Cryptic gene pools in the Hypericum perforatum-H. maculatum complex: diploid persistence versus trapped polyploid...

Area of Science:

• Evolutionary biology
• Plant genetics
• Ecology

Background:

• Pleistocene range fluctuations in Central Europe facilitated hybridization and introgression between Hypericum perforatum and Hypericum maculatum.
• Gene pools are merging at higher ploidy levels, raising questions about ecological niche constraints on polyploid evolution.

Purpose of the Study:

• To investigate if polyploid hybrid gene pools are confined to the ecological niche space of their diploid ancestors.
• To test the hypothesis of geographical parthenogenesis in these plant lineages.

Main Methods:

• Utilized DNA sequence data from nuclear ribosomal DNA and plastid loci.
• Estimated ploidy levels and employed ecological niche modeling.
• Characterized diploid and polyploid gene pools to understand spatio-temporal gene flow patterns.

Main Results:

• Diploid gene pools of H. perforatum and H. maculatum are distinct, with divergence dating to the early Pleistocene.
• Polyploids exhibit extensive gene flow across all three diploid gene pools, with geographical distance correlations breaking down beyond 250 km.
• Hybrid polyploids show minimal niche differentiation from parental gene pools, except for some H. maculatum combinations.

Conclusions:

• Limited inter- and intraspecific gene flow at the diploid level reflects Pleistocene evolutionary history.
• Secondary contact and hybridization at the polyploid level did not lead to significant niche divergence.
• Absence of niche divergence prevents further differentiation and geographical partitioning, trapping polyploids within ancestral ecological niches.