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Data from: Phylogenomic structure and speciation in an emerging model: The Sphagnum magellanicum complex (Bryophyta)

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Sep 02, 2022 version files 30.55 GB

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Abstract

The moss genus Sphagnum has unparalleled ecological importance because some 30% of the total terrestrial carbon pool is bound up in Sphagnum-dominated peatlands. A major peat-former, S. magellanicum, is one of two species for which a reference-quality genome exists to facilitate research in ecological genomics, but recently published work indicated that S. magellanicum s. str. is restricted to South America and two other species, S. divinum and S. medium occur in North America and Europe. We report herein that there are four clades/species within the S. magellanicum complex in eastern North America, two in South America, and another in eastern Asia. The reference genome belongs to S. divinum. Phylogenetic analyses at the whole genome and chromosome levels, using genome resequencing and RADseq, resolve sister group relationships within the complex. Species are monophyletic in most analyses and exhibit tens of thousands (RADseq) to millions (resequencing) of fixed nucleotide differences, but two, referred to informally as S. diabolicum and S. magni because they have not been formally described, are differentiated by only hundreds (RADseq) to thousands (resequencing) of differences. Data from 14 of the 19 resequenced chromosomes (7 chromosomes for RADseq) resolve the reciprocal monophyly of S. magni and S. diabolicum. These two appear to be in the process of speciation and because they differ in geographic ranges and the climate zones they occupy – S. diabolicum in boreal peatlands and S. magni in warm temperate to subtropical communities of the southern U.S. – they provide an exciting opportunity for comparative genomic analyses of climate niche evolution. Introgression among species in the complex is demonstrated using D-statistics and f4-ratios. One ecologically important functional trait that underlies peat (carbon) accumulation, tissue decomposability, does not differ between segregate North American species in the S. magellanicum complex although previous research showed that many related Sphagnum species have evolved differences in decomposability/carbon sequestration. Phylogenetic resolution and more accurate species delimitation in the S. magellanicum complex substantially increase the value of this group for studying the early evolutionary stages of climate adaptation, and ecological evolution more broadly.