Sphagnum species are ecologically prominent wetland plants with xerophytic adaptations and succession-directing acidification capabilities. Species are organized along environmental gradients of pH, cation concentrations, hummock and hollow, wet versus dry, shade versus sun, coastal versus inland, and cold versus warm. The known factors responsible for this organization include cation-exchange capacity, desiccation tolerance, desiccation resistance, water-holding capacity, drying rates, and photosynthetic response at differing water contents. Small-scale distribution of Sphagnum species can be better explained for ombrotrophic sites than for minerotrophic sites.

The vertical distributions of nine Sphagnum species and four associated mosses in two bogs (Adirondack Mountains, New York) were analyzed for interspecific and interbog differences. Based on 4300 sample points, Sphagnum mean heights ranged from 12 to 43 cm above the water table and the sequence of species was similar in both bogs (S. cuspidatum and S. majus) < (S. fallax and S. angustifolium) < (S. magellanicum, S. rubellum, and S. russowii) < (S. fuscum and S. nemoreum). However, at Bloomingdale Bog, a relatively dry mire with many well-developed hummocks and narrow hollows, mosses had significantly greater means (by 4-12 cm) than at Raybrook Bog, a relatively wet mire with wide Sphagnum carpets and fewer hummocks. South- and east-facing hummock slopes tended to be gentler than the north and west slopes, but the mosses’ mean heights did not vary with aspect. The abundance of hummocks at Bloomingdale seems responsible for not only the greater mean heights, but also for broader ranges and greater vertical overlap with other species. However, the ability of each species to dominate a certain array of height classes did not differ between bogs. Within each bog, hummock species tended to have larger vertical ranges than hollow species, implying a lesser ability of hollow mosses to tolerate the full range of conditions along the hummock-hollow gradient.

For all illustrations in this publication the following letter designations apply:A. Habit sketch B. Branch leaf from spreading branch C. Transverse section of branch leaf from spreading branch D. Convex surface, upper middle region, of branch leaf from spreading branch DM. Same as D but middle region DL. Same as D but lower middle region E. Concave surface, upper middle region, of branch leaf from spreading branch EM. Same as E but middle region EL. Same as E but lower middle region F. Apex of spreading branch leaf G. Border of spreading branch leaf H. Cortical cells of spreading branches E Stem leaf J. Stem leaf hyaline cells, upper middle region, convex surface, anisophyllous form K. Stem leaf hyaline cells, upper middle region, convex surface, hemiisophyllous form L. Stem leaf hyaline cells, upper middle region, concave surface, anisophyllous form M. Stem leaf hyaline cells, upper middle region, concave surface, hemiisophyllous form N. Stem transverse section O. Stem cortex, surface view P. Hanging branch leaf, upper middle region, convex surface viTABLE1.MIRETYPES: WATER CHEMISTRY-HYDROLOGIC CRITERIA I.Bog-Water supply strictly atmospheric.A. Raised hog-Convex in transverse section.B. Blanket bog-Irregular in transverse section, following land contours.C. Flat bog-Flat in transverse section. II.Fen-Water supply influenced by mineral soil ground water.A. Poor fen-Water supply low in dissolved nutrients and strongly to moderately acid. B. Medium fen-Water supply, dissolved nutrients, and acidity intermediate between poor and rich fen.C. Rich fen-Water supply relatively high in dissolved nutrients and weakly acid to weakly basic.Flat bogs occur in drier climates than the previous bog types, and are usually located as central portions of larger mire complexes, of which the marginal vegetation is fen influenced by mineral soil water. As their name implies, flat bogs have a surface that appears flat in cross section.Since there are no obligate bog plants-all characteristic bog species also occur in poor fens (Maimer, 1962 ) flat bogs must be recognized vegetationally by a lack of obligate fen species. A monotonous hummock-hollow topography typifies flat bogs and, due to the limited number of plants able to tolerate the highly acidic and very weakly mineralized substrate, species diversity is low. In New York, true flat bogs are apparently quite rare. The only one well known to this author occurs as part of an extensive mire complex near Bloomingdale, N.Y. on the northern fringe of the Adirondacks. A large central portion of the mire is a very hummocky, true flat bog with a limited number of sphagna-S. nemoreum, S. rubellum, S. fuscum, S. fallax, S. angustifolium and rarely S. cuspidatum.Any mire in which the subsurface water has any contact with mineral soil is herein considered a fen. Fens are thus always minerotrophic as opposed to the ombrotrophic bogs. The term "bog" or "valley bog" as employed by most British and North American ecologists (see esp. Tansley, 1939 ; Dansereau and Segadas-Vianna, 1952 ; Jeglu...

