Repeated evolution of uniparental reproduction in Sellaphora (Bacillariophyceae) |
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Authors: | Aloisie Poulíčková Shinya Sato Katharine M. Evans Victor A. Chepurnov David G. Mann |
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Affiliation: | 1. Department of Botany, Faculty of Science, Palacky University in Olomouc, ?lechtitel? 11, CZ-783 71, Olomouc, Czech Republicaloisie.poulickova@upol.cz;3. Fukui Prefectural University, 1-1 Gakuen-cho, Obama City, Fukui 917-0003, Japan;4. Royal Botanic Garden Edinburgh, Edinburgh EH3 3LR, Scotland, UK;5. Royal Botanic Garden Edinburgh, Edinburgh EH3 3LR, Scotland, UK;6. Laboratory of Protistology and Aquatic Ecology, Ghent University, Krijgslaan 281-S8, 9000 Gent, Belgium;7. Tomalgae C.V.B.A, Graaf van Hoornestraat 1, 9850 Nevele, Belgium;8. Aquatic Ecosystems, Institute for Food and Agricultural Research and Technology (IRTA), Crta de Poble Nou Km 5.5, E-43540 Sant Carles de la Ràpita, Catalunya, Spain |
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Abstract: | Diatoms possess a remarkable life cycle in which cell size decreases slowly during vegetative cell division and then increases rapidly via special expanding cells called ‘auxospores’, which are usually formed as a result of biparental sexual reproduction. However, auxospores are sometimes produced by single unpaired cells, i.e. uniparentally. We examined the nature of uniparental auxosporulation in Sellaphora and used a two-gene dataset to study phylogenetic relationships between uniparental and biparental Sellaphora demes and species; we tested whether uniparental reproduction has evolved once or repeatedly in the genus. In at least two of the uniparental demes auxosporulation occurred through autogamy (i.e. intra-tetrad mating within an undivided cell). Maximum likelihood phylogenies indicated four lineages of uniparental Sellaphora and significance tests of alternative topologies, in which combinations of uniparental Sellaphora were constrained to be monophyletic, coupled with likelihood reconstruction of ancestral character states, led to rejection of the hypothesis that uniparental auxosporulation evolved only once in the genus. Uniparentally reproducing lineages appear to arise not infrequently in diatoms but do not persist. Two small extranuclear bodies, apparently containing DNA and lying outside the chloroplast (one close to each pole of the cell), were revealed by DAPI staining. |
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Keywords: | ancestral state reconstruction autogamy auxosporulation cox1 DAPI diatoms evolution of automixis molecular phylogeny rbcL Sellaphora pupula agg uniparental auxosporulation |
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