Abstract
BackgroundSympatric sister species provide an opportunity to investigate the genetic mechanisms and evolutionary forces that maintain species boundaries. The persistence of morphologically and genetically distinct populations in sympatry can only occur if some degree of reproductive isolation exists. A pair of sympatric sister species of Primulina (P. depressa and P. danxiaensis) was used to explore the genetic architecture of hybrid male sterility.ResultsWe mapped one major- and seven minor-effect quantitative trait loci (QTLs) that underlie pollen fertility rate (PFR). These loci jointly explained 55.4% of the phenotypic variation in the F2 population. A Bateson–Dobzhansky–Muller (BDM) model involving three loci was observed in this system. We found genotypic correlations between hybrid male sterility and flower morphology, consistent with the weak but significant phenotypic correlations between PFR and floral traits.ConclusionsHybrid male sterility in Primulina is controlled by a polygenic genetic basis with a complex pattern. The genetic incompatibility involves a three-locus BDM model. Hybrid male sterility is genetically correlated with floral morphology and divergence hitchhiking may occur between them.
Highlights
Sympatric sister species provide an opportunity to investigate the genetic mechanisms and evolutionary forces that maintain species boundaries
We studied Mid-parent heterosis (MPH) for hybrid fertility and 12 flower and leaf traits to unravel the mechanism of postzygotic isolation between P. depressa and P. danxiaensis in sympatry
In this study, we found that hybrid male sterility in Primulina is controlled by a polygenic genetic basis
Summary
Sympatric sister species provide an opportunity to investigate the genetic mechanisms and evolutionary forces that maintain species boundaries. A pair of sympatric sister species of Primulina (P. depressa and P. danxiaensis) was used to explore the genetic architecture of hybrid male sterility. Barriers to genetic exchange between diverging populations promote reproductive isolation and, speciation. Genetic divergence of barriers between populations involves the evolution of prezygotic and postzygotic isolation [1,2,3]. It has been hypothesized that postzygotic reproductive isolation accumulates via increasing genomic incompatibilities [10,11,12], and that it is the by-product of genomic divergence [13]. Various genetic mechanisms of hybrid male sterility were proposed [14]. Cytoplasmic male sterility (CMS) is another common genic incompatibility mechanism, which results from a mitochondrial–nuclear mismatch. The hybrid CMS mechanism has been widely studied in model species such as
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