Diversidade de Mimosa L. (Leguminosae) nos campos rupestres de Minas Gerais: taxonomia, distribuição geográfica e filogeografia

• Autor(a) principal: Dutra, Valquíria Ferreira
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/357
• topic: Leguminosae; Mimosa; Campos rupestres; Distribuição geográfica; Conservação; Minas Gerais; Leguminosae; Mimosa; Campos rupestres; Geographical distribution; Conservation; Minas Gerais; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

Campos rupestres (rocky field habitats) occur in the Espinhaço Range (MG and BA) and isolated floristic islands in Goiás, southwest and south of Minas Gerais, Pará, Rondônia, Roraima, São Paulo and Federal District. These fields show a combination of physical factors that associated with species adaptations to the environment and biotic evolution in response to climatic and geological history of the region leads to high biodiversity, which has drawn the attention of researchers to their conservation. Mimosa is one of the largest genera of Leguminosae and the best represented of Mimosoideae in the campos rupestres. Mimosa is characterized by bipinnate leaves, leaflets sessile, the 1st pair of each pinna commonly differentiated into paraphyllidia, flowers 3-5-6-merous, isostemonous or diplostemonous, filaments white, pinkish or yellow, free or short monadelphous, fruit craspedium or sacellus. Although the genus Mimosa is monophyletic, it has several problems of intraspecific delimitation. This work presents the diversity, patterns of geographical distribution, the conservation status of Mimosa species in campus rupestres of Minas Gerais (CRMG) and the phylogeography of M. radula. The studies were based on the examination of about 4000 specimens from 23 herbaria, field observations and collection of botanical material in Conservation Units of the Espinhaço Range and disjunct areas. The study provides descriptions, identification keys, illustrations and comments on the taxonomy, popular names, uses, geographical distribution and habitat preference of the species. IUCN criteria were used for determining the conservation status of each taxon. The trnD-trnT region of the chloroplast genome was used to investigate the phylogeographic structure of M.radula. In these fields, the genus is represented by 75 species. This number is 1.7 times greater than the reports found in the literature. Most species are included in the section Mimosa (31 spp), followed by section Habbasia (19 spp) and Batocaulon (15 spp). Calothamnos presents nine species and Mimadenia, a section with fewer representatives, only one. The most important taxonomic characteristics of the genus are the types of indument and armament, leaf characteristics (especially number of pinnae and leaflets), the calyx shape and indument and venation of corolla lobes. Were described 12 new species and made four synonymizations. The species have distribution in four macroregions: wide geographical distribution (1%), tropical America (3.1%), South America (12.4%) and restricted to Brazil (83.5%). In Brazil, seven distribution patterns were identified: widely distributed (1.2%), Central Brazil (12.4%), Meridional Brazil (1.2%), Southeast Brazil (7.4%), campos rupestres of Minas Gerais and Goiás (9.8%), endemic of Espinhaço Range (9.8%) and distribution restricted to campos rupestres of Minas Gerais (58.2%). Regarding the conservation status, 31.1% of the taxa were classified as "least concern", 9.3% as "near threatened", 21.6% as "vulnerable", 19.6% as "endangered", 14.4% as "critically endangered", and 3% as presumed extinct. The high rate of endemism of Mimosa in campos rupestres of Minas Gerais corroborates the importance of the genus in these habitats and surpasses the 30% estimated for their flora. The results show that 38 taxa should be included on the Red List of Threatened Species in Minas Gerais, in which the main threats to these taxa are the degradation or loss of their habitat. The phylogeographic analysis of 13 populations derived from four varieties of M. radula collected in Minas Gerais and Goiás identified 15 haplotypes. The haplotypes were not shared among varieties and a single network containing all the 15 haplotypes was obtained. The results emphasize the importance of studies on the Brazilian flora, at regional level, to define areas with high species diversity and to support programs of biodiversity conservation.