Microbial evolution: patterns of diversity in aquatic protists

• Main Author: Logares, Ramiro
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Limnology, Department of Ecology, Lund University 2007
• Subjects: Environmental Sciences; Ecology; dinoflagellates; biodiversity; lakes; Evolution; diversification; microbes; biogeography; Antarctic; Arctic; Antarc*
• Online Access: https://lup.lub.lu.se/record/600754; https://portal.research.lu.se/files/5861489/600819.pdf

Little is known about how microbes diversify in nature. In contrast to the more studied multicellular organisms, microbes can have a) huge population sizes, b) high reproductive rates and c) long-distance dispersal. These characteristics can affect their tempo and mode of diversification in ways that still need to be understood. For instance, it has been proposed that the huge population sizes and the potential for long-distance dispersal in microbes would restrain their overall diversification, generating a pattern consisting of relatively few cosmopolitan species in global scales. However, recent genetic data started to reveal that a) microbial biodiversity is much higher than previously estimated, b) that there are cosmopolitan as well as endemic species and, c) that vast diversity can be hidden within identical morphologies (reviewed in Paper 1). In Paper 2, I investigated one of the first cases of two phenotypically differentiated dinoflagellate (unicellular eukaryote) morphospecies which are genetically very similar. These two species were found to be part of a lineage which has diversified recently in evolutionary terms (Paper 3). I proposed that this diversification can be associated to transitions between environments, since the dinoflagellate lineage in question encompasses marine, brackish and freshwater strains/species from the Arctic, Antarctic and Europe. In Paper 4, several dinoflagellate species were investigated in marine-derived coastal Antarctic lakes. These lakes have evolved in 6,000 years from originally marine conditions into salinities ranging from freshwater to hypersaline. It was found that most dinoflagellate species present in these lakes have a marine origin, and that the new environmental conditions in the lakes have likely promoted the extinction of most colonizing dinoflagellates, leaving behind a few species. In Paper 5, I explored the genetic diversity within Antarctic and European lakes. The results indicated that there is normally a high genetic diversity within lakes, instead ...