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Владение чувствительностью

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DNA sequence data from the nr ITS 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.

  Combined nrDNA cpDNA
S. lapazense & S. sericeum      
Boreal (313)      
Nonboreal (120)      
Boreal (subsampled:120) 48 (� 3) 49 (� 3) 47 (� 4)
Tropical (110)      
Boreal (subsampled:110) 46 (� 3) 48 (� 3) 44 (� 4)
Neotropical (74)      
Boreal (subsampled:74) 39 (� 2) 40 (� 3) 38 (� 3)
New World (237)      
Old World (196)      
New World (subsampled:196) 62 (� 2) 67 (� 2) 55 (� 2)

Reference:

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

    Phylogeny, species delimitation, and interspecific hybridization in Sphagnum section Acutifolia Nucleotide sequences for six nuclear and one chloroplast loci were used to reconstruct phylogenetic relationships in the section Acutifolia. The combined data matrix, which includes 136 accessions (129 ingroup taxa and 7 outgroups) and 5126 nucleotide sites, was analyzed using Bayesian inference. Most of the individual morphospecies generally recognized in the section were represented by multiple populations, in some cases by up to 16 accessions from throughout the Northern Hemisphere. Results of the combined seven-locus analysis resolved many of the species as monophyletic, but the deeper nodes were generally without support. Separate analyses of single-locus data sets revealed significant conflicts, indicating interspecific gene flow within the section. Sequence data allowed likely parentage to be identified for several species of hybrid origin, and identified individual accessions that appear to be genetic admixtures. Taxonomic conclusions that can be made from the analyses include: 1. Sphagnum wulfianum and S. aongstroemii should both be included in section Acutifolia, 2. S. subtile cannot be separated from S. capillifolium, and the two should be synonymized, 3. S. capillifolium and S. rubellum each contain a monophyletic core of populations and should be retained as separate species, but 4. S. rubellum cannot be separated from S. andersonianum and S. bartlettianum and they should be merged, 5. S. tenerum is highly differentiated from S. capillifolium and should be treated as a separate species, 6. inter-specific mixed ancestry is demonstrated for S. russowii (a likely allopolyploid), S. skyense, S. arcticum, and S. olafii. Interspecific recombination appears to be rather common in the Acutifolia, yet species, for the most part, maintain cohesiveness. Fig. 1. Phylogenetic reconstruction for Sphagnum sect. Acutifolia, based on heterogeneous Bayesian analyses of seven genomic regions. Thick branches are supported at � 95% Bayesian joint posterior probability. The accession of S. subtile (no. 1281, identified by J. Shaw and L. E. Anderson) indicated by a solid black circle does not group with other accessions of the morphospecies. Reference: Shaw, A. J., C. J. Cox, & S. B. Boles. 2005. Phylogeny, species delimitation, and interspecific hybridization in Sphagnum section Acutifolia. Systematic Botany 30: 16-33. reprint  
 

 

 

Владение чувствительностью




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