Characterization of 30 microsatellite markers in distylous Primula sinolisteri (Primulaceae) using HiSeq sequencing

Characterization of 30 microsatellite markers for distylous Primula denticulata (Primulaceae) using HiSeq sequencing

Primula denticulata exhibits considerable variation in floral morphology and flowering phenology along elevational gradients in SW China. We isolated 30 microsatellite markers from P. denticulata to facilitate further investigation of population genetics and floral evolution in this species. We used the HiSeq X-Ten sequencing system to develop a set of markers, and measured polymorphism and genetic diversity in a sample of 72 individuals from three natural populations of P. denticulata subsp. denticulata. The markers displayed relatively high polymorphism, with the number of alleles ranging from two to seven (mean = 3.567). The observed and expected heterozygosity ranged from 0 to 1.000 and 0.041 to 0.702, respectively. Twenty-eight of the loci were also successfully amplified in P. denticulata subsp. sinodenticulata. The microsatellite markers we have identified will provide valuable tools for investigations of the population genetic structure, mating systems and phylogeography of the P. denticulata complex, and will help to address questions concerning the ecological and genetic mechanisms responsible for the evolution of reproductive traits in the species.

Phylogenomic analysis reveals multiple evolutionary origins of selfing from outcrossing in a lineage of heterostylous plants

Evolutionary transitions from outcrossing to selfing often occur in heterostylous plants. Selfing homostyles originate within distylous populations and frequently evolve to become reproductively isolated species. We investigated this process in 10 species of Primula section Obconicolisteri using phylogenomic approaches and inferred how often homostyly originated from distyly and its consequences for population genetic diversity and floral trait evolution. We estimated phylogenetic relationships and reconstructed character evolution using the whole plastome comprised of 76 protein-coding genes. To investigate mating patterns and genetic diversity we screened 15 microsatellite loci in 40 populations. We compared floral traits among distylous and homostylous populations to determine how phenotypically differentiated homostyles were from their distylous ancestors. Section Obconicolisteri was monophyletic and we estimated multiple independent transitions from distyly to homostyly. High selfing rates characterised homostylous populations and this was associated with reduced genetic diversity. Flower size and pollen production were reduced in homostylous populations, but pollen size was significantly larger in some homostyles than in distylous morphs. Repeated transitions to selfing in section Obconicolisteri are likely to have been fostered by the complex montane environments that species occupy. Unsatisfactory pollinator service is likely to have promoted reproductive assurance in homostyles leading to subsequent population divergence through isolation.