Ochnaceae is a family of flowering plants in the order Malpighiales. In the APG III system of classification of flowering plants, Ochnaceae is defined broadly, to include about 550 species, and encompasses what some taxonomists have treated as the separate families Medusagynaceae and Quiinaceae. but two works published after APG III have accepted the small families Medusagynaceae and Quiinaceae. These have not been accepted by APG IV (2016).
In this article, "Ochnaceae" will refer to the larger circumscription of the family, which is otherwise known as Ochnaceae sensu lato or as the ochnoids. In this sense the family includes 32 genera with about 550 species.
Ochnaceae, defined broadly or narrowly, is pantropical in distribution, with a few species cultivated outside of this range. Ochnaceae is most diverse in the Neotropics, with a second center of diversity in tropical Africa. In eight of the genera in tribe Sauvagesieae, the flower changes form after opening, by continued growth of tissue within the flower. Ochna thomasiana is probably the most commonly planted, but it is often misidentified in the horticultural literature.
The leaves of Cespedesia are sometimes to in length and are used for roofing. An herbal tea is made from the pantropical weed Sauvagesia erecta.
In its evolution, Ochnaceae has been unusual, in "reverting" to character states that are regarded as ancestral or primitive. For example, an actinomorphic floral symmetry has appeared twice in the subfamily Ochnoideae. Also, two clades of Ochnaceae, one in Ochnoideae and another in Quiinoideae have a derived condition very close to apocarpy. The complete separation of the carpels (apocarpy) is thought to be the ancestral state for angiosperms.
Fossils attributed to Ochnaceae are known from the early Eocene of Mississippi. The age of the family is very roughly estimated at 100 million years.
A great many genus names have been published in Ochnaceae. In a taxonomic revision of Ochnaceae, as three families, in 2014, only 32 of these genera were accepted; one in Medusagynaceae, four in Quiinaceae, and 27 in Ochnaceae s.s.
Genera
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The following list of 36 genera consists of Neckia, which was resurrected in 2014, Polythecanthum and Sinia, plus the 32 genera that were described in the most recent revision of Ochnaceae. The classification is from Schneider et alii (2014). In the APG III system, Strasburgeria is grouped with Ixerba to form the family Strasburgeriaceae in the rosid order Crossosomatales.
More rarely, the genus Diegodendron was thought to be close to Strasburgeria and Ochnaceae. Molecular phylogenetic studies have strongly supported the inclusion of Diegodendron in the rosid order Malvales, and it is sometimes treated as a monospecific family therein. Otherwise, it has been placed in Bixaceae, though there is reason to suspect that it might be closer to Sphaerosepalaceae. but Clusiaceae was divided in 2009
There are only a few morphological characters that unite the clusioids with Ochnaceae. The petal aestivation is often contort in the clusioids, and usually so in Ochnaceae. In both groups, the flowers usually bear numerous stamens, and in the ovary, the placentation is mostly axile. In the ovules, the nucellus is often thin, and the outer integument is usually thicker than the inner.
Taxonomy
Ochnaceae is divided into three subfamilies: Medusagynoideae, Quiinoideae, and Ochnoideae.
Medusagynoideae consists of a single species, Medusagyne oppositifolia. It is endemic to the island of Mahé in the Seychelles.
Quiinoideae comprises about 48 species in four genera: Froesia, Quiina, Touroulia, and Lacunaria. It is restricted to tropical America. Froesia is distinct from the other three genera. Its flowers are always bisexual, and the fruit consists of three structures that resemble follicles, except that they are not quite entirely separate from each other.
The subfamily Ochnoideae was revised in 2014 as Ochnaceae sensu stricto. Secondary apocarpy is especially rare and has arisen most notably in Rosaceae, Apocynaceae, Sapindales, and Malvales. At that time, he described Elvasia, a new genus in the family, and he included three others: Ochna, Walkera, and Gomphia. Walkera was described by Johann Christian Daniel von Schreber in 1789, but is no longer recognized. Its type species was described as Gomphia serrata by Andrias Kanis in 1968, but it is now placed in the genus Campylospermum. Gomphia has long been a source of confusion and it was not recognized in the most recent revision of Ochnaceae. He regarded Lauradia (Lavradia) as separate from Sauvagesia, and placed both of them in Violaceae. He added the genus Castela to Ochnaceae, but it is now part of Simaroubaceae. De Candolle believed that Simaroubaceae was closely related to Ochnaceae, but it is now placed in the order Sapindales. The group without endosperm corresponds to de Candolle's concept of Ochnaceae, and to the modern tribe Ochneae. The group with endosperm is now known to be paraphyletic and consists of the tribes Testuleeae, Luxemburgieae, and Sauvagesieae. In 1876, in a flora of Brazil, Engler described many new species in Ochnaceae, especially in its largest genus, Ouratea. He described 85 species in Ouratea, 17 of which he named as new species at that time. He also transferred 63 species to Ouratea from other genera.
The genera Quiina and Touroulia had been known since 1775, when they were described by Jean Baptiste Aublet, and they were variously classified by 19th century taxonomists. Jacques Denys Choisy erected the family Quiinaceae (as Quiinacées) for them in 1849, but he did not meet the requirements for valid publication of a botanical name. The name Quiinaceae was validated by Engler in Flora Brasiliensis in 1888.
The genus Medusagyne had been described by John Gilbert Baker in 1877, in a flora of Mauritius and the Seychelles, but it was not until 1924 that it was segregated into its own monogeneric family.
In 1893, Ernest Friedrich Gilg covered Ochnaceae, and Adolf Engler covered Quiinaceae for the first edition of Die Natürlichen Pflanzenfamilien. Engler wrote a description of Medusagyne in a supplement to the first edition of DNP in 1897. He placed Medusagyne under the heading "Zweifelhafte, möglicherweise zu den Guttiferae gehörige Gattung" (Doubtful, possibly a genus belonging to Guttiferae). Guttiferae is an obsolete name for Clusiaceae.
In 1902, Philippe van Tieghem recognized six families in what is now the subfamily Ochnoideae. These were Luxemburgiaceae, Sauvagesiaceae, Wallaceaceae, Euthemidaceae, Lophiraceae, and Ochnaceae. Three of these, (Wallaceaceae, Euthemidaceae, and Lophiraceae) were monogeneric and were erected by van Tieghem at that time. His Luxemburgiaceae included the basal clades of what is now the tribe Sauvagesieae. Van Tieghem named a great many genera in 1902, circumscribing them very narrowly. In what is now the subtribe Ochninae, he delineated 53 genera. The most recent revision of that group divides it into six genera.
In 1925, for the second edition of DNP, Engler and Gilg expanded on their treatment of Quiinaceae and Ochnaceae, respectively, compared to what they had written in 1893. Medusagynaceae was covered in the same volume of DNP by Adolf Engler and Hans Melchior.
For the second edition of DNP, Engler recognized two genera, Quiina and Touroulia, in Quiinaceae. Lacunaria and Froesia were discovered later and named in 1925 and 1948, respectively.
In that same volume, Gilg divided his Ochnaceae (equivalent to modern Ochnoideae) into 21 genera, including Indovethia, Leitgebia, Vausagesia, and Lauradia (as Lavradia), which are now regarded as synonyms of Sauvagesia. In that same year, Neckia, a 28th genus for Ochnoideae, was resurrected in a molecular phylogenetic study based on four chloroplast DNA loci, and nuclear ribosomal ITS.