Ament-Velásquez, S. L.; Figuet, E.; Ballenghien, M.; Zattara, E. E.; Norenburg, J. L.; Fernández-Álvarez, F. A.; Bierne, J.; Bierne, N.; Galtier, N. (2016). Population genomics of sexual and asexual lineages in fissiparous ribbon worms (Lineus, Nemertea): hybridization, polyploidy and the Meselson effect. Molecular Ecology. 25(14): 3356–3369.

276099

10.1111/mec.13717 [view]

Ament-Velásquez, S. L.; Figuet, E.; Ballenghien, M.; Zattara, E. E.; Norenburg, J. L.; Fernández-Álvarez, F. A.; Bierne, J.; Bierne, N.; Galtier, N.

2016

25(14): 3356–3369

Publication

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Comparative population genetics in asexual vs. sexual species offers the opportunity to investigate the impact of asexuality on genome evolution. Here, we analyse coding sequence polymorphism and divergence patterns in the fascinating Lineus ribbon worms, a group of marine, carnivorous nemerteans with unusual regeneration abilities, and in which asexual reproduction by fissiparity is documented. The population geno- mics of the ?fisiparous L. pseudolacteus is characterized by an extremely high level of heterozygosity and unexpectedly elevated pN/pS ratio, in apparent agreement with the- oretical expectations under clonal evolution. Analysis of among-species allele sharing and read-count distribution, however, reveals that L. pseudolacteus is a triploid hybrid between Atlantic populations of L. sanguineus and L. lacteus. We model and quantify the relative impact of hybridity, polyploidy and asexuality on molecular variation pat- terns in L. pseudolacteus and conclude that (i) the peculiarities of L. pseudolacteus pop- ulation genomics result in the ?fist place from hybridization and (ii) the accumulation of new mutations through the Meselson effect is more than compensated by processes of heterozygosity erosion, such as gene conversion or gene copy loss. This study illus- trates the complexity of the evolutionary processes associated with asexuality and iden- ti?fis L. pseudolacteus as a promising model to study the ?fist steps of polyploid genome evolution in an asexual context.

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