Asexual genome evolution in the apomictic Ranunculus auricomus complex: examining the effects of hybridization and mutation accumulation

Asexual lineages are thought to be prone to extinction because of deleterious mutation accumulation (Muller's ratchet). Here we analyze genomic effects of hybridity, polyploidy and allelic divergence in apomictic plants, and identify loci under divergent selection among sexual/apomictic lineages. RNAseq was used to sequence the flower-specific transcriptomes of 5 genotypes of the Ranunculus auricomus complex, representing 3 sexual and 2 apomictic reproductive biotypes. The 5 sequence libraries were pooled and de novo assembly performed, and the resultant assembly was used as a backbone for a subsequent alignment of each separate library. High quality single nucleotide (SNP) and insertion-deletion (indel) polymorphisms were mined from each library. Annotated genes for which open reading frames (ORF) could be determined were analyzed for signatures of divergent versus stabilizing selection. A comparison between all genotypes supports the hypothesis of Pleistocene hybrid origin of both apo...