Peridiscaceae

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Peridiscaceae
Peridiscus lucidus (Hooker).png
Botanical illustration of Peridiscus lucidus
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Saxifragales
Family: Peridiscaceae
Kuhlm. [1]
Type genus
Peridiscus
Genera

Peridiscaceae is a family of flowering plants in the order Saxifragales. [2] Four genera comprise this family: Medusandra, Soyauxia, Peridiscus , and Whittonia ., [3] with a total of 12 known species. [4] It has a disjunct distribution, with Peridiscus occurring in Venezuela and northern Brazil, Whittonia in Guyana, [5] Medusandra in Cameroon, and Soyauxia in tropical West Africa. [6] Whittonia is possibly extinct, being known from only one specimen collected below Kaieteur Falls in Guyana. In 2006, archeologists attempted to rediscover it, however, it proved unsuccessful. [3]

Contents

The largest genus is Soyauxia, with about seven species. Medusandra has two species. Peridiscus and Whittonia each contain one species. The Peridiscaceae are small trees or erect shrubs of wet tropical forests.

It was not until 2009 that all four of the genera were united into a single family. [3] Peridiscus and Whittonia are clearly close relatives. This pair, and the other two genera have long been considered anomalous, being variously classified by different authors.

Description

The following description was created by combining descriptions of Medusandra and Peridiscus by John Hutchinson [7] with descriptions of Soyauxia, Peridiscus, and Whittonia by Clemens Bayer. [5]

Peridiscaceae are small trees or erect shrubs. The leaves are stipulate, alternate, and simple, with margins that are entire or remotely crenulate (Medusandra). The petiole is pulvinate, at its apex, sometimes obscurely so. The stipules are in the axils of the leaves, sometimes enclosing an axillary bud.

The inflorescence is a cluster of axillary racemes or spikes, the clusters often being reduced to a pair of racemes or to a single raceme. The flowers are bisexual and actinomorphic. The sepals are 4 to 7 in number, and free, that is, separate from each other. Medusandra and Soyauxia have five petals. Peridiscus and Whittonia have none.

Medusandra lacks a nectary disk and has five stamens, inserted opposite the petals, and alternating with five long, hairy staminodes. In the others, the stamens are numerous and arranged in a ring around the nectary disk. The anthers are tetrathecal in Medusandra and Soyauxia; bithecal in Peridiscus and Whittonia.

The perianth parts are attached below the ovary. The ovary is therefore superior, but appears half-inferior in Peridiscus because the ovary is embedded in the large, fleshy disk. The gynoecium consists of three or four carpels, united to form a unilocular ovary. The placentation is apical, with two ovules at the apex of each carpel. The ovary has a central column in Medusandra and Soyauxia. Each carpel bears a stylulus and these are well separated at the apex of the ovary.

The fruit is one-seeded; a capsule in Medusandra and Soyauxia; a drupe in Peridiscus and Whittonia.

History

George Bentham established the genus Peridiscus in 1862, naming its only species Peridiscus lucidus. He placed it in a group which he called "Tribus Flacourtieae" and which later would be known as the family Flacourtiaceae. [8] Bentham wrote no etymology for this name, but it is generally believed that the name refers to the fact that the stamens are attached along the outer edge of the nectary disk. [9]

Daniel Oliver established the genus Soyauxia in 1880 for Soyauxia gabonensis , placing it in the family Passifloraceae. [10] He named it for the German botanist and plant collector Hermann Soyaux, [11] saying "Mons. Soyaux, now settled in the Gaboon, well deserves that his name should be associated with one of his interesting discoveries in that region". [10]

The family Flacourtiaceae was, as Hermann Sleumer said, a fiction, [12] [13] and Peridiscus was, from the outset, one of its most doubtful members. [5] [7] Recognizing its distinctiveness, João Kuhlmann segregated it into its own family in 1947. [14]

In 1952, John Brenan named and described Medusandra, erecting a new family, Medusandraceae to accommodate it. [15] In 1953, Brenan transferred Soyauxia from Passifloraceae to Medusandraceae, [16] but few others agreed with his classification. In 1954, John Hutchinson and John McEwen Dalziel followed Brenan's treatment in the second edition of their Flora of West Tropical Africa. Hutchinson, however, soon recanted, explaining in some detail why he thought that Medusandra and Soyauxia were not related. [7]

In 1962, Noel Y. Sandwith named and described Whittonia. [17] In an accompanying article, Charles Russell Metcalfe discussed its close relationship to Peridiscus. For four decades thereafter, Peridiscaceae was viewed as a family of uncertain taxonomic position, containing two genera.

