HOW RICH IS THE FLORA OF BRAZILIAN CERRADOS

An attempt is made to summarize what is known about the richness of the total terrestrial angiosperm flora of the "cerrados" (as a complex of formations) in Brazil, based on published surveys and species lists. A "refined" list of arboreal and shrubby species was compiled from a total of 145 individual lists from 78 localities, taking into account synonymy and recent taxonomic changes. The refined list had 1709 references to taxonomic entities at the species level (973 identified with confidence and 31 with aff or cf.), 572 references to generic entities (363 genera identified with confidence), and 210 references to the family level (88 families identified with confidence). There are many unidentified arboreal and shrubby taxa at the specific, generic, and family levels, indicating that a considerable amount of taxonomic research remains to be done on the cerrado flora, and that this flora may be much richer than is generally assumed. Depending on the assumptions made, these data suggest a total of around 1000 to 2000 arboreal and shrubby species and 2000 to 5000 herbaceous ones, yielding estimates for the total cerrado flora (terrestrial angiosperms) ranging from 3000 to 7000 species. These limits, especially the upper one, are dubious, but give an idea of the magnitude of the angiosperm flora in the Brazilian cerrados. Surveys of cerrados are very unevenly distributed, and studies of relatively unknown sites may reveal much more diversity than that presently known. On reading accounts of floristic studies on cerrados in Brazil, one rapidly comes to realize that the majority of authors, either implicitly or explicitly, consider the cerrado flora to be well known and to have low richness. For example, Rizzini (1963, 1971) estimated around 600 species and a little over 200 genera for the whole cerrado arboreal and shrubby flora, but Heringer et al. (1977) cited 193 arboreal and shrubby species and confirmed less than 150 genera. Even recent studies (e.g., Leitao Filho, 1992; Ratter et al., 1997) have estimated the number of arboreal-shrubby species for the cerrados as being around 800. Eiten (1990) has been one of the few authors to suggest that the thickstemmed arboreal-shrubby flora contains more than 1000 species and that the denser physiognomies may reach more than 150 arboreal and shrubby species per hectare. Castro (1994; see Ratter et al., 1997) made an extensive survey of the literature in order to gather support for the idea that the arboreal and shrubby flora of the Brazilian cerrados is much richer than previously assumed. It could be argued that as the cerrados consist of physiognomies that are predominantly grasslands, the greatest floristic richness should be encountered in the non-woody (herbaceous-subshrubby) component of the vegetation. Surveys of this component have been rare in Brazil (Mantovani & Martins, 1993). Comparing the non-woody component in different localities in Brazil, Mantovani (1983) found a local richness that varied between 165 species in the Serra Dourada (state of Goias) and 640 in the municipality of Lagoa Santa (state of Minas Gerais). In an area of 343.42 ha of a cerrado in the Reserva Biologica de Moji GuaGu (state of Sao Paulo), Mantovani and Martins (1993) found 403 species of non-woody angiosperms. The herbaceous-subshrubby angiosperm flora of the cerrados therefore appears to be richer than the arboreal-shrubby flora, but its richness varies with physiognomy (Mantovani, 1987). It can also be argued that the maximum physiognomic and floristic expression, together with maximum spatial continuity, should occur in the "nuclear" (Labouriau, 1966), "central" (Rizzini, 1963), or "core" (Eiten, 1972; Ferri, 1977a) areas. An implication of this reasoning is that marginal and disjunct areas (Ratter et al., 1988a) should have a relatively impoverished flora in comparison to the nuclear area, although they may be supplemented by floristic elements from the surrounding vegetation formations (Eiten, 1972; Fernandes & Bezerra, 1990; Rizzini, 1963). These elements, which occur preferentially in other formations and I Research was developed in the Curso de Pos-Graduaca-o em Biologia Vegetal, Instituto de Biologia, Universidade Estadual de Campinas, Brazil. We thank Esmeralda Zancheta Borges for preparation of the map in Figure 1. 2 Departamento de Biologia, Centro de Ciencias da Natureza, Universidade Federal do Piauf, Campus da Ininga, Teresina 64049-550, PI, Brazil. 3Departamento de Botanica, Instituto de Biologia, Universidade Estadual de Campinas, Caixa Postal 6109, Campinas 13083-970, SP, Brazil. * To whom correspondence should be sent. ANN. MISSOURI BOT. GARD. 86: 192-224. 1999. This content downloaded from 143.106. 162.91 on Tue, 22 Oct 2013 06:17:21 AM All use subject to JSTOR Terms and Conditions Volume 86, Number 1 Castro et al. 193 1999 Flora of Brazilian Cerrados sporadically in cerrados, were called "accessory" species or elements by Rizzini (1963). Species that occur exclusively in cerrado formations, or show a marked preference for cerrados, were termed "characteristic" species ("especies peculiares ou proprias") by Rizzini (1963). He considered that only the woody species occurring in the "cerraddo" (forest physiognomy) could be designated characteristic species, that is, essentially the arboreal-shrubby species. However, because of a large number of accessory species (sensu Rizzini, 1963), marginal and disjunct cerrado areas generally show considerable floristic richness. Although this might suggest that cerrados in marginal or disjunct areas should gradually grade into other formations, they are usually fairly easily distinguished from other formations in the neighborhood by their physiognomy and floristic omposition, often with a number of common wellknown species. The fact that a species occurs, grows, and reproduces successfully in an area shows that it is adapted to the local conditions. It is possible to construct a continuum of species ranging from those restricted to very local areas within a single vegetation type to those that are very widespread and occur in several different formations. The distinction between "characteristic" and "accessory" species therefore seems rather artificial and debatable, lacking in ecological significance. The spatial and temporal abundance of the different species also cannot be ignored. While it might be argued that a species typical of other formations and occurring only sporadically in cerrados should be considered an accessory species (e.g., Ficus spp.), it is possible to find examples of species that occur with very low abundance but only in cerrado areas (such as Eugenia aurata), along with numerous intermediate situations (such as Copaifera langsdorffii or Vochysia tucanorum) in which species that are common in other formations also occur in some abundance in many cerrados. Once again, it is virtually impossible to find a clear distinction between "accessory" and "characteristic" species. Most floristic studies, moreover, do not include information on abundance, making it difficult to use