Evolution of a transposon in Daphnia hybrid genomes
1 Département de Biologie, Université du Québec à Rimouski, 300, allée des Ursulines, G5L 3A1, Rimouski, Québec, Canada
2 Centre d’Études Nordiques, Université Laval, Pavillon Abitibi-Price, 2405, rue de la Terrasse, Local 1202, G1V 0A6, Québec, Canada
3 Current address: Great Lake Institute of Environmental Research, University of Windsor, 401 Sunset Avenue, N9B 3P4, Windsor, Canada
4 Department of Integrative Biology, University of Guelph, Science complex, N1G 2 W1, Guelph, ON, Canada
5 College of Engineering, University of Illinois at Chicago, (M/C 159), 851 South Morgan, 60607, Chicago, IL, USA
Mobile DNA 2013, 4:7 doi:10.1186/1759-8753-4-7Published: 6 February 2013
Transposable elements play a major role in genome evolution. Their capacity to move and/or multiply in the genome of their host may have profound impacts on phenotypes, and may have dramatic consequences on genome structure. Hybrid and polyploid clones have arisen multiple times in the Daphnia pulex complex and are thought to reproduce by obligate parthenogenesis. Our study examines the evolution of a DNA transposable element named Pokey in the D. pulex complex.
Portions of Pokey elements inserted in the 28S rRNA genes from various Daphnia hybrids (diploids and polyploids) were sequenced and compared to sequences from a previous study to understand the evolutionary history of the elements. Pokey sequences show a complex phylogenetic pattern. We found evidence of recombination events in numerous Pokey alleles from diploid and polyploid hybrids and also from non-hybrid diploids. The recombination rate in Pokey elements is comparable to recombination rates previously estimated for 28S rRNA genes in the congener, Daphnia obtusa. Some recombinant Pokey alleles were encountered in Daphnia isolates from multiple locations and habitats.
Phylogenetic and recombination analyses showed that recombination is a major force that shapes Pokey evolution. Based on Pokey phylogenies, reticulation has played and still plays an important role in shaping the diversity of the D. pulex complex. Horizontal transfer of Pokey seems to be rare and hybrids often possess Pokey elements derived from recombination among alleles encountered in the putative parental species. The insertion of Pokey in hotspots of recombination may have important impacts on the diversity and fitness of this transposable element.