In the year 2000, a DNA sequence for the rbcL gene of Whittonia was produced and used in a molecular phylogenetic study of the eudicots. [18] This study placed Peridiscaceae in a clade with Elatinaceae and Malpighiaceae, a very surprising and unexpected result. On the basis of this phylogeny, the Angiosperm Phylogeny Group placed Peridiscaceae in Malpighiales when they published the APG II system of plant classification in 2003. [19] It was soon found that the rbcL sequence for Whittonia was a chimera, formed by DNA from unidentified plants that had contaminated the sample. [20] No subsequent attempt to extract DNA from Whittonia has been made.

In 2004, using DNA from Peridiscus, it was shown that Elatinaceae and Malpighiaceae are indeed sister families and that Peridiscaceae belong to Saxifragales. [20] Medusandra and Soyauxia, meanwhile, were listed in APG II in an appendix entitled "TAXA OF UNCERTAIN POSITION". [19]

DNA from Soyauxia was eventually obtained, and in 2007, it was shown that Soyauxia is most closely related to Peridiscus and, presumably, Whittonia. [21] Since this result has a good morphological basis, Soyauxia was duly transferred to Peridiscaceae. This study also found strong statistical support for the inclusion of Peridiscaceae in Saxifragales, but no strong support for any particular position within that order. [21]

In 2008, in a study employing a large amount of chloroplast DNA data, as well as some mitochondrial and nuclear DNA, it was shown that Peridiscaceae is sister to the rest of Saxifragales. [22]

It had been suspected that Medusandra might belong somewhere in Malpighiales, but a phylogeny of that order, generated in 2009, placed Medusandra in Saxifragales. The authors had included Medusandra and a few other members of Saxifragales in their outgroup, finding strong support for a clade of [Medusandra + (Soyauxia + Peridiscus)]. [3] When the APG III system was published in October 2009, Peridiscaceae was expanded to include Medusandra and Soyauxia. [1] John Brenan, 57 years before, had been prescient in his perception of a relationship between Medusandra and Soyauxia.

Phylogeny

The phylogeny is diagrammed as a phylogenetic tree below. The relationships shown are from Wurdack and Davis (2009) [3] except for the position of Whittonia, for which no DNA sequences are known. Peridiscus and Whittonia are undoubtedly sister taxa due to their many shared morphological characters.

Peridiscaceae 

Medusandra

Soyauxia

Peridiscus

Whittonia

Related Research Articles

<span class="mw-page-title-main">Malpighiales</span> Eudicot order of flowering plants

The Malpighiales comprise one of the largest orders of flowering plants, containing about 36 families and more than 16,000 species, about 7.8% of the eudicots. The order is very diverse, containing plants as different as the willow, violet, poinsettia, manchineel, rafflesia and coca plant, and are hard to recognize except with molecular phylogenetic evidence. It is not part of any of the classification systems based only on plant morphology. Molecular clock calculations estimate the origin of stem group Malpighiales at around 100 million years ago (Mya) and the origin of crown group Malpighiales at about 90 Mya.

<span class="mw-page-title-main">Rosales</span> Order of flowering plants

Rosales is an order of flowering plants. It is sister to a clade consisting of Fagales and Cucurbitales. It contains about 7,700 species, distributed into about 260 genera. Rosales comprise nine families, the type family being the rose family, Rosaceae. The largest of these families are Rosaceae (90/2500) and Urticaceae (54/2600). The order Rosales is divided into three clades that have never been assigned a taxonomic rank. The basal clade consists of the family Rosaceae; another clade consists of four families, including Rhamnaceae; and the third clade consists of the four urticalean families.

<span class="mw-page-title-main">Saxifragales</span> Order of Eudicot flowering plants in the Superrosid clade

The Saxifragales (saxifrages) are an order of flowering plants (Angiosperms). They are an extremely diverse group of plants which include trees, shrubs, perennial herbs, succulent and aquatic plants. The degree of diversity in terms of vegetative and floral features makes it difficult to define common features that unify the order.

