Clerodendrum


Clerodendrum is a genus of flowering plants in the family Verbenaceae. Its common names include glorybower, bagflower and bleeding-heart. It is currently classified in the subfamily Ajugoideae, being one of several genera transferred from Verbenaceae to Lamiaceae in the 1990s, based on phylogenetic analysis of morphological and molecular data.
Estimates of the number of species in Clerodendrum vary widely, from about 150 to about 450. This is partly because about 30 species have been transferred to Rotheca, about 30 more to Volkameria, and 1 to Ovieda. The type species for the genus is Clerodendrum infortunatum. It is native to Sri Lanka and the Andaman Islands.
The genus is native to tropical and warm temperate regions of the world, with most of the species occurring in tropical Africa and southern Asia, but with a few in the tropical Americas and northern Australasia, and a few extending north into the temperate zone in eastern Asia.
They are shrubs, lianas, and small trees, usually growing to tall, with opposite or whorled leaves. C. floribundum can grow to tall. Clerodendrum fistulosum and Clerodendrum myrmecophila have hollow stems that are inhabited by ants. Clerodendrum trichotomum is a common ornamental in warmer parts of the world. Eight other species are also grown in the tropics for their abundant and attractive flowers. One of these, Clerodendrum macrostegium, suckers abundantly from the roots, often producing a thicket within a few years.
The following species are cultivated in the UK:
Clerodendrum species are used as food plants by the larvae of some Lepidoptera species including Endoclita malabaricus and Endoclita sericeus. Both butterflies and hummingbirds are often attracted to blooming clerodendrum.

Description

The following description is based on the one by Yuan and applies to only the monophyletic circumscription of Clerodendrum.
Clerodendrum is a genus of small trees, shrubs, lianas, and subherbaceous perennials. Leaves decussate or whorled, never spiny as in some close relatives.
Inflorescence usually terminal. Sepals usually connate, often colored, usually accrescent. Corolla red to yellow, pink, or white. Corolla tube 5-lobed, the lobes usually unequal.
Stamens 4, usually in 2 pairs of unequal length and projecting well beyond the mouth of the corolla.
Ovary incompletely 4-locular. Ovules 4. Style terminal on the ovary, bifid.
Fruit a drupe, usually with 4 grooves or lobes, 4-seeded.

Pollination

Clerodendrum and its relatives have an unusual pollination syndrome which avoids self-pollination. This mating system combines dichogamy and herkogamy.
The flowers are protandrous. When the flower opens, the stamens stand erect, parallel to the central axis of the flower, while the style bends over, holding the stigma beyond the rim of the corolla. After the pollen is shed, the stamens curl up or bend over, and the style straightens out, bringing the stigma to the center of the flower. Except for Aegiphila, which is heterostylous, this breeding strategy is shared by all members of the clade consisting of Kalaharia, Clerodendrum, Volkameria, Aegiphila, Ovieda, Tetraclea, and Amasonia.

History

Clerodendrum was named by Linnaeus in Species Plantarum in 1753. The name is derived from two Greek words, kleros, meaning "chance or fate" or "clergy", and dendron, "a tree". It refers to the considerable variation in reports of the usefulness of Clerodendrum in medicine, and also to the fact the trees were used for religious purposes in Asia.
Regional revisions of Clerodendrum have been done for local floras, but the last monograph of the entire genus was by John Isaac Briquet in 1895. He recognized about 90 species, defining the genus broadly to include species that others had placed in Rotheca, Volkameria, and Ovieda. His circumscription was followed by most authors for the next 100 years, even though it was widely believed to be problematic.
In 1997, phylogenetic analysis of DNA data showed that Clerodendrum, as then understood, was polyphyletic. This situation was remedied in 1998 with the revival of Rotheca. This taxonomic change was based on previous work and on a molecular phylogenetic study that was not published until the following year.
In 2004, a study of DNA sequences showed that the monospecific Australian genus Huxleya was embedded in a clade of Clerodendrum species that had formerly been placed in Volkameria. Huxleya was then sunk into synonymy with Clerodendrum. The 2004 study sampled Aegiphila, Tetraclea, and Amasonia, three New World genera of Ajugoideae that had not previously been sampled for DNA. The results of this study cast doubt, once again, upon the monophyly of Clerodendrum.
In 2010, a study of four chloroplast DNA intergenic spacers showed that part of Clerodendrum was closer to the New world genera than to other Clerodendrum, and that one species of Clerodendrum was nested within the clade of New World genera. The authors of this study resurrected the genus Volkameria and assigned to it about 30 species that had been in Clerodendrum. They also resurrected Ovieda as a monotypic genus consisting of Ovieda spinosa. Volkameria and Ovieda had been erected by Linnaeus in 1753. Modern cladistic analysis has largely vindicated his concepts of Clerodendrum and its relatives.

Traditional medicinal use

Clerodendrum glandulosum. Coleb leaf aqueous extract is traditionally used by people of North-East India to alleviate symptoms of diabetes, obesity and hypertension.
Among the Hmar and Zomi tribes in the North East India Anphui is also being used as a dish/curry.

Systematics

Clerodendrum is strongly supported as monophyletic in molecular phylogenetic analyses. It consists of two clades, each of which receives strong bootstrap support. One clade contains mostly African species. The other is mostly Asian. The African and Asian groups can not confidently be divided into sections without more extensive sampling of taxa in phylogenetic studies. The Madagascan species, in particular, are poorly studied.
It appears that the long, narrow corolla tube evolved only once in Clerodendrum, and appeared again, among its relatives, in Ovieda.

Species

Plants of the World Online currently includes: