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University of Cape Town (2011)

Ecological and evolutionary processes in two southern African endemic birds

Ribeiro, Angela M

Titre : Ecological and evolutionary processes in two southern African endemic birds

Auteur : Ribeiro, Angela M

Université de soutenance : University of Cape Town.

Grade : Doctor of Philosophy (PhD) 2011

Résumé
Understanding the continuous process of divergence that leads to the formation of species requires the simultaneous think about ecology, evolution and its intertwining relationship. In this dissertation, I propose a population-level framework that integrates ecology and population genetics to rethink the mechanisms that promote divergence. To accomplish that I studied two southern African endemic Cercotrichas scrub -robins : C. coryphaeus and C. signata. Despite its phylogenetic proximity the two study species occupy the two ends of the habitat spectrum available in southern Africa : semi-arid Karoo vs. Forest. First, I combined behavioural ecology with individual-based genetic data in the Karoo scrubrobin examined the role of social relationships in shaping mating patterns and dispersal behaviour and ultimately influence the evolution of dispersal. Second, using the knowledge obtained about the dispersal biology of the Karoo scrub-robin, I tested whether natural selection can counter-balance gene flow and hence promote local adaptation along the aridity gradient that characterizes the range of the species. The results suggested that selective pressures on physiology, mediated by the mtDNA genome, might facilitate the adaptation to new climatic conditions. Third, prompted by the previous findings, I examined the historical context of a spatial and demographic expansion to understand the role of natural selection in the colonization of a new environment, in the Karoo scrub-robin. Lastly, I evaluated how the ecogeographical context affects the divergence process in the forest-dweller C. signata.

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Page publiée le 3 février 2019