<span class="mw-page-title-main">Santalales</span> Order of flowering plants

The Santalales are an order of flowering plants with a cosmopolitan distribution, but heavily concentrated in tropical and subtropical regions. It derives its name from its type genus Santalum (sandalwood). Mistletoe is the common name for a number of parasitic plants within the order.

<span class="mw-page-title-main">Celastrales</span> Order of flowering plants, mostly from tropics and subtropics

The Celastrales are an order of flowering plants found throughout the tropics and subtropics, with only a few species extending far into the temperate regions. The 1200 to 1350 species are in about 100 genera. All but seven of these genera are in the large family Celastraceae. Until recently, the composition of the order and its division into families varied greatly from one author to another.

<span class="mw-page-title-main">Hamamelidaceae</span> Witch-hazel, a shrub or small tree

Hamamelidaceae, commonly referred to as the witch-hazel family, is a family of flowering plants in the order Saxifragales. The clade consists of shrubs and small trees positioned within the woody clade of the core Saxifragales. An earlier system, the Cronquist system, recognized Hamamelidaceae in the Hamamelidales order.

<span class="mw-page-title-main">Violales</span> Order of eudicot flowering plants

Violales is a botanical name of an order of flowering plants and takes its name from the included family Violaceae; it was proposed by Lindley (1853). The name has been used in several systems, although some systems used the name Parietales for similar groupings. In the 1981 version of the influential Cronquist system, order Violales was placed in subclass Dilleniidae with a circumscription consisting of the families listed below. Some classifications such as that of Dahlgren placed the Violales in the superorder Violiflorae.

<span class="mw-page-title-main">Flacourtiaceae</span> Family of flowering plants

The Flacourtiaceae is a defunct family of flowering plants whose former members have been scattered to various families, mostly to the Achariaceae and Salicaceae. It was so vaguely defined that hardly anything seemed out of place there and it became a dumping ground for odd and anomalous genera, gradually making the family even more heterogeneous. In 1975, Hermann Sleumer noted that "Flacourtiaceae as a family is a fiction; only the tribes are homogeneous."

<span class="mw-page-title-main">Angiosperm Phylogeny Group</span> Collaborative research group for the classification of flowering plants

The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botanists who collaborate to establish a consensus on the taxonomy of flowering plants (angiosperms) that reflects new knowledge about plant relationships discovered through phylogenetic studies.

<span class="mw-page-title-main">Saxifragaceae</span> Family of flowering plants in the Eudicot order Saxifragales

Saxifragaceae is a family of herbaceous perennial flowering plants, within the core eudicot order Saxifragales. The taxonomy of the family has been greatly revised and the scope much reduced in the era of molecular phylogenetic analysis. The family is divided into ten clades, with about 640 known species in about 35 accepted genera. About half of these consist of a single species, but about 400 of the species are in the type genus Saxifraga. The family is predominantly distributed in the northern hemisphere, but also in the Andes in South America.

<span class="mw-page-title-main">Achariaceae</span> Family of flowering plants

Achariaceae is a family of flowering plants consisting of 32-33 genera with about 155 species of tropical herbs, shrubs, and trees. The APG IV system has greatly expanded the scope of the family by including many genera previously classified in Flacourtiaceae. Molecular data strongly support the inclusion of this family in the order Malpighiales.

<span class="mw-page-title-main">Elatinaceae</span> Family of flowering plants

Elatinaceae is a family of flowering plants with ca 35 species in two genera: Elatine and Bergia. The Elatine are mostly aquatic herbs, and the Bergia are subshrubs to shrubs. Elatine species are widely distributed throughout the world from temperate to tropical zones, with its greatest diversity found in temperate zones. Bergia is found in temperate to tropical Eurasia and Africa, with two tropical and one tropical to temperate species in the Americas. The center for biodiversity of Bergia is the Old World tropics, and this is also the center for biodiversity for the family. Neither genus is found in arctic ecosystems.

