Adaptive radiation is the evolution of ecological and phenotypic diversity within a rapidly
multiplying lineage, a phenomenon that is considered responsible for a great part of Earthʼs
biodiversity. It occurs as a response to ecological opportunity in the form of competitor-free
habitat, extinction of antagonists, or the emergence of a key innovation. One of the most
spectacular adaptive radiations in the marine realm is the diversification of notothenioid fishes in
the freezing waters of Antarctica. This radiation has led to a unique dominance of the Antarctic
marine habitat by notothenioids, and is often assumed to result from the key innovation of
freeze resistance. Antifreeze glycoproteins are present in blood and tissue of Antarctic
notothenioids and enable them to survive in their sub-zero environment. Notothenioids are
further characterized by prolonged pelagic larval stages, that have been suggested to contribute
to high levels of inter-population gene flow with oceanic currents, which seems to contradict the
high speciation rates observed in the notothenioid adaptive radiation. This doctoral work uses
molecular tools to investigate the character of gene flow in notothenioids as well as the origin of
their diversification. It is demonstrated that larval dispersal is a common agent of long-distance
gene flow in many notothenioid species. The key innovation hypothesis is corroborated by an
extensive molecular dating of the divergence events of notothenioids and related acanthomorph
fishes. New tools for the analysis of microsatellite markers and for Bayesian divergence date
estimation are developed
