What Assemblages of species have long intrigued and fascinated scientists. We have greatly advanced our understanding of what determines the build-up of diversity and the distribution of life on Earth by drawing on ecological, distributional and phylogenetic data. However, the symbiosis between animals and their intestinal microbiota has largely been ignored in this context, despite the well-established fact that microbial communities are essential for host growth, development, immunity, and even behaviour. The Digestive Tract Microbiota (DTM) plays a plethora of important roles, including the degradation of macromolecules, nutrient absorption, synthesis of essential molecules, immunization, and detoxification. Why This project will provide a fundamental understanding of the microbiota of passerine birds by identifying compositional and functional differences across digestive tract compartments, and whether the avian DTM is shaped mainly by the environment (habitat or elevation), the diet (frugivore, insectivore, or omnivore) or the evolutionary history (relatedness) of the host birds. Furthermore, this research will assess the specific roles of the DTM and their importance for adaptation of their hosts to particular environments, and ultimately how this influences the distribution of species in space and time. How Fieldwork will be carried out in Papua New Guinea in collaboration with the Binatang research center and its staff. Analysis of the microbial communities will be done by using MiSeq amplicon sequencing of the 16S rRNA gene. I will supplement the comparative 16S rRNA analyses with population-(meta)genomic functional analyses of some select bird species and assess the genetic potential of their associated DTM. SSR I aim to explore factors that have influenced species' range dynamics and led to the distributions of birds (and other vertebrates) on Earth today. While this is interesting in its own right, it also has implications for our abilities to conserve the biodiversity that surrounds us. To conserve, we need to know not only what is out there and where it is, but how it got there.