Hydnoraceae C. Agardh.

Family Description

Distribution Map

Prosopanche is known from southern South America and Costa Rica. Hydnora is found in Africa and Madagascar. This is a classic example of a Gondwanan distribution. The ancestor of the two genera likely occupied Gondwana prior to the separation of that continent into Africa and South America ca. 100 million years ago. The amazing discovery of Prosopanche in Central America (Gomez and Gomez 1981) demonstrates a wide range disjunction for the genus. The taxon has been considered a new species (P. costaricensis) or conspecific with P. americana of South America.

List of Genera

Photographs

Hydnora abyssinica

• Comparison of flowers (in longitudinal section) of H. abyssinica, H. africana, and H. esculenta. Link goes to ResearchGate.
• Photos, flowers and other useful information. Photos by Ottmar Kullmer (African Plants, A Photo Guide). Link goes to Useful Tropical Plants.
• Photo of a beautiful open flower. Photo by Jabruson. Link goes to Minden Pictures.

Hydnora africana

• Habit on host plant, Euphorbia mauritanica, near Worcester, South Africa. Photo by D. L. Nickrent.
• Flower connected to horizontal rhizome-like pilot root. Note the blackened and withered perianths littering the soil nearby. Near Worcester, South Africa. Photo by D. L. Nickrent.
• Close-up of 3-merous flower. Near Worcester, South Africa. Photo by D. L. Nickrent.
• Day one flower (right) and day two flower (left), showing "bait bodies" along edges of perianth lobes. Karasburg District, Namibia. 29 December 2002, Photo by L. J. Musselman.
• Pilot root (dark) showing attachment by haustorial root to the root of the host plant (Euphorbia - light colored). Near Worcester, South Africa. Photo by D. L. Nickrent.
• Young fruit forming from inferior ovary of flower (left) and a flower bud (right) opened to show anther attachment to perianth lobe. Near Worcester, South Africa. Photo by D. L. Nickrent.
• Mature fruit, sectioned. Karasburg District, Namibia. 28 December 2002 . Photo by L. J. Musselman.
• Photos. A series of excellent photos of the flower. South Africa. Photos by Martin Heigan. Link goes to Flickr.
• Photos. Photos of the flowers. Namaqualand, Northern Cape, South Africa. Photos by Leon Olickers. Link goes to Flickr.

Hydnora esculenta

• Flower. Berenty Private Reserve, Madagascar. Photo by Jay F. Bolin. Link goes to ODU Plant Site.
  
• Flower. Photograph by Pete Oxford (Minden Pictures), Berenty Private Reserve, Madagascar.
• Open flower. From Berenty Private Reserve, Madagascar. Photo by Shirley Sekarajasingham. Link goes to Flickr.
• Photos, one showing the beetles that are involved in pollination. Link goes to Useful Tropical Plants.
  
• Fruit with withered, black perianth still attached at the top. Photograph by George Williams.
• Good photo of pilot root with haustorial roots (bumps) along its length. Photograph by George Williams.
• Fruit sectioned showing the parietal placentae. The pulp and seeds of the fruit are sweet andactively sought by lemurs.Photograph by George Williams.
• Fruit closeup showing the seeds.Photograph by George Williams.

Hydnora johannis

• Flowers with ruler for scale. Ethiopia: Harar Province. Photograph by William Burger [No. 3490], 9 May 1964. Slide no. 520. archived at Kew.
• A somewhat desiccated specimen. Ethiopia: N of Midago. Photograph by William Burger [s.n.], 9 May 1964. Slide no. 4173 archived at Kew.
• Flower, sectioned longitudinally, with ruler. Ethiopia, N of Midago. Photo by William Burger. 10 May, 1964. Slide no. 4174 archived at Kew.
• Top view of flowers emerging from grassy area. Tanganyika: Kondoa District. Photograph by Roger Polhill and Paolo [no. 1139], 11 Jan. 1962. Slide no. 1959 archived at Kew.
• Flower being pollinated by an orgy of beetles! From "Sex Lives of Flowers" by Meeuse, p. 92.  Photo by Malcolm J. Coe of Oxford Scientific Films.
• Fruit sectoned longitudinally. Yemen. Photograph by Eric Danell.

