Theophrastaceae

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.

Description

The two subclades or tribes of Theophrastoideae, Theophrasteae (Theophrastaceae ''s.s.'') and Samoleae, share only the presence of staminodes. The species of ''Samolus'' are herbaceous perennials and characterised by perigynous flowers. The remaining genera (Theophrastaceae ''s.s.'') are generally evergreen shrubs or small trees, with hypogynous flowers.

Taxonomy

History

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. 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). Jussieu's families were the Lysimachiae, including ''Primula'' and ''Theophrasta'' and the Sapotae, including ''Myrsine'', these being the three main lineages in modern understanding of the Primulaceae.

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. 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.

Theophrastaceae were included in the order Primulales by Cronquist (1988). 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), 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.

Phylogeny

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.

Subdivision

The phylogenetic relationships of the 8 accepted genera are shown in the cladogram, in which ''Samolus'' forms the basal group and is sister to all other Theophrastoideae (Theophrastaceae ''s.s.''), the remaining genera forming two subclades. Alternatively these two subclasses have been designated as two tribes, Samoleae and Theophrasteae:

The Theophrasteae consist of seven genera and about 100 species, while Samoleae has only the single genus ''Samolus'', with about 12–15 dozen species. In 1903, Theophrastaceae consisted of four genera, ''Clavija'', ''Jacquinia'', '' Deherainia'', and ''Theophrasta''. In 1904, a species of ''Deherainia'' was segregated to form the novel genus '' Neomezia'', to create five genera and in 1993 a species of ''Jacquinia'' was segregated to form a sixth genus, '' Votschia''. Molecular phylogenetic analyses revealed that ''Jacquinia'' was still paraphyletic consisting of two separate and distinct clades, necessitating splitting off another new genus, '' Bonellia'', to make seven genera in total in this tribe.

Etymology

Theophrastoideae takes its name from the nominative and type genus, Theophrasta, named by Linnaeus after the Ancient Greek philosopher and biologist Theophrastus.

Botanical authority

The botanical authority for the previous family, Theophrastaceae, belongs to David Don (D.Don) for his first description of the family in 1835. The subsequently submerged subfamily bears the authority of Alphonse de Candolle (A.DC.) for his formal conspectus of Theophrastaceae in 1844. The authority for the tribe Theophrasteae is that of Bartling who used the term Theophrastea to describe a grouping of genera, including Theophrasta within the family Ardisiaceae in 1830. This represents the earliest creation of a suprageneric taxon for these genera. The Ardisiaceae were later included in the other primuloid family, Myrsinaceae (Myrsinoideae).

Distribution and habitat

Distribution

The species of Theophrasteae are largely neotropical, confined to Mesoamerica, Central and South America and the Caribbean.

In contrast ''Samolus'' species are mainly restricted to different continents in the Southern Hemisphere with about 4–6 species restricted to North America. However the generic type, '' Samolus valerandi'' is near cosmopolitan in its distribution.

Habitat

Theophrastaceae ''s.s.'' are mainly found in lowland regions which have a seasonal, dry climate, and prefer coastal thickets, dry shrub vegetation, or dry deciduous or semideciduous forests. However a number of species of ''Clavija'' are found in low montane and lowland rain forests.

Unlike much of the traditional Theophrastoideae, ''Samolus'' is found in either flooded areas around rivers and lakes, or in salt marshes.

References

Bibliography

Books

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Samolus

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APG

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Websites

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External links

{{Authority control

Primulaceae
Asterid subfamilies
Taxa named by Alphonse Pyramus de Candolle