Global patterns of peatmoss biodiversity

DNA sequence data from the nrITS and the cpDNA trnL-trnF regions were used to quantify geographic partitioning of global biodiversity in Sphagnum, and to compare patterns of molecular diversity with patterns of species richness. Molecular diversity was estimated for boreal, tropical, Neotropical, nonboreal (tropical plus Southern Hemisphere), Old World, and New World partitions, based on a total of 436 accessions. Diversity was partitioned among geographic regions in terms of combined nuclear and chloroplast sequence data and separately for the ITS and trnL data sets. Levels of variation were estimated using phylogenetic diversity (PD) and the number of polymorphic nucleotide sites.

Estimates of species richness suggest that peatmoss diversity is higher in New World than Old World regions, and that the Neotropics constitute a "hotspot" of diversity (Fig. 1). Molecular estimates, in contrast, indicate that peatmoss biodiversity is almost evenly divided between New and Old World regions,and that the Neotropics account for only 20-35% of global peatmoss diversity. Levels of tropical and boreal peatmoss molecular diversity were comparable.

S. sericeum from the Old World tropics and S. lapazense from Bolivia, are remarkably divergent in nucleotide sequences from all other Sphagna and together account for almost 20% of all peatmoss diversity (Table 1), although they are represented by only 3 of the 436 accessions (0.7%). These species clearly demonstrate the nonequivalence of species biodiversity value.

Table 1. Phylogenetic diversity (PD) estimates for peatmosses (Sphagnum) partitioned among geographic regions. Three highly divergent accessions of S. lapazense (South America) and S. sericeum (Malaysia and Borneo) were not included in the analyses. Values represent percentages of total PD (tree length). The total data set includes 436 accessions. Values in parentheses following the regions are sample sizes. Mean values (± sd) for subsamples are based on from 100 random samples of the size indicated parenthetically.

Reference:

Shaw, A. J., C. J. Cox, & S. B. Boles. 2003. Global patterns of peatmoss biodiversity. Molecular Ecology 12: 2553-2570. reprint

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