Spatial Genetic Structure of the Abundant and Widespread Peatmoss Sphagnum magellanicum Brid.

Abstract

Spore-producing organisms have small dispersal units enabling them to become widespread across continents. However, barriers to gene flow and cryptic speciation may exist. The common, haploid peatmoss Sphagnum magellanicum occurs in both the Northern and Southern hemisphere, and is commonly used as a model in studies of peatland ecology and peatmoss physiology. Even though it will likely act as a rich source in functional genomics studies in years to come, surprisingly little is known about levels of genetic variability and structuring in this species. Here, we assess for the first time how genetic variation in S. magellanicum is spatially structured across its full distribution range (Northern Hemisphere and South America). The morphologically similar species S. alaskense was included for comparison. In total, 195 plants were genotyped at 15 microsatellite loci. Sequences from two plastid loci (trnG and trnL) were obtained from 30 samples. Our results show that S. alaskense and almost all plants of S. magellanicum in the northern Pacific area are diploids and share the same gene pool. Haploid plants occur in South America, Europe, eastern North America, western North America, and southern Asia, and five genetically differentiated groups with different distribution ranges were found. Our results indicate that S. magellanicum consists of several distinct genetic groups, seemingly with little or no gene flow among them. Noteworthy, the geographical separation of diploids and haploids is strikingly similar to patterns found within other haploid Sphagnum species spanning the Northern Hemisphere. Our results confirm a genetic division between the Beringian and the Atlantic that seems to be a general pattern in Sphagnum taxa. The pattern of strong genetic population structuring throughout the distribution range of morphologically similar plants need to be considered in future functional genomic studies of S. magellanicum.

Environmental and taxonomic controls of carbon and oxygen stable isotope composition in <i>Sphagnum</i> across broad climatic and geographic ranges

“…However, S. magellanicum is a species with a very broad niche and found in a range of habitats with varying degrees of groundwater influence (Flatberg 2013). These species are easy to identify but recent research has shown that the dark European morph of S. fuscum is conspecific to the North American S. beothuk (Kyrkjeeide et al 2015), and S. magellanicum has been shown to consist of two genetically diverged morphotypes (Kyrkjeeide et al 2016). Unpublished genetic data suggest that samples collected in our study consist of both S. magellanicum morphs (approximately 50/50) and possibly one or two samples of S. beothuk (Pers.…”

Photosynthesis, growth, and decay traits in Sphagnum – a multispecies comparison

“…While this too could be a habitat effect, it has recently been suggested that mire margin populations of S. magellanicum may differ genetically (perhaps even taxonomically) from bog populations (Kyrkjeeide et al. ). Open, ombrotrophic bog is the main habitat of S. fuscum , and the low decay in bog compared to fen is compatible with this.…”

Range change evolution of peat mosses (Sphagnum) within and between climate zones

“…This assumption may be violated in a few cases, but in general, even species with intercontinental ranges appear to conform to the monophyly assumption and indeed, genetic divergence among plants growing on separate continents is often minimal, even though some geographically correlated genetic structure is the rule rather than the exception (e.g., Kyrkjeeide, Hassel, Flatberg, Shaw, Brochmann, et al, 2016;Kyrkjeeide, Hassel, Flatberg, Shaw, Yousefi, et al, 2016;Shaw et al, 2014;Shaw, Shaw, Johnson, Devos, & Carter, 2015;Stenøien, Shaw, Shaw, Hassel, & Gunnarsson, 2011;Szövényi, Terracciano, Ricca, Giordano, & Shaw, 2008). This assumption may be violated in a few cases, but in general, even species with intercontinental ranges appear to conform to the monophyly assumption and indeed, genetic divergence among plants growing on separate continents is often minimal, even though some geographically correlated genetic structure is the rule rather than the exception (e.g., Kyrkjeeide, Hassel, Flatberg, Shaw, Brochmann, et al, 2016;Kyrkjeeide, Hassel, Flatberg, Shaw, Yousefi, et al, 2016;Shaw et al, 2014;Shaw, Shaw, Johnson, Devos, & Carter, 2015;Stenøien, Shaw, Shaw, Hassel, & Gunnarsson, 2011;Szövényi, Terracciano, Ricca, Giordano, & Shaw, 2008).…”