Pequenas plantas com grandes adaptações: briófitas em afloramentos rochosos ferruginosos em Minas Gerais, Brasil

Abstract

Ironstone outcrops or "Cangas", in Brazil, are located mainly in the Quadrilátero Ferrífero (QF) region of Minas Gerais (MG). They are recognized as having unique environmental traits, such as high variations in daily temperatures, high UV exposure, constant winds, impermeable soils with low water retention capacity, and especially their high levels of iron in the soil. This set of environmental characteristics favors the colonization of xelotolerant plants, as well as provide a high frequency of rare and / or endemic plant species. Unfortunately, however, these areas are heavily threatened by high mineral exploitation, deforestation and uncontrolled urbanization. Bryophytes are a group of plants present in the Cangas, very poorly understood and little studied. These plants have important roles in maintaining soil moisture and nutrient levels, facilitating the establishment of larger plants. In this way, the main goals of this study were 1) To investigate and characterize how bryophytes reproduce under the adverse conditions found in Cangas (Chapter I); 2) To describe the bryophyte communities associated with ironstone outcrops, and to evaluate the influence of environmental filtration at local and regional scales (Chapter II); And 3) To recognize the bryoflora present in the Cangas of the State Park of Serra do Rola-Moça (RM), relating the patterns of geographical distribution with reproductive traits of bryophytes (Chapter III). Thus, in the first chapter we recorded reproductive modes, asexual propagation structures, sexual systems, sexual expression, reproductive success and the sex ratio of bryophytes. We emphasize the role of important species of dioecious mosses, which contribute with abundant asexual propagules in the Cangas. In the second chapter, we characterize the bryophyte community in the Cangas, in terms of their different microhabitats / substrates, and levels of anthropogenic disturbance. We found that the Cangas harbor a high diversity of bryophytes when compared to rocky outcrops of another nature, although the composition of mosses and liverworts varies especially in response to anthropogenic disturbances. Finally, in the third chapter, we observed that the RM houses a large bryoflora (70 spp.). Most of the species presented a large geographical distribution in the Neotropics and in more than 10 Brazilian states. Possibly, species distribution patterns are justified by the effectiveness of dispersal and establishment of their diaspores. The data gathered in this study show the importance of continuing the conservation efforts of the natural areas with ironstone outcrops in the country. This study was a pioneer in filling important gaps in the knowledge of the bryophyte communities in Cangas, highlighting the importance of floristic surveys and species life history data for the conservation of taxa and the ecosystem as a whole.