Organellar genome evolution and phylogeographic relationships among populations of freshwater brown algae: Heribaudiella fluviatilis, Bodanella lauterborni and Pleurocladia lacustris
Of an estimated 2,000 brown algal species, less than 1% occur in freshwater environments, and their evolutionary and biogeographic relationships have been poorly understood. Historically, the freshwater brown alga Pleurocladia lacustris has been classified within either the Ectocarpaceae or Chordariaceae. The taxonomic placement of Heribaudiella fluviatilis and Bodanella lauterborni are also unclear. The aim of this dissertation is to clarify the phylogenetic position and the evolution of these species by analyzing their complete mitochondrial and plastid genome sequences, and describing the phylogeographic relationships among different freshwater brown algal populations. This study was the first to fully sequence the organellar genome of any freshwater brown alga. An analysis of the genome architecture, gene content and order between the freshwater brown algae organellar genomes and other published brown algal organellar genomes are presented. Pleurocladia lacustris has a typical mitochondrial and plastid genome architecture exhibited by other species of brown algae. Heribaudiella fluviatilis and Bodanella lauterborni have typical plastid architecture, but a unique mitochondrial genome composed of two separate DNA molecules. Gene order is relatively conserved among brown algal mitochondrial genomes, and less so than plastid genomes. However, based on their unique mitochondrial genome structure, H. fluviatilis and B. lauterborni mitochondrial genome gene order differs substantially from other published brown algal mitochondrial genomes. Phylogenies generated using multiple DNA markers confirm that P. lacustris is a member of the Ectocarpaceae. As supported by a phylogenetic tree based on multiple DNA markers, H. fluviatilis and B. lauterborni form a monophyletic group sister to the Sphacelariales. These results support the recognition of a new order Heribaudiales. Moreover, four distinct lineages of Heribaudiella from different localities were identified, here recognized as four species. Unlike the relatively high genetic variation found in Heribaudiella, the variation within P. lacustris is comparatively low. Four haplotypes in P. lacustris were found in this study.
Molecular biology|Evolution and Development
Wang, Xian, "Organellar genome evolution and phylogeographic relationships among populations of freshwater brown algae: Heribaudiella fluviatilis, Bodanella lauterborni and Pleurocladia lacustris" (2014). ETD Collection for Fordham University. AAI3643391.