Organellar phylogenomics of an emerging model system: Sphagnum (peatmoss).
Sphagnum-dominated peatlands contain approx. 30 % of the terrestrial carbon pool in the form of partially decomposed plant material (peat), and, as a consequence, Sphagnum is currently a focus of studies on biogeochemistry and control of global climate. Sphagnum species differ in ecologically important traits that scale up to impact ecosystem function, and sequencing of the genome from selected Sphagnum species is currently underway. As an emerging model system, these resources for Sphagnum will facilitate linking nucleotide variation to plant functional traits, and through those traits to ecosystem processes. A solid phylogenetic framework for Sphagnum is crucial to comparative analyses of species-specific traits, but relationships among major clades within Sphagnum have been recalcitrant to resolution because the genus underwent a rapid radiation. Herein a well-supported hypothesis for phylogenetic relationships among major clades within Sphagnum based on organellar genome sequences (plastid, mitochondrial) is provided.



We obtained nucleotide sequences (273 753 nucleotides in total) from the two organellar genomes from 38 species (including three outgroups). Phylogenetic analyses were conducted using a variety of methods applied to nucleotide and amino acid sequences. The Sphagnum phylogeny was rooted with sequences from the related Sphagnopsida genera, Eosphagnum and Flatbergium



Phylogenetic analyses of the data converge on the following subgeneric relationships: (Rigida (((Subsecunda) (Cuspidata)) ((Sphagnum) (Acutifolia))). All relationships were strongly supported. Species in the two major clades (i.e. Subsecunda + Cuspidata and Sphagnum + Acutifolia), which include >90 % of all Sphagnum species, differ in ecological niches and these differences correlate with other functional traits that impact biogeochemical cycling. Mitochondrial intron presence/absence are variable among species and genera of the Sphagnopsida. Two new nomenclatural combinations are made, in the genera Eosphagnum and Flatbergium



Newly resolved relationships now permit phylogenetic analyses of morphological, biochemical and ecological traits among Sphagnum species. The results clarify long-standing disagreements about subgeneric relationships and intrageneric classification.
Department of Biology, Duke University, Durham, NC 27708, USA shaw@duke.edu.
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Jonathan Shaw
Department of Biology, Duke University, Durham, NC 27708, USA.
Nicolas
N
Devos
Department of Ecology and Evolutionary Biology, 75 North Eagleville Road, Storrs, CT 06269, USA.
Yang
Y
Liu
Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, Edif. 7, 8005-139 Faro, Portugal.
Cymon J
CJ
Cox
Department of Ecology and Evolutionary Biology, 75 North Eagleville Road, Storrs, CT 06269, USA.
Bernard
B
Goffinet
NTNU University Museum, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Kjell Ivar
KI
Flatberg
Department of Biology, Duke University, Durham, NC 27708, USA.
Blanka
B
Shaw
D017753:Ecosystem; D019143:Evolution, Molecular; D054629:Genome, Mitochondrial / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics; D054627:Genome, Plastid / Q000235:genetics*; D023281:Genomics; D008954:Models, Biological; D010802:Phylogeny; D018087:Plastids / Q000235:genetics; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D044003:Sphagnopsida / Q000145:classification* / Q000235:genetics
Bryophytes; Sphagnum; mitochondrial genome; organellar genomes; peatmoss; phylogenomics; plastid genome