Theophrastoideae is a small subfamily of flowering plants in the family Primulaceae. It was formerly recognized as a separate family Theophrastaceae. As previously circumscribed, the family consisted of eight genera and 95 species of trees or shrubs, native to tropical regions of the Americas.
The two subclades or tribes of Theophrastoideae, Theophrasteae (Theophrastaceae s.s.) and Samoleae, share only the presence of staminodes. The species of Samolus are perennial, herbaceous or suffrutescent (shrubby) and characterised by perigynous flowers.[4] The remaining genera (Theophrastaceae s.s.) are generally evergreen shrubs or small trees, with hypogynous flowers.[5][6]
Linnaeus, in formally describing the genera, placed Theophrasta and related genera in a group he named Pentandria Monogynia (i.e 5 stamens, one pistil), his system being based on sexual characteristics.[7] Jussieu arranged Linnaeus' genera in a hierarchical system of ranks 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).[8] Jussieu's families were the Lysimachiae, including Primula and Theophrasta[9] and the Sapotae, including Myrsine, these being the three main lineages in modern understanding of the Primulaceae.[10]
Don described a family of Theophrasteaceae in 1836, with four genera, Theophrasta, Clavija, Jacquinia and Leonia, of which the latter was determined unrelated, and placed this family as closely related to Myrsineae and Sapoteae.[3] Later, De Candolle more formally described a family, Theophrastaceae, based on the genus Theophrasta, in 1844, with six genera, Theophrasta, Clavija, Jacquinia, Oncinus, Monotheca and Reptonia. The latter three are no longer considered related.[2]
Theophrastaceae were included in the order Primulales by Cronquist (1988).[11] The APG system (1998) submerged that order in an enlarged order Ericales (Ericales s.l.), a basal group in the asterids, where the families of Primulales formed a monophyletic primuloid clade. Subsequent molecular phylogenetic analysis showed that the genus Samolus (brook weeds),[4] with about 12–15 additional species and traditionally placed within Primulaceae, as tribe Samoleae, was more closely related to the Theophrastaceae and suggested its transfer. Briefly Samolus was considered a separate family, Samolaceae. The third revision of the APG, APG III (2009) realigned all the primuloid families within a greatly enlarged Primulaceae (Primulaceae s.l.), in which each of the existing families became a subfamily. The newly described Theophrastoideae included Samolus, vastly increasing the area of distribution.[12][13]
The cladogram below shows the infrafamilial phylogenetic relationships of Primulaceae, together with the subfamilial crown ages. Maesoideae forms the basal group, while Primuloideae and Myrsinoideae are in a sister group relationship.[14][15][16][17]