COMPOSIÇÃO DE CANGAS BRASILEIRAS: PANORAMA ECOLÓGICO E FILOGENÉTICO DE GRUPOS BOTÂNICOS

Abstract

Cangas are ecological systems of complex evolution, being one of the oldest exposed surfaces on the planet. They are located in global biodiversity hotspots, sheltering plant communities characterized by high levels of endemism, high diversity (alpha and beta), rare, and threatened species. In addition to their environmental relevance, they are economically important, as they cover iron ore deposits. However, the canga areas and their natural communities are little covered by conservation policies. In this sense, we aim to evaluate and establish, through phylogenetic analysis and critical and descriptive analysis, the floristic composition of cangas in Brazilian phytogeographic domains. Data collection was carried out through a systematic literature review analyzed from 1969 to 2019 (50 years). First, we evaluated the floristic composition using the Venn-Euler diagram, the non-metric multidimensional scaling (NMDS) analysis, and the ward.D2 ordering method. Subsequently, we carried out the phylogenetic reconstruction of the under- and over-represented clades for plant community conservation in the Amazon, Caatinga, Cerrado, Atlantic Forest, and Pantanal biomes. We identified the families Poaceae, Orchidaceae, Melastomataceae, and Asteraceae as the most recurrent in canga habitats. We also verified the predominance of the genera Myrcia, Baccharis, Paspalum, Ipomoea, and Paepalanthus. The Venn-Euler diagram indicated a variation in the composition of exclusive and common botanical groups at different taxonomic levels. The Amazon and Atlantic Forest biomes have the greatest number of unique species, genera, and families. The pattern of Ward similarity clusters was reflected in the NMDS analysis, and NTI and NRI values indicate that cangas from the sampled biomes have low floristic similarity, indicating niche phylogenetic conservatism. The general pattern of distribution and floristics composition of cangas in Brazilian biomes is mainly characterized by a high diversity of species related to few botanical families. The phylogenetic structures of such plant communities suggest that environmental filters favored occurrences closely related to floristic species.