Bird diversity and diversification: Different processes converging to the same pattern?

Latitudinal diversity gradient is one of the oldest known trends in the distribution of life on the Earth. Scientists have been trying to find causes of its formation for more than two hundred years. There are several hypotheses suggested to explain this gradient. Recently, it is one of the main themes of discussion among ecologists and evolutionary biologists. By this Thesis, I will try to contribute to understanding of processes that generate the latitudinal diversity gradient. Particularly, I study if there is a relationship between ambient temperature and diversification rate. Is this relationship different for individual groups of animals? I choose birds as a model group. Specifically, these six families of birds: Accipitridae, Columbidae, Furnariidae, Picidae, Psittacidae and Strigidae. These groups include more than 1500 species. Each of them has the same universal gradient of diversity, with the highest diversity concentrated in the tropics. My objective was to find out, whether the universal gradients of bird's diversity had been shaped by the same historical processes. Or alternatively, whether different evolutionary trajectories had converged to the same gradients. The main outcome of my work is a discovery that some of the selected families diversified faster in warmer climates..