Lecantheae and/or Elatostemateae

Elatostema umbellatum var. majus, photographed by Michael Becker.

The Elatostemateae is a tribe of plants in the Urticaceae, the family that includes the nettles (Urticaceae in general have been looked at in an earlier post). Elatostemateae are mostly distinguished from other members of the Urticaceae by their generally tripartite perianth in the female flowers and their brush-like stigmas (Friis 1993). There seems to be some conflict over the appropriate name to call this group: Conn & Hadiah (2009) argued for the use of Elatostemateae, but many authors had previously called this group the Lecantheae. The argument hinges purely on a question of priority a bit too tedious to examine here.

Lecanthus peduncularis, photographed by Li-Chieh Pan.

The question may or may not be moot, anyway. Recent phylogenetic analyses of the Urticaceae have generally agreed that the Elatostemateae can be divided between two clades, one including the genus Elatostema and the other the genera Lecanthus and Pilea. The two groups are morphologically as well as molecularly distinguishable: species of Pilea and Lecanthus generally have opposite leaves, but in Elatostema one of each leaf pair has been greatly reduced (or lost) so that the leaves appear alternate. However, it is currently uncertain whether these two groups together form an exclusive clade. In the analyses by Hadiah et al. (2008), trnL-F sequence data was consistent with a monophyletic Elatostemateae, but rbcL data placed the Lecanthus-Pilea group closer to the tribe Urticeae than to Elatostema. This is not inherently unreasonable: as members of the Urticeae also have brush-like stigmas like those of Elatostemateae, the main distinction between the two tribes is the plesiomorphic absence in the latter of the stinging hairs that characterise the Urticeae.

Pilea fairchildiana, previously Sarcopilea domingensis, from Javier Francisco-Ortega.

Whether monophyletic or not, the Elatostemateae are mostly a tropical and subtropical group. They are mostly herbs and subshrubs, with a smaller number of shrub species. The centre of diversity is in the Old World; only the genus Pilea is found in the Americas. Members of the Elatostema group may be either all included in a single genus or divided between genera Elatostema, Procris and Pellionia distinguished by inflorescence characters. Pilea, the largest genus in the group, includes species in both the Old and New Worlds, of which some are commonly succulent. The Hispaniolan species Pilea fairchildiana has developed a rosulate growth form, remarkably similar to members of genera in the unrelated family Crassulaceae, such as Aeonium and Sempervivum. Until very recently, this species was considered distinctive enough to be placed in a separate genus Sarcopilea; Jestrow et al. (2012) demonstrated its more nested position. Economic usages of Lecantheae species are few: the leaves of some Pilea species, such as the artillery plants* P. microphylla and P. melastomoides, have some limited use as aromatic herbs, while some species of the Elatostema group are apparently used in Indonesia as shampoo.

*The name 'artillery plant' apparently refers to the way in while the male flowers fire forth their pollen, which is supposed to resemble gunsmoke.

REFERENCES

Conn, B. J., & J. T. Hadiah. 2008. Nomenclature of tribes within the Urticaceae. Kew Bulletin 64; 349-352.

Friis, I. 1993. Urticaceae. In: Kubitzki, K., J. G. Rohwer & V. Bittrich (eds) The Families and Genera of Vascular Plants vol. 2. Flowering Plants. Dicotyledons. Magnoliid, hamamelid and caryophylliid families pp. 612-629. Springer.

Hadiah, J. T., B. J. Conn & C. J. Quinn. 2008. Infra-familial phylogeny of Urticaceae, using chloroplast sequence data. Australian Systematic Botany 21: 375-385.

Jestrow, B., J. J. Valdés, F. Jiménez Rodríguez & J. Francisco-Ortega. 2012. Phylogenetic placement of the Dominican Republic endemic genus Sarcopilea (Urticaceae). Taxon 61 (3): 592-600.