Violaceae is a
family of
flowering plants established in 1802, consisting of about 1000 species in about 25 genera. It takes its name from the
genusViola, the violets and
pansies.
Older classifications such as the
Cronquist system placed the Violaceae in an
order named after it, the
Violales or the
Parietales. However,
molecular phylogeny studies place the family in the
Malpighiales as reflected in the
Angiosperm Phylogeny Group (APG) classification, with 41 other families, where it is situated in the parietal
clade of 11 families. Most of the species are found in three large genera, Viola, Rinorea and Hybanthus. The other genera are largely
monotypic or oligotypic. The genera are grouped into four clades within the family. The species are largely tropical or subtropical but Viola has a number of species in
temperate regions. Many genera have a very restricted distribution.
Description
Though the best-known genus, Viola, is
herbaceous, most species are
shrubs,
lianas or small
trees. The simple
leaves are alternate or opposite, often with leafy stipules or the stipules are reduced in size. Some species have palmate or deeply dissected leaves. Many species are
acaulescent. The flower are solitary in
panicles. Some species have
cleistogamous flowers produced after or before the production of typical flowers with petals. Flowers are bisexual or unisexual (e.g. Melicytus),
actinomorphic but typically
zygomorphic with a
calyx of five sepals that are persistent after flowering. Corollae have five mostly unequal petals, and the anterior petal is larger and often spurred. Plants have five stamens with the abaxial stamen often spurred at the base. The gynoecium is a compound pistil of three united carpels with one
locule. Styles are simple, with the ovary superior and containing many ovules. The fruits are capsules split by way of three seams. Seeds have
endosperm.[3][4][5]
Taxonomy
That Viola, previously included by
Jussieu (1789) under
Cisti,[6] should have its own family was first proposed by
Ventenat in 1799,[7] and in 1803 placed the Viola species in a new genus, Ionidium which he described as "Famille des violettes."[8][4] However, in the meantime
Batsch established the Violaceae, as a suprageneric rank under the name of Violariae (1802), and as the first formal description, bears his name as the
botanical authority.[9] Batsch included eight
genera in this
family.[10] Although Violariae continued to be used by some authors, such as
Don (1831)[11] and
Bentham and Hooker (1862) (as Violarieae),[12] most authors, such as
Engler (1895),[13] adopted the alternative name Violaceae, proposed by
de Lamarck and
de Candolle in 1805,[14] and later by
Gingins (1823)[15] and
Saint-Hilaire (1824).[16] With the establishment of higher suprafamiliar orders, which he called "Alliances",
Lindley (1853) placed his Violaceae within the
Violales.[17]
The Violaceae are a medium-sized family with about 22–28
genera, and about 1,000–1,100
species. Most of the genera are
monotypic or
oligotypic, but the three genera Viola (about 600 species), Rinorea (about 250 species), and Hybanthus include 98% of the species with about half the species in Viola, and more than three-quarters of the remainder in the other two genera.[3][24][21][4]
Many attempts have been made at an intrafamilial classification, but these have largely been artificial, based on floral characteristics. Subdivisions were recognized almost immediately. Early classifications identified two major divisions, that were followed by most taxonomists;[15][17]
These also had
biogeographical correlation, with the latter being almost exclusively South American and African, and the former being distributed in Europe in addition to the Americas.[17] In contrast, Bentham and Hooker (and some others) divided Alsodeieae, giving three tribes;
Violeae. Strictly zygomorphic
Paypayroleae. Actinomorphic wth some zygomorphic features
Alsodeieae. Strictly actinomorphic
Melchior utilized a more complex classification with two subfamilies, tribes and subtribes to recognize the place of Leonia within the Violaceae;.[4]
The historical subdivisions shown here are those of the system of Hekking (1988), based largely on floral symmetry, petal aestivation and petal morphology. In this system, most genera occur in the Rinoreae and Violeae tribes.[25] Three
subfamilies have been recognized: the Violoideae, Leonioideae, and Fusispermoideae.[26][3]
Molecular phylogenetic studies have revealed that many of these divisions were not
monophyletic, partly due to
homoplasy. These studies demonstrate four major clades within the family.[3]
In Clade 1, Schweiggeria and Noisettia are monotypic and form a sister group to Viola. In addition to the major clades, there were a number of unplaced segregates.[3]
Etymology
The family derives its name from the nominative genus, Viola.
Distribution and habitat
The Violaceae have an overall
cosmopolitan distribution,[3] but are essentially tropical and subtropical, with the exception of the numerous Northern Hemisphere temperate species of Viola, the largest genus, which is also occurs at higher altitudes in its tropical and subtropical regions, where the shrub, tree and lianescent species are concentrated. In those regions, most representative genera are the mainly woody Rinorea and Hybanthus.[25] While Viola, Hybanthus, and Rinorea are widely distributed in both hemispheres, the remaining genera are relatively restricted in their distribution. Some are restricted to a single continent while others have a limited area involving just a single
archipelago.[4] About 70 species are found in Brazil.[25][27]