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Summary: Sphagnum magellanicum is one of two Sphagnum species for which a reference‐quality genome exists to facilitate research in ecological genomics.Phylogenetic and comparative genomic analyses were conducted based on resequencing data from 48 samples and RADseq analyses based on 187 samples.We report herein that there are four clades/species within the S. magellanicum complex in eastern North America and that the reference genome belongs to Sphagnum divinum. The species exhibit tens of thousands (RADseq) to millions (resequencing) of fixed nucleotide differences. Two species, however, referred to informally as S. diabolicum and S. magni because they have not been formally described, are differentiated by only 100 (RADseq) to 1000 (resequencing) of differences. Introgression among species in the complex is demonstrated using D‐statistics and f4 ratios. One ecologically important functional trait, tissue decomposability, which underlies peat (carbon) accumulation, does not differ between segregates in the S. magellanicum complex, although previous research showed that many closely 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. [ABSTRACT FROM AUTHOR]

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here, we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eastern half of North America, including three metal-contaminated sites. Methanogenic community structure was analysed through Illumina amplicon sequencing of the mcrA gene. Whether metal-contaminated sites were included or not, metal concentrations in peat were a primary driver of methanogenic community composition, particularly nickel, a trace element required in the F430 cofactor in methyl-coenzyme M reductase that is also toxic at high concentrations. Copper was also a strong predictor, likely due to inhibition at toxic levels and/or to cooccurrence with nickel, since copper enzymes are not known to be present in anaerobic archaea. The methanogenic groups Methanocellales and Methanosarcinales were prevalent in peatlands with low nickel concentrations, while Methanomicrobiales and Methanomassiliicoccales were abundant in peatlands with higher nickel concentrations. Results suggest that peat-associated trace metals are predictors of methanogenic communities in peatlands. [ABSTRACT FROM AUTHOR]

Methanogenic archaea are ubiquitous in peat soils; however, their diversity and distributions within and among peatland ecosystems are not well known. We used comprehensive clone libraries of 16S rRNA gene sequences to investigate spatial patterns in diversity (richness, evenness of taxa) and composition (taxonomic, phylogenetic) of the methanogenic community in six peatlands arrayed 775 km from eastern Ontario, Canada to West Virginia, USA. Five sites were Sphagnum (moss) and shrub dominated; one site was sedge dominated; and, potential rates of methane (CH) production ranged from 15 to 450 nmol/g day. The gradient allowed us to examine influences of site conditions, site history, and climate on community composition. The region had representatives of methanogens from four taxonomic orders. We observed 29 operationally defined units (OTUs) based on >97% sequence identity. One OTU accounted for 43% of all clones, whereas 15 OTUs were rare with <1% of the total number of clones. The number of OTUs per site ranged from 4 to 21, and statistical analysis suggested diversity of 4-43 per site. Eighteen of the OTUs were endemic to one site; albeit, most endemics occurred in the sedge dominated site. One OTU was cosmopolitan, occurring in all six sites. We found a positive relationship between methanogen diversity and rates of CH production per site (Pearson r = 0.93). Turnover in community composition between sites was weakly related to geographic distance between sites, whereas variation in soil pH and annual temperature played larger roles. About 50% of the variation in community composition was unexplained by distance, pH, mean climate, and site age. We conclude that methanogen diversity in peatlands of the central Appalachian region is shaped by present-day environmental conditions, suggesting an influence of impending climatic and environmental changes. [ABSTRACT FROM AUTHOR]

Although Sphagnum (moss)-dominated, northern peatland ecosystems harbor methane (CH4)-producing microorganisms (methanogens) and are a significant source of atmospheric CH4, rates of CH4 production vary widely among different systems. Very little work has been done to examine whether concentrations of cations and metal elements may account for the variability. We examined ratesof CH4 production in peat from five geographically and functionally disparate Sphagnum-dominated peatlands by incubating peat samples in vitro with and without additions of trace metals (Fe, Ni, Co) and base cations (Ca, Li, Na). In peat from the most mineral poorsites, the addition of metals and Na enhanced CH4 production beyond that observed in controls. The same treatments in mineral rich sites yielded no effect or an inhibition of CH4 production. None of the treatments affected anaerobic respiration, measured as CO2 production, in the in vitro incubations of peat, except added citrate, suggesting that methanogens, and not the entireanaerobic community, can be limited by the availability of metal elements and cations. [ABSTRACT FROM AUTHOR]

Premise: Sphagnum magellanicum (Sphagnaceae, Bryophyta) has been considered to be a single semi-cosmopolitan species, but recent molecular analyses have shown that it comprises a complex of at least seven reciprocally monophyletic groups, that are difficult or impossible to distinguish morphologically., Methods: Newly developed barcode markers and RADseq analyses were used to identify species among 808 samples from 119 sites. Molecular approaches were used to assess the geographic ranges of four North American species, the frequency at which they occur sympatrically, and ecological differentiation among them. Microhabitats were classified with regard to hydrology and shade. Hierarchical modelling of species communities was used to assess climate variation among the species. Climate niches were projected back to 22,000 years BP to assess the likelihood that the North American species had sympatric ranges during the late Pleistocene., Results: The species exhibited parallel morphological variation, making them extremely difficult to distinguish phenotypically. Two to three species frequently co-occurred within peatlands. They had broadly overlapping microhabitat and climate niches. Barcode- versus RADseq-based identifications were in conflict for 6% of the samples and always involved S. diabolicum vs. S. magniae., Conclusions: These species co-occur within peatlands at scales that could permit interbreeding, yet they remain largely distinct genetically and phylogenetically. The four cryptic species exhibited distinct geographic and ecological patterns. Conflicting identifications from barcode vs. RADseq analyses for S. diabolicum versus S. magniae could reflect incomplete speciation or hybridization. They comprise a valuable study system for additional work on climate adaptation., (© 2024 Botanical Society of America.)