Facts
This page gives more detailed information on the Melastomataceae than the Melastomataceae HomePage. A family description, the distribution, and some notes on the classification are provided.
Description
The Melastomataceae are herbs, shrubs, trees, or climbers and epiphytes, ranging in heigth from 10 cm to 30-50 m. The leaves are normally decussate and simple, with a characteristic acrodromous venation (except most species of the Memecyloideae). Anisophylly is common in some groups. Inflorescences are typically determinate thyrsoid ramification systems (often cymes), or rarely single flowers. Flowers are 3- to 5-merous, but varies often even in single plants. They have normally two whorls of stamens or staminodes which are arranged in lateralsymmetry. The stamens open with 1 or 2 apical pores, or with an apical slit, and their connectives typically have appendages and/or are prolonged. The placentation is normally axillary, but sometimes laterally or basally. The fruits are berries or capsules of various types.
Distribution
The family can be found pantropically and subtropically, with only the genus Rhexia occuring in temperate regions (southeastern and eastern USA). The Americas have the highest number of species, about 3000, concentrated in northern South America (Venezuela, Ecuador, northwestern Brazil). Tropical West and East Africa harbours only c. 250 species, and Madagascar 250. The remaining species, about 1000, occur in Asia, Oceania, and northern Australia, with a concentration in central Malesia (Borneo).
Habitats are mainly Tropical Rainforests, but also swamps, riverbanks, and savannas. Several species are weeds occurring in disturbed places.
Classification
The family was established in 1789 by the French botanist Jussieu, but the first species were described by Linné (1753). Earlier descriptions are not valid according to the ICBN. Important contributions to a classification were made by De Candolle (1828), Triana (1871), and Cogniaux (1891). More recent workers are Vliet et al. (1981), and Renner (1993).
Recent molecular studies by Clausing and Renner (in press) showed that Melastomataceae and Memecylaceae have to be united, although the exact relationships remain unclear. Several traditional recognized tribes appeared to be polyphyletic (e.g. Miconieae), whereas other large groups could be confirmed (e.g. Melastomeae). Within the family, acrodromal venation evolved basally after the separation of Memecyloideae and Pternandra. In contrast, pedoconnectives and cochleate seeds evolved apically in Microlicieae+Melastomeae and Melastomeae, respectively.