Spatial variation in Latin American tree biodiversity: patterns and determinants
bioregionalization, Latin America, floristic patterns, tree biodiversity, sub-regions, biogeographic units, Amazonia, Cerrado-Pantanal, neotropical flora
Bioregionalization is the effort to find and map geographical boundaries for sets of distinct biotas at different spatial scales. The clear delineation of biogeographical units based on community data can provide a framework for testing hypotheses and for guiding biodiversity conservation efforts. The aim of this research is to identify biogeographical units of trees in Latin America, the floristic relationships between the units identified, and the main factors driving the bioregionalization. We used a community-level modelling approach, and hierarchical and non-hierarchical classification techniques to map the biogeographic units at different spatial scales. This thesis is divided into three articles. In Article I, we mapped 13 woody plant subregions for the entire geographical extent of the Amazon Forest. The hierarchical subregion classification showed a broad Andean-Cratonic east-west division. Variation in subregions was explained jointly by human factors and spatial structure followed by environmental factors and spatial structure combined. In Article II, we mapped 18 subregions based on species occurrences and four subregions based on species abundances for the Cerrado-Pantanal complex. Variation in subregions were explained mainly by contemporary environmental factors and spatial structure in both occurrence and abundance datasets. The occurrence and abundance-based subregions proved to be complementary approaches to disentangle the macroecological patterns in the Cerrado-Pantanal complex. In Article III, we identify geographical units of Latin American tree flora at different spatial scales and discuss the ecological and evolutionary factors that may have driven the spatial structure of the tree biodiversity. We mapped 128 sub-, 54 meso-, 16 macro-, and nine supra-regions of trees for the Latin America. Sub-regions located in central America, the Andes, and the Brazilian coast showed the highest number of restricted species. Meanwhile, some subregions located in Mexico, Chile and Argentina had the highest taxonomic distinctiveness values. We believe that our results make an important contribution to understanding the patterns and processes shaping Neotropical and Latin American biodiversity.