Lasianthus

Lasianthus is a genus of flowering plants in the family Rubiaceae. They are tropical subshrubs, shrubs, or rarely, small trees. They inhabit the understory of primary forests.

Lasianthus has about 180 species. The type species for the genus is Lasianthus cyanocarpus. ^[2] In 2012, a revision of Lasianthus in Malesia described 131 species.^[3] Another 30 or so species grow elsewhere in tropical Asia.^[4] Most of these are described in Flora of China^[5] or in A Revised Handbook to the Flora of Ceylon.^[6] 14 or 15 species are native to the Western Ghats of southwestern India, including the endemic Lasianthus agasthyamalayanus.^[7] Fifteen species^[8] or perhaps as many as 20 species^[9] are known from tropical Africa. Two species (Lasianthus panamensis and Lasianthus lanceolatus),^[10] or possibly three, are native to the neotropics.^[8] Lasianthus strigosus, from Queensland, is the only species known from Australia. The Australian Ixora baileyana had at one time been placed in Lasianthus as Lasianthus graciliflorus.^[11]

Dried specimens of Lasianthus often shed their flowers and fruit. For this reason, misidentification is common, even in herbaria.

The name Lasianthus has been misapplied to Lisianthius (also spelled as "Lisianthus" or "Lisyanthus"^[12]), a genus in Gentianaceae. Lasianthus alatus Aublet is a misspelling of Lisyanthus alatus Aublet, a species now placed in Chelonanthus.

Species

As of March 2023, Plants of the World Online accepted the following species:^[1]

Description

Subshrubs, shrubs, or rarely, small trees. - Leaves opposite, distichous. Stipules interpetiolar, usually persistent. - Inflorescences axillary, usually sessile. Flowers small, white. - Calyx with 3 to 6 teeth or lobes; persistent. Corolla with 4 to 6 lobes; throat usually villous. - Stamens 4 to 6, inserted on corolla throat. Anthers dorsifixed. - Stigma with lanceolate or linear lobes. Ovary multilocular. - Ovules basal, erect, 1 per locule. - Fruit a small drupe, usually blue. Pyrenes with thick walls.

History

The generic name Lasianthus is derived from the Greek lasios, "shaggy, velvety, hairy", and anthos, "flower".^[13] The genus was named by William Jack in 1823.^[14][15]

Some authors have recognized Dressleriopsis and Litosanthes as genera separate from Lasianthus. Dressleriopsis was sunk into Lasianthus in 1982.^[10]

Litosanthes was erected by Carl Ludwig Blume in 1823. It was synonymized under Lasianthus in 1992.^[16] DNA sequence analysis has not resolved the question of whether Litosanthes is nested within Lasianthus or separate from it.

Affinities

Lasianthus, Saldinia, and Trichostachys form the tribe Lasiantheae in the subfamily Rubioideae. Perama is related to this group and might be included within it.^[17] Lasiantheae was formerly thought to be close to Psychotria, but is now known to be a basal clade in Rubioideae. It is sister to the large clade containing Coussarea, Psychotria, Spermacoce, and many other genera.^[18]

Saprosma and Amaracarpus were traditionally thought to be close to Lasianthus. Saprosma is polyphyletic, with only part of it related to Lasianthus.^[17] Amaracarpus is close to Psychotria. The African genera Batopedina and Dirichletia have also been suggested as relatives of Lasianthus.

Taxonomy

Only one molecular phylogenetic study has sampled more than a few species from the tribe Lasiantheae. In that study, 11 species of Lasianthus were sampled, but few relationships were resolved.^[17]

In 2012, a revision of the Malesian species divided Lasianthus into 3 sections, based on the following type species: L. section Stipulares (Lasianthus stipularis), L. section Lasianthus (Lasianthus cyanocarpus), and L. section Nudiflorae (Lasianthus blumeanus).^[3] They did not recognize L. section Pedunculatae (Lasianthus biermanii), which some previous authors had recognized. They considered it to be indistinguishable from L. section Lasianthus.

References