceae appear to have come from their hosts (Tetrastigma). Because the hosts are not closely related to the parasites (as shown bymolecular phylogeny results for other parts of the genome), this is believed to be the result ofhorizontal gene transfer.^[9][10] Especially high rates of HGT have been found to take place in Rafflesiaceae mitochondrial genes when compared tonuclear genes and to HGT inautotrophic plants.^[11]

• Barkman, T.J., S.-H. Lim, K. Mat Salleh and J. Nais. 2004. Mitochondrial DNA sequences reveal the photosynthetic relatives ofRafflesia, the world's largest flower.Proceedings of the National Academy of Sciences of USA101:787–792.
• Charles C. Davis, Maribeth Latvis, Daniel L. Nickrent, Kenneth J. Wurdack, David A. Baum. 2007. Floral gigantism in Rafflesiaceae. Science Express, published online January 11, 2007 (online abstracthere).
• Filipowicz, N. and Renner, S.S., 2010. The worldwide holoparasitic Apodanthaceae confidently placed in the Cucurbitales by nuclear and mitochondrial gene trees.BMC Evolutionary Biology,10: p. 219.
• Meijer, W. 1997. Rafflesiaceae, inFlora Malesiana I,13: 1–42.
• Molina, J., Hazzouri, K.M., Nickrent, D., Geisler, M., Meyer, R.S., Pentony, M.M., Flowers, J.M., Pelser, P., Barcelona, J., Inovejas, S.A. and Uy, I., 2014. Possible loss of the chloroplast genome in the parasitic flowering plant Rafflesia lagascae (Rafflesiaceae).Molecular biology and evolution,31: 793–803.
• Nickrent, D.L., A. Blarer, Y.-L. Qiu, R. Vidal-Russell and F.E. Anderson. 2004. Phylogenetic inference in Rafflesiales: the influence of rate heterogeneity and horizontal gene transfer.BMC Evolutionary Biology4:40 (HTML abstractPDF fulltext).

• Rafflesiaceae atAngiosperm Phylogeny Web
• Parasitic Plant Connection: Rafflesiaceae
• BBC news : Family found for gigantic flowers