Botanical Journal of the Linnean Society, 2007, 153, 401–416. With 5 figures © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153, 401–416 401 Blackwell Publishing LtdOxford, UKBOJBotanical Journal of the Linnean Society0024-4074© 2007 The Linnean Society of London? 2007 1534 401416 Original Article VARIABILITY OF SYNGONANTHUS MUCUGENSIS (ERIOCAULACEAE) A. C. S. PEREIRA Et al . *Corresponding author. E-mail: borba@gmx.net Genetic and morphological variability of the endangered Syngonanthus mucugensis Giul. (Eriocaulaceae) from the Chapada Diamantina, Brazil: implications for conservation and taxonomy ANA CARINA S. PEREIRA 1 , EDUARDO L. BORBA 2 * and ANA MARIA GIULIETTI 1 1 Departamento de Ciências Biológicas, Laboratório de Sistemática Molecular de Plantas, Universidade Estadual de Feira de Santana, Rodovia BR 116, km 3, Feira de Santana, Bahia, 44031-460, Brazil 2 Departamento de Botânica, Laboratório de Sistemática, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenue Antônio Carlos, 6627, Pampulha, Belo Horizonte, Minas Gerais, 31270- 901, Brazil Received December 2005; accepted for publication October 2006 Allozymic and morphometric studies were carried out on ten populations of Syngonanthus mucugensis (Eriocaul- aceae), a species from north-eastern Brazil threatened by extinction. Genetic and morphological variability was low or moderately low in all populations, being lower in populations from Rio de Contas/Catolés (P L = 14.3–21.4, A = 1.1– 1.2, H e = 0.026–0.059, D2M = 26.893–33.157) than in those from Mucugê (P L = 28.6–35.7, A = 1.3–1.5, H e = 0.078– 0.164, D2M = 28.999–45.077). A high coefficient of endogamy (F is = 0.257) was found, which can be explained by the reproductive characteristics and distribution of the species. The values for genetic and morphological structuring (F st = 0.512 and A MRPP = 0.175, respectively) were high as a result of the differentiation between populations from the two areas. The mean genetic identity between populations from the two areas (0.812) was much lower than between populations from the same area (Mucugê, 0.980; Rio de Contas/Catolés, 0.997). These results indicate that we are dealing with two distinct taxa and, as a result of the nature of the morphological differences found, a new subspecies is described for the populations of the region of Rio de Contas and Catolés, Syngonanthus mucugensis ssp. riocontensis. Such conclusions raise important implications for the conservation of Syngonanthus mucugensis, and will be used in the drawing up of management plans for its conservation. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153, 401–416. ADDITIONAL KEYWORDS: allozyme – campo rupestre – endemism – morphometrics. INTRODUCTION The Espinhaço range is the principal mountain chain in eastern Brazil, extending for more than 1000 km from north to south, from the middle of Minas Gerais State to the central-north of Bahia state. It consists of two main regions: the Diamantina plateau in Minas Gerais and the Chapada Diamantina in Bahia. In these areas, the vegetation above an altitude of 900 m is known as ‘campo rupestre’, which is characterized by the occurrence of sandy and stony soils with her- baceous and shrubby vegetation in islands of outcrop- ping, usually quartzitic, rock. The campos rupestres are renowned for their species richness with many endemic elements, especially at the species level (Giulietti & Pirani, 1988; Giulietti, Pirani & Harley, 1997). As a result of the discontinuity between these mountain ranges, a large proportion of the species that occur there are found as disjunct populations. This disjunction has been cited as one of the main fac- tors in the differentiation of populations, leading to the high degree of endemism found in such areas (Giulietti & Pirani, 1988; Harley, 1988; Borba et al., 2001; Jesus et al., 2001). It has been estimated that 30% of the campo rupestre taxa are restricted to this