Summary of Doctoral Theses in Ornithology (2011–2012 Academic Year)

Abstract

Large scale study of diversity patterns has the purpose of describing emergent properties of the ecosystems and biota which in occasions do not manifest in more detail-scale investigations. At the biogeographic and macroecological scales, diversity patterns are the product of biota's responses to current environmental conditions and past environmental changes that can be researched based on evolutionary phenomena (speciation, extinction) or historical events (dispersion). Works integrating macroecology and macroevolution are developing and the scientific community is still on the phase of creating and trying to reach a consensus on methodologies allowing such integration. This thesis uses four case studies with the aim of supporting the suitability of schemes incorporating contemporary, evolutionary and historical aspects of the biotas to reach more complete explanations for the mechanisms generating diversity patterns. During the development of this thesis we have created databases using empirical data from different geographical regions, which have been analyzed using geographical information systems, statistical models and phylogenetic analysis methods. Besides, all case studies share in common the assemblage approach, which uses grid cells uniformly distributed across the study area as analysis units. The choice of this approach is related to the fact that all patterns and processes studied have a geographical expression and therefore their study requires spatially explicit methods. Intending to achieve a wide range of representation, the case studies analyze three diversity patterns (i.e. species richness, body size, range size), three different taxonomie groups (i.e. reptiles, birds and mammals) and three geographical regions (i.e. east and south of Africa, the New World, the Globe). Far from trying to find methodological unification, the analyses are adapted to the idiosyncrasy of each specific question that are studied in the following cases. In the first place, we explore the species richness patterns of five reptile groups from south and east Africa and both relationships with current climate and probable ancestral relationships with palaeoclimates where the groups were originated are analyzed. Information was provided by the fossil record, dated phylogenies and palaeoclimatic reconstructions. We found coincidence between climatic conditions preferred nowadays and ancestral climatic conditions for the different groups of reptiles suggesting that niche conservatism is valid to interpret African reptile richness patterns. Secondly, we investigate the extent to which evolutionary relationships between species of oscine passerine birds can explain their geographical range size patterns in the New World. Range size patterns are documented for migratory and non-migratory species and are partitioned into the portion explained by evolutionary relationships and the portion that is independent from them by using phylogenetic methods of partition of the variance. The results indicate that range size is moderately heritable for this group of birds and hence its study needs to account for the role played by evolution. Furthermore, the patterns are different for migratory and non-migratory species, supporting the effect of mesoscale climatic gradients that are found in mountainous regions. Regional differences and phylogenetic structure found in migratory ranges, suggest the convenience of including other biological traits as dispersal ability, to reach a better understanding of the processes conditioning the biogeography of oscine range size. In third place, we examine the relative contributions of deep evolutionary relationships to the global bird body size gradient, distinguishing between the part of the gradient which is phylogenetically structured from the part that is independent from the phylogeny and thus might respond to adaptive phenomena under the family level. In this case, apart from the phylogenetic partition of the