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Abstract
One of the fundamental questions in biology is the origin of species. Considerable insights into the processes that drive speciation have come from ancient lake systems. In this thesis, I present insights into speciation processes by investigating the species radiations of the ancient Malili Lakes of Sulawesi, Indonesia. The nature of adaptive radiations in the lakes suggests that intraspecific competition for extremely limited resources has driven taxa to adapt to specific habitats and food sources. The copepod populations of Sulawesi reveal that colonization order governs the geographic distribution of zooplankton in freshwater ecosystems. In many Malili Lakes taxa, hybridization between closely related lineages drives diversification, likely by increasing phenotypic diversity within populations. Furthermore, hybridization may be much more common in planktonic taxa than previously thought. Future research in these remarkable habitats is sure to reveal much about the role of hybridization and the origins of biodiversity on earth.
