José Maria Cardoso da Silva

CHAPTER 12 – The Speciation of South American and African Birds in Montane Regions

The chapter examines macroscale patterns of avian species richness and relates this to macroscale patterns of diversification in tropical forests. It investigates where recent speciation has been most intensive and where old lineages (which show only phyletic speciation) predominate. The analysis provides evidence for bursts of speciation in montane regions during the Quaternary climatic–vegetational fluctuations and does not support the hypothesis that avian diversification was intensive in the lowland regions during this period. As montane regions are highly heterogeneous with regard to vegetation, climate, and topography, there is a good chance that areas of paleoecological stability may exist as small pockets within them. The case studies described here illustrate some aspects of the biogeographic dynamics that must be considered in order to understand the processes involved in the evolution of the rich avifauna of tropical forests. It is evident that a great deal of avian diversity has been generated in recent times within tropical montane regions and that further studies are needed to understand its magnitude. In particular, the prediction in the model hypothesis that lowland rainforest biota are recruited from radiations in montane regions needs to be fully tested using phylogenetic studies.

Avian inventory of the cerrado region, South America: implications for biological conservation

The distribution of the ornithological localities in the cerrado region of South America is analysed. When plotted out, the distribution of total sampling localities appears to be even. However, when only those localities at which birds have been sampled in any depth (> 80 specimens collected or >100 species recorded) are considered a different pattern emerges: c.70% of the cerrado region has never been satisfactorily sampled for birds, and similar or worse situations have been reported for other groups of organisms. Priority areas for future ornithological exploration in the cerrado region are most of the states of Tocantins, Maranhao, and Mato Grosso do Sul, southern Goias, and western Minas Gerais. In these areas, inventory efforts could be focused mainly on the avifaunas of tropical dry forests, gallery forests and “campos rupestres”. Because the biological diversity in the cerrado region is poorly known and most of this region has already been modified by human activity, it is suggested that the most feasible way to define both a set of priority areas for conservation and a coherent reserve system is to focus analyses on ecosystems and landscapes rather than on species, subspecies or populations.A distribuicao das localidades ornitologicas na regiao do cerrado, America do Sul, e analisada. Quando todas as localidades sao plotadas em um mapa, o inventario das aves nessa regiao parece ser bem distribuido. Entretanto, quando somente aquelas localidades que tern sido amostradas com certa intensidade (>80 especimes coletados ou >100 especies registradas) sao plotadas, um padrao bastante distinto e encontrado: cerca de 70% da regiao do cerrado tem nunca sido amostrada satisfatoriamente para aves, e situacoes similares ou piores tern sido tambem descritas para o inventario de outros grupos de organismos. Areas prioritarias para futuras exploracoes ornitologicas na regiao do cerrado sao grande parte dos estados do Tocantins, Maranhao e Mato Grosso do Sul, sul de Goias e oeste de Minas Gerais. Nestas areas, inventarios poderiam ser direcionados principalmente para as avifaunas de florestas secas tropicais, florestas de galeria e campos rupestres. Em virtude da diversidade biologica na regiao do cerrado ser pouco conhecida e de grande parte dessa regiao ja ter sido modificada pelas atividades humanas, e sugerido que a melhor estrategia para definir um conjunto de areas prioritarias para conservacao e um coerente sistema de reservas seria concentrar analises sobre ecossistemas e paisagens ao inves de especies, subespecies ou populacoes.