Linking evolutionary processes and taxonomy in the peatmoss group Sphagnum subg. Cuspidata

Duke University, Durham NC

Investigators

Abstract

Peatmosses (genus Sphagnum) cover huge areas of the Northern Hemisphere where they help regulate regional patterns of water drainage, and in the far North, the extent of permafrost (permanently frozen ground). Within these Sphagnum-dominated peatland ecosystems, peatmosses store vast amounts of carbon in the form of partially decomposed peat and create environments for unique assemblages of other plants, animals, and microbes. There are an estimated 250-400 peatmoss species although the exact number of species and their genealogical relationships remain to be tested. This project focuses on species delimitation, estimating genealogical relationships, and producing a new taxonomic classification for one group of peatmosses: Sphagnum subg. Cuspidata. Undergraduates, graduate students and post-doctoral researchers will be trained in diverse field and laboratory techniques and receive hands-on experience working in Sphagnum-dominated peatland ecosystems. A series of workshops and field courses will engage both professional and amateur naturalists in the project, and a new illustrated book will introduce preschool children to the diversity of plant life. All DNA sequence data generated by the project will be deposited in public databases and other research products will be freely accessible. The central aims of this project are to assess species delimitation, phylogenetic relationships, interspecific admixture, and inter- / intra-specific genome structure in Sphagnum, subgenus Cuspidata. Subgenus Cuspidata includes approximately 20-25 species. The project covers a broad range of geographic scales including proximate populations, regional metapopulations, and plants from different continents, and includes three integrated parts. The first aim uses RADSeq to test hypotheses of phylogeographic structure among plants collected in Europe, eastern North America, western North America, Asia, and specifically, whether eastern North American and European plants form a clade sister to plants from western North America and Asia. The RADSeq data will be used to delimit phylogenetic species, including estimates of genetic admixture among species and intraspecific, geographic metapopulation systems. The second aim uses whole genome sequencing to test hypotheses about genomic differentiation among species and geographically disjunct population systems, as well as genomic regions that are shared among species- and population-level clades. A major goal is to assess the physical architecture of shared and differentiated genomic regions across the 19 chromosomes of haploid gametophytes. Comparative analyses will test hypotheses that species differ in genes related to nutrient requirements and water relations, two important niche gradients that differentiate members of Sphagnum subg. Cuspidata. The comparative analyses are facilitated by rich genomic resources available for Sphagnum, including a reference genome and genetic map for a species in subg. Cuspidata (S. fallax). The third and final aim integrates and synthesizes data within a taxonomic revision of the subgenus, including identification keys, descriptions, nomenclatural revisions, illustrations, and distribution maps. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.