Patterns of Species and Lineage Diversity in the Atlantic Rainforest of Brazil

Abstract

The Atlantic rainforest of Brazil harbors outstanding species richness and levels of endemism, representing one of the most biodiverse regions on Earth. Yet, a lot is still unknown about the spatial and temporal evolution of its biota. While the history of the region is complex, with taxa often showing distinct richness patterns and evolutionary histories, some trends are common to a variety of lineages. Higher species richness is often found in the topographically complex coast of Rio de Janeiro and Sao Paulo, but the variety of environmental spaces available within this domain, tied to the different niches explored by its species, also support the existence of other patterns of species accumulation. The biological communities that inhabit the southern portions of the Atlantic forest are clearly distinct from those that occupy the northern range of the domain: several taxa undergo turnover in the Doce river valley (state of Espirito Santo), while others shift further south (near the Rio de Janeiro/Sao Paulo state boundary), or further north (state of Bahia). Areas of endemism have been recognized within the forest; while their boundaries do not perfectly match across all taxonomic groups, a nested pattern is detected, with contiguous areas of endemism defined by low-dispersal organisms (e.g., harvestmen) often fitting within more inclusive endemism centers defined by high-dispersal groups (e.g., birds). To date, the fauna and flora has been compartmentalized into five main areas of endemism: (1) Pernambuco, (2) Coastal Bahia, (3) Central Bahia, (4) Serra do Mar (often with further subregions), and (5) Parana/Araucaria (Fig. 16.2). Here, we summarize main spatial patterns of diversity, flagging areas of higher species accumulation, turnover, and endemism. We also review main patterns of lineage divergence and population structure recovered from molecular phylogenies and phylogeographic studies, and explore some of the most common diversification hypotheses proposed for the Atlantic forest biota to date. We demonstrate that the spatial turnover of lineages within species largely mirrors that of species within communities; both climate change and geographic barriers appear to have acted in combination to produce patterns of diversification. However, while geographic patterns of species and genetic diversity are similar across Atlantic forest organisms, their underlying processes are not.