Abstract
• Background and Aims: New plant species can evolve through the reinforcement of reproductive isolation via local adaptation along habitat gradients. Peat mosses (Sphagnaceae) are an emerging model system for the study of evolutionary genomics and have well-documented niche differentiation among species. Recent molecular studies have demonstrated that the globally distributed species Sphagnum magellanicum is a complex of morphologically cryptic lineages that are phylogenetically and ecologically distinct. Here, we describe the architecture of genomic differentiation between two sister species in this complex known from eastern North America: the northern S. diabolicum and the largely southern S. magniae. • Methods: We sampled plant populations from across a latitudinal gradient in eastern North America and performed whole genome and restriction-site associated DNA sequencing. These sequencing data were then analyzed computationally. • Key Results: Using sliding-window population genetic analyses we find that differentiation is concentrated within ‘islands’ of the genome spanning up to 400 kb that are characterized by elevated genetic divergence, suppressed recombination, reduced nucleotide diversity and increased rates of non-synonymous substitution. Sequence variants that are significantly associated with genetic structure and bioclimatic variables occur within genes that have functional enrichment for biological processes including abiotic stress response, photoperiodism and hormone-mediated signalling. Demographic modelling demonstrates that these two species diverged no more than 225 000 generations ago with secondary contact occurring where their ranges overlap. • Conclusions: We suggest that this heterogeneity of genomic differentiation is a result of linked selection and reflects the role of local adaptation to contrasting climatic zones in driving speciation. This research provides insight into the process of speciation in a group of ecologically important plants and strengthens our predictive understanding of how plant populations will respond as Earth’s climate rapidly changes.
| Original language | English |
|---|---|
| Pages (from-to) | 499-512 |
| Number of pages | 14 |
| Journal | Annals of Botany |
| Volume | 132 |
| Issue number | 3 |
| DOIs | |
| State | Published - Aug 18 2023 |
Funding
We thank Jane Grimwood and Jenell Webber of the Genome Sequencing Center at HudsonAlpha for preparing and sequencing the genome resequencing libraries. This paper has been authored at UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide licence to publish or reproduce the published form of this paper, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public.access-plan ). B.P. was supported by funding from the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract no. DE-AC05–00OR22725. The work (proposal: 10.46936/10.25585/60001030) (A.J.S.) conducted by the U.S. Department of Energy Joint Genome Institute ( https://ror.org/04xm1d337 ), a DOE Office of Science User Facility, is supported by the Office of Science of the U.S. Department of Energy under contract no. DE-AC02-05CH11231. This research used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory. Additional support was provided by the DOE BER Early Career Research Program to D.J.W. and by NSF grants DEB-1737899 and DEB-1928514 to A.J.S. This research was also supported in part by the Tom and Bruce Shinn Fund from the North Carolina Native Plant Society.
Keywords
- Sphagnum
- climate
- comparative genomics
- molecular adaptation
- selection
- speciation