Rhamnaceae in the Brazilian Semi-arid

Rita Baltazar de Lima & Ana Maria Giulietti

The Rhamnaceae is a family that comprises plants of a wide variety of habits: from herbs to trees and lianas, which occur in tropical and subtropical forests all over the world. Despite this high diversity of habit, the species in this family are easily recognizable, because they share certain floral characters, such as sepals with midrib prominent beneath, petals unguiculate , convolute, cucullate or conchiform, the stamens opposite the petals and the nectar disc involving the floral receptacle.

The Rhamnaceae in Brazil

Originally, given the name “Rhamneae”, the family was studied in 1861 by Reissek who wrote a thesis accounting for the tribes, genera and species which occurred in Brazil. The author identified 12 genera and 48 species of Rhamnaceae in the Brazilian flora, having proposed two new genera and 36 new species. Later, other taxa were proposed by Warming, Moore , Glaziou, Urban, Pilger, Mansfeld, Ducke, Suessenguth, Fróes, Rizzini and Grey-Wilson. Taxonomic reviews, including genera with a distribution in Brazil, were carried out in 1860 by Miers, and more recently by Johnston, Johnston & Johnston and Tortosa. Floristic studies for the family were also carried out by several contemporary authors. However, the most complete taxonomic study of the Rhamnaceae family in Brazil was carried out only in 2000, a century after Reissek’s work, by the senior author of the present paper .

In Brazil, the Rhamnaceae have a wide distribution, occurring from North to South, with the semi-arid region being one of the Brazilian centres of diversity of the family. Here, 20 species (seven of them endemic) have been recorded, included in eight genera: Alvimiantha, Colubrina, Crumenaria, Gouania, Reissekia, Rhamnidium, Rhamnus and Ziziphus, and occurring in various vegetation formations in the semi-arid region. Among the genera Ziziphus is certainly the one which is best known by local people, represented by Z. joazeiro, or the ‘juazeiro’ as it is popularly known by the ‘sertanejos’ , who highly prize this tree for its many uses in the region.

Economic Potential of the Rhamnaceae in the Brazilian Semi-arid

Although most species in this family have not yet had their economic potential properly recognized, many of its representatives are used as ornamental plants moreover for arborisation of gardens in town squares and for medicinal purposes, some being frequently used in popular medicine, in the manufacture of cosmetics, toothpaste and other antiseptic products. Some Rhamnaceae are also used for feeding goats, pigs and cattle during the dry season. Its wood is used in furniture and in the production of firewood and charcoal, while the stems of some liana species can be used in craftwork. The flowers of most species produce abundant nectar, important in honey production. Fruits, in some species, are sweet and have already been used in the production of sweets and jam. Pieces of bark of some species, locally known as ‘juazeiros’, are sold in local markets, as medicine for oral use in cases of gastritis and as an expectorant syrup, and also for topic use in cases of dandruff. However, some species do not form large populations, and as a result, conservation status is critical, often without having their economic potential investigated.

Before IMSEAR (Chapter 1), the diversity of Rhamnaceae for the Brazilian Semi-arid region was little known. No complete and reliable systematic study of the family had been carried out in the region and our knowledge about the species living there was minimal. Also, the lack of reliable bibliography resulted in many incorrect identifications, particularly due to the taxonomic problems involving a number of species, especially in genera such as Gouania and Ziziphus. The study carried out by the senior author has also gathered information on Rhamnaceae of the Semi-arid, which was previously fragmented and dispersed throughout the literature. Descriptions, illustrations, comments and maps, showing the geographical distribution of all species of Rhamnaceae in the Brazilian semi-arid region, have also now been made available (see model example of one species). As a result, we now have the means to identify all Rhamnaceae, likely to be found in the Caatinga Biome, at both generic and species level. The availability of such a body of information has contributed significantly to extending our knowledge of the family and to supporting research aimed at conservation of the Caatinga and the adequate use of its natural resources. Particularly in the case of the Rhamnaceae, researches have provided us with information on local uses of species. From this popular knowledge it will be possible to determine the chemical profile of those species selected for their possible economic potential, widening the options for local communities who wish to improve their incomes and their way of life.

In these ways, the knowledge gained by IMSEAR has helped to produce new perspectives in the search to minimize ecological and social problems in the Semi-arid region. Meanwhile, the publication of the ‘Serie Livros’ will make the results of floristic inventories, carried out in the region, available to a wider public, initiating other research opportunities, particularly those aimed at conservation, and providing the catalyst to adapt scientific knowledge for popular use, and promoting sustainable development for the region.

Lima , R.B. 2000. Rhamnaceae do Brasil. Ph.D. thesis. Universidade de São Paulo, São Paulo.

NT. People who live in the semi-arid region.