<span class="mw-page-title-main">Rafflesiaceae</span> Family of flowering plants

The Rafflesiaceae are a family of rare parasitic plants comprising 36 species in 3 genera found in the tropical forests of east and southeast Asia, including Rafflesia arnoldii, which has the largest flowers of all plants. The plants are endoparasites of vines in the genus Tetrastigma (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.

<span class="mw-page-title-main">Huerteales</span> Order of flowering plants

Huerteales is the botanical name for an order of flowering plants. It is one of the 17 orders that make up the large eudicot group known as the rosids in the APG III system of plant classification. Within the rosids, it is one of the orders in Malvidae, a group formerly known as eurosids II and now known informally as the malvids. This is true whether Malvidae is circumscribed broadly to include eight orders as in APG III, or more narrowly to include only four orders. Huerteales consists of four small families, Petenaeaceae, Gerrardinaceae, Tapisciaceae, and Dipentodontaceae.

<i>Medusandra</i> Genus of flowering plants

Medusandra is a genus of flowering plants in the family Peridiscaceae. It has two species, Medusandra richardsiana and Medusandra mpomiana. M. richardsiana is the most common and well known. Both species are native to Cameroon and adjacent countries.

Soyauxia is a genus of flowering plants in the family Peridiscaceae. They are small trees or erect shrubs from wet forests of tropical West Africa. Eight specific names have been published in Soyauxia. Additional species have been discovered, but their names and descriptions will not be published until 2009 or 2010. The type species for the genus is Soyauxia gabonensis.

<span class="mw-page-title-main">Lepidobotryaceae</span> Family of flowering plants

Lepidobotryaceae is a family of plants in the order Celastrales. It contains only two species: Lepidobotrys staudtii and Ruptiliocarpon caracolito.

Lepuropetalon is a genus of flowering plants in the family Celastraceae. Before it was placed in the family when it was defined by the Angiosperm Phylogeny Group's APG III system in 2009, it had been placed with Parnassia in the family Parnassiaceae, now usually treated as a segregate of Celastraceae. When their most recent revision of Angiosperm classification was published in 2016, it retained its position in the family Celastraceae. Lepuropetalon has only one species, Lepuropetalon spathulatum. It is a winter annual that is most abundant in eastern Texas and western Louisiana. From there, it occurs sporadically southward into Mexico, and eastward through the Atlantic and Gulf coastal plain, and rarely in the Piedmont Plateau, to North Carolina. It has a disjunct distribution. In addition to the area mentioned above, it is also found in Uruguay and central Chile.

When the APG II system of plant classification was published in April 2003, fifteen genera and three families were placed incertae sedis in the angiosperms, and were listed in a section of the appendix entitled "Taxa of uncertain position".

<span class="mw-page-title-main">Pentapetalae</span> Group of eudicots known as core eudicots

In phylogenetic nomenclature, the Pentapetalae are a large group of eudicots that were informally referred to as the "core eudicots" in some papers on angiosperm phylogenetics. They comprise an extremely large and diverse group that accounting about 65% of the species richness of the angiosperms, with wide variability in habit, morphology, chemistry, geographic distribution, and other attributes. Classical systematics, based solely on morphological information, was not able to recognize this group. In fact, the circumscription of the Pentapetalae as a clade is based on strong evidence obtained from DNA molecular analysis data.

