Filogenia molecular, biogeografia e aspectos evolutivos de Pilosocereus (Cactaceae)

Abstract

The genus Pilosocereus belongs to Cactaceae (subfamily Cactoideae) and is one of the largest and most widely distributed genera within the tribe Cereeae. With 42 species divided in two subgenera, Pilosocereus and Gounellea the group is disjunctly distributed in the Neotropics and centered in eastern Brazil, occurring in many different types of habitats associated with xeric environments. Due to its morphological features, providing great adaptability to xeric environments (as all Cacti), Pilosocereus species are often dominant and play an important ecological and ethnobotanical role where they occur. However, there were few studies so far that focused on the genera as a whole. Thus, this thesis aimed to investigate the phylogenetic relationship, biogeography and evolutionary aspects of the genus Pilosocereus. The first Chapter focused in investigating Pilosocereus diversification processes in arid habitats in the Neotropics, using phylogenetic relationships, clades divergence times and reconstruction of ancestral areas. The conclusion was that the genus is not monophyletic and that the main clade (Pilosocereus sensu stricto) diversified very recently (mainly in Late Pleistocene), with origin in the Caatinga and posterior migration events to other xeric environments in North/Central America, Northwest of South America and Caribbe. In Chapter 2, the phylogenetic relationships in the genus were reconstructed through Bayesian and Maximum Parsimony analyses, with expanded taxon sampling and genomic regions in comparison with previously published works. Again, the genus was found as non-monophyletic, as well as four heterotypic species, what led to the proposition of taxonomic changes, including the resurrection of three species, three new synonyms, a new name in the species rank and a new name in the generic rank, Xiquexique (composed of the species formally positioned in P. subg. Gounellea), while Pilosocereus was newly circumscrybed with 42 species and four subspecies. Finally, Chapter 3 presents the distribution patterns, richness, endemism and current conservation scenario for all species of the group. Some taxa are restricted to vegetation types, but most of them are widely distributed in different environmental gradients. The greatest species richness and phylogenetic diversity are found in the states of Bahia and Minas Gerais, with areas of endemism in Eastern Brazil and Mexico. Thus, this thesis had a multidisciplinary approach in order to elucidate different aspects of the biology of this large and diverse group, which remained unknown until now.