The monoicous peatmoss Sphagnum subnitens has a tripartite distribution that includes disjunct population systems in Europe (including the Azores), northwestern North America and New Zealand. Regional genetic diversity was highest in European S. subnitens but in northwestern North America, a single microsatellite-based multilocus haploid genotype was detected across 16 sites ranging from Coos County, Oregon, to Kavalga Island in the Western Aleutians (a distance of some 4115 km). Two multilocus haploid genotypes were detected across 14 sites on South Island, New Zealand. The microsatellite-based regional genetic diversity detected in New Zealand and North American S. subnitens is the lowest reported for any Sphagnum. The low genetic diversity detected in both of these regions most likely resulted from a founder event associated with vegetative propagation and complete selfing, with one founding haploid plant in northwest North America and two in New Zealand. Thus, one plant appears to have contributed 100% of the gene pool for the population systems of S. subnitens occurring in northwest North America, and this is arguably the most genetically uniform group of plants having a widespread distribution yet detected. Although having a distribution spanning 12.5° of latitude and 56° of longitude, there was no evidence of any genetic diversification in S. subnitens in northwest North America. No genetic structure was detected among the three regions, and it appears that European plants of S. subnitens provided the source for New Zealand and northwest North American populations.

Phylogenetic analyses of genome structure and nucleotide sequences from mitochondrial, plastid, and nuclear genes have corroborated the view held by botanists for over a century that the bryophyte groups (mosses, liverworts, hornworts) comprise early-diverging land plant lineages that originated before the appearance of vascular plants ( Haeckel, 1876 ;Campbell, 1895 ;Bower, 1935 ;Kenrick and Crane, 1997 ;Shaw and Renzaglia, 2004 ). Early cladistic analyses based on morphological characters ( Mishler and Churchill, 1984 ) showed that the three bryophyte groups, classifi ed by most botanists of the time as a single phylum because of their similar gametophyte-dominant life cycles, more likely represent a paraphyletic grade that diverged before the emergence of the vascular plants. In fact, Haeckel ' s (1876) tree similarly shows mosses and liverworts as a paraphyletic grade basal to the vascular plants. Recent data sets appear to favor the hypothesis that liverworts (phylum Marchantiophyta) comprise the earliest-diverging lineage, followed by the mosses (Bryophyta) and hornworts (Anthocerophyta) ( Qiu et al., 1998 ;Nickrent et al., 2000 ;Shaw and Renzaglia, 2004 ). However, the most data-rich studies to date, based on chloroplast or mitochondrial organellar proteins, like analyses based on sperm cell morphology ( Garbary et al., 1993 ), identify a clade uniting liverworts and mosses, and additional data are still needed before we can consider the branching order of early land plant lineages to be fi nally resolved ( Nishiyama et al., 2004 ;Rodr í guez-Ezpeleta et al., 2007 ;Terasawa et al., 2007 ; but see also Qiu, et al., 2006 ).Notwithstanding that much remains to do, great progress has been made toward resolving phylogenetic relationships within the mosses (phylum Bryophyta s.s.) (e.g., Cox and Hedderson, 1999 ;Cox et al., 2000 ;Newton et al., 2000 ; Goffi net et al., 2001 ;Stech and Frey, 2008 ; Goffi net et al., 2009 ;Wahrmund et al., 2010 ). Major clades resolved by molecular data to a large extent mirror previous classifi cations based on morphology (e.g., Fleischer, 1923 ; Brotherus, 1924 Brotherus, -1925Vitt, 1984 • Premise of the study : The Sphagnopsida, an early-diverging lineage of mosses (phylum Bryophyta), are morphologically and ecologically unique and have profound impacts on global climate. The Sphagnopsida are currently classifi ed in two genera, Sphagnum (peat mosses) with some 350 -500 species and Ambuchanania with one species. An analysis of phylogenetic relationships among species and genera in the Sphagnopsida were conducted to resolve major lineages and relationships among species within the Sphagnopsida.• Methods : Phylogenetic analyses of nucleotide sequences from the nuclear, plastid, and mitochondrial genomes (11 704 nucleotides total) were conducted and analyzed using maximum likelihood and Bayesian inference employing seven different substitution models of varying complexity.• Key results : Phylogenetic analyses resolved three lineages within the Sphagnopsida: (1) Sphagnum serice...