References

  1. 1 2 Angiosperm Phylogeny Group (2009). "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III" (PDF). Botanical Journal of the Linnean Society. 161 (2): 105–121. doi: 10.1111/j.1095-8339.2009.00996.x . Retrieved 2013-07-06.
  2. ↑ Peter F. Stevens. 2001 onwards. "Peridiscaceae". At: Angiosperm Phylogeny Website At: Missouri Botanical Garden Website. (see External links below).
  3. 1 2 3 4 5 Kenneth J. Wurdack and Charles C. Davis. 2009. "Malpighiales phylogenetics: Gaining ground on one of the most recalcitrant clades in the angiosperm tree of life." American Journal of Botany96(8):1551-1570.
  4. ↑ Christenhusz, M. J. M. & Byng, J. W. (2016). "The number of known plants species in the world and its annual increase". Phytotaxa. 261 (3): 201–217. doi: 10.11646/phytotaxa.261.3.1 .
  5. 1 2 3 Clemens Bayer. 2007. "Peridiscaceae" pages 297-300. In: Klaus Kubitski (editor). The Families and Genera of Vascular Plants volume IX. Springer-Verlag: Berlin;Heidelberg, Germany. ISBN   978-3-540-32214-6
  6. ↑ Vernon H. Heywood, Richard K. Brummitt, Ole Seberg, and Alastair Culham. Flowering Plant Families of the World. Firefly Books: Ontario, Canada. (2007). ISBN   1-55407-206-9
  7. 1 2 3 John Hutchinson. The Families of Flowering Plants, Third Edition (1973). Oxford University Press: London.
  8. ↑ George Bentham and Joseph Dalton Hooker. 1862. Genera Plantarum volume 1, part 1, page 127. A. Black, William Pamplin, Lovell Reeve & Co., Williams & Norgate: London, England. (see External links below).
  9. ↑ Umberto Quattrocchi. 2000. CRC World Dictionary of Plant Names. volume III, page 2010. CRC Press: Baton Rouge, New York, London, Washington DC. ISBN   978-0-8493-2673-8. (see External links below)
  10. 1 2 Joseph Dalton Hooker. 1880. Hooker's Icones Plantarum volume XIV (volume IV of the third series):page 73 and plate 1393. (see External links below).
  11. ↑ Umberto Quattrocchi. 2000. CRC World Dictionary of Plant Names. volume IV, page 2521. CRC Press: Baton Rouge, New York, London, Washington DC. ISBN   978-0-8493-2677-6.
  12. ↑ Regis B. Miller (1975). "Systematic anatomy of the xylem and comments on the relationships of Flacourtiaceae". Journal of the Arnold Arboretum56(1):79.
  13. ↑ Mark W. Chase, Sue Zmarzty, M. Dolores Lledó, Kenneth J. Wurdack, Susan M. Swensen, and Michael F. Fay. 2002. "When in doubt, put it in Flacourtiaceae: a molecular phylogenetic analysis based on plastid rbcL DNA sequences." Kew Bulletin57(1):141-181.
  14. ↑ João G. Kuhlmann. 1947. "Peridiscaceae (Kuhlmann)". Arquivos do Serviço Florestal 3(1):3-7.
  15. ↑ John P.M. Brenan. 1952. "Plants of the Cambridge Expedition, 1947-1948: II. A new order of flowering plants from the British Cameroons". Kew Bulletin7:227-236.
  16. ↑ John P.M. Brenan. 1953. "Soyauxia, a second genus of Medusandraceae". Kew Bulletin8:507-511.
  17. ↑ Noel Y. Sandwith. 1962. "Contributions to the flora of tropical America: LXIX. A new genus of Peridiscaceae". Kew Bulletin15:467-471.
  18. ↑ Vincent Savolainen, Michael F. Fay, Dirk C. Albach, Anders Backlund, Michelle van der Bank, Kenneth M. Cameron, S.A. Johnson, M. Dolores Lledo, Jean-Christophe Pintaud, Martyn P. Powell, Mary Clare Sheahan, Douglas E. Soltis, Pamela S. Soltis, Peter Weston, W. Mark Whitten, Kenneth J. Wurdack and Mark W. Chase. 2000. "Phylogeny of the eudicots: a nearly complete familial analysis based on rbcL gene sequences". Kew Bulletin55(2):257-309.
  19. 1 2 The Angiosperm Phylogeny Group. 2003. "An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG II". Botanical Journal of the Linnean Society141(4):399-436.
  20. 1 2 Davis, C. C. & Chase, M. W. (2004). "Elatinaceae are sister to Malpighiaceae; Peridiscaceae belong to Saxifragales". American Journal of Botany. 91 (2): 262–273. doi: 10.3732/ajb.91.2.262 . hdl: 2027.42/141309 . PMID   21653382.
  21. 1 2 Soltis 2007.
  22. ↑ Shuguang Jian, Pamela S. Soltis, Matthew A. Gitzendanner, Michael J. Moore, Ruiqi Li, Tory A. Hendry, Yin-Long Qiu, Amit Dhingra, Charles D. Bell, and Douglas E. Soltis. 2008. "Resolving an Ancient, Rapid Radiation in Saxifragales". Systematic Biology57(1):38-57.

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