Hydnora longicollis

• Flower L.S. comparisons - left H. longicollis, middle H. africana, right H. visseri. This species, formerly H. africana var. longicollis, was recognized as a distinct species by Bolin et al. (2011. A new species of Hydnora (Hydnoraceae) from southern Africa. Systematic Botany 36:255-260).
• Illustration. Beautiful drawing of the plant (from Welwitsch, F. 1869. Sertum Angolense ... Trans. Linn. Soc. London 27, plate 21).

Hydnora triceps

• Flower. This species is almost completely subterranean! Only the three small openings in the flower are present near the surface of the ground.
• Flowers, longitudinally sectioned.
• Fruits, showing various stages of drying after being eaten by an unknown animal. Near Port Nolloth, South Africa. 23 December 2002. Photo by L. J. Musselman.
• Fruits, beginning to dehisce. Near Port Nolloth, South Africa. 23 December 2002. Photo by L. J. Musselman.
• Fruit freshly cut fruit, pericarp has not darkened. Near Port Nolloth, South Africa. 23 December 2002. Photo by L. J. Musselman.
• Fruit sectioned, close-up, showing seeds. Near Port Nolloth, South Africa. 23 December 2002. Photo by L. J. Musselman.
• Comparison of fruits of Hydnora triceps (right) and H. africana (left), both immature. Steinkopf Road a few kilometers east of Port Nolloth, Namibia. Photo by L. J. Musselman.

Hydnora visseri

• Flower. This Namibian species is a recent segregate of H. africana.  See Bolin J. F., Maass E., Musselman L. J. 2011. A new species of Hydnora (Hydnoraceae) from southern Africa. Systematic Botany 36:255-260.

Prosopanche americana

• A bud just emerging from the soil. Near Cordoba, Argentina. Photo by Andrea Coccuci.
• The bud at an early stage of opening. Only the top parts of the flower emerge from the soil - the rest remain underground. Near Cordoba, Argentina. Photo by Andrea Coccuci.
• Flower, fully open, showing the dome-like, fused androecium. Near Cordoba, Argentina. Photo by Andrea Coccuci.
• Flower, with androecium releasing pollen, excavated to show the inferior ovary. Near Cordoba, Argentina. Photo by Andrea Coccuci.
• Close-up of synandrium. Lihue Calel, Argentina. 1996? Photo by J. Mauseth
• The strange flower is shown here emerging from the soil in a field in Argentina. The plant is parasitic on the roots of Prosopis, a tree in the legume family. Photo by Lytton Musselman, Argentina.
• Fruit emerging from the soil. Note the darkened remnants of the perianth at the apex of the fruit and the circumscissile dehiscence. Photo by Lytton Musselman.
• Fruit excavated to show circumscissile dehiscence. Photo by Lytton Musselman
• Pilot root with numerous haustorial roots emerging from it. Those haustorial roots that have broken off ooze white latex. Photo by Lytton Musselman.
• Prosopanche grows as far north as Bolivia and Peru. This plant was found emerging from the soil in a garden (parasitic on Solanum) in Santa Cruz, which occurs in the tropical part of Bolivia. Another photo showing the a younger open flower that was partially excavated. Photos May 2003 by Dr. Pierre L. Ibisch.
• Prosopanche fruits, from the same Bolivian plants shown above. This slide of a sectioned fruit shows the white fleshy endocarp pulp surrounding numerous seeds. Cocucci and Cocucci (1996) estimate 35,000 per fruit!). This slide, shows a close-up of the pulp being visited by numerous ants. Cocucci and Cocucci suggest that seed dispersal is endozoochorous, probably involving nocturnal mammals (rodents, foxes, and armadillos). Although ants clearly visit these fruits, it has not been documented whether they effectively disperse the seeds. Photos July 2003 by Dr. Pierre L. Ibisch.
• This Prosopanche occurs in the Braulio Carrillo National Park near the Quebrada Gonzalez station, 500 m elevation, Costa Rica. The plant is parasitic on roots of rain forest trees on the very wet Atlantic slope, quite different than the habitat of the species growing in Argentina. Although named as a new species (P. costaricensis L. D. Gómez & Gómez-Laur.), Coccuci and Coccuci (1996) consider this name a synonym of P. americana. Photo by B. Hammel.
• Photos of plants called P. costaricensis. Costa Rica. Link goes to Flora of the World.
  
• Prosopanche flowers sectioned. Costa Rica, Limon, Pococi, P.N. Braulio Carrillo; Llanura de Santa Clara. Barry Hammel, Paul & Hiltje Maas (No. 18037). Link goes to TROPICOS image library at MO.

