title: Freshwater protists do not go with the flow: population structure in Gonyostomum semen independent of connectivity among lakes.
abstract: Many recent studies have found genetically differentiated populations in microorganisms despite potentially high dispersal. We designed a study to specifically examine the importance of physical dispersal barriers, i.e. geographic distance and lack of hydrological connectivity, in restricting gene flow and enhancing divergence in limnic microorganisms. We focused on the nuisance microalga Gonyostomum semen, which has recently expanded in Northern Europe and differentiated into genetically distinct populations. G. semen was sampled from six lakes distributed in two adjacent watersheds, which thereby comprised, both connected and non-connected lakes. The individual isolates were genotyped by amplified fragment length polymorphism. Several lake populations were differentiated from each other, but connectivity within watersheds could not explain the observed population genetic pattern. However, isolation by distance was moderate and might limit the gene flow among distant populations. In addition, we found low, but significant linkage disequilibrium, which indicates regular sexual recombination in this species, despite its high degree of asexual reproduction. Therefore, we conclude that the genetic properties of microalgae with occasional sexual reproduction essentially mirror regularly recombining species. Furthermore, the data indicated bottlenecks supporting the hypothesized recent range expansion of this species.
authors.affiliation: Aquatic Ecology, Lund University, Sölvegatan 37, 22362, Lund, Sweden.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Sassenhagen
authors.affiliation: Department of Marine Sciences, University of Gothenburg, Box 461, Gothenburg, 40530, Sweden.
authors.forename: Josefin
authors.initials: J
authors.lastname: Sefbom
authors.affiliation: Evolutionary Genetics, Lund University, Sölvegatan 35, Lund, 22362, Sweden.
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Säll
authors.affiliation: Department of Marine Sciences, University of Gothenburg, Box 461, Gothenburg, 40530, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Godhe
authors.affiliation: Aquatic Ecology, Lund University, Sölvegatan 37, 22362, Lund, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Rengefors
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D059001:Aquatic Organisms / Q000235:genetics*; D005060:Europe; D051456:Gene Flow; D005828:Genetics, Population; D005838:Genotype; D060106:Lakes; D015810:Linkage Disequilibrium / Q000235:genetics; D011110:Polymorphism, Genetic; D058009:Stramenopiles / Q000235:genetics* / Q000302:isolation & purification