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The Primulaceae ( ), commonly known as the primrose family (but not related to the Onagraceae), are a family of Herbaceous plant and woody including some favourite garden plants and wildflowers. Most are Perennial plant though some species, such as scarlet pimpernel, are annual plant.
Previously one of three families in the order Primulales, it underwent considerable genus re-alignment once molecular phylogenetic methods were used for taxonomic classification. The order was then submerged in a much enlarged order Ericales and became a greatly enlarged Primulaceae sensu lato ( s.l). In this new classification of the Angiosperm Phylogeny Group, each of the Primulales families was reduced to the rank of subfamily of Primulaceae s.l. The original Primulaceae (Primulaceae sensu stricto or s.s.) then became subfamily Primuloideae, and one genus ( Maesa) was raised to the rank of a separate subfamily, making four in all.
The sepal has 4 to 9 lobes and persists after flowering. They are grouped in unbranched, indeterminate clusters such as racemes, spikes, corymbs or umbels.
Linnaeus (1753) placed Primula and related primuloid genera in the Hexandria Monogynia (six stamens one pistil) in his sexual classification based on reproductive characteristics. Jussieu arranged Linnaeus' genera in a Taxonomic rank based on the relative value of a much wider range of characteristics. In his Genera plantarum (1789) he organised the primuloid genera into two Ordo (families), within a class (VIII) he called Dicotyledones Monopetalae Corolla Hypogyna, based on the cotyledons (two), form of the petals (fused), and position of the corolla with respect to the ovary (below). Jussieu's families were the Lysimachiae, including Primula and Theophrasta and the Sapotae, including Myrsine, these being the three main lineages in modern understanding.
The most complete treatment of the Primulaceae family, with nearly 1,000 species arranged into 22 genera, was by Pax and Knuth in 1905 in the Engler system. They divided the family into five tribes (and several subtribes); Androsaceae, Cyclamineae, Lysimachieae, Samoleae and Corideae. Many systems since have lacked consistency, but generally recognised two major groups as either tribes or subfamilies, the Lysimachieae and Primuleae (the Androsaceae of Pax and Knuth), with the largest genera being Primula, Lysimachia and Androsace. In the Cronquist system (1988), Arthur Cronquist included the three closely related families, Primulaceae, Myrsinaceae and Theophrastaceae in the order Primulales, of subclass Dilleniidae, based on plant morphology characteristics, in particular, ovaries with free-central placentation, a feature considered synapomorphic. His circumscription of Primulaceae included about 800 species.
In the first consensus taxonomic classification, the Angiosperm Phylogeny Group (APG 1998), these proposals were recognised by including Primulaceae within Ericales, as Eudicots, forming one of three clades in the Asterids (Asteridae). Maesa was formally segregated in 2000. Further changes came from analysis of DNA sequence data. This led to the move of genera (primarily terrestrial non-basal-rosette) from Primulaceae to Mysinaceae and Theophrastaceae. At that time Primulaceae was considered to consist of nine tribes (Primuleae, Androsaceae, Ardisiandreae, Lysimachieae, Glauceae, Anagallideae, Corideae, Cyclamineae, and Samoleae). Notably, Lysimachieae and three smaller tribes, Corideae, Cyclamineae and Ardisiandreae, were transferred to Myrsinaceae, and Samoleae to Theophrastaceae. This enlarged Myrsinaceae is distinguished as Myrsinaceae s.l. in comparison to the previous smaller family, Myrsinaceae s.s. (less Maesa). Some authors preferred to raise Samoleae to its own family, Samolaceae, but this has not been accepted by subsequent authors, placing it within Theophrastaceae, while recognising its distinct position within that grouping. These transfers, to preserve monophyly at the family level essentially left two tribes remaining in Primulaceae, the Primuleae and Androsaceae, with about 15 genera sharing a number of common characteristics. These additional changes were reflected in the 2003 revision of the APG system (APG II), where the now four primuloid families were among 23 in Ericales. This restricted Primulaceae sensu stricto ( s.s.) consisted of three groups: The Primulae, including Primula, the largest genus; the Androsaceae, including Androsace, the second largest genus; together with a small third group containing Soldanella, Hottonia, Omphalogramma and Bryocarpum.
The APG third classification system (APG III, 2009) discussed all the taxonomic challenges arising from the phylogenetic studies, and placed all primuloid genera into one large Primulaceae s.l., corresponding to Cronquist's Primulales. They stated that "The biggest problem for APG III was the question of how to treat Primulaceae and their immediate relatives, a closely related group that in the past has often been recognized as a separate order". The decision to treat all genera as a single family was based on the observation that the new circumscriptions had little in the way of apomorphies, but the entire group had numerous synapomorphies and were easy to recognise. This resulted in an Ericales with 22 families. Consequently, the four primuloid families were reduced to the rank of subfamilies within Primulaceae s.l.
The primuloids probably originated in a shared Neotropical/Indo-Malaysian ancestral range, with the Primulaceae/Ebenaceae clade occupying the neotropics. Theophrastoideae is nearly all neotropical with a more recent migration out of the realm found in the aquatic Samolus genus. The divergence between Theophrastoideae and Primuloideae-Myrsinoideae at 70 mya represents a vicariant event between the Neotropics and the Palearctic realm in the case of the latter. The Primuloideae originating in the Palearctic, persisted till the last 16 mya, when it started to shift into the Nearctic.
Christenhusz et al. (2016, 2017) list 53 genus and 2,790 species, varying from 1 in Maesoideae to 38 in Myrsinoideae, with 8 in Theophrastoideae and the remaining 6 in Primuloideae. Byng (2014) and Plants of the World Online list 55 accepted genera. The generic limits of Myrsinoideae are not fully resolved and the status of a number of genera is under revision.
| alt=Flowers and leaves of Maesa lanceolata]] | Maesoideae (A. DC.) A. DC. Once included in the Primulaceae tribe Samoleae, it has most commonly been considered as part of family Myrsinaceae, till segregated into its own family and then submerged as a Primulaceae s.l. subfamily. It has characteristics that distinguish it from Myrsinaceae and forms the basal group of the clade as sister to all other subfamilies. |
| alt=Flowers and leaves of Myrsine africana]] | Myrsinoideae Burnett
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| alt=Flowers of Primula veris]] |
Primuloideae Burnett Subdivision has included the tribes Androsaceae and Primulae. Takhtajan (1997) gives the four genera of Androsaceae as Androsace (including Douglasia), Vitaliana, Stimpsonia and Pomatosace, and the ten genera of Primulae as Omphalogramma, Bryocarpum, Primula, Dionysia, Cortusa, Kauffmannia, Hottonia, Srediskya, Dodecatheon and Soldanella. In contrast Kallersjo et al. (2000) place all genera in Primulae, and list thirteen in all: Androsace, Douglasia, Omphalogramma, Soldanella, Dodecatheon, Cortusa, Primula, Dionysia, Vitaliana, Hottonia, Bryocarpum, and Pomatosace. These two (or one) tribes represent the remaining genera in Primuloideae (Primulaceae s.s.) following redistribution among the Primulales on molecular grounds. The 600 species mainly belong to Androsace and Primula and belong to the mountainous regions of Europe and Asia (mainly China).
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| alt=Specimen of Theophrasta jussieui]] |
Theophrastoideae A. DC.
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