Prosopanche bonacinae

• Flower attached to root. Argentina. Photo by L. J. Musselman
• Flower of this species compared to P. americana (right). Argentina. Photo by L. J. Musselman
• Older flower, with perianth dehiscing and fruit forming. Argentina. Photo by L. J. Musselman
• Young fruit. Argentina. Photo by L. J. Musselman
• Root connected to host root (smaller). Argentina. Photo by L. J. Musselman.

The Hydnora Page (L. J. Musselman, ODU).

	Bolin, J. F., E. Maass, and L. J. Musselman. 2009. Pollination biology of Hydnora africana thunb. (Hydnoraceae) in Namibia: brood-site mimicry with insect imprisonment. Int. J. Plant Sci. 170: 157–163.
	Hydnora on the cover of American Journal of Botany. See article by Tennakoon et al. on the vegetative morphology and anatomy of H. triceps, a hypogeous root holoparasite.  AJB 2007, vol. 94, 1439-1449.

Phylogeny & Classification

This family contains two genera, Prosopanche (S. and C. America), and Hydnora (Africa and Madagascar). As with Balanophoraceae, Cronquist and Takhtajan differed in their classifications of this family. Cronquist placed it in Rosidae in Rafflesiales, Takhtajan in Magnoliidae with Rafflesianae.  Both were incorrect with regard to a relationship with Rafflesiaceae.  Takhtajan was closer in placing the family in Magnoliidae, for indeed molecular data place Hydnoraceae in Piperales (Nickrent et al. 2002, pdf HERE). This was later confirmed by Naumann J, et al. (2013. Single-copy nuclear genes place haustorial Hydnoraceae within Piperales and reveal a Cretaceous origin of multiple parasitic angiosperm lineages. PLoS ONE 8:e79204).

The APG3 (2009) classification recognized five families in Piperales: Aristolochiaceae, Hydnoraceae, Lactoridaceae, Piperaceae, and Saururaceae.  The Angiosperm Phylogeny Website by Peter Stevens shows a tree with Hydnoraceae sister to Aristolochiaceae plus Lactoridaceae, however, the text lumps these groups, recognizing subfamily Hydnoroideae.  In APG4 (2016), three families were recognized, Saururaceae and Piperaceae, with Hydnoraceae and Lactoridaceae lumped into Aristolochiaceae. The justification for the lumping derives from the work of Naumann et al. (2013) who used 19 genes as well as Massoni et al. (2014, Increased sampling of both genes and taxa improves resolution of phylogenetic relationships within Magnoliidae, a large and early-diverging clade of angiosperms. Molecular Phylogenetics and Evolution 70:84–93) who used a 12 gene dataset. All of these molecular studies detected the same six groups that correspond to the above five familes plus one other; a part of Aristolochiaceae (subfamily Asaroideae) is distinct. It is worth noting the the topologies of the Naumann and Massoni phylogenetic trees do not agree with regard to the six groups, plus the introduction of Hydnoraceae lowers bootstrap values at key nodes. It seems that instead of lumping the shrubby Lactoridaceae (1 species, L. fernandeziana), the morphologically bizarre holoparasite family Hydnoraceae, and Aristolochiaceae (9 genera 465 species according to Mabberley 2008), it would be simpler to simply elevate Asaroideae Burnett to the rank of family and leave the rest of the classifications alone! This new family (Asaraceae) would contain Asarum (ca. 80 spp.) and Saruma (1 species, S. henryi). As I have argued (as have others), it is important for members of our field to recognize the history of names when considering re-classifications and to introduce the least number of disruptions. For these reasons, I continue to recognize Hydnoraceae as a distinct family in Piperales.

The most recent and comprehensive molecular phylogenetic study to examine the above topic is the following:

Jost M, Samain M-S, Marques I, Graham SW, Wanke S. 2021. Discordant phylogenomic placement of Hydnoraceae and Lactoridaceae within Piperales using data from all three genomes. Frontiers in Plant Science 12:642598-642598. Available HERE)

That study "favored recognition of four monophyletic and morphologically well circumscribed families in the perianth-bearing Piperales: Aristolochiaceae, Asaraceae, Hydnoraceae, and Lactoridaceae", in other words, exactly what I proposed above. Despite being edited in September 2021, whoever authored the Wikipedia page still insists on placing Hydnora and Prosopanche in Hydnoroideae within Aristolochiaceae. As of January 2022, the Jost et al. (2021) paper